Estuarine Ecology Programme REPORT - New Zealand€¦ · The Estuarine Ecology Programme (EEP) was...

JUNE 2009

ESTUARINE ECOLOGY PROGRAMME

ENVIRONMENTAL ASSESSMENT OF AHURIRI AND

PORANGAHAU ESTUARIES

Project No

EAM040

Prepared for

HAWKE’S BAY REGIONAL COUNCIL

EMT 09/22

HBRC Plan Number 4145

Prepared by

SHADE SMITH

CLIENT REF: EAM040


Report prepared by: SHADE SMITH MSc (Hons)

Marine Scientist

Reviewed by: JASON STRONG MSc (Hons)

Environmental Scientist

CLIENT REF: EAM040


TABLE OF CONTENTS

Executive summary 1

1.0 Introduction 2

1.1 Site Descriptions 2

1.1.1 Ahuriri Estuary 2

1.1.2 Porangahau Estuary 3

1.2 Statutory Context 3

1.3 Objectives 3

1.4 Recommendations from 2008 4

2.0 Sampling Sites and Methodology 4

2.1 Site and Station Selection 4

2.2 Sediment Composition and Quality 7

2.3 Macroinvertebrate Sampling 8

2.4 Data Analysis 8

2.4.1 Sediment Characteristics 8

2.4.2 Biological Characteristics 9

3.0 Results 9

3.1 Sediment Characteristics 9

3.1.1 Sediment Texture: Present Survey 9

3.1.2 Sediment Texture: Inter-Survey Comparison 10

3.1.3 Sediment Quality: Present Survey 11

3.1.4 Sediment Quality: Inter-Survey Comparison 20

3.1.5 Overview 24

3.2 Biological Characteristics 26

3.2.1 Infaunal Summary Indices: Present Survey 26

3.2.2 Infaunal Summary Indices: Inter-Survey Comparison 28

3.2.3 Infaunal Multivariate Analysis: Present Survey 30

3.2.4 Infaunal Multivariate Analysis: Inter-Survey Comparison 33

3.2.5 Epifaunal Summary Indices: Present Survey 36

3.2.6 Epifaunal Summary Indices: Inter-Survey Comparison 36

3.2.7 Epifaunal Multivariate Analysis: Present Survey 37

3.2.8 Epifaunal Multivariate Analysis: Inter-Survey Comparison 40

3.2.9 Overview 43

4.0 Summary 45

5.0 Conclusion 46

6.0 Recommendations 46

7.0 References 47

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TABLE OF CONTENTS

Apendices

Appendix 1: Sampling Stations 49

Appendix 2: Sediment Data 51

Appendix 3: Infauna Data 56

Appendix 4: Epifauna Data 59

Appenidix 5: Inter-Survey Comparison: PERMANOVA’s, SIMPER’s 61

Appendic 6: Report Limitations 68

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EXECUTIVE SUMMARY

Estuaries represent the downstream receiving environments of the freshwater drainage network and are

sensitive to the same effects of land-use activities as streams and rivers throughout the catchment. In New

Zealand, estuaries are being recognised as the coastal environments most at risk, as they are the

depositional end-point for the accumulative contaminants from the surrounding catchment.

Under the Resource Management Act (1991), Hawke’s Bay Regional Council must establish, implement and

review objectives, policies and methods to promote the sustainable management of the coastal area, and

monitor the effectiveness of plans. The Estuarine Ecology Programme (EEP) was developed as part of the

Coastal Monitoring Strategy to determine and monitor the long-term health and sustainability of Hawke’s

Bay’s estuaries.

As part of the EEP sampling was undertaken at Ahuriri and Porangahau Estuaries in line with the Estuarine

Environmental Assessment and Monitoring: A National Protocol. At each of five sites (four sites within Ahuriri

Estuary, one site within Porangahau Estuary), 12 infaunal cores, 10 surficial sediment samples, 10 sediment

cores were collected, and 10 epifaunal quadrats assessed.

Concentrations of contaminants of concern at all sites are below environmental guidelines designed to

protect ecological values. However, at site AHUD (adjacent to the Tyne Street Drain) concentrations of

trace metals are above relevant regional background levels and zinc is just below guideline values.

There also appears to be an increase in fine sediments, at sites AHUA and AHUB which at site AHUA may be

influencing infaunal communities.

As expected, faunal composition tended to be strongly driven by the sediment composition at each site,

with clear differences evident among the assemblages of infaunal organisms at each of the five sites. .

Groupings were less evident among sites and between years for the epifauna, but differences were

significant.

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1.0 INTRODUCTION

As the interface between land and sea, intertidal, estuarine and fringing coastal habitats are distinctive and

dynamic environments. The animals and plants living in estuaries must contend with harsh physical and

chemical conditions, such as prolonged periods of emersion and immersion, and associated changes in

salinity, temperature and oxygen availability.

In addition to providing valuable habitat for bird roosting, feeding and breeding, and important spawning

and nursery grounds for fish, estuaries also provide the ecological services that help to sustain environmental

quality and integrity. Estuaries not only buffer the effects of land-use extending to the open ocean, but

conversely, also buffer the effects of the ocean on the land. They are productive habitats, have an

important role in water regulation, water quality enhancement, and can assist in the mitigation of erosion

caused by scouring and wave action.

Estuaries represent the downstream receiving environment of the freshwater drainage network, so it is

understandable that they are sensitive to the same effects of land-use activities as streams and rivers

throughout the catchment. In New Zealand, estuaries are being recognised as the coastal environments

most at risk, as they are the depositional end-point for the accumulative contaminants from the surrounding

catchment.

Sedimentation has been identified as having the potential to threaten the health and sustainability of

estuaries, and compromise the ecological values they contain. As land-use has changed, estuaries have

gone from a typical sedimentation regime of approximately 1mm per year, to up to ten times this amount in

some areas (Hume and Swales, 2003). Increased sediment loading can have both sub-lethal and lethal

effects on the animals and plants living in the estuary. An increased level of suspended solids in the water

column increases turbidity, restricting access to light for the plants and thereby restricting photosynthesis

and algal and macrophyte production rates. Increased turbidity can also alter the functional capabilities

of the system from one dominated by visual predators to one dominated by organisms that utilise chemo-

sensory techniques for feeding, and can alter the benthic community from suspension to deposit feeders

(Watling and Norse, 1998). Reproductive condition and feeding rates in filter feeders can be decreased

(e.g. Pecten novaezelandiae – scallop; Boccardia syrtis – polychaete), and increased mortality can occur

in some species (e.g. Macomona liliana – wedge shell) (Nicholls et al, 2002).

In addition to the long-term effects of elevated sediment levels, acute episodic events such as storms can

cause large deposits of sediments in some parts of the estuary. These can bury marine organisms, affecting

access to light, food and oxygen, and result in the accumulation of waste products (Airoldi, 2003). The

biological communities present in marine and estuarine ecosystems are largely driven by the physical

environment, of which the sediment composition plays a significant role. Therefore, changes in the

composition caused by the deposition of fine muds will ultimately cause a change in the ecology of the

area.

Given the importance of estuary ecosystems and the services they provide, and the real risk to the integrity

of the system from the threats they are facing, monitoring of the long-term health and state is required to

ensure that these vital ecosystems are being sustained in a way that will retain these key functions.

1.1 SITE DESCRIPTIONS

1.1.1 Ahuriri Estuary

Formed in the wake of the 1931 earthquake, the Ahuriri Estuary (Te Whanganui-A-Orutu) is located in the

area of the former Ahuriri Lagoon (Figure 2.1). The seismic activity lifted the bed of the lagoon between 1.5

to 3.4 metres, exposing approximately 1300 hectares of land (HDC, HBRC, NCC, and DoC, 1992).

Subsequent drainage and reclamation has reduced the area to its current size of approximately 470 ha of

true estuary, and around 175 hectares of associated wetlands (Cromarty and Scott, 1996).

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The estuary has a tidal exchange of approximately 495 million litres, and seawater to freshwater ratio of

approximately 10:1. Approximately 60% of the estuary drains at low tide (Cromarty and Scott, 1996),

exposing mud, coarse sand and shingle intertidal habitats.

Despite extensive modification, the estuary continues to support a diverse array of flora and fauna,

throughout a range of habitats. It is an important breeding, roosting and feeding area for a number of

water birds, and makes a significant contribution to Hawke’s Bays marine fisheries (Kilner and Ackroyd,

1978). About twenty-nine species of fish use the estuary during some component of their life cycle. Whilst

many (e.g. kahawai, grey mullet, yellow-bellied flounder, stargazer, parore) use the area for feeding,

moving into the estuary on the incoming tide, and retreating back out to sea on the receding tide, around

eleven species of fish also use the estuary as a nursery or spawning ground. These include commercially

important species such as yellow-bellied flounder, grey mullet, sand flounder, common sole, and yellow-

eyed mullet.

Ahuriri Estuary is listed as a Significant Conservation Area under the proposed Regional Coastal Environment

Plan (HBRC, 2006), and a Wildlife Refuge offers protection to areas between the Southern Marsh, Westshore

Lagoon and the estuary from the low level bridge to Pandora Bridge.

1.1.2 PORANGAHAU ESTUARY

At approximately 750 ha in size, Porangahau Estuary is one of the few large estuaries on the north eastern

coast of New Zealand. Situated at the mouth of the Porangahau River, the estuary is the downstream

receiving environment of a catchment dominated by high producing exotic grassland characteristic of

sheep and beef farming. The river-mouth estuary is formed behind a large un-vegetated inshore bar, and

breaks through at one or more locations along the bar to meet the sea.

The estuary and associated dunes and wetlands have been identified as an area recommended for

protection (RAP 22, from RCP, (HBRC, 1999)). The estuary has been recognised for its fisheries values based

on the unique and diverse assemblage of fish species, and constitutes a nationally important fisheries

habitat for whitebait, flounder, mullet and kahawai (Davis, 1987). The adjacent dune provides important

feeding and roosting area for a number of migratory birds (HBRC, 1999), and the estuary provides the only

known breeding site in the region for Caspian terns (Davis, 1987).

Porangahau Estuary is listed as a Significant Conservation Area under the Regional Coastal Plan (HBRC,

1999) and the proposed Regional Coastal Environment Plan (HBRC, 2006).

1.2 STATUTORY CONTEXT

Hawke’s Bay Regional Council has established a long-term Estuarine Ecology Project (Madarasz, 2006) to

provide for a repeated assessment of the estuarine flora and fauna, necessary to determine the state and

health of the estuarine ecosystem, and the effectiveness of Council policy. Under the Resource

Management Act (1991), Hawke’s Bay Regional Council must establish, implement and review objectives,

policies and methods to promote the sustainable management of the coastal area. Council is also

required to monitor the suitability and effectiveness of policy statements and/or plans. The Estuarine

Ecology programme provides the mechanism for this effectiveness monitoring.

1.3 OBJECTIVES

The Estuarine Ecology Project will:

1. Assess the state and health of Hawke’s Bay’s estuarine environments;

2. Assess temporal change in Hawke’s Bay’s estuaries in order to determine optimal monitoring frequency;

and

3. Provide the information necessary for Council to assess the effects of management practises and

policy provisions.

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1.4 RECOMMENDATIONS FROM 2008

Several recommendations were made at the completion of the 2008 monitoring. The following explains

how these recommendations were implemented in 2009.

1. That continued monitoring is undertaken in line with the methodology set out in this report; A C T I O N :

Monitoring was undertaken in March 2009.

2. That heavy metals concentrations in the flesh of shellfish and/or mud snails (sensu Mapua, Nelson) are

assessed at site AHUD; ACTION: This has not as yet been undertaken. However, amphipod toxicity

testing, using sediment from AHUD, conducted in 2008 showed no significant difference in survival

compared to a control.

3. That trace metal concentration on the silt/clay fraction (<63mm), are analysed independently at a

few sites of varying sediment composition to confirm the use of normalised data for relative

differences; ACTION: Three sites at AHUD were also analysed for trace metal concentrations on the

<63mm sediment fraction.

4. That toxicity testing is performed on sediments from site AHUD to identify the actual risk of

contaminants at this site to estuarine fauna; ACTION: Toxicity testing carried out by NIWA.

5. To reduce the sampling frequency for site AHUC from the monitoring programme. This site has been

shown to display similar characteristics to site AHUB and monitoring could be reduced to one in three

years to (or the last year of monitoring if less than a three year period) to track whether this similarity

remains; ACTION: Site AHUC not sampled this year.

6. If budget permits a further depositional site (similar silt/clay content to site AHUD but away from

specific point source discharges) should be added to provide a comparison for site AHUD; ACTION:

Site AHUE identified as having similar mud/silt properties to site AHUD and included in sampling

programme for this year.

7. That the ‘Your Choice’ stormwater programme is continued and the effectiveness monitored.

2.0 SAMPLING SITES AND METHODOLOGY

2.1 SITE AND STATION SELECTION

Sampling was undertaken in line with the Estuarine Environmental Assessment and Monitoring: A National

Protocol (Robertson et al., 2002). Use of the protocol enables the comparison of Hawke’s Bays estuaries

with other estuaries elsewhere in the country, and promotes a robust, scientifically defensible methodology

for estuarine monitoring. Sampling was conducted at low tide at Porangahau on the 10th March and at low

tide at Ahuriri on the 11th and 12th March 2009.

Four sites in the Ahuriri Estuary (sites AHUA, AHUB, AHUD and AHUE) and one in the Porangahau Estuary (site

PORA) were selected to best represent the estuary condition and characteristics within a standardised

benthic habitat, i.e. muddy sand, in the low intertidal zone. Broad scale habitat mapping, conducted by

the Cawthron Institute in June 2005, highlighted areas that meet criteria of the national protocol, and sites

were selected from these areas (Figure 1 and 2). This year the site AHUE was added to the Ahuriri group of

sites, while sampling at the previously surveyed site AHUC was discontinued.

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At each site a 60x30m (where sufficient quantity of habitat allowed) grid was marked out into 12 sections of

equal size. Within each section a randomly selected station was sampled. At each station (12 within each

site), an infaunal and sediment core were taken and an epifaunal/floral quadrat assessed (Figure 3).

Surficial sediment samples and epifaunal quadrats for analysis were only collected at the first 10 sites.

Figures 3 and 4 show the actual location of each sampling station for each site, and GPS coordinates for

each station are included in Appendix 1.

FIGURE 1: AHURIRI ESTUARINE ECOLOGY MONITORING SITES.

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FIGURE 2: PORANGAHAU ESTUARINE ECOLOGY MONITORING SITE.

FIGURE 3: AERIAL PHOTOGRAPHS SHOWING THE LOCATIONS OF SAMPLING STATIONS AT EACH AHURIRI ESTUARY SITE.

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FIGURE 4: AERIAL PHOTOGRAPH SHOWING THE LOCATION OF SAMPLING STATIONS AT THE PORANGAHAU ESTUARY SITE.

