APPENDIX B

Radiological Assessment

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Radiological Protection Institute of Ireland An lnst i t i l i id E i reannach urn Chosa int Ra i deo l a i o ch

24* April 2007

Mr. J. Byrne Brunel House North Quay Arklow Co. Wicklow Ireland

Dear Mr. Byrne

I attach a copy of the results of the radiological analyses of samples from Arklow River, Dock Co. Wicklow An Invoice will follow in due course.

The results indicate that dumping of these materials at sea will not result in a radiological hazard.

The Department of the Communication {Pat Corcoran) has been informed and if you have any queries, please do not hesitate to contact me for assistance.

Y ,*

Yours sincerely

David Pollard Principal Scientific Officer

3 Clonskeagh Square Tel: +353 1269 7766 E-mail: Ipii@ipii.ie Chairman: prof. Eugene Kennedy C/msf(eagh Road Fax: +353 1 269 7437 website: www.Ipii.ie Chief ~ecdlve: DL Ann McGany Dublin 14

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Radiological Protection Institute of Ireland An Inst i t ih id t i r e a n n a c h urn C h o s a i n t R a i d e o l a l o c h

Laboratory Test Report

Report Date: 20fh April 2007

Samples Tested on Behalf of: J P Byrne & Partners Brunel House North Quay Arklow CO Wicklow

Laboratory Analysis: High Resolution Gamma Spectrometry with appropriate density correction

Sample Type: Marine Sediment

Date of Receipt: 22"* March 2007 Date of Analysis 23d March- 13& April 2007

Results:

RPII Client Coordinates Nuclide Activity Reference Reference Concentration

1 (Bq/kg, dry) K-40 722 f 80 1-131 Less than 3

CT07003 56 Sample 1 52.47.51N CS- 134 Less than 2 006.08.67W CS-137 25.9 f 1.4

Ra-226 Less than 80 U-23 5 7*2 U-23 8 66k 12 K-40 526 f 58 1-131 Less than 2

CT0700357 Sample 2 52.47.59N CS-134 Less than 2 006.08.63W CS-1 37 14.2 f 0.8

Ra-226 Less than 86 U-235 1 2 k 3 U-238 261 f 11 K-40 214 f 22 1-131 Less than 1

CT0700358 Sample 3 52.47.66N CS- 134 Lessthan1 ~ . 006.08.69W CS- 1 3 7 5.9 f 0.4 '

Ra-226 Less than 69 U-235 Less than 4 U-238 61 * 4

3 Cronskeagh Square Tel: +353 1 269 7766 E-mail: rpii@rpi\./e Wmm: prof. Eugene Kennedy Clonskeagh Raad Fa: +353 1 269 7437 Wbsite: w.rpn.ie Chief Executive: Dc Ann McGany Dublin 14

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9 An Ins t i t ih id g i reannach urn Chosa int Ra i deo l a i o ch

K-40 439 f 48 1-131 Less than 2

CT0700359 Sample 4 52.47.56N CS- 134 Less than 1 006.08.32W CS-137 8.8 f 0.6

Ra-226 Less than 105 U-23 5 Less than 6 U-23 8 410* 16

Note: (1) Quoted uncertainties are *l SD counting statistics

The Radiological Protection Institute of Ireland received eight samples of sediment fi-om Aquatic Services Unit. The samples were prepared for high-resolution gamma spectrometry by placing an aliquot of sample in a well-defined counting geometry. The sample was measured on a high-resolution gamma spectrometer. Appropriate density corrections were applied to the resultant spectra to take account of the differences in sample density. Dry to wet weight ratios were determined for each sample. Results are quoted on a dry weight basis.

Stephanie Long Laboratory Manager

Notes: This report relates only to the samples tested. This report shall not be reproduced except in full, without the approval of the Institute The following scientific officers may sign test reports on behalf of the lab manager: Mr David Pollard, Ms Mary Fegan, Mr Kevin Kelleher, Ms Alison Dowdall Where applicable, the number following the symbol * is the combined standard uncertainty and not a confidence interval.

Page 2 of 2 LDC72 3 Clomkeagh Stp~rn Tel: +353 1 269 7766 E-mail: pii@pii.ie Chaiman: Rot Eugene Kennedy Clonskeagh Road Fax: +353 1 269 7437 Website: www.ipii.ie Chief Eimtive: DL Ann McGany Dublin 14

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APPENDIX C1

Ecological Assessment 2007

... x.

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P

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Report on a proposed dredge disposal site, Co. Wicklow

Produced by

Aqua-fact International Services Ltd

February 5,2008

A

AQUA-FACT INTERNATIONAL SERVICES Itd 12 KlLKERRlN park T U N rd GALWAY city www.aauafact.le info@aquafad.ie tel+353 (0) 91 756812 fax +353 (0) 91 756888

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I I I I I I I I I I I I I

A report on a proposed dredge disuosal site, Co. Wicklow. Executive summary JN89

EXECUTIVE SUMMARY

Aqua-Fact International Services Ltd. was contracted by Arklow Harbour Commissioners to

carry out a sea bed survey at a proposed dredge disposal site north east of Arklow, Co. Wicklow (see

Figure 1 for location map).

* -

Figure I : Site map off the coast of Arklow showing the seven sampling sites.

It is proposed to dispose of 100,000m3 of marine sediment at the site. The used previously as a dredge spoil disposal site.

.”- --

locati,on’had been

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A report on a uroDosed dredge disuosal site. Co. Wicklow. Executive summarv JN899

tm This part of the Irish Sea experiences very strong tidal currents with velocities reaching ca 2

m sec-' on Spring tides. These velocities rework the sediments and fine material is exported from the

area. The sediments are therefore characterised by coarse sand, stones, gravels and shell debris. Any

fine material that is disposed off at this site will therefore be exported away fiom this location. From

previous studies, it is known that the area is low in numbers of species and numbers of individuals.

I P

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Sea bed samples were collected at the seven locations shown in the figure and these were

analysed for different types of marine animals including sea WO&, 'shellfish and sea stars etc. and

also for the type of sediment present and the level of organic carbon present. The information was

then analysed using statistical software especially developed for such applications.

The biological survey recorded only 51 species which is a low number compared to some

other areas. This is attributed to the strong hydrodynamic regime that operates in the site causing

organic-rich material to be exported and also giving rise to constant reworking of the sediment.

Organic material is the basic food resource of many marine species and if this resource is only

present in low percentages, there simply is not sufficient food to support a diverse group of animals.

This factor, added to the fact that sediment is being continuously reworked, gives rise to low

numbers of animals and low individual species numbers. None of the animals recorded are

considered as being rare or unusual and the habitat type is not listed in the EU Habitats Directive.

The area is characterised by shelly coarse sands and gravels with low levels of orga&

carbon. This reflects the fast current speeds that occur at the site.

This site has been used in the past as a dredge spoil disposal site. The last time it was used

was ca. 11 years ago. From the findings of this survey, there are no signs of this previous disposal

event.

The disposal of ca 100,OOO tonnes of material at the disposal site will result in the smothering

and destruction of the existing biological community present. The local oceanographic conditions at

the site will cause the deposited material to be redistributed over the area and this will also cause the

disposed sediment to be fully oxidised. Re-colonisation of this sediment will therefore be fast and

may even allow later stage colonisers to establish themselves without requiring the usual pioneering

stages. '

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JN899 A reDort on a Drouosed dredge disDosai site, Co. Wicklow

1.0 INTRODUCTION

Aqua-Fact International Services Ltd. was contracted by Arklow Harbour Commissioners to

carry out a benthic survey at a proposed dredge disposal site north east of Arklow, Co. Wicklow (see

Figure 1 for location map). The site is situated off the southeast coast of Ireland and lies south of

Mizen Head and water depths range from between 15 - 18 m.