2.2 SEDIMENT COMPOSITION AND QUALITY

At each of the 12 stations the sediment profile was examined for qualitative sediment properties and to

determine the depth of the redox discontinuity potential layer (RDPL – the boundary between the

oxygenated and anoxic sediments).

Following visual assessments surficial sediments (top 2cm) were sampled at 10 of the 12 stations using a small plastic scoop and placed in pre-labelled, plastic, re-sealable bags. Samples were refrigerated overnight

and the following day, one chilled sub-sample, of approximately 250g, was sent to the Cawthron Institute,

Nelson for sediment textural, chlorophyll a and Ash Free Dry Weight (AFDW) analysis. Another 250g sub-

sample was sent to Hill Laboratories, Hamilton for trace metal and nutrient concentration analysis.

Sediments were analysed for basic sediment textural composition with particles grouped into 3 size classes; granules (>2mm), sand (63µm – 2mm) and fines/mud (<63µm). The data were standardised to obtain a

distribution of granules, sand and fines/mud totalling 100%. Sediments were also analysed for trace metal

concentrations, with the following tested for; Arsenic (As), Cadmium (Cd), Chromium (Cr), Copper (Cu),

Nickel (Ni), Lead (Pb) and Zinc (Zn). Nutrients tested for included Total Nitrogen and Total Recoverable

Phosphorus. Analytical methods used are detailed in Table 1.

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TABLE 1: SUMMARY OF ANALYTICAL METHODS USED FOR SEDIMENT ANALYSES

2.3 MACROINVERTEBRATE SAMPLING

At each station an infaunal core was collected using a circular PVC 130mm (internal diam.) core (total area

0.013m2). Samples were collected by pushing the core into the sediment to a depth of 150mm (Robertson

et al., 2002) and digging down the outside of the core, placing a hand over the bottom and extracting the

core and intact sample. Samples were ejected from the core into a 0.5mm mesh sieve and sediment

gently washed through, leaving infauna on the screen. Samples were then washed into sample jars with

95% Ethanol and fixed in same. After transporting samples back to the lab a few drops of Rose Bengal

solution was added to each sample, and left for several hours to allow samples to uptake the stain.

Samples were then poured into shallow trays and all biological material carefully picked out. The material

was then examined under a dissecting microscope, and all biology enumerated and identified to the

lowest possible taxonomic grouping.

0.25m2 quadrats were also placed on the substratum at the each of the first ten stations at each site and epifauna contained within identified and enumerated.

2.4 DATA ANALYSIS 2.4.1 Sediment characteristics

Spatial differences in sediment characteristics (texture, trace metals, nutrients, organic matter – expressed

as AFDW, and chlorophyll a) between sites in the present survey were explored using one-way ANOVA

(StatSoft, 2004). Differences between sites and years (2006 – present) were explored using a two factor

ANOVA, with the factors being site and year. The assumption of homogeneity of variance for ANOVA was

checked using Levene’s test.

Trace metal results were compared against national sediment quality guidelines (ANZECC, 2000) These guidelines or Interim Sediment Quality Guidelines (ISQG) consist of upper (ISQG-high) and lower (ISQG-low)

thresholds above which biological effects can be expected. Where trace metal concentrations are below

ISQG-low values then adverse biological effects are expected only on rare occasions. Trace metal

concentrations falling between ISQG-low and ISQG-high are expected to cause adverse biological effects

occasionally, while a result above the ISQG-high would be expected to cause adverse biological effects

frequently.

Currently there are no guidelines for assessing the effects of sediment-bound nutrients such as nitrogen or phosphorus, on the environment. If there are no obvious signs of nutrient enrichment at a site it may be

difficult to assess a particular site for the effects of nutrient enrichment. Therefore concentrations of these

nutrients were compared against New Zealand estuarine reference sites (Robertson et al., 2002).

Parameter Method Description

Texture Sieving, gravimetric, Air drying 35°

C overnight

Granules > 2mm

Sand 63µm – 2mm

Fines/mud < 63µm

Metals As,Cd,Cr,Cu,Hg,Ni,Pb,Zn Dry/sieve sample, Digestion

US EPA 200.2

Air dry 35°C/2mm sieve

Nitric/HCl acid digestion, ICP-MS

Total N thermal conductivity detector

(Elementar Analyser)

Catalytic combustion (900°C, O2), separa-

tion

Total Recoverable P USEPA 200.2 Nitric/Hydrochloric acid digestion, ICP-MS

Chlorophyll a NIWA periphyton monitoring

manual

acetone extraction, fluorometric

Organic content (AFDW) APHA 21st Ed. 2540 D+ E (Mod.) Air Dry 60°C/Ignition in muffle furnace 550°

C, 1hr, gravimetric

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2.4.2 Biological characteristics

Benthic infaunal and epifaunal data were compared between sites, and between years. Differences in

abundance, diversity indices, richness and evenness (collectively known as biological summary indicies)

were explored by single or two factor ANOVA (StatSoft, 2004) with post hoc analysis of individual terms by

Tukeys HSD test.

Data were also contrasted using non-metric multidimensional scaling (Kruskal and Wish, 1978) ordination

based on the Bray-Curtis distance matrix in PRIMER v5 (Clarke and Gorley, 2001).

The model was based on permutation of raw data for the fixed factor ‘site’ and or ‘year’. Data were

ln(x+1) transformed before analysis, as this type of transformation scales down the effect of highly abundant

species thus increasing the equitability of the dataset (variance standardisation). The major taxa

contributing to the similarities of each site were identified using analysis of similarities (Clarke and Gorley,

2001; Clarke and Warwick, 1994).

3.0 RESULTS

3.1 SEDIMENT CHARACTERISTICS

3.1.1 Sediment texture: present survey

Visual assessment of Ahuriri cores revealed a high variability in RDPL depths between and within sites (Table

2). This variability was a general reflection of the differing proportions of the mud to sand fractions of the

observed cores from each site. Conversely cores from Porangahau were fairly consistent in both RDPL

depth and constitution with cores deemed to be uniformly mud. In addition, none of the sites at either

estuary showed signs of significant organic enrichment, or noticeable odours associated with the sediment.

TABLE 2: MEAN DEPTH OF THE REDOX POTENTIAL DISCONTINUITY LAYER (RDPL)FOR SITES IN THE AHURIRI (AHU) AND PORANGAHAU (POR)

ESTUARIES (± 1 SE)

Sediment grain size analyses showed significant differences in sediment composition occurred between

sites. Ahuriri Estuary was predominantly characterised by fine sands, whilst Porangahau had a far greater

silt/clay fraction (Figure 5). Inter-site differences were evident among Ahuriri sites, with sites AHUE and AHUD

muddier than sites AHUA and AHUB. At site AHUE it was evident that fine sediment had been depositing on

a historical gravel/shell bank, while at site AHUD a large number of plastic fragments, glass and pieces of foil

were found incorporated throughout sediments. As well as general differences between sites there was

also intra-site differences, with patches of gravel (e.g. at site AHUA) and mud (e.g. at sites AHUB and AHUD)

evident at Ahuriri while sediments at Porangahau were consistent throughout stations sampled.

Site RPDL depth (mm) Observation of sediment matrix

AHUA 38 ± 9 Sand some mud/gravel

AHUB 67 ± 9 Sand some mud

AHUD 25 ± 7 Mud some sand

AHUE 43 ± 13 Mud/sand/shell/gravel

PORA 3 ± 1 mud

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3.1.2 Sediment texture: inter-survey comparison

Statistically significant differences in sediment texture between the 2006 and 2007 surveys and the present

survey were evident in sand and the silt/clay (“fine”) fractions at both site AHUA (F(3, 40)=6.01, p = 0.002 –

sand, F(3, 40)=8.25, p < 0.001 – fines) and site AHUB (F(3, 40)=6.26, p = 0.001 – sand, F(3, 40)=5.94, p = 0.002 –

fines), while at site AHUD there was no difference between years (Figure 6b, 6c). The increasing fines

fraction and corresponding decrease in sand between the initial 2006 survey and the present represents an

average increase of 8.6%w/w and 9.4%w/w in the fine sediments at sites AHUA and AHUB respectively and

an average decrease of 11.6%w/w and 10.0%w/w of sandy sediments at sites AHUA and AHUB respectively.

Because of the relatively small amount of fines at the sites compared to sand, essentially the increase in the

fines fraction represents a doubling of the amount of fine sediments while sand decreased relatively a lot

less, between 11-13%. At site PORA there was a significant difference, being an increase, between the 2007

and present survey in gravels (F(2, 29)=4.26, p = 0.024), while the sand and fines fraction differed significantly

between the 2008 survey and the present, being a decrease (F(2, 29)=3.50, p = 0.043) and increase (F(2,

29)=3.81, p = 0.034) respectively (Figure 6b, 6c).

FIGURE 5: COMPARISON OF SEDIMENT TEXTURE AT STATIONS WITHIN AHURIRI (AHU) AND PORANGAHAU (POR) ESTUARIES (TOP) AND MEAN

PROPORTIONS OF GRAVEL, SAND AND CLAY/SILT (BOTTOM) DURING THE PRESENT SURVEY. ERROR BARS ± 1SE.

A1

A2

A3

A4

A5

A6

A7

A8

A9

A10

B1

B2

B3

B4

B5

B6

B7

B8

B9

B10

E1

E2

E3

E4

E5

E6

E7

E8

E9

E10

D1

D2

D3

D4

D5

D6

D7

D8

D9

D10

P1

P2

P3

P4

P5

P6

P7

P8

P9

P10

% w

et weight

0

20

40

60

80

100

Gravel (>2mm)

Sands (<2mm - 63um)

Silt and Clay (<63um)

AHUA AHUB AHUE AHUD PORA

% w

et weight

0

20

40

60

80

100

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FIGURE 6: COMPARISON OF MEAN SEDIMENT TEXTURAL FRACTIONS; A) GRAVEL, B) CLAY/SILT AND C) SAND AT SITES WITHIN AHURIRI (AHU)

AND PORANGAHAU (POR) ESTUARIES FROM ANNUAL MONITORING SURVEYS (2006 – PRESENT). ERROR BARS ± 1S.E.

3.1.3 Sediment quality: present survey

Trace metals

Trace metals were present in the sediments at levels not exceeding ANZECC sediment quality guidelines

(Figure 7). At these levels the contaminant load at each site would rarely be expected to induce adverse

biological effects. It is worthwhile noting however that site AHUD is approaching the ISQG – Low limit for

Zinc.

2006 2007 2008 2009

% C

lay/s

ilt (<63µm

) ±

1SE

0

10

20

30

40

50

2006 2007 2008 2009

% G

ravel (>

2m

m) ± 1

SE

0

5

10

15

20

Site AHUA

Site AHUB

Site AHUC

Site AHUD

Site AHUE

Site PORA

2006 2007 2008 2009

% S

ands (63µm

-2m

m) ± 1

SE

40

50

60

70

80

90

100

A. B.

C.

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FIGURE 7: MEAN TRACE METAL CONCENTRATIONS AT AHURIRI (AHU) AND PORANGAHAU (POR) ESTUARINE SITES DURING THE PRESENT

SURVEY (2009). ERROR BARS ± 1 SE, RESULTS EXPRESSED ON A DRY WEIGHT BASIS.


Arsenic (mg/kg) +/- se

0

2

4

6

8

10


Lead (mg/kg) +/- se

0

5

10

15

20

25

30

35


Zinc (mg/kg) +/- se

0

50

100

150

200

250


Cadmium (mg/kg) +/- se

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35


Chro

mium (mg/kg) +/- se

0

10

20

30

40

50


Copper (m

g/kg) +/- se

0

5

10

15

20

25


Nickel (m

g/kg) +/- se

0

2

4

6

8

10

12

14

ISQG-Low: 1.5mg/kg ISQG- Low: 80mg/kg

ISQG-Low: 65mg/kg ISQG-Low: 21mg/kg

ISQG-Low: 50mg/kg ISQG-Low: 200mg/kg

ISQG-Low: 20mg/kg

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Nutrients

Across all sites within the Ahuriri Estuary sediment phosphorus levels varied between 280–1400mg/kg, with a

mean of 447 ± 31 mg/kg (1SE). At Porangahau, levels varied between 350–450 mg/kg, with a mean of 396 ±

35mg/kg (1SE). Comparing between sites, site AHUD was significantly higher (F(4, 45)=8.87, p < 0.001) in

phosphorus than any other site (Figure 8).

Within the Ahuriri Estuary sediment nitrogen levels were highest at site AHUE, and although not significantly

different to site AHUD they were significantly higher than sites AHUA (p = 0.01) and AHUB (p = 0.04). Across

the estuary nitrogen levels were in general quite low varying between levels below the detection limit

(0.005g/100g) to 0.12g/100g and averaging 0.052 ± 0.004g/100g (1SE). Porangahau recorded the highest

average levels of nitrogen, however as there were no obvious signs of nuisance algal growth at any of the

sites, it is unlikely that sediments were nutrient enriched.

Organic matter and Chlorophyll a

In terms of sediment associated organic matter, as measured by the AFDW of samples, levels in Ahuriri

Estuary ranged between 0.6–3.5%w/w with a mean of 1.96 ± 0.1%w/w (1SE). Levels at Porangahau ranged

between 0.27–3.7%w/w with a mean of 1.63 ± 0.39%w/w (1SE). There was no significant difference between

any of the monitoring sites at either estuary and the levels found were within average levels reported for

coastal Hawke’s Bay sediments (Smith, 2007).

Assessment of sediment associated chlorophyll a provides a measure of the live biomass of the

microphytobenthic community and thus trophic status of a site. It can also be a preliminary indicator of

nutrient enrichment if levels are unusually high. In the current survey levels across sites within the Ahuriri

Estuary varied between 2300–14000mg/m3, averaging 5003 ± 328mg/m3 (1SE) while Porangahau levels

varied between 1800–4500mg/m3, averaging 2910 ± 260mg/m3 (1SE). There was no significant difference

between the Ahuriri sites. However including the Porangahau site in the comparison, it was evident that

Chlorophyll a at PORA was significantly lower than two of the Ahuriri sites AHUA (p = 0.008) and AHUE (p =

0.002).

CLIENT REF: EAM040


FIGURE 8: MEAN NUTRIENT (N AND P), ORGANIC MATTER (AFDW) AND CHLOROPHYLL A CONCENTRATIONS AT AHURIRI (AHU) AND

PORANGAHAU (POR) ESTUARINE SITES DURING THE PRESENT SURVEY (2009). ERROR BARS ± 1 SE.

Comparison between sites: present survey

To account for differences in sediment composition among sites, sediment data (AFDW, nutrients and

metals) were normalised to 100% of the mud/fines component. Normalisation1 of data allows an accurate

assessment of between site data, and also allows comparison against other Hawke’s Bay and New Zealand

reference estuary sites.

Metals

When normalised for mud/fines content, site AHUD had significantly elevated levels of chromium, copper,

lead and zinc compared to all other Ahuriri sites (all p < 0.001). Moreover, site AHUD was also significantly

higher in arsenic compared to site AHUA (p = 0.036) and significantly higher in cadmium compared to site

AHUB (p = 0.049) Figure 9).

1.Reactive surface properties of fine sediments such as in the silt/clay fraction have been shown to promote preferential adhesion of trace

metals. Therefore, differences in trace metal concentrations between sites may simply reflect differences in the proportion of sediments in

this fraction. Normalising sediment contaminant data allows standardisation of sediment contaminants to sediment composition.


Tota

l N

itro

gen (g/1

00g) +/- s

e

0.00

0.02

0.04

0.06

0.08

0.10

AHUA AHUB AHUE AHUD PORA Tota

l R

ecovera

ble

Phosphoru

s (m

g/k

g) +/- s

e

0

200

400

600

800


Ash F

ree D

ry W

eig

ht (%

w/w

)

0.0

0.5

1.0

1.5

2.0

2.5

3.0


Chlo

rophyll

a (µg/k

g)

0

2000

4000

6000

8000

CLIENT REF: EAM040


In general the lowest concentrations of trace metals were found at Porangahau, with significant differences

evident in normalised levels of nickel (F(4, 45)=9.04, p<0.001) lower than any of the Ahuriri sites. Furthermore

normalised levels of lead were significantly lower at Porangahau than sites AHUB (p=0.008), AHUD (p<0.001)

and AHUE (p=0.003) while levels of chromium and zinc were significantly lower than sites AHUA, AHUB and

AHUD (all p<0.002) (Figure 9).

In general, with the exception of nickel, all contaminants displayed similar patterns between sites.

Contaminant levels were consistently highest at site AHUD and lowest at site PORA.

In general, many of the normalised trace metal contaminant levels at Ahuriri and Porangahau occur within

the mid-range observed in New Zealand reference estuaries (Table 3), except for site AHUD which was

grouped among the more polluted reference estuaries. Comparing normalised trace metal levels in the

present survey to normalised background levels of Hawke’s Bay estuaries and lagoons site AHUD showed

elevated levels for all trace metals analysed except nickel (Table 3). Furthermore site PORA showed

elevated levels of copper, site AHUE had elevated levels of lead and zinc and all sites reported levels

above derived background levels for arsenic (Table 3).

CLIENT REF: EAM040


FIGURE 9: MEAN TRACE METAL CONCENTRATIONS AT AHURIRI (AHU) AND PORANGAHAU (POR) ESTUARINE SITES DURING THE PRESENT

SURVEY (2009) NORMALISED TO 100% MUD/FINES CONTENT. ERROR BARS ± 1 SE, RESULTS EXPRESSED ON A DRY WEIGHT BASIS.


Cadmium ± 1SE

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8


Chro

mium ± 1SE

0

50

100

150

200


Copper ± 1SE

0

20

40

60

80

100


Nickel ± 1SE

0

10

20

30

40

50

60


Lead ± 1SE

0

20

40

60

80

100

120

140

160


Zinc ± 1SE

0

200

400

600

800


Arsenic ± 1SE

0

10

20

30

40

50

CLIENT REF: EAM040


To assess the efficacy of normalising whole sediment trace metal levels to 100% fines content (i.e. particles

sized <63mm), an additional analysis of trace metal levels of the fines component was also undertaken at

three stations at site AHUD.

The results indicate that although the normalisation process typically overestimates the true trace metal

levels attached to the <63mm sediment fraction (Figure 10), the ratio concentration of the <63mm trace

metal levels to the normalised trace metal levels, is reasonably consistent across all trace metals (Figure 10),

making it a good estimate of relative concentrations between sites.

FIGURE 10: PLOT SHOWING THE VARIOUS RATIOS OF THE NORMALISED TRACE METAL DATA (ALL SEDIMENT FRACTIONS) TO TRACE METAL

LEVELS ON THE <63MM SEDIMENT FRACTION FOR 3 RANDOMLY SELECTED STATIONS WITHIN SITE AHUD.

Arsenic

Cadmium

ChromiumCopper

LeadNick

elZinc

Ratio N

orm

alis

ed tra

ce m

eta

l le

vels

:63µm

tra

ce m

eta

l le

vels

0.0

0.5

1.0

1.5

2.0

AHUD1

AHUD2

AHUD5

CLIENT REF: EAM040


SITE

Tota

l

Recovera

ble

Cadm

ium

Tota

l

Recovera

ble

Chro

mium

Tota

l

Recovera

ble

Copper

Tota

l

Recovera

ble

Nic

kel

Tota

l

Recovera

ble

Lead

Tota

l

Recovera

ble

Zinc

Tota

l

Recovera

ble

Arsenic

B

GL

BG

L1

B

GL1

BG

L1

BG

L1

B

GL1

BG

L1

Ah

uriri

AH

UA

20

09

0.23

0

.42

75.88

1

03

.56

31.84

5

4.3

6

46.04

7

3.6

3

48.78

5

4.3

6

303.55

3

04

.70

19.63

1

9.3

4

Ah

uriri

AH

UB

20

09

0.19

0

.47

86.31

1

15

.74

37.49

6

0.7

5

49.12

8

2.2

9

58.68

6

0.7

5

334.94

3

40

.54

24.53

2

1.6

1

Ah

uriri

AH

UD

20

09

1.10

0

.30

171.87

7

3.2

9

80.95

3

8.4

7

35.54

5

2.1

1

121.75

3

8.4

7

616.01

2

15

.64

36.38

1

3.6

8

Ah

uriri

AH

UE 2

00

9

0.20

0

.29

56.42

7

2.6

6

34.58

3

8.1

4

34.54

5

1.6

6

62.86

3

8.1

4

235.04

2

13

.79

21.96

1

3.5

7

Po

ran

-

ga

ha

u

PO

RA

20

09

0.09

0

.15

21.60

3

7.6

2

23.86

1

9.7

4

19.94

2

6.7

4

11.82

1

9.7

4

79.27

1

10

.67

12.84

7

.02

Ah

uriri

Ge

org

es2

0

.67

80

.43

58

.18

46

.92

77

.08

60

1.8

8

3

3.5

1

Ah

uriri

Pu

rim

u2

1.0

2

9

5.5

1

4

0.2

65

.31

55

.92

36

9.3

9

5

1.0

2

Ah

uriri

Ra

il B

rid

ge

2

1.4

1

1

57

.63

55

.08

10

4.5

2

1

09

.04

64

9.7

2

9

8.8

7

Oth

er

NZ

Ota

ma

tea

3

0.7

1

3

6.4

8

2

4.5

6

1

6.7

3

2

0.2

8

6

9.9

8

N

S

Oth

er

NZ

Oh

iwa

3

0.4

9

3

6.8

2

2

0.0

2

1

9.4

16

.92

13

7.8

1

N

S

Oth

er

NZ

Ru

ata

niw

ha

3

1.0

9

2

60

.87

77

.17

14

8.9

1

5

1.0

9

4

07

.61

NS

Oth

er

NZ

Wa

ime

a3

1.2

2

2

75

.97

39

.18

29

5.9

2

3

0.2

17

0.6

1

N

S

Oth

er

NZ

Ha

ve

loc

k3

1.5

7

2

55

.49

56

.02

13

8.7

4

2

9.3

2

2

25

.13

NS

Oth

er

NZ

Av

on

-

He

ath

co

te3

1.8

5

2

88

.89

59

.26

12

2.2

2

1

16

.67

70

9.2

6

N

S

Oth

er

NZ

Ka

iko

rai3

0

.37

17

7.9

4

6

1.7

6

5

7.3

5

1

66

.54

67

7.2

1

N

S

Oth

er

NZ

Ne

w R

ive

r3

5.8

8

6

52

.94

22

3.5

3

2

94

.12

41

.18

10

05

.9

N

S

TABLE 3: COMPARISON O

F M

EAN TRACE M

ETAL LEVELS NORMALISED TO 100% M

UD/FINES CONTENT FOR AHURIRI (AHU) AND PORANGAHAU (POR) ESTUARINE SITES FROM THE PRESENT

STUDY (2009) TO M

EAN HAWKE’S BAY BACKGROUND LEVELS FROM LAGOON AND ESTUARINE SITES (BGL) NORMALISED TO THE M

UD/FINES CONTENT O

F EACH RESPECTIVE STATION IN

THE PRESENT STUDY. FURTHER C

OMPARISONS INCLUDE N

ORMALISED D

ATA FROM A

PREVIOUS SEDIM

ENT STUDY W

ITHIN THE A

HURIRI ESTUARY A

ND A

RANGE O

F A

VERAGE VALUES

FROM NEW ZEALAND ESTUARINE REFERENCE SITES.

1. (S

tro

ng

, 2

00

5).

2

. (B

en

ne

tt,

20

06

).

3. (

Ro

be

rtso

n e

t a

l.,

20

02

). Sh

ad

ed

c

ells

in

dic

ate

e

lev

ate

d le

ve

ls c

om

pa

red

to

b

ac

kg

rou

nd

le

ve

ls fo

r

Ha

wke

’s B

ay e

stu

arie

s a

nd

la

go

on

s.

CLIENT REF: EAM040


Nutrients

When normalised to 100% mud content, sediment nitrogen levels across all sites and for both estuaries did

not differ significantly (Figure 11). Comparing sediment phosphorus levels between sites; only a single

significant result was evident, being elevated levels at site AHUD compared to PORA (p = 0.003)(Figure 11).

When compared against New Zealand reference estuaries, levels within Ahuriri lay in the mid range of

values while Porangahau recorded the lowest values among all sites and reference estuaries (Table 4).

Organic matter

Normalised levels of organic matter (AFDW) were not significantly different among Ahuriri sites but between

estuaries PORA was significantly lower than any of the Ahuriri sites (F(4, 45)=8.59, p < 0.001) (Figure 11).

Compared to New Zealand reference estuaries levels of organic matter recorded during the present survey

were ranked in the lower half of the range of results (Table 4).

TABLE 4: COMPARISON OF THE MEAN TOTAL RECOVERABLE PHOSPHORUS (TRP), MEAN TOTAL NITROGEN (TN) AND MEAN ORGANIC MATTER

(AFDW) NORMALISED TO 100% MUD/FINES CONTENT FOR AHURIRI (AHU) AND PORANGAHAU (POR) ESTUARINE SITES FROM THE PRESENT

STUDY (2009), AND NEW ZEALAND ESTUARY REFERENCE SITES.

1.(Robertson et al., 2002).

SITE TRP (mg/kg) (± 1SD)

TN (mg/kg) (± 1SD)

AFDW (%w/w) (± 1SD)

Ahuriri AHUA 2009 1965 ± 376 2070 ± 918 8.96 ± 2.11

Ahuriri AHUB 2009 2254 ± 858 2507 ± 1438 11.36 ± 4.62

Ahuriri AHUD 2009 2881 ± 2331 2255 ± 832 8.49 ± 3.03

Ahuriri AHUE 2009 1939 ± 647 2672 ± 454 9.38 ± 2.86

Porangahau PORA 2009 857 ± 104 1663 ± 203 2.56 ± 0.81

Other NZ Otamatea1 1117 ± 637 3084 ± 584 10.94 ± 0.26

Other NZ Ohiwa1 1815 ± 1045 3919 ± 1370 13 ± 8.4

Other NZ Ruataniwha1 5193 ± 365 3094 ± 549 13.8 ± 3

Other NZ Waimea1 2241 ± 949 2000 ± 1000 6.2 ± 1.6

Other NZ Havelock1 1754 ± 317 2217 ± 876 8.4 ± 0.8

Other NZ Avon-Heathcote1 6736 ± 1529 6230 ± 2321 20.1 ± 4.7

Other NZ New River1 17397 ± 3036 17104 ± 5576 39.5 ± 9.4

CLIENT REF: EAM040


FIGURE 11: MEAN NUTRIENT (N AND P) AND ORGANIC MATTER (AFDW) CONCENTRATIONS AT AHURIRI (AHU) AND PORANGAHAU (POR)

ESTUARINE SITES, NORMALISED TO 100% MUD/FINES CONTENT. ERROR BARS ± 1 SE.

3.1.4 Sediment quality: inter-survey comparison

Metals

At site AHUA normalised levels of cadmium, copper, and zinc in the present survey are significantly lower

than all other survey results (all p ≤ 0.002) (Figure 12). Similarly at site AHUD normalised levels of chromium

and zinc in the present survey are significantly reduced compared to each survey since the initial 2007

survey (all p ≤ 0.005) (Figure 12).

Site AHUA also exhibited significantly lower levels of chromium, nickel and lead in the present survey compared to the surveys of 2006 (all p ≤ 0.004), 2007 (all p ≤ 0.001), while at site AHUD levels of copper and

lead were significantly lower in the present survey compared to the initial 2007 survey (p = 0.003, p = 0.001)

(Figure 12). At site AHUB normalised levels of all trace metals tested for were in general lower in the present

survey than those reported in the 2006 and 2007 surveys, yet the comparison between the two latest surveys

of 2008/2009 yielded no significant differences (Figure 12).


Tota

l N

itro

gen (+/- s

e)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35


Tota

l R

ecovera

ble

Phosphoru

s (+/- s

e)

0

1000

2000

3000

4000


AFD

W (+/- s

e)

0

2

4

6

8

10

12

14

CLIENT REF: EAM040


At PORA normalised levels of copper and chromium are significantly higher in the present survey compared

to the previous two surveys of 2007 (p = 0.04, p = 0.006) and 2008 (both p < 0.001), while cadmium is

significantly higher in the present survey compared to last year (p = 0.04) but not the initial 2007 survey

(Figure 12). Among the other trace metals analysed, there were no significant differences.

Nutrients

Examining the normalised data from all surveys to date sediment nitrogen levels at AHUA and AHUD were

significantly lower in the present survey compared to the previous year (p < 0.001, p = 0.024) but were no

different to the results from the 2006/2007 surveys (Figure 13). Site AHUB showed no significant difference in

nitrogen levels between the 2006/2008 and present surveys but these years were significantly lower than

normalised results from the 2007 survey (all p ≤ 0.02) (Figure 13). Nitrogen levels at site PORA did not differ

significantly between years.

Normalised phosphorus levels at site AHUA and site AHUB have decreased for the second successive year

and although there is no difference between this year and last levels are significantly lower than the initial

2006 survey (p < 0.001, p = 0.017) (Figure 13). At sites AHUD there was no significant difference between

years, while at PORA normalised phosphorus levels were significantly lower in the present survey compared

to last year (p = 0.003).

Organic matter and Chlorophyll a

This was the second year normalised levels of organic matter (AFDW) were lower among sites AHUA and

AHUB. For all Ahuriri sites organic matter was significantly lower in the present survey compared to the 2007

survey (all p < 0.01). At site PORA there has been no change in normalised organic matter levels over time.