Figure 1 : Site map off the coast of A.rklow showing the seven sampling sites.

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A mrt on a Drowsed dredge dismsal site; Co. Wicklow JN899

It is proposed to dispose of 100,000m3 of marine sediment at the site. The location had been

used previously as a dredge spoil disposal site.

1

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2.0 DESK TOP s"JJJY

2.1 Introduction

This part of the Irish Sea experiences very strong tidal currents with velocities reaching ca 2 * *

m sec-' on Spring tides. These velocities rework the sediments and h e material is exported fiom

the area. The sediments are therefore characterised by coarse sand, stones, gravels and shell debris.

Any fine material that is disposed off at this site will therefore be exported away from this location.

Previous studies include Boelens et al. (1 999) and Wilson et al. (2002) and both recorded coarse

sand and shell for this area while Boelens et al. (1999) also comment that the benthic community in

the area is a Venus assemblage. 8

2.2 Fisheries

An accurate representation of fish numbers caught off the Wexford coast, specifically the

study region opposite Courtown, is not possible as the catches landed by Irish boats are brought to a

number of different harbours. Arklow, Wicklow, Kinsale and Wexford are the biggest ports in the

area and the majority of catch would be landed at these ports. According to a BIM fisheries officer

there are no appreciable landings of whitefish into Courtown Harbour. However, finfish tonnages

have varied over recent years as can be seen &om Table 4.6 below.

Harbour 2000 2001 2002

920 1077 393

Courtown 460 425 324

KilmoreQuay 1978 1850 1997

Kinsale 1774 1691 1726

Wexford 266 251 209

Wicklow 2211 4455 6241

A m o w

Table 2.2.1 : CSO statistics showing finfish tonnages into east coast harbours (2000-2004)

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A reuort on a promxed dredge dimsal site. Co. Wicklow JN899

The main fisheries in the Courtown area are similar to those of the Arklow bank, Codling

Bank and the numerous sand banks along the south-east coast. Whelk (Bucciniurn andaturn) and

Mussel (Mytilw edulis) dominate, with some mixed white fish trawling (dogfish). The south east

coast has been identified as a herring (Clupea harengus) nursery ground by CEFAS (2000) and the

Marine Institute (1999) reported that herring from this division accounted for 16% of the total

reported Region III pelagic landings of 760,000 tonnes in 1995. Many of the Arklow boats, however

previously used for finfish trawling are now adapted for the more lucrative whelk fishing. Vessels

less than 10 metres in length are not required to declare catches and therefore landing figures may be

underestimated.

2.2 WHELK FISHERY

The whelk fishery in Ireland is mainly concentrated on the Southern Irish Sea where the

whelk is found on mud, sand and gravel banks within five nautical miles of the shore. Landings of

whelk are heavily concentrated on the southeast coast ofthe Irish Sea, fiom Howth Harbour in Co.

Dublin to Came in CO Wexford (52O10' to 53").

This fishery is divided into four regions, see Figure 4.9 below; Dublin (16% of landings up to

1998), Arklow (40% of the whelk catch - The Codling Bank is a substantial part of this sector and it

supports heavy local concentrations of whelk), Courtown (16% of whelk landings) and Wexford

(Densities of whelk in this sector are relatively low - 27% of landings up to 1998). The Courtown

sector extends h m 52" 44' to 52" 25' and lands approximately 16% of the whelk catch. Catches of

between 400 and 500 tonnes have been landed into Courtown in the past number of years. In 1990

total recorded whelk landings for the Southeast coast were 56t and by 1996 they had risen to 6,575t;

after this, landings declined and stabilised at between 3,600 and 4,600 tannually for a short period.

Table 2.2.1 on the following page shows landing data for whelk in southeast fisheries for 2003-2004.