Chlorophyll a levels rose for a third successive year at sites AHUA and AHUB (all p < 0.02), while levels at site

AHUD although significantly higher than in 2007 (p = 0.02) were no different to 2008. No significant temporal

difference was detected at site PORA (Figure 13).

CLIENT REF: EAM040


FIGURE 12: COMPARISON OF MEAN ANNUAL (2006 – PRESENT) SEDIMENT TRACE METAL LEVELS NORMALISED TO 100% MUD/FINES CONTENT

AT AHURIRI (AHU) AND PORANGAHAU (POR) ESTUARINE MONITORING SITES. ERROR BARS ± 1 SE.

2006 2007 2008 2009

Cadmium ± 1SE

0.0

0.5

1.0

1.5

2.0

2.52006 2007 2008 2009

Chro

mium ± 1SE

0

50

100

150

200

250

300

350

2006 2007 2008 2009

Copper ± 1SE

0

20

40

60

80

100

120

1402006 2007 2008 2009

Nickel ± 1SE

0

20

40

60

80

100

120

140

2006 2007 2008 2009

Lead ± 1SE

0

50

100

150

200

250

2006 2007 2008 2009

Zinc ± 1SE

0

200

400

600

800

1000

1200

1400

1600

2008 2009

Arsenic ± 1SE

10

15

20

25

30

35

40

45

50

Site AHUA

Site AHUB

Site AHUD

Site AHUC

Site AHUE

Site PORA

CLIENT REF: EAM040


FIGURE 13: COMPARISON OF MEAN ANNUAL (2006 – PRESENT) SEDIMENT NUTRIENT AND ORGANIC MATTER LEVELS NORMALISED TO 100%

MUD/FINES CONTENT AND NON-NORMALISED CHLOROPHYLL A LEVELS AT AHURIRI (AHU) AND PORANGAHAU (POR) ESTUARINE MONITORING

SITES. ERROR BARS ± 1 SE.

2006 2007 2008 2009

AFD

W ±

1SE

0

5

10

15

20

25

302006 2007 2008 2009

nitro

gen ±

1SE

0.0

0.2

0.4

0.6

0.8

1.0

2006 2007 2008 2009

Chl. a ±

1S

E

0

2000

4000

6000

8000

Site AHUA

Site AHUB

Site AHUD

Site AHUE

Site PORA

2006 2007 2008 2009

phosphoru

s ±

1SE

0

1000

2000

3000

4000

5000

6000

7000

CLIENT REF: EAM040


3.1.5 Overview

Site AHUA

• Second shallowest RPD layer (oxygenated layer) among Ahuriri sites

• Predominantly sandy sediment but increasing fines fraction over time (doubling of fines fraction since

2006)

• Low levels of trace metals, with lower and lower levels recorded over successive years.

• No apparent nutrient enrichment, and lower in phosphorus than in initial 2006/2007 surveys and lies in

the mid range for nutrients (total N, total P) compared to other New Zealand estuaries.

• Organic matter low and further decreasing over time while Chlorophyll a levels increasing over time.

Site AHUB

• Deepest RPD layer among Ahuriri sites

• Highest sand content, but increasing in fines (doubling of fines fraction since 2006).

• Present levels of trace metals significantly lower compared to initial 2006, 2007 survey results.

• No apparent nutrient enrichment, phosphorus levels also decreasing over time, while nitrogen is more

variable.

• Overall nutrient levels lie in the mid range of values compared to other New Zealand estuaries.

• Organic matter low and further decreasing over time while Chlorophyll a levels increasing over time.

Site AHUD

• Shallowest RPD layer among Ahuriri sites

• Highest mud content among Ahuriri sites, no significant change in composition over time. Numerous

fragments of plastic incorporated with sediments.

• Moderate to high levels of trace metals, especially zinc, but all below ANZECC ISQG-low guidelines,

and levels decreasing with each successive survey.

• Highest trace metal levels among all Ahuriri sites with levels lying in the upper (i.e. more polluted) range

compared to other New Zealand estuaries and exceeding background levels for Hawke’s Bay

estuarine and lagoon sites.

• No apparent nutrient enrichment and no significant difference in nutrient levels compared to initial

2006, 2007 surveys.

• Presently, organic matter significantly lower than 2007, 2008 surveyed levels, while chlorophyll a

generally increasing over time, but significantly different to 2007 levels only.

CLIENT REF: EAM040


Site AHUE

• First year of monitoring at this site.

• Second shallowest RPD layer among Ahuriri sites.

• Sediment mostly muddy sand with patches of a gravely shell pan beneath the surface sediments

across the site.

• Low levels of trace metals, but normalised levels of lead and zinc are elevated compared to

normalised background levels for Hawke’s Bay estuaries and lagoons.

• Highest nitrogen and organic matter levels among Ahuriri sites.

• Overall nutrient levels lie in the mid range of values compared to other New Zealand estuaries.

Site PORA

• Shallowest RDP layer in either estuary

• Sediments comprised of a high proportion of fines with a significantly higher level of fines in the present

survey compared to last year.

• Lowest normalised levels of trace metals among all sites, but normalised levels of copper elevated

compared to normalised background levels of Hawke’s Bay estuaries and lagoons.

• Lowest normalised nutrient (N and P) and organic matter levels among all sites, including other New

Zealand estuaries.

• Low levels of chlorophyll a and generally very little variation between years.

CLIENT REF: EAM040


3.2 BIOLOGICAL CHARACTERISTICS

3.2.1 Infaunal summary indices: present survey

A complete list of benthic infaunal data from the present survey is included in Appendix 3.

Total number of individuals (N) at Ahuriri sites ranged between 3 and 134 core-1, averaging 29.6, while at

Porangahau N ranged between 5 and 26 core-1, averaging 13.6. For a list of the highest contributing spe-

cies to the N of each site see Table 6.

The most abundant species among Ahuriri sites was the cockle, Austrovenus stutchburyi, accounting for ap-

proximately 36% of all individuals counted. On average site AHUE recorded the highest cockle abundance

(23.7 ± 5.3 (1SE) core-1), followed by site AHUA (12.1 ± 3.5 core-1), site AHUB (5.5 ± 2.1 core-1) and site AHUD

(3.7 ± 0.9 core-1. Of those individuals found at sites AHUA, AHUB and AHUE a large proportion (43 – 45%)

were new recruits, while at site AHUD the proportion of new recruits was less than 1%. For the purposes of

this study new recruits are defined as identifiable individuals that have entered the population, and are rep-

resented here as individuals ≤5mm shell length. Examining the size frequency distribution of cockles at the

various Ahuriri sites it is evident that a continuum of recruitment success occurs between sites, with the pat-

tern of recruitment mirroring that of abundance, i.e. site AHUE recording the highest number of recruits, fol-

lowed by site AHUA, site AHUB and finally site AHUD, which had virtually no recruitment (Figure 14). There is

also evidence of a number of size cohorts emerging across all sites, and particularly at sites AHUE and AHUA

(Figure 14).

Overall the six most numerous taxa among Ahuriri sites, in decreasing order, were, cockles, the spionid poly-

chaete worm, Aonides trifida, the estuarine limpet, Notoacmea helmsi, wedge shell, Macomona liliana,

mud crab; Helice crassa, and the polychaete worm Nicon aestuariensis (Appendix 3). Collectively, these six

taxa accounted for approximately 83% of all the individuals counted.

At site PORA the most abundant species was the anthozoan anemone Edwardsia sp. followed by the spi-

onid polychaete, Scolecolepides sp., crane-fly (Erioptera) larvae, and nereid polychaete Nicon aestuarien-

sis. Collectively these species accounted for approximately 76% of all individuals counted.

CLIENT REF: EAM040


FIGURE 14: SIZE – FREQUENCY PLOTS OF AUSTROVENUS STUTCHBURYI (COCKLES) FROM AHURIRI (AHU) ESTUARINE MONITORING SITES.

0 5 10 15 20 25 30

frequency

0

10

20

30

40

50

AHUA

0 5 10 15 20 25 30

frequency

0

10

20

30

40

50

AHUB

0 5 10 15 20 25 30

frequency

0

10

20

30

40

50

AHUD

shell length (mm)

0 5 10 15 20 25 30

frequency

0

10

20

30

40

50

AHUE

CLIENT REF: EAM040


Number of taxa (S), or species diversity in each core from the present survey ranged from 3 – 9 with an

average of 5.9 (site AHUA), 2 – 10 with an average of 6.7 (site AHUB), 3 – 6 with an average of 4.1 (site

AHUD), 3 – 12 with an average of 6.8 (site AHUE) and 2 – 6 with an average of 4.7 (site PORA) (Figure 15b)

The Shannon-Weiner diversity index (H’) is a measure of the likelihood that the next individual will be the

same species as the previous individual, the higher the number the more diverse the sample. In the present

survey site AHUB had the highest average H’ followed by site AHUA, PORA, AHUD and finally AHUE (Figure

15c).

Pielou’s evenness (J’) is a measure of the similarity of the abundances of different species in a group or

community, and the nearer values are to 1 the more even abundances are among species. In the present

survey the highest average value for evenness occurred at site AHUB (0.83), followed by site PORA (0.77),

site AHUA (0.71), and site AHUE (0.64) (Figure 15d).

Margalef’s Richness (d) is a measure of biodiversity based on the number of species, adjusted for the

number of individuals sampled, with values increasing with the number of species and decreasing with

relative increases in number of individuals. In the present survey site AHUB had the highest average d,

followed by AHUE, AHUA, PORA and lastly AHUD (Figure 15e).

3.2.2 Infaunal summary indices: inter-survey comparison

Analysing all previous survey data on abundance, or number of individuals (N), at site AHUA it is evident that

following a significant decrease in numbers between the 2006/2007 surveys numbers have remained

relatively constant (Figure 15a). At site AHUB N has increased significantly in the present survey compared

to results from both the 2007/2008 surveys but not compared to 2006 (Figure 15a). Site AHUD has seen no

significant change in N between last year and the present but remains significantly higher than the initial

2007 result (Figure 15a). At PORA N has not differed significantly between any of the annual surveys (Figure

15a).

Between years significant differences in the number of taxa (S) occurred at sites AHUB and PORA only

(Figure 15b). The difference in S at site AHUB was between the present survey and the 2007 survey, with this

year being the second annual increase in S. At site PORA the difference stemmed from the low number of

taxa recorded there in the initial 2006 survey. Since 2007 however there has been no change in S at site

PORA.

Similar to the differences observed for S, the temporal comparison for H’ shows the only significant

differences occurred at sites AHUB and PORA, with the present survey result for S higher than the 2007 result

(site AHUB) and the 2006 result lower than all successive results (site PORA) (Figure 15c).

In terms of J’ there has been a significant decrease at sites AHUA and AHUD, with J’ lower in the present

survey at site AHUA compared to the previous year and site AHUD lower in the present survey compared to

the initial 2007 (Figure 15d). At site PORA the present survey result for J’ was no different to any of the

previous three annual surveys however the 2007/2008 results were significantly elevated compared to the

initial 2006 survey result (Figure 15d).

The only significant difference between years and within sites for d was at site PORA where results in the

2007/2008 and present surveys were elevated compared to the initial 2006 survey (Figure 15e).

CLIENT REF: EAM040


FIGURE 15: PLOTS COMPARING MEANS OF A) INDIVIDUAL ABUNDANCE, B) NUMBER OF TAXA, C) SHANNON-WEINER DIVERSITY INDEX, D)

PIELOU’S EVENNESS AND E) MARGALEF’S RICHNESS OF BENTHIC MACROINFAUNA FROM ANNUAL MONITORING SURVEYS (2006 – PRESENT) AT

ESTUARINE MONITORING SITES WITHIN THE AHURIRI (AHU) AND PORANGAHAU (POR) ESTUARIES. ERROR BARS ± 1SE

2006 2007 2008 2009

Mean #

of ta

xa (S)

0

2

4

6

8

10

2006 2007 2008 2009

Mean #

of in

divid

uals (N)

0

10

20

30

40

50

60

2006 2007 2008 2009

Mean S

hannon-W

ein

er Divers

ity Index (H')

0.0

0.4

0.8

1.2

1.6

2.0

A. B.

C.

Site AHUA

Site AHUB

Site AHUC

Site AHUD

Site AHUE

Site PORA

2006 2007 2008 2009

Mean M

arg

ale

f's R

ichness (d)

0.0

0.5

1.0

1.5

2.0

2006 2007 2008 2009

Mean P

ielo

u's E

venness (J')

0.0

0.2

0.4

0.6

0.8

1.0

D.

E.

CLIENT REF: EAM040


3.2.3 Infaunal multivariate analyses: present survey

Multivariate analysis of infaunal data allows a comparison between sites, and years in multidimensional

space. Similarities in species abundance between sites and years are expressed on a two dimensional

plane called a multi-dimensional scaling (MDS) plot. The plot comparing infaunal communities between

Ahuriri sites and the Porangahau site in the present survey shows that they can indeed be separated out

(Figure 16 and Appendix 3). A permutational multivariate analysis of variance confirmed the spatial

variation (Table 5) observed in the MDS plot while pair-wise a posteriori comparisons revealed that each site

was significantly different from every other site (p = 0.04). A species correlation plot and SIMPER analysis

identify the species associations that account for these observed differences in community structure

between sites and are shown in Figure 17 and Table 6. These analyses show a number of key species

primarily driving the community variability; Edwardsia sp. (site PORA), Macomona liliana (sites AHUA and

AHUB), and Helice crassa (sites AHUD and AHUE) (Figure 17 and Table 6).

Examining the community structure at each site, it is evident that generally site PORA is distinct from Ahuriri

sites, the exceptions being stations P1 and P8 from which Edwardsia sp. was absent (Figure 16). Species

contributing most to the observed assemblage included; Erioptera larvae, Scolecolepides sp., and

Edwardsia sp. (Table 6). This association is illustrated on the left of the species correlation plot (Figure 17).

At sites AHUD and AHUE, the infaunal community was characterised primarily by Austrovenus stutchburyi,

Nicon aestuariensis, and Helice crassa (Table 6). Despite the similarities in community composition a clear

difference between the sites is evident with the common occurrence of Notoacmea helmsi at site AHUE

accounting for a large part of the differentiation (Figure 16). This limpet was found attached to the many

old cockle and wedge shells within the sediment matrix at sites AHUE and AHUB. The other important

difference between AHUD and AHUE was the relative abundance of Austrovenus stutchburyi at site AHUE

compared to site AHUD.

Infaunal community structure at sites AHUA and AHUB were more similar to one another than to sites AHUD

and AHUE but were nonetheless distinct and also more variable than sites AHUD and AHUE (Figure 16).

However in general the community assemblage at sites AHUA and AHUB could be characterised by the

Austrovenus stutchburyi, Aonides trifida, and Macomona liliana association (Table 6).

CLIENT REF: EAM040


FIGURE 16: METRIC MDS PLOT OF BENTHIC MACROINFAUNA DATA FROM THE PRESENT (2009) SURVEY AT AHURIRI (AHU) AND PORANGAHAU

(POR) ESTUARINE MONITORING SITES. DATA WERE TRANSFORMED LN(X+1) PRIOR TO ANALYSIS AND GROUPINGS ARE BASED ON BRAY-

CURTIS DISSIMILARITIES.

TABLE 5: PERMANOVA RESULTS EXAMINING THE EFFECT OF SITE (AHUA – PORA) ON ESTUARY INFAUNA. ALL DATA WERE TRANSFORMED

(LN(X+1)), AND ANALYSIS WAS BASED ON BRAY-CURTIS DISSIMILARITIES. P (PERM) INDICATES THE PERMUTATIONAL P-VALUE, P(MC)

INDICATES THE MONTE CARLO P-VALUE.

-2 -1 0 1 2

-2

-1

0

1

2

A1

A2A3

A4

A5

A6

A7

A8

A9

A10

A11

A12

B1B2

B3

B4

B5B6

B7

B8

B9

B10

B11B12

E1

E2

E3

E4E5

E6

E7

E8

E9E10E11

E12

D1

D2

D3D4

D5

D6

D7D8

D9

D10

D11

D12

P1

P2

P3P4

P5P6

P7

P8

P9

P10

P11

P12

Site AHUAA1

Site AHUBB1

Site AHUEE1

Site AHUDD1

Site PORAP1

Stress 0.19

Source df SS Mean Square F-Value P (perm) P (MC)

Site 4 58796.6 14699.2 8.95 0.0017 0. 0.0017

Residual 55 90297.1 1641.8

Total 59 149093.7

CLIENT REF: EAM040


FIGURE 17: PLOT SHOWING CORRELATIONS BETWEEN INFAUNAL SPECIES ABUNDANCES AND MDS AXES FROM PREVIOUS PLOT AT AHURIRI

AND PORANGAHAU ESTUARINE MONITORING SITES DURING THE PRESENT SURVEY (2009).

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

Edwardsia sp.

Nemertea

Cominella

Diloma subro

Notoacmea

Zeacumantus sub

Arthritica

Austrovenus

Macomona

Aonides trifida

Prionospio sp.

Scolecolepides

Heteromastus

Erioptera larva

Armandia

Nicon aestua.

Mysidacea

Amphipoda

Halicarcinus v.

Helice crassa

Elminius modes.

Paraonid

Scolelepis sp.

Onuphis Auck.

Lumbrinereis sp

Nematode

Halicarcinus w.Crab megalopae

Isopoda

Harpact copepodPeronaea g.

Nucula spp.

Amphibolidae

CLIENT REF: EAM040


TABLE 6: LIST OF INFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES WITHIN AHURIRI (AHU) AND PORANGAHAU

(POR) ESTUARIES (SIMPER LN(X+1) TRANSFORMED DATA, PRIMER). TOP 90% OF CONTRIBUTING SPECIES.

3.2.4 Infaunal multivariate analyses: inter-survey comparison

Sites AHUA and PORA show distinct grouping indicating apparent temporal variation in community

composition while at sites AHUB and AHUD temporal variability is less evident (Figure 18a, 18b, and Figure

19a, 19b). Although 2D stress values for all MDS plots range between 0.17 and 0.22 indicating reasonably

high levels of distortion in the data as represented in the MDS plot, PERMANOVA results confirm differences

between years for all sites (all p < 0.01 – Appendix 5). Pair-wise a posteriori comparisons between years

(within sites) identified significant differences in community structure between each annual survey at sites

AHUA and PORA (all p < 0.01), while at sites AHUB and AHUD although most years differed significantly to

one another (all p < 0.05) there were some years where community structure did not differ significantly (e.g.

between 2006/2007 for site AHUB, and between 2007/2008 for both sites AHUB and AHUD).

Site Species Av. abund Av. Sim Sim/SD Contrib % Cum%

AHUA

(av. sim.

42%)

Austrovenus stutchburyi 9.08 14.89 1.32 35.65 35.65

Macomona liliana 4.67 10.4 1.05 24.89 60.54

Helice crassa 1.58 3.77 0.59 9.02 69.57

Aonides trifida 6.58 3.7 0.4 8.86 78.43

Edwardsia sp. 1.08 3.63 0.81 8.69 87.12

Nemertea 2.25 2.38 0.49 5.7 92.82

AHUB

(av. sim.

42%)


Notoacmea helmsi 9.75 8.17 1.02 19.57 40.75


Aonides trifida 10.08 6.23 0.97 14.92 73.1

Nicon aestuariensis 1.67 3.47 0.7 8.32 81.41

Prionospio sp. 3 2.62 0.65 6.27 87.68

Heteromastus filiformis 3 2.37 0.53 5.67 93.35

AHUD

(av. sim.

51%)

Helice crassa 2.92 19.29 1.38 38.16 38.16

Austrovenus stutchburyi 3.67 15.67 1.23 31 69.16


Scolecolepides sp. 1.08 5.95 0.8 11.76 93.18

AHUE

(av. sim.

56%)


Helice crassa 4.33 13.49 2.36 23.98 68.36


Nicon aestuariensis 1 2.5 0.66 4.44 88.48

Prionospio sp. 0.67 2.02 0.67 3.59 92.07

PORA

(av. sim.

38%)

Edwardsia sp. 4.17 16.21 1.04 42.85 42.85


Erioptera larvae 1.25 7.27 1.03 19.22 84.49


CLIENT REF: EAM040


Examining the underlying infaunal species dynamics that account for these differences in community

structure, at site AHUA it is evident that over time the community is becoming comprised of more species

likely to be associated with fine sediments, such as Helice crassa, Scolecolepides sp. and Edwardsia sp.

(Figure18c). Moreover, the temporal SIMPER analysis for site AHUA also confirms a general pattern of a

decrease over time of species sensitive to fine sediments such as Aonides trifida, and Macomona liliana.

At site AHUB there is less obvious grouping evident however the SIMPER analysis shows the estuarine limpet

Notoacmea helmsi accounting for the largest proportion of community temporal variation, with an

abundance of limpets found in the present survey compared to virtually none in any of the previous surveys.

Additionally, increased numbers of Macomona liliana and Aonides trifida in the present survey compared

to previous surveys also contribute significantly to the observed temporal differences in community

structure. The species correlation plot shows the effect of these species on community structure through

time with the location of these species on the right skewing the plot to the right also (Figure 18d).

FIGURE 18: METRIC MDS PLOTS OF BENTHIC MACROINFAUNA DATA FROM ANNUAL MONITORING SURVEYS (2006 – 2009) AT ESTUARINE

MONITORING SITES AND CORRESPONDING SPECIES CORRELATION PLOTS: A) SITE AHUA, B) SITE AHUB, C) SITE AHUA SPECIES CORRELATION

PLOT, D) SITE AHUB SPECIES CORRELATION PLOT. DATA WERE TRANSFORMED LN(X+1) PRIOR TO ANALYSIS AND GROUPINGS ARE BASED ON

BRAY-CURTIS DISSIMILARITIES.

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

Edwardsia sp.

Edwardsia tri

Nemertea

Cominella glan

Diloma sub

Notoacmea

Zeacumantus l

Zeacumantus s

Macomona

Oligochaeta

Aonides trifida

Microspio spp.

Prionospio sp.

Scolecolepides

Heteromastus

Erioptera Nicon aestGlycera ovigera

Goniada sp.

Halicarcinus v

Helice crassa

Macrophthalmus Elminius mod

Scolelepis sp.

NematodeAmphibolidae

-3 -2 -1 0 1 2 3

-3

-2

-1

0

1

2

3AHUA 2006

AHUA 2007

AHUA 2008

AHUA 2009

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

Edwardsia sp.

Edwardsia tri

Nemertea

Cominella glan

Diloma subNotoacmea

Zeacumantus l

Arthritica bi

Austrovenus

Macomona Paphies aust

Aonides trifida

Microspio spp.

Prionospio sp.

Scolecolepides

Erioptera

Armandia mac

Nicon aest

Goniada sp.

Pectinaria austHelice crassa

Macrophthalmus

Elminius mod

Scolelepis sp.

Onuphis Auck

Halicarcinus w

-3 -2 -1 0 1 2 3

-3

-2

-1

0

1

2

3AHUB 2006

AHUB 2007

AHUB 2008

AHUB 2009

A.

C. D.

B.

2D stress 0.18 2D stress 0.19

CLIENT REF: EAM040


At site AHUD community structure appears to have changed very little over time, with no obvious grouping

in the MDS plot. The SIMPER analysis however, shows a group of four species, including Austrovenus

stutchburyi, Scolecolepides spp., Helice crassa, and Nicon aestuariensis, accounting for the vast majority of

community temporal variation (Appendix 5). Generally speaking, the relative abundance of these species

has changed over time e.g. Austrovenus stutchburyi and Helice crassa predominate in the present surveys

whereas in the previous surveys Scolecolepides spp., and Nicon aestuariensis were more common. This

difference however is not considered ecologically significant as all these species, except Austrovenus

stutchburyi, are more commonly associated with sites having a high fines component.

At site PORA the relatively high stress value (0.22) somewhat distorts groupings, however it appears the 2008

and present survey group out to the right of the plot, indicating a shift in composition over the last two years

compared to the initial two surveys. The SIMPER analysis shows this difference is principally driven by lower

numbers of the bivalve Arthritica bifurca in the latter surveys compared to the initial 2006/2007 surveys, and

conversely higher numbers of Edwardsia spp., and crane fly larvae (Erioptera) in 2008/2009 compared to

2006/2007 (Appendix 5).

FIGURE 19: METRIC MDS PLOTS OF BENTHIC MACROINFAUNA DATA FROM ANNUAL MONITORING SURVEYS (2007 – 2009 SITE AHUD, 2006 – 2009

SITE PORA) ESTUARINE MONITORING SITES AND CORRESPONDING SPECIES CORRELATION PLOTS: A) SITE AHUD, B) SITE PORA, C) SITE AHUD

SPECIES CORRELATION PLOT, D) SITE PORA SPECIES CORRELATION PLOT. DATA WERE TRANSFORMED LN(X+1) PRIOR TO ANALYSIS AND

GROUPINGS ARE BASED ON BRAY-CURTIS DISSIMILARITIES.

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

Edwardsia sp.

Nemertea

Cominella glan

Arthritica bi

Austrovenus Macomona

Oligochaeta

Orbinia pap

Aonides tri

Prionospio sp.

Scolecolepides

Pseudonerine

Erioptera

Nicon aestPerinereis nun

Platynereis

Mysidacea

Amphipoda

Halicarcinus v

Helice crassa

Halicarcinus w

Crab mega

Isopoda

Upogenia

Nucula spp.

-3 -2 -1 0 1 2 3

-3

-2

-1

0

1

2

3PORA 2006

PORA 2007

PORA 2008

PORA 2009

-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

Edwardsia sp.Nemertea

Cominella glan

Arthritica

Austrovenus

Macomona Aonides tri

Microspio spp.Prionospio sp.

Scolecolepides

Erioptera

Armandia mac

Nicon aest

Perinereis nun

Platynereis

Mysidacea

Halicarcinus v

Helice crassa

LumbrinereisIsopoda

-3 -2 -1 0 1 2 3

-3

-2

-1

0

1

2

3AHUD 2007

AHUD 2008

AHUD 2009

2D stress 0.17 2D stress 0.22

A B

C D

CLIENT REF: EAM040


3.2.5 Epifaunal summary indices: present survey

A complete list of benthic epifaunal data from the present survey is included in Appendix 4.

For a list of the highest contributing species to the N of each site see Table 8. Total number of individuals per

quadrat (N) at Ahuriri sites ranged between 0 and 81, averaging 11.6 quadrat-1, while at Porangahau the

sole epifaunal species found was the mud snail, Amphibola crenata which ranged between 4 and 13,

averaging 11 individuals quadrat-1. Given only one epifaunal species was found at site PORA the diversity

indices for H’, J’ and d were not calculated.

The most abundant species among Ahuriri sites was the turret shell, Zeacumantus lutulentus, accounting for

approximately 26% of all individuals counted. Together with its congener, Zeacumantus subcarinatus, turret

shells accounted for around 48% of all epifauna. Site AHUA recorded the highest turret shell abundance

(129), followed by site AHUD (56), site AHUE (50) and site AHUB (16).

Overall the four most numerous epifaunal taxa among Ahuriri sites, in decreasing order, were the two turret

shell species, the mudflat topshell, Diloma subrostrata, and the estuarine barnacle, Eliminius modestus.

(Appendix 4). Collectively, these four taxa accounted for approximately 76% of all the individuals counted.

Examining diversity, number of taxa (S) at each site in each quadrat from the present survey ranged from 1

– 5 with an average of 2.6 at site AHUA, 1 – 4 with an average of 2.3 at site AHUB, 1 – 4 with an average of

2.6 at site AHUD, and 2 – 4 with an average of 2.9 at site AHUE (Figure 20b)

Site averaged Shannon-Weiner diversity index (H’) scores showed that site AHUE, had the highest score

followed by sites AHUA, AHUD and then AHUB (Figure 20c).

Margalef’s Richness (d) scores showed a similar pattern with site AHUE again having the highest average

score followed by sites AHUD, and AHUA, and lastly AHUB (Figure 20e).

Despite the relatively low diversity among sites Pielou’s evenness (J’) scores indicated that abundances of

species were fairly even among stations within sites with site AHUD (0.84) having the highest average score

followed by site AHUA (0.83), site AHUE (0.80), then site AHUB (0.76) (Figure 20d).

3.2.6 Epifaunal summary indices: inter-survey comparison

At sites AHUA and AHUD the number of individuals (N) has remained relatively constant through time with

no significant differences observed between years (Figure 20a). At site AHUB last years’ result for N was the

highest to date and was significantly higher than the initial 2006 survey. This year, N was no different to

results from any other year. Similarly at site PORA last years result for N was significantly higher than the initial

2007 result but this years result was not significantly different to either the 2008, or 2007 results.

Between years significant differences in the number of taxa (S) occurred at site AHUB only (Figure 20b). The

difference in S at site AHUB was between the 2008/2006 surveys. At all other sites no significant differences

in S were evident.

The temporal comparison for H’ reveals relatively little changes at sites, with the only significant differences

occurring at site AHUB (between 2006/2008) and site AHUA (between 2006/2007) (Figure 20c).

Margalef’s richness (d) scores also differed very little between years, with no significant differences evident

at sites AHUB, AHUD or PORA and none in the last three years at site AHUA, with the sole difference between

the 2006/2007 results (Figure 20e).

Examining J’, at site AHUA there has been an incremental increase over time resulting in a significant

difference this year compared to the initial 2006 survey. Conversely J’ has decreased at site PORA

(2007/2008), while at sites AHUB and AHUD J’ no differences have been observed through time at all (Figure

20d).