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A mrt on a ~ m s e d WE e disoosal site. Co. Wicklow JN899

Figure 2.2.1: Map showing Southeast coast whelk fishery divided into four sectors (Fahy, 2000).

2003

Arklow 754

courtown 297

Wexford 354.03

KilmoreQuay 4.59

2004

Arklow 675

courtown 300

Wexford 267.02

Kilmore Quay 5.58

Whelk catch quantities in tonnes

Table 2.2.1: Whelk landing data for south-east harbours Erom 2003-2004.

As can be seen the catch quantities have declined considerably over time. However, it must

be reiterated that these figures are not exact as boats less than 10 metres in length do not have to

declare catch quantities and these make up a significant proportion of the vessels fishing for whelk

out of the above harbours.

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A r e ~ r t on a Drowsed dredge dismsal site, Co. Wicklow JN899

Rshery locations

Within the coastal areas stretching fiom 52'10' to 53030', whelk are distributed over north-

south orientated mud, sand and gravel banks in strong tidal currents most of which are within 5

nautical miles of shore. The majority of whelk is fished close to the ports at which they are landed

but some are likely to have been fished farther away.

Courtown is a small port, liable to silt up, and its fleet of smaller boats does not venture

firther north than 52O44'. The southern boundary of the Courtom sector is shared with the Arklow

fleet and ArMow vessels often fish within the Courtown sector. Heavy concentrations of whelk are

fished by the Courtown boats. There was some variation in landings into Courtown which, in 1994

contained a large proportion of undersized individuals (Fig 4. lo), their numbers declining until 1997

and then increasing again in 1999.

1990 ?$$2 1994 1996 I!ilW 2000

Figure 2.2.2 : Relative contribution of four sectors of the whelk fishery in the south west Irish Sea to

the total landings. The Arklow sector is largely dependent on the Codling Bank (Fahy, 2002).

Courtown Harbour

According to Fahy et al. (2000) a total of eighteen fishermen are recorded landing whelk

catches into Courtown between 1995 and 1998. Of these, one operator was recorded on only seven

occasions while only six fishermen were continuously recorded for the four-year period, After 1996,

the peak year for landings, the numbers of fishermen declined from fifteen to fourteen in 1997

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A mrt on a mowsed dredge dimsal site, Co. Wicklow JN899

L diminished M e r to seven in 1998 and to four in 2000. The maximum recorded number of whelk

boats in Courtown was given as eleven; this was &om the early 1990s. I

Following a survey of catches and fishing effort of Courtown fishermen, Fahy et al. (2000)

recorded that the number of pots fished per vessel had not altered. According to Courtown fishermen

there are a number of reasons for the 12- 13 trains per boat with 30 pots per train. Strong currents on

the banks limit the time gear can be left at sea; also smaller Courtown vessels have not been

exchanged for larger boats. Courtown fishermen also consider the &rease in catch tonnages to be

attributed to the reduction in the numbers of vessels within the Courtown sector and therefore a

larger harvest for those remaining (Fahy et al., 2000).

I

1 I I

In the study carried out by Fahy et al. (2002) on dredging of the Codling Bank, the physical

elimination of the benthic community by the removal of the upper sediment in the dredged area was

predicted. However, the widespread nature of the benthos, the limited size of the dredge site (1/800th

I

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- of the Codling Bank) and the short period of disturbance would, it was anticipated, favour a rapid

recolonisation of the area of disturbance. The period of actual recovery would vary with the species

involved. b

Re-settlement by planktonic larvae would be fast. Whelk do not have a planktonic stage, for

which reason local populations acquire distinctive characteristics so that, in theory at least,

recolonisation by whelk would be a relatively slow process (Fahy, et al. 2002).