3.2.7 Epifaunal multivariate analyses: present survey

CLIENT REF: EAM040


A species correlation plot and SIMPER analysis identify and quantify the similarities in community structure

between sites and are shown in Figure 22 and Table 8. The key species driving epifaunal community

structure at Ahuriri are the turret shells and mudflat topshell, Diloma subrostrata, and Amphibola crenata at

Porangahau.

FIGURE 20: PLOTS COMPARING MEANS OF A) INDIVIDUAL ABUNDANCE, B) NUMBER OF TAXA, C) SHANNON-WEINER DIVERSITY INDEX, D)

PIELOU’S EVENNESS AND E) MARGALEF’S RICHNESS OF EPIFAUNA FROM ANNUAL MONITORING SURVEYS (2006 – PRESENT) AT ESTUARINE

MONITORING SITES WITHIN THE AHURIRI (AHU) AND PORANGAHAU (POR) ESTUARIES. ERROR BARS ± 1SE

2006 2007 2008 2009

Mean # o

f taxa (S)

0

1

2

3

4

5

2006 2007 2008 2009

Mean # o

f individuals (N)

0

10

20

30

40

50

2006 2007 2008 2009

Mean S

hannon-W

einer Divers

ity Index (H')

0.0

0.2

0.4

0.6

0.8

1.0

1.2

A. B.

C.

Site AHUA

Site AHUB

Site AHUC

Site AHUD

Site AHUE

Site PORA

2006 2007 2008 2009

Mean M

arg

alef's

Richness (d)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

2006 2007 2008 2009

Mean P

ielou's E

venness (J')

0.0

0.2

0.4

0.6

0.8

1.0

1.2

D.

E.

CLIENT REF: EAM040


Figure 21: Metric MDS plot of epifaunal data from the present (2009) survey at Ahuriri (AHU) and

Porangahau (POR) estuarine monitoring sites. Data were transformed ln(x+1) prior to analysis and groupings

are based on Bray-Curtis dissimilarities. Depauperate stations were removed from analysis.

TABLE 7: PERMANOVA RESULTS EXAMINING THE EFFECT OF SITE (AHUA – PORA) ON ESTUARY EPIFAUNA. ALL DATA WERE TRANSFORMED

(LN(X+1)), AND ANALYSIS WAS BASED ON BRAY-CURTIS DISSIMILARITIES. P (PERM) INDICATES THE PERMUTATIONAL P-VALUE, P(MC)

INDICATES THE MONTE CARLO P-VALUE.

-2 -1 0 1 2

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

A1

A2

A3

A5

A6

A7

A8

A9

A10B1B2

B3B4B5

B6

B7

B8B9

B10

D1

D2

D3

D4

D5

D6

D7

D8

D9

D10

E1

E2

E3

E4

E5

E6

E7

E8

E9P1

P2P3P4P5

P6P7

P8

P9P10

site AHUAA1

site AHUBB1

site AHUDD1

site AHUEE1

site PORAP1

2D Stress 0.08


Site 4 90400.46 22600.12 14.57 0.0010 0.0010

Residual 45 69809.76 1551.36

Total 49 160210.22

CLIENT REF: EAM040


FIGURE 22: PLOT SHOWING CORRELATIONS BETWEEN EPIFAUNAL SPECIES ABUNDANCES AND MDS AXES FROM PREVIOUS PLOT AT AHURIRI

AND PORANGAHAU ESTUARINE MONITORING SITES DURING THE PRESENT SURVEY (2009).

TABLE 8: LIST OF EPIFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES WITHIN AHURIRI (AHU) AND PORANGAHAU

(POR) ESTUARIES (SIMPER LN(X+1) TRANSFORMED DATA, PRIMER). TOP 90% OF CONTRIBUTING SPECIES.

-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

Cominella gland

Diloma subrostr

Zeacumantus lut

Zeacumantus sub

AmphibolaAustrovenus

Helice crassa

Eliminus mod

Diloma zelandic

Microlenchus

Notoacmea

Paphies aust

Cominella mac

Site Species Av. abund Av. Sim Sim/SD Contrib % Cum%

AHUA

(av. sim.

38%)

Diloma subrostrata 3.30 14.01 1.08 36.56 36.56

Zeacumantus lutulentus 4.70 13.60 0.86 35.48 72.04

Zeacumantus subcarinatus 8.80 7.05 0.50 18.39 90.43

AHUB

(av. sim.

50%)


Eliminius modestus 4.18 5.02 0.41 10.00 96.71

AHUD

(av. sim.

52%)


Cominella glandiformis 0.70 4.09 0.50 7.83 93.32

AHUE

(av. sim.

45%)



Paphies australis 3.00 2.46 0.30 5.42 95.01

PORA

(av. sim.

91%) Amphibola crenata 9.17 91.00 12.51 100.00 100.00

CLIENT REF: EAM040


3.2.8 Epifaunal multivariate analyses: inter-survey comparison

Some temporal variability in epifaunal community structure at sites is evident, with a degree of data

grouping visible at all sites (Figures 23a, 23b and Figure 24a, 24b). PERMANOVA results confirm differences

between years for all sites (all p < 0.02 – Appendix 5). Pair-wise a posteriori comparisons between years

(within sites) identified the community structure at site AHUB to be highly variable, with all years significantly

different to one another (all p < 0.04). Whereas at sites AHUA, AHUD and PORA there were some years

where there was no evidence to suggest community structure was different. These years were 2006/2008,

and 2007/2008 at site AHUA (p = 0.14, 0.11 respectively), 2007/2009 at site AHUD (p = 0.07) and 2008/2009 at

site PORA (p = 0.16).

The MDS plot representing the community through time at site AHUA shows a strong grouping of the 2009

data towards the top of the plot (Figure 23a). This grouping is driven by Notoacmea helmsi and Z.

subcarinatus (Figure 23c). The corresponding SIMPER analysis confirms the role of these key species in

differentiating the 2009 community from that of the 2007/2008 surveys. The main differences between these

surveys and the present were that these species were not sampled in the 2007/2008 surveys and fewer D.

subrostrata were sampled in 2009 compared to 2007/2008 (Appendix 5).

Site AHUB exhibited high between years variation in community structure yet showed low within site

variability during some surveys. The MDS plot shows strong grouping of the 2007 and 2008 communities

indicative of low within site variability while the 2006 and 2009 communities were more diverse and less even

(Figure 23b). SIMPER analysis identified three species accounting for the majority of the observed temporal

variability; the estuarine barnacle Eliminius modestus, mudflat topshell, D. subrostrata, and cockles.

The community at site AHUD has remained reasonable stable through time but maintains a high diversity of

fine sediment tolerant species, as evidenced by the broad groupings in the MDS plot (Figure 24a). The MDS

plot and species correlation plots turret shell, Z. lutulentus, mud snail, Amphibola crenata, and cockles

accounting for the majority of variation in community structure between years.

The MDS plot and species correlation plots clearly show the dynamics of the epifaunal community at play

at site PORA (Figures 24b, 24d). During the initial 2007 survey of site PORA the epifaunal community

comprised two species, A. crenata and cockles. Last year 5 cockles were sampled and this year none were

observed.

CLIENT REF: EAM040


FIGURE 23: METRIC MDS PLOTS OF BENTHIC EPIFAUNA DATA FROM ANNUAL MONITORING SURVEYS (2006 – 2009) AT ESTUARINE MONITORING

SITES AND CORRESPONDING SPECIES CORRELATION PLOTS: A) SITE AHUA, B) SITE AHUB, C) SITE AHUA SPECIES CORRELATION PLOT, D) SITE

AHUB SPECIES CORRELATION PLOT. DATA WERE TRANSFORMED LN(X+1) PRIOR TO ANALYSIS AND GROUPINGS ARE BASED ON BRAY-CURTIS

DISSIMILARITIES.

-3 -2 -1 0 1 2 3

-3

-2

-1

0

1

2

3AHUB 2006

AHUB 2007

AHUB 2008

AHUB 2009

-3 -2 -1 0 1 2 3

-3

-2

-1

0

1

2

3AHUA 2006

AHUA 2007

AHUA 2008

AHUA 2009

2D Stress 0.16 2D Stress 0.13

-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

Cominella gland

Diloma subrostr

Zeacumantus lut

Zeacumantus sub

AmphibolaAustrovenus

Helice crassa

Eliminus mod

Diloma zelandic

Microlenchus

-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

Cominella gland

Diloma subrostr

Zeacumantus lut

Zeacumantus sub

Macomona lilAustrovenus

Eliminus mod

Microlenchus

Notoacmea

A. B.

C. D.

CLIENT REF: EAM040


FIGURE 24: METRIC MDS PLOTS OF BENTHIC EPIFAUNA DATA FROM ANNUAL MONITORING SURVEYS (2007 – 2009) AT ESTUARINE MONITORING

SITES AND CORRESPONDING SPECIES CORRELATION PLOTS: A) SITE AHUD, B) SITE PORA, C) SITE AHUD SPECIES CORRELATION PLOT, D) SITE

PORA SPECIES CORRELATION PLOT. DATA WERE TRANSFORMED LN(X+1) PRIOR TO ANALYSIS AND GROUPINGS ARE BASED ON BRAY-CURTIS

DISSIMILARITIES.

-2 -1 0 1 2

-2

-1

0

1

2PORA 2007

PORA 2008

PORA 2009

2D Stress 0.04

-3 -2 -1 0 1 2 3

-3

-2

-1

0

1

2

3AHUD 2007

AHUD 2008

AHUD 2009

2D Stress 0.15

-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

Zeacumantus lut

Amphibola

Austrovenus

-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

Cominella gland

Diloma subrostr

Zeacumantus lut

Zeacumantus sub

Amphibola

Austrovenus

Helice crassa Cominella mac

C. D.

B.A.

CLIENT REF: EAM040


3.2.9 Overview

Site AHUA

• Moderate numbers of cockles, including large proportion of new recruits

• Highest number of turret shells, Zeacumantus sp. of all Ahuriri sites

• Average of 5.9 infaunal species core-1, moderate infaunal species diversity,

• Average of 2.3 epifaunal species quadrat-1, low epifaunal diversity

• Relatively stable in terms of both infaunal and epifaunal diversity, richness and evenness indices over

time.

• Infaunal assemblage during present survey characterised by the Austrovenus stutchburyi, Aonides

trifida, and Macomona liliana association.

• Epifaunal community structure dominated by the turret shell, Zeacumantus lutulentus and the mudflat

topshell, Diloma subrostrata

• High interannual variability in infaunal community structure, but community tending toward one

dominated by fine sediment tolerant species.

• Limited variability in epifaunal community structure over time

Site AHUB

• Low numbers of cockles, high proportion of these were juvenile recruits. (<5mm shell length)

• Lowest number of turret shells, Zeacumantus sp. of all Ahuriri sites

• Average of 6.7 infaunal species core-1, highest infaunal species diversity, richness and evenness among

Ahuriri sites

• Average of 2.3 epifaunal species quadrat-1, low epifaunal diversity

• Increased numbers of infaunal individuals and taxa over time

• Little change in epifaunal diversity, richness, or evenness indices over time

• Infaunal assemblage during present survey characterised by the Austrovenus stutchburyi, Aonides

trifida, and Macomona liliana association.

• Epifaunal community structure dominated by the turret shell, Zeacumantus lutulentus and the mudflat

topshell, Diloma subrostrata

• Some variability in infaunal community structure over time, with the present survey having increased

numbers of Aonides trifida, and Macomona liliana compared to previous surveys

• Limited variability in epifaunal community structure over time

CLIENT REF: EAM040


Site AHUD

• Lowest numbers of cockles among Ahuriri sites

• Second highest number of turret shells, Zeacumantus sp. among Ahuriri sites

• Average of 4.1 infaunal species core-1, low infaunal S-W diversity, richness and evenness indices

• Average of 2.6 epifaunal species quadrat-1, low epifaunal diversity, but high evenness indices

• Relatively stable diversity and evenness indices but number of individuals higher than initial 2007 survey.

• Little change in epifaunal species diversity, richness, or evenness indices over time

• Infaunal assemblage during present survey characterised by Austrovenus stutchburyi, Nicon

aestuariensis, and Helice crassa.

• Epifaunal community structure characterised by the turret shell fine sediment tolerant species,

Zeacumantus lutulentus, mudflat topshell, Diloma subrostrata, mud whelk, Cominella glandiformis, mud

snail, and Amphibola crenata.

• Little change in infaunal community structure over time

• Low variability in epifaunal community structure over time

Site AHUE

• First year of monitoring

• Highly productive recruitment site for cockles, highest numbers among Ahuriri sites

• Second highest number of turret shells, Zeacumantus sp. among Ahuriri sites

• Average of 6.8 infaunal species core-1, low infaunal S-W diversity, but high evenness

• Average of 2.9 epifaunal species quadrat-1, highest epifaunal S-W diversity, but still relatively low and

highest richness among Ahuriri sites.

• Infaunal assemblage during present survey characterised by Austrovenus stutchburyi, Nicon

aestuariensis, and Helice crassa.

• Similar epifaunal community structure to site AHUA with community structure characterised by

Zeacumantus lutulentus and the mudflat topshell, Diloma subrostrata.

Site PORA

• Average of 4.7 infaunal species core-1, moderate infaunal S-W diversity, richness indices and evenness

• Epifaunal community now solely comprised of mud snail, Amphibola crenata, with fewer cockles

sampled then previous years.

• Relatively stable numbers of infaunal individuals, species diversity, evenness and richness over time.

• Infaunal assemblage during present survey characterised by Edwardsia sp., the spionid polychaete,

Scolecolepides sp., crane-fly (Erioptera) larvae, and nereid polychaete Nicon aestuariensis.

• High variability in infaunal community structure over time with increased numbers of Edwardsia sp

occurring over last two years and fewer of the bivalve, Arthritica bifurca.

CLIENT REF: EAM040


4.0 SUMMARY

Sediment characteristics

Overall, sediments at site AHUA were the most similar to site AHUB in terms of composition and contaminant

status, and also in the relative changes of these parameters over time. Site AHUE was more similar to AHUD,

in terms of composition but resembled sites AHUA and AHUB more in terms of contaminant status. Site

AHUD was the most polluted of all sites. PORA represents a meaningful rural comparison to the urbanised

Ahuriri sites and in general yielded the lowest levels of contaminants among all sites.

The increase in fines at sites AHUA and AHUB over time and concomitant decrease in, particularly, trace

metal contamination is suggested to be a result of increased input and subsequent deposition of fine

sediments into the estuary. Although there was no significant change to composition at site AHUD this is the

second year where the fines fraction has increased and sand has decreased. Given the much higher level

of fines at site AHUD compared to sites AHUA and AHUB, and that monitoring at site AHUD only began in

2007 it is not surprising the changes to composition at site AHUD are not yet significant. Thus, the decreases

in trace metals at site AHUD are also suggested to be a result of the deposition of fine sediments. Although

the ‘Your Choice’ stormwater programme has been in operation a number of years, it is unknown what the

contribution of this programme is to the observed decrease in trace metal levels. It is suggested that the

data collected from monitoring of the Ahuriri stormwater discharges be analysed alongside the state of the

environment data to quantify in real terms the efficacy of the ‘Your Choice’ stormwater programme.

Furthermore, there is also a clear need to assess sediment dynamics along the length of the estuary, and

particularly to identify the main source areas of sediments.

Biological characteristics

Infaunal patterns at Ahuriri were generally typical of northern east coast estuaries in New Zealand, with

spatial variation between sites indicative of differences in sediment composition. This was particularly

evident between sites AHUD, AHUE and the other Ahuriri sites. Community variability between sites

appeared to be largely driven by key species that are either sensitive or tolerant to increased silt/clay

content. These analyses suggest that at site PORA the fine sediment tolerant anemone Edwardsia sp. is the

key driver, while at Ahuriri sites AHUA and AHUB Macomona liliana, generally sensitive to increased fines, is

important, while at sites AHUD and AHUE the fines tolerant Helice crassa is key.

Interesting inter-survey differences in infaunal populations were identified at sites AHUA and PORA which

showed communities tending towards species more tolerant of fine sediments. Given the apparent

increase in fines at site AHUA in the present survey it is suggested that the infaunal community may be

responding to these changes. It appears that increasing sediment fines content has a positive effect on the

occurrence of Helice crassa, Edwardsia sp., Scolecolepides sp., and Nicon aestuariensis, and a negative

effect on Macomona liliana and Aonides trifida. These generalisations are applicable across both estuaries.

However, there were also examples where some species did not respond consistently to the higher fines

content. For example Austrovenus stutchburyi, showed a wide tolerance to fines content, although it is

known to generally prefer sediments with low fines content (Thrush et al., 2003).

Epifaunal communities were not as variable either spatially or temporally as their infaunal counterparts. The

predominance of turret shells and the mudflat topshell throughout Ahuriri sites and generally low species

diversity suggests that epifaunal communities are generally more robust to environmental perturbations

than their infaunal counterparts.

CLIENT REF: EAM040


5.0 CONCLUSION

These surveys were the fourth consecutive annual monitoring of the Ahuriri and Porangahau Estuary systems.

Estuaries are dynamic systems at the end-point of freshwater systems. Ensuring the integrity of these systems

over time requires long-term monitoring to identify where trends in state may be indicating a reduction in

environmental quality.

The surveys provided a good snapshot of the estuarine ecology, with important structural points being; a

healthy supply of cockle recruits at Ahuriri, key drivers of infaunal community structure are Edwardsia sp.

(site PORA), Macomona liliana (sites AHUA and AHUB), Helice crassa (sites AHUD and AHUE), and epifaunal

community drivers are Zeacumantus sp. and Diloma subrostrata (Ahuriri) and Amphibola crenata

(Porangahau).

There is also evidence that fine sediments have been accumulating at some sites around Ahuriri estuary

(e.g. sites AHUA and AHUB) and that at some sites the infaunal community is responding to this change (e.g.

site AHUA).

It is also clear that sediment contamination at the most polluted site (site AHUD) is above relevant regional

background levels. However, these levels appear to be decreasing over time, but the underlying reasons

as to why the contaminant levels are reducing is less clear. Possible reasons include; reduction in

contaminant loads of stormwater going into the estuary or increases in fine sediments that have been

buffering the contaminant load.

The results of the surveys suggest that site specific differences in sediment characteristics are an important

determinant to the spatial patterns of the resident biota. Further investigation of the underlying processes

influencing sediment characteristics is thus warranted.

6.0 RECOMMENDATIONS

• That continued monitoring is undertaken at the same sites as the present survey, and in line with the

methodology set out in this report.

• That heavy metals concentration in the flesh of shellfish and/or mud snails are assessed at site AHUD.

• Investigate the feasibility of explicit monitoring of sedimentation at various points along the estuaries

using sediment traps.

CLIENT REF: EAM040


7.0 REFERENCES

Airoldi, L., 2003. The effects of sedimentation on rocky coast assemblages. Oceanogr. Mar. Biol. Annu. Rev.,

41: 161-236.

ANZECC, 2000. Australian and New Zealand guidelines for fresh and marine water quality 2000, Volume 1.,

National Water Quality Management Strategy Paper No. 4. Australian and New Zealand Environment and

Conservation Council and Agriculture and Resource Management Council of Australia and New Zealand,

Canberra.

Bennett, C., 2006. Ahuriri Stormwater Discharge Compliance Monitoring. . Cawthron Report No. 1146,

Cawthron, Napier.

Clarke, K.R. and Gorley, R.N., 2001. PRIMER v5: User manual. PRIMER-E Ltd, Plymouth Marine Laboratory,

United Kingdom.

Clarke, K.R. and Warwick, R.M., 1994. Changes in marine communities; an approach to statistical analysis

and interpretation. Natural Environment Research Council, United Kingdom, 144 pp.

Cromarty, P. and Scott, D.A., 1996. A directory of wetlands in New Zealand. In: D.o. Conservation (Editor),

Wellington, New Zealand, pp. 395.

Davis, S.F., 1987. Wetlands of national importance to fisheries. New Zealand Freshwater Fisheries Report

Number 90, Freshwater Fisheries Centre, MAFFish, Christchurch.

HBRC, 1999. Regional Coastal Plan. ISBN 1-877174-16-5, Hawke's Bay Regional Council, Napier.

HBRC, 2006. Regional Coastal Environment Plan: Proposed - August 2006 (As amended by Council Decisions

Issued 19 July 2008). ISBN 1-877405-23-X. HBRC Plan Number 4071, Hawke's Bay Regional Council, Napier.

HDC, HBRC, NCC and DoC, 1992. Ahuriri Management Plan. , Hastings District Council, Hawke’s Bay

Regional Council, City of Napier, and Department of Conservation.

Hume, T. and Swales, A., 2003. How estuaries grow old. , NIWA Water and Atmosphere.

Kilner, A.R. and Ackroyd, J.M., 1978. Fish and invertebrate macrofauna of the Ahuriri Estuary, Napier. Fisheries

Technical Report No. 153, New Zealand Ministry of Agriculture and Fisheries, Wellington, New Zealand.

Kruskal, J.B. and Wish, M., 1978. Multidimensional scaling. Sage University, Beverely Hills, California.

Madarasz, A.L., 2006. Coastal Monitoring Strategy for Hawke's Bay: 2006-2011. EMI 06/07

HBRC plan number 3850.

Nicholls, P., 2002. Determining impacts on marine ecosystems: the concept of key species. Water and

Atmosphere, 10(2).

Robertson, B.M. et al., 2002. Estuarine environmental assessment and monitoring: a national protocol

Sustainable Management Fund Contract No. 5096, Prepared for supporting Councils and the Ministry for the

Environment

Smith, S., 2007. Coastal Sediment Characteristics of the Hawke Bay. . Report prepared for the Hawke's Bay

Regional Council. EMI 07/24. HBRC Plan no. 3975, EAM Ltd., Napier.

StatSoft, 2004. STATISTICA version 7, data analysis software system. www.statsoft.com.

CLIENT REF: EAM040


7.0 REFERENCES

Strong, J.M., 2005. Background sediment trace metal concentrations of major estuarine, and lagoon

systems in the Hawke's Bay region, New Zealand. MSc Thesis, University of Auckland.

Thrush, S.F., Hewitt, J. E. , Norkko, A., Nicholls, P.E., Funnell, G.A. and Ellis, J.I., 2003. Habitat change in

estuaries: predicting broad-scale responses of intertidal macrofauna to sediment mud content. Marine

Ecology Progress Series, Vol. 263: 101-112.

Watling, L. and Norse, E.A., 1998. Disturbance of the seabed by mobile fishing gear: A comparison to forest

clearcutting. Conservation Biology, 12: 1180-1197.

CLIENT REF: EAM040


APPENDIX 1 SAMPLING STATION

CLIENT REF: EAM040


TABLE A1-1: LOCATIONS OF STATIONS SAMPLED AT SITES AHUA, AHUB, AHUD, AHUE AND PORA FOR THE PRESENT SURVEY.

AHUA NZ Map Grid Coordinates AHUB NZ Map Grid Coordinates

Station Northing Easting Station Northing Easting

A1 6184000 2843550 B1 6183595 2843587

A2 6183992 2843580 B2 6183626 2843559

A3 6183999 2843541 B3 6183623 2843572

A4 6183966 2843544 B4 6183570 2843566

A5 6184018 2843516 B5 6183600 2843586

A6 6183985 2843539 B6 6183601 2843561

A7 6183993 2843522 B7 6183621 2843553

A8 6183978 2843541 B8 6183580 2843572

A9 6183999 2843499 B9 6183590 2843564

A10 6184000 2843507 B10 6183613 2843548

A11 6184028 2843511 B11 6183612 2843575

A12 6184019 2843532 B12 6183578 2843586

AHUD NZ Map Grid Coordinates AHUE NZ Map Grid Coordinates

Station Northing Easting Station Northing Easting

D1 6183609 2844230 E1 6184108 2844049

D2 6183596 2844234 E2 6184112 2844036

D3 6183624 2844245 E3 6184122 2844064

D4 6183600 2844251 E4 6184085 2844022

D5 6183582 2844259 E5 6184118 2844035

D6 6183576 2844274 E6 6184138 2844061

D7 6183579 2844263 E7 6184131 2844054

D8 6183611 2844263 E8 6184117 2844042

D9 6183588 2844284 E9 6184128 2844045

D10 6183611 2844253 E10 6184108 2844063

D11 6183590 2844273 E11 6184095 2844039

D12 6183603 2844273 E12 6184103 2844028

PORA NZ Map Grid Coordinates

Station Northing Easting

P1 6098702 2823685

P2 6098707 2823663

P3 6098725 2823646

P4 6098692 2823647

P5 6098713 2823637

P6 6098691 2823633

P7 6098697 2823620

P8 6098706 2823646

P9 6098698 2823640

P10 6098714 2823652

P11 6098708 2823634

P12 6098686 2823640

CLIENT REF: EAM040


APPENDIX 2 SEDIMENT DATA

CLIENT REF: EAM040


SEDIMENT TEXTURE

TABLES A2-1: SEDIMENT TEXTURE, AFDW AND CHLOROPHYLL A LEVELS OF STATIONS SAMPLED DURING THE PRESENT SURVEY FOR SITES

AHUA, AHUB, AHUD, AHUE AND PORA.

Site Station Gravel (>2mm)

(%w/w)

Sand

(63µm – 2mm)

(%w/w)

Clay/Silt

(<63µm)

(%w/w)

AFDW

(%w/w)

Chl a

(mg/m3)

AHUA A1 24.7 52.3 23 2.4 4700

A2 0.9 85.6 13.5 1.4 5400

A3 11.5 77.2 11.4 1.2 6200

A4 <0.1 78.9 21.1 1.1 14000

A5 1.4 84.3 14.3 1.7 5300

A6 2.6 82.5 14.9 1.5 4200

A7 0.3 83.4 16.3 1.3 4000

A8 0.1 82.8 17.1 1.6 3600

A9 0.1 77.4 22.4 1.6 5500

A10 2.1 75.3 22.5 1.5 6700


(%w/w)

Sand

(63µm – 2mm)

(%w/w)

Clay/Silt

(<63µm)

(%w/w)

AFDW

(%w/w)

Chl a

(mg/m3)

AHUB B1 1 88.5 10.5 1.7 6200

B2 3.3 76.2 20.5 1.8 6400

B3 0.2 81.8 18 1.6 7000

B4 1.2 79.6 19.2 1.8 4300

B5 0.5 84.7 14.8 1.7 3800

B6 0.5 87.4 12.1 1.3 4900

B7 0.2 91.6 8.1 1.8 5400

B8 <0.1 68.5 31.4 1.9 3800

B9 0.3 78.2 21.5 2.3 4000

B10 0.3 84.4 15.3 1.4 7600


(%w/w)

Sand

(63µm – 2mm)

(%w/w)

Clay/Silt

(<63µm)

(%w/w)

AFDW

(%w/w)

Chl a

(mg/m3)

AHUD D1 <0.1 42.3 57.7 2.5 2800

D2 0.1 52.6 47.4 2.2 6100

D3 6.5 78 15.5 2.2 4500

D4 0.6 77.1 22.2 1.7 7900

D5 0.6 56.3 43 2.8 4300

D6 0.3 80.7 19 2 9500

D7 1.6 82 16.3 1.8 5900

D8 0.9 71.1 28 2.1 8300

D9 2.5 81.3 16.2 1.6 8100

D10 0.8 74.9 24.4 2.1 6900

CLIENT REF: EAM040



(%w/w)

Sand

(63µm – 2mm)

(%w/w)

Clay/Silt

(<63µm)

(%w/w)

AFDW

(%w/w)

Chl a

(mg/m3)

AHUE E1 25.8 55.9 18.3 1.9 4500

E2 17.4 55 27.5 0.64 4500

E3 14.6 57.4 28 2.4 6100

E4 10.4 77.5 12.1 1.5 2300

E5 16.9 55.1 28 3 5800

E6 17 50.7 32.3 2.6 5100

E7 22.3 46.1 31.6 3.4 5200

E8 18.6 51.6 29.8 3.5 5000

E9 21.2 46.8 32.1 2.7 6500

E10 10.2 68.8 21 2.2 8300


(%w/w)

Sand

(63µm – 2mm)

(%w/w)

Clay/Silt

(<63µm)

(%w/w)

AFDW

(%w/w)

Chl a

(mg/m3)

PORA P1 2 48.5 49.5 0.27 4500

P2 0.5 42.6 56.9 0.59 3200

P3 0.5 53.3 46.2 1.3 2800

P4 3.1 47.4 49.5 1.2 3900

P5 2.9 55.2 41.9 1.5 1800

P6 3.9 54.4 41.7 1.2 1900

P7 3.2 58.9 37.8 0.32 2800

P8 0.6 44 55.4 3.7 3000

P9 0.5 59.1 40.4 3 2500

P10 14 37.7 48.3 3.2 2700

CLIENT REF: EAM040


SEDIMENT QUALITY

TABLES A2-2: SEDIMENT NUTRIENT AND TRACE METAL LEVELS OF STATIONS SAMPLED DURING THE PRESENT SURVEY FOR SITES AHUA,

AHUB, AHUD, AHUE AND PORA.