!!i

!!!I

2.3 MUSSELS !!I!

In mussels, spawning is protracted in many populations in Ireland with a peak of spawning in

spring and summer. A typical life cycle is as follows: resting gonads begin to develop fiom October

to November, gametogenesis occurs throughout winter so that gonads are ripe in early spring. A

partial spawning in spring is followed by rapid gametogenesis; gonads ripen by early summer,

resulting in a less intensive secondary spawning in summer to late August or September (Seed,

1969). Mantle tissues store nutrient reserves between August and October, ready for gametogenesis

in winter when food is scarce (Seed & Suchanek, 1992). Larvae spawned in spring can take

advantage of the phytoplankton bloom. The secondary spawning is opportunistic, depending on

m 1

I favourable environmental conditions and food availability. Gametogenesis and spawking varies with

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A mort on a moDosed dredge &md site. Co. Wicklow JN899

geographic location, e.g. southern populations ofien spawn before more northern populations (Seed

& Suchanek, 1992). Reproductive strategies in Mytilus edulis probably vary depending on

environmental conditions (Newell et al., 1982).

Mussel larvae spend 2-4 weeks in the plankton, initially settling on macroalgae and hydroids,

before undertaking secondary migration to form seed beds. These beds generally form on patches of

hard substrata such as cobble and gravel @are 1976). The beds becplqe apparent in spring and early

summer in the intertidal and subtidal zone, and can be very dense. Generally, mussel growth is

initially rapid, but in dense beds, growth decreases and mortality increases over the summer.

Mussels have been observed to release byssal attachments to the substratum possibly due to

physiological stress fkom overcrowding. This, combined with the onset of winter storms, often

disperses the seed beds before the mussels become reproductive (Saurel et al. 2004). However, some

beds, presumed dispersed, may actually be buried under sediment, and mussels may survive over

winter (Mark Grayy CCW, pers. comm.).

Most seed mussel beds are unlikely to produce adult mussels. However, this does not mean

that they have no ecological significance. Small mussels are a food source for a variety of predators,

including starfish (Asterias rubens), shore crabs (Carcinus maenus) and flatfish (flounder

Platichthys Jlesus, plaice Pleuronectes platessa and dab Limanda limanda) @are 1976, Seed 1976,

Seed and Suchanek 1992, Buschbaum 2002). The presence of seed mussel beds is also likely to

affect epifauna and infauna in and around the bed area, as is the case with adult mussel beds

(Beadman et al. 2004).

Harvesting seed mussel beds may be deleterious since it reduces the role that seed mussel

beds play in the ecosystem. However, harvesting may be beneficial, by reducing smothering of

infauna, and by thinning out the mussels and reducing nutritional stress that leads to density

dependent mortality. Harvesting may even allow the survival of seed beds, which would otherwise

be dispersed, in their first winter.

The mussel seed beds occurring on the East Coast are an important fishery resource and are

regularly fished for by boats from Arklow and Wicklow, as well as Wexford boats. The mussel seed

settlement waries annually and have been recorded from the Arklow Bank as well as $0 the southwest

of the India Bank and to the south of the Glassgorman Bank. According to the Department of the 4

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1.

A reDort on a movosed dredge diwosal site. Co. Wicklow JN899

1

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Marine, the main beds are located at Cahore Point. The mussel seed settlement is unpredictable and

new mussel beds could form on any of the suitable substrates present on the southeast coast. Seed is

taken from these beds and relayed to the commercial mussel aquaculture operations around the

country. Of these mussel seed beds, Cahore Point is the most important. There are approximately 18

boats licensed by the Department of the Marine operating in this area.

According to Bord Iascaigh Mhara, the Irish Sea Fisheries , . Board, Wexford Harbour alone !

produced approximately 8,250 tonnes per annum and the mussels are sold at an average price of

€705 per tonne, totalling €5,816,250 per annum for Wexford Harbour. The mussel industry in

Wexford Harbour also supports 31 full-time jobs, 19 part-time and 8 casual jobs. Further landing

data for Wexford Harbour was provided by the Department of Communications, Marine and Natural

Resources; 6,837 tonnes of blue mussel was landed in 2003 and 5,937 was landed in 2004.

!

Figure 2.3.1: Seed mussel bed locations on the east coast, 1992-2004 (Bord Iascaigh Mhara).

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I. I- I I I I I I I I I I 1 I 1 I

A mort on a Dromsed dredge dimosal site. Co. Wicklow JN899

Whale and Dolphin populations

The Irish Whale and Dolphin Group was contacted by Aqua-Fact International Services Ltd.

in relation to the disopsal of sediments north east of Arklow. The most common cetacean sighted in

the Irish Sea is the Harbour Porpoise. This has been recorded in densities of up to O.l&als per km surveyed. This is considered a predominantly inshore species and h-as been recorded repeatedly

along the coast of the Western Irish Sea from Dublin Bay to Rosslare. Populations of the Harbour

Porpoise have been estimated at ca 20,000 animals off the Southwe& doast of Ireland. The next most

common species recorded in the Irish Sea is the Bottle-Nosed Dolphin, although this is most

commonly recorded f?om the Welsh Coast as opposed to the Western shore of the Irish Sea. Both the

Harbour Porpoise and the Bottle-Nosed Dolphin are listed in Annex I1 of the Habitats Directive.

Both Common and Risso’s Dolphin, Minke whale, Fin whale, Ora, Beaked whales and Pilot

whales are all recorded occasionally in the Irish Sea and have been sighted in the Courtown area.

However, sightings are more common on the South coast in the Celtic Sea. In April 2004 a stranded

beaked whale was recorded fkom the shore near Courtown Strand and again in August 2004 a beaked

whale was washed up at Pollshone Point near Courtown, Co. Wexford. Neither of these have been

positively identified to species level.

SEAL POPULA~ONS

There are two species of seal that occur in Ireland, the Grey Seal and the Common Seal. Both

species are listed in Annex II of the Habitats Directive and also are protected under the Wildlife Act

of 1972.

The Wexford population of Grey seals was estimated at between 450 and 580 animals (Kiely

et al. 2000) and a Grey seal colony exists on Raven Point, near the proposed development. There is

also a colony reported from the small island off Roney Point near Courtown beach. These seals are

expected to use the waters of the proposed development site. I ??le University College Cork carried out a study on the populations of Grey Seals in the Irish

Sea between 1996 and 1998. It included the main fishing harbours of Dunmore East, Helvick, Howth

and Kilmore Quay, all of which were included in the study of seal/ fisheries interactions.

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A remrt on a oro~osed dredge disoosal site. Co. Wicklow JN899

Ground counts of annual pup production recorded 177 newborn pups at Irish study sites. The

Great Saltee islands (Co. Wexford) were identified as the most important pupping sites in the South-

eastern Irish Sea. The pup census data collected in Ireland yielded a minimum all-age population

estimate for the Irish Sea of 5,198-6,976 grey seals. This estimate was supported by photo-

identification mark-recapture data which delivered an estimate of 5,613'seals (0.2% CV).

The results of this study underline the site-specific and seasonal

abundance patterns. The largest grey seql haul-outs on the east coast of Ireland

nature of grey seal

were recorded during

the months of July and August, the most important site being Lambay Island, Co. Dublin. Sites on

the south-east coast of Ireland contained significant numbers of grey seals year-round, peaking

during the annual breeding (Sept.-Dec.) and moulting seasons (Nov.-Mar.). The most important of

these sites were the Great Saltee and The Raven Point (Co. Wexford).

No movement of identifiable seals was recorded between sites in Co. Wexford and Co.

Dublin, though, on a smaller scale, individual seals were recorded moving between local sites in east

and south-east Ireland. Repeated photographic captures suggested that adult female grey seals may

show a level of inter-annual faithfulness to particular sites, otherwise known as site fidelity. The

strong associations of individual seals with particular areas were noteworthy at Lambay Island, the

Great Saltee, Coninginore Rocks (Co. Wexford) and Blackrock (Co.Wexford).