Site Station TRP

(mg/kg)

TN

(g/100g)

As

(mg/kg)

Cd

(mg/kg)

Cr

(mg/kg)

Cu

(mg/kg)

Pb

(mg/kg)

Ni

(mg/kg)

Zn

( m g /

kg)

AHUA A1 470 0.085 4.6 0.074 18 11 12 9.3 70

A2 280 <0.051 3.7 0.051 12 5.1 7.9 6.8 50

A3 310 <0.051 3.3 0.056 13 5.4 7.7 7 54

A4 330 0.051 2.6 0.022 13 4.6 7.5 7.6 42

A5 320 0.051 2.6 0.042 13 5 7.5 7 54

A6 320 <0.051 2.7 0.026 12 4.6 7.7 7.4 48

A7 320 <0.051 3 0.025 11 4.2 6.9 7.7 44

A8 320 <0.051 3.1 0.027 12 5 7.8 8.8 52

A9 340 <0.051 4.2 0.021 12 4.9 10 8.5 47

A10 340 <0.051 3.6 0.023 12 4.7 8.4 8.3 46

Site Station TRP

(mg/kg)

TN

(g/100g)

As

(mg/kg)

Cd

(mg/kg)

Cr

(mg/kg)

Cu

(mg/kg)

Pb

(mg/kg)

Ni

(mg/kg)

Zn

( m g /

kg)

AHUB B1 330 <0.051 2.6 0.029 12 5.5 7.8 7.2 52

B2 410 0.12 4.3 0.024 13 6.9 10 7.3 52

B3 350 0.062 4.1 0.03 14 7 9.6 7.9 52

B4 330 0.052 3.3 0.037 14 6.6 8.9 7.2 56

B5 320 <0.051 2.9 0.026 12 5.1 7.6 7.1 48

B6 310 <0.051 3.9 0.022 13 5.2 9 7.2 49

B7 330 <0.051 3.5 0.028 12 4.5 7.6 7.1 42

B8 330 <0.051 3.1 0.04 13 5.6 8.2 7.4 56

B9 330 <0.051 4.3 0.038 14 6.2 10 8 56

B10 360 <0.051 5.3 0.017 14 5.5 11 7.6 51

Site Station TRP

(mg/kg)

TN

(g/100g)

As

(mg/kg)

Cd

(mg/kg)

Cr

(mg/kg)

Cu

(mg/kg)

Pb

(mg/kg)

Ni

(mg/kg)

Zn

( m g /

kg)

AHUD D1 530 0.076 6 0.25 53 21 35 9.3 210

D2 540 0.08 6.4 0.13 52 22 36 9.3 160

D3 1400 0.061 13 0.86 38 20 41 8.3 180

D4 690 0.059 6.2 0.13 36 15 28 8.6 140

D5 500 0.071 10 0.17 51 23 28 8.9 170

D6 430 0.052 11 0.065 38 20 21 7.7 98

D7 380 <0.051 9.9 0.095 30 17 19 8.5 100

D8 680 0.075 5.4 0.23 51 19 35 8.4 180

D9 490 <0.051 6.4 0.16 35 17 21 7.7 130

D10 830 0.068 6.7 0.24 51 23 35 8.9 170

CLIENT REF: EAM040


Site Station TRP

(mg/kg)

TN

(g/100g)

As

(mg/kg)

Cd

(mg/kg)

Cr

(mg/kg)

Cu

(mg/kg)

Pb

(mg/kg)

Ni

(mg/kg)

Zn

( m g /

kg)

AHUE E1 490 0.067 6.5 0.043 13 7.6 19 7.9 54

E2 430 0.068 4.6 0.052 14 9.4 15 8.7 59

E3 480 0.08 5.5 0.054 14 9.1 14 8.2 59

E4 410 <0.051 5 0.027 11 5.8 13 7.7 46

E5 480 0.08 5 0.054 14 8.9 15 8.3 57

E6 450 0.071 4.6 0.055 14 9.3 15 8.7 60

E7 480 0.076 4.9 0.055 16 9.9 14 8.6 64

E8 450 0.074 4.5 0.06 15 9.7 15 8.7 62

E9 520 0.092 4.4 0.07 16 11 15 9.3 68

E10 480 0.06 6.3 0.04 12 6.5 15 7.5 50

Site Station TRP

(mg/kg)

TN

(g/100g

)

As

(mg/kg)

Cd

(mg/kg)

Cr

(mg/kg)

Cu

(mg/kg)

Pb

(mg/kg)

Ni

(mg/kg)

Zn

( m g /

kg)

PORA P1 450 0.1 6.3 0.05 11 12 6.4 10 41

P2 390 0.097 4.9 0.059 9.8 13 6.2 10 39

P3 440 0.082 7 0.042 11 12 6 10 40

P4 350 0.07 5.5 0.046 9.4 11 5.2 8.8 34

P5 360 0.073 5.8 0.048 9.7 11 5.3 9.4 36

P6 380 0.068 6.1 0.04 9.6 11 4.9 8.7 35

P7 360 0.058 6 0.02 8.5 9 4.5 7.9 31

P8 420 0.076 5.5 0.052 10 10 5.3 8.6 37

P9 390 0.063 6.1 0.036 9.8 9.7 5.1 8.8 35

P10 420 0.091 5.5 0.051 11 12 6 10 39

CLIENT REF: EAM040


APPENDIX 5 INTER-SURVEY COMPARISON: PERMANOVA’S

SIMPER’S

CLIENT REF: EAM040


TABLES A5-1: PERMANOVA RESULTS EXAMINING THE EFFECT OF YEAR ON INFAUNA AT ESTUARINE MONITORING SITES WITHIN THE AHURIRI

(AHU) AND PORANGAHAU (POR) ESTUARIES. ALL DATA WERE TRANSFORMED (LN(X+1)), AND ANALYSIS WAS BASED ON BRAY-CURTIS

DISSIMILARITIES. P (PERM) INDICATES THE PERMUTATIONAL P-VALUE, P(MC) INDICATES THE MONTE CARLO P-VALUE.

AHUA


Site 3 26612.1 8870.7 7.60 0.0012 0.0012

Residual 44 51304.1 1166.1

Total 47 77916.2

AHUB


Site 3 16355.7 5451.9 3.38 0.0012 0.0012

Residual 44 70868.9 1610.6

Total 47 87224.6

AHUD


Site 2 8803.8592 4401.9296 3.0680 0.0062 0.0050

Residual 33 47347.6884 1434.7784

Total 35 56151.5475

PORA


Site 3 40391.8758 13463.9586 7.4012 0.0012 0.0012

Residual 44 80042.6823 1819.1519

Total 47 120434.5581

CLIENT REF: EAM040


TABLE A5-2: PERMANOVA RESULTS EXAMINING THE EFFECT OF YEAR ON EPIFAUNA AT ESTUARINE MONITORING SITES WITHIN THE AHURIRI

(AHU) AND PORANGAHAU (POR) ESTUARIES. ALL DATA WERE TRANSFORMED (LN(X+1)), AND ANALYSIS WAS BASED ON BRAY-CURTIS

DISSIMILARITIES. P (PERM) INDICATES THE PERMUTATIONAL P-VALUE, P(MC) INDICATES THE MONTE CARLO P-VALUE.

AHUA


Site 3 13509.1596 4503.0532 4.1328 0.0010 0.0010

Residual 36 39225.1193 1089.5866

Total 39 52734.2789

AHUB


Site 3 17480.5458 5826.8486 4.7654 0.0010 0.0010

Residual 36 44018.2675 1222.7297

Total 39 61498.8133

AHUD


Site 2 13153.9043 6576.9522 2.8397 0.0020 0.0060

Residual 27 62534.0562 2316.0762

Total 29 75687.9605

PORA


Site 2 36686.9163 18343.4581 33.5510 0.0010 0.0010

Residual 27 14761.7882 546.7329

Total 29 51448.7045

CLIENT REF: EAM040


TABLE A5-3: LIST OF INFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES AND YEARS AT AHURIRI SITE A (AHUA)

(SIMPER LN(X+1) TRANSFORMED DATA, PRIMER). TOP 80% OF CONTRIBUTING SPECIES.

TABLE A5-4: LIST OF INFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES AND YEARS AT AHURIRI SITE B (AHUB)


Site Year Species Av.

abund

Av. Sim Sim/

SD

Contrib % Cum%

AHUA

2006

(av. sim.

72%)


Aonides trifida 19.25 19.18 3.39 26.7 54.14

Heteromastus filiformis 4.83 11.92 3.07 16.59 70.73


AHUA

2007

(av. sim.

59%)

Aonides trifida 11.33 18.84 1.88 31.76 31.76




AHUA

2008

(av. sim.

50%)



Scolecolepides sp. 1.42 6.44 0.93 13 75.46

Prionospio sp. 1.42 4.08 0.61 8.23 83.69

AHUA

2009

(av. sim.

42%)



Helice crassa 1.58 3.77 0.59 9.02 69.57

Aonides trifida 6.58 3.7 0.4 8.86 78.43

Edwardsia sp. 1.08 3.63 0.81 8.69 87.12


abund

Av. Sim Sim/

SD

Contrib % Cum%

AHUB 2006

(av. sim.

55%)



Aonides trifida 2.5 7.06 0.98 12.8 86

AHUB 2007

(av. sim.

47%)



AHUB 2009

(av. sim.

42%)




AHUB




Aonides trifida 10.08 6.23 0.97 14.92 73.1


2009

(av. sim.

42%)

CLIENT REF: EAM040


TABLE A5-5: LIST OF INFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES AND YEARS AT AHURIRI SITE D (AHUD)


TABLE A5-6: LIST OF INFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES AND YEARS AT PORANGAHAU SITE A

(PORA) (SIMPER LN(X+1) TRANSFORMED DATA, PRIMER). TOP 80% OF CONTRIBUTING SPECIES.


abund

Av. Sim Sim/

SD

Contrib % Cum%

AHUD

2007

(av. sim.

54)

Nicon aestuariensis 2 23.1 1.84 42.71 42.71



AHUD

2008

(av. sim.

46%)




AHUD

2009

(av. sim.

41%)

Helice crassa 2.92 19.29 1.38 38.16 38.16




abund

Av. Sim Sim/

SD

Contrib % Cum%

PORA 2006

(av. sim.

55%)



Aonides trifida 2.5 7.06 0.98 12.8 86

PORA 2007

(av. sim.

47%)



PORA 2009

(av. sim.

42%)




PORA




Aonides trifida 10.08 6.23 0.97 14.92 73.1


2009

(av. sim.

42%)

CLIENT REF: EAM040


TABLE A5-7: LIST OF EPIFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES AND YEARS AT AHURIRI SITE A (AHUA)


TABLE A5-8: LIST OF EPIFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES AND YEARS AT AHURIRI SITE B (AHUB)



abund

Av. Sim Sim/

SD

Contrib % Cum%

AHUA 2006

(av. sim.

69%)



AHUA 2007

(av. sim.

65%)




AHUA 2009

(av. sim.

73%)



AHUA

2009

(av. sim.

38%)





abund

Av. Sim Sim/

SD

Contrib % Cum%

AHUB 2006

(av. sim.

37%)



AHUB 2007

(av. sim.

66%)



AHUB 2009

(av. sim.

66%)


Eliminus modestus 15.67 16.62 1.04 25.34 89.69


AHUB

2009

(av. sim.

50%)


Zeacumantus lutulentus 4.18 5.02 0.41 10 96.71

CLIENT REF: EAM040


TABLE A5-9: LIST OF INFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES AND YEARS AT AHURIRI SITE D (AHUD)


TABLE A5-10: LIST OF EPIFAUNA SPECIES THAT CONTRIBUTE MOST TO THE SIMILARITY AMONG SITES AND YEARS AT PORANGAHAU SITE A

(PORA) (SIMPER LN(X+1) TRANSFORMED DATA, PRIMER). TOP 80% OF CONTRIBUTING SPECIES.


abund

Av. Sim Sim/

SD

Contrib % Cum%

AHUD

2007

(av. sim.

32)


Helice crassa 0.64 4.16 0.32 12.79 77.94

Amphibola crenata 1.73 3.3 0.24 10.17 88.11

AHUD

2008

(av. sim.

27%)




AHUD

2009

(av. sim.

52%)


Cominella glandiformis 0.7 4.09 0.5 7.83 93.32


abund

Av. Sim Sim/

SD

Contrib % Cum%

PORA 2007

(av. sim.

62%) Austrovenus stutchburyi 5.5 59.03 1.97 95.32 95.32

PORA 2008

(av. sim.

84%) Amphibola crenata 10.17 82.28 9.3 98.25 98.25

PORA 2009

(av. sim.

91%) Amphibola crenata 9.17 91 12.51 100 100

CLIENT REF: EAM040


APPENDIX 6 REPORT LIMITATIONS

CLIENT REF: EAM040


REPORT LIMITATIONS

This Document has been provided by Environmental Assessments & Monitoring Ltd (EAM) subject to the

following limitations:

I. This Document has been prepared for the particular purpose outlined in EAM’s proposal and no

responsibility is accepted for the use of this Document, in whole or in part, in other contexts or for any

other purpose.

II. The scope and the period of EAM’s Services are as described in EAM’s proposal, and are subject to

restrictions and limitations. EAM did not perform a complete assessment of all possible conditions or

circumstances that may exist at the site referenced in the Document. If a service is not expressly

indicated, do not assume it has been provided. If a matter is not addressed, do not assume that any

determination has been made by EAM in regards to it.

III. Conditions may exist which were undetectable given the limited nature of the enquiry EAM was

retained to undertake with respect to the site. Variations in conditions may occur between

investigatory locations, and there may be special conditions pertaining to the site which have not

been revealed by the investigation and which have not therefore been taken into account in the

Document. Accordingly, additional studies and actions may be required.

IV. In addition, it is recognized that the passage of time affects the information and assessment provided

in this Document. EAM’s opinions are based upon information that existed at the time of the

production of the Document. It is understood that the services provided allowed EAM to form no

more than an opinion of the actual conditions of the site at the time the site was visited and cannot

be used to assess the effect of any subsequent changes in the quality of the site, or its surroundings,

or any laws or regulations.

V. Any assessments made in this Document are based on the conditions indicated from published

sources and the investigation described. No warranty is included, either express or implied, that the

actual conditions will conform exactly to the assessments contained in this Document.

VI. Where data supplied by the Client or other external sources, including previous site investigation

data, have been used, it has been assumed that the information is correct unless otherwise stated.

No responsibility is accepted by EAM for incomplete or inaccurate data supplied by others.

VII. The Client acknowledges that EAM may have retained sub-consultants affiliated with EAM to provide

Services for the benefit o EAM. EAM will be fully responsible to the Client for the Services and work

done by all of its sub-consultants and subcontractors. The Client agrees that it will only assert claims

against and seek to recover losses, damages or other liabilities from EAM and not EAM’s affiliated

companies, and their employees, officers and directors.

VIII. This Document is provided for sole use by the Client and is confidential to it and its professional

advisers. No responsibility whatsoever for the contents of this Document will be accepted to any

person other than the Client. Any use which a third party makes of this Document, or any reliance on

or decisions to be made based on it, is the responsibility of such third parties. EAM accepts no

responsibility for damages, if any, suffered by any third party as a result of decisions made or actions

based on this Document.

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