. .

2.4 Wexford Reef SAC.

This biogenic reef lies to the north of Wicklow Head and the main species is the tube building

polychaete, Sabellaria alveolata.

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3. RESULTS

3.1 BENTHIC INVESTIGATIONS 3.1.1 METHODOLOGY

SAMPLING

To carry out the assessment of the proposed site, 5 sampling stations were selected within the

site and two were located outside to act as possible reference sites (see, Figure 1). Sampling took

place in June 2007 with 5 replicate samples being taken at each of the 7 stations. An additional

sample was taken for organic carbon and particle size analyses. Initially it was planned to sample

the sea bed remotely using a grab but due to the compact nature of the sediment and the large

quantities of shell, this proved impossible. The samples were therefore recovered by divers using

cores (20 cm diameter, 40 cm long). The following analysis techniques were used for these two

piXaIlleters:

. .

ORGANIC CARBON

Approximately 1 Og of sediment were taken fiom the parent samples for organic carbon

analysis. The organic carbon content of the sediment sample was measured on the total sample

using the chromic acid oxidation method described in Holme and Mchtyre (1 984).

PARTICLE SIZE ANALYSIS

Approximately lOOg of sediment were taken fiom a single core sample at each station for

granulometric analysis. The analyses were carried out according to Holme and Mchtyre (1984),

each sample being passed through a nest of graded sieves at intervals of 4.0,2.0, 1.0,0.710,0.500,

0.325,0.250,0.180,0.125,0.090 and 0.063mm. Each grade was weighqd and the value expressed

as a percentage of the dry weight of the total sample.

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I Stations were located using DGPS, this positioning method is accurate to within cu. lm.

Refer to Table 3.2.2 for station coordinates. I!

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52.850

52.799

52.822

52.829

52.828

52.837

52.829

6.048

6.0793

6.0605

6.0705

6.0588

6.0588

6.0471

1 6 . 4

. . 1 4 . 3

1 7 . 1

15.9

16.7

16.9

17.3

Table 3.2.2: Subtidal cores sample station co-ordinates, June 2007.

SEDIMENT GRAIN SIZE CLASSIFICATION SCHEME

The Udden-Wentworth (commonly called the Wentworth scale) grade scale was used for

classifling the diameters of sediments analysed in the current work (see Table 3.2.3). Particles

larger than 64 mm in diameter are classified as cobbles. Smaller particles are pebbles, granules,

sand and silt. Those smaller than 0.0039 mm are clay. It remains the grade scale that is most

commonly used by geologists and geomorphologists, although somewhat different particle size

classifications are used by soil scientists and engineers. The "phi scale" is a commonly-used

modification of the Wentworth system that allows the use of simple whole numbers for class

boundaries by applying the logarithmic transform: phi = -log2d, where d is the particle diameter.

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Table 3.2.3: The Udden-Wentworth scale (Wentworth, 1922) - the sediment granulometry scheme

followed for the particle size analysis (see Table 3.2.2.1 for results).

DIVE SURVEY

At each of the benthic sampling sites experienced scientific divers attempted to carry out a visual survey of the sea-bed for the presence of surface-dwelling species e.g. starfish, lobsters etc. - Benthic communities observed during the dive survey were to be described as well as description of

plant and animal species observed. Due to high levels of suspended sediment in the water at the

time of the survey visibility was extremely poor. Under these conditions it was not possible to take

representative photographs of the seafloor in this area, nor was it possible to make a record of visual

observations taken at the various sampling sites. The description of the animal and plant

communities present here is therefore based on the results provided by the dive core sampling

portion of the survey.

BENTHIC FAUNAL ANALYSIS

Data on each sample, e.g. station number, water depth, date, depth of sediment, smell, colour

and visible macrofauna were logged in a field notebook. Each replicate core for the famd returns

was wet-sieved on a lmm mm mesh sieve not more than 24 hours after collection, stained with a i

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IJ

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vital dye, fixed with 10% buffered formalin and preserved in 70% alcohol. Samples were then sorted

under a microscope (x 10 magnification), into five main groups: Polychaeta, Mollusca, Crustacea

and others. The taxa were then identified to species level where possible and counted. Refer to

Appendix I for a complete species list. Statistical evaluation was undertaken using PlRIMER

analysis techniques.

A data matrix of all the faunal abundance data was compiled and later used for statistical

analyses. The faunal analysis was carried out using the PRIMER @'(Plymouth Routines in

Multivariate Ecological Research) programme.

Univariate statistics in the form of diversity indices were calculated. The following diversity

indices were calculated:

1) Margalef's species richness index @), (Margalef, 1958). s-1 D=-

lo&N

where: N is the number of individuals

S is the number of species

2) Pielou's Evenness index (J), (Pielou, 1977).

H' (observed) J=

H- where: HI- is the maximum possible diversity, which could be achieved if all

species were equally abundant (= log2S)

3) Shannon-Wiener diversity index (H'), (Pielou, 1977).

where: PI is the proportion of the total count accounted for by the i* taxa

Species richness is a measure of the total number of species present for a given number of

individuals. Evenness is a measure of how evenly the individuals are distributed amang different

species. The diversity index incorporates both of these parameters. Richness ranges ftom 0 (low

richness) to 12 (high richness), evenness ranges fiom 0 (low evenness) to 1 (high evenness),

diversity ranges from 0 (low diversity) to 5 (high diversity). '

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A reDort on a Drowsed dredge disaosal site. Co. Wicklow JN899

The PRIMER Q programme (Clarke & Warwick, 2001) was used to cany out multivariate

analyses on the station-by-station faunal data. All species/abundance data were fourth root

transformed and used to prepare a Bray-Curtis similarity matrix in PRIMER@. The fourth root

transformation was used, in order to down-weigh the importance of the highly abundant species and

allows the mid-range and rarer species to play a part in the similarity calculation. The similarity

matrix was then used in classificatiodcluster analysis. The aim of this analysis was to find "natural

groupings' of samples, i.e. samples within a group that are more s&il& to each other, than they are

similar to samples in different groups (Clarke & Warwick, Zoc. cit.). The PRIMER @ programme

CLUSTER carried out this analysis by successively fusing the samples into groups and the groups

into larger clusters, beginning with the highest mutual similarities then gradually reducing the

similarity level at which groups are formed. The result is represented graphically in a dendrogram,

the x-axis representing the full set of samples and the y-axis representing similarity levels at which

two samples/groups are said to have fused.

The Bray-Curtis similarity matrix was also subjected to a non-metric multi-dimensional

scaling (MDS) algorithm (Kruskal& Wish, 1978), using the PRTMER @ program MDS. This

programme produces an ordination, which is a map of the samples in two- or three-dimensions,

whereby the placement of samples reflects the similarity of their biological communities rather than

their simple geographical location (Clarke & Warwick, 2001). With regard to stress values, they

give an indication of how well the multi-dimensional similarity matrix is represented by the two-

dimensional plot. They are calculated by comparing the interpoint distances in the similarity matrix

with the corresponding interpoint distances on the 2-d plot. Perfect or near perfect matches are rare

in field data, especially in the absence of a single overriding forcing factor such as an organic

enrichment gradient. Stress values increase not only with the reducing dimensionality (lack of clear

forcing structure), but also with increasing quantity of data (it is a sum of the squares type regression

coefficient). Clarke and Warwick (Zoc. cit.) have provided a classification of the reliability of M D S plots based on stress values, having compiled simulation studies of stress value behaviour and

archived empirical data. This classification generally holds well for 2-d ordinations of the type used

in this study. Their classification is given on the following page:

0 Stress value < 0.05: Excellent representation of the data with no prospgct of

misinterpretation. - 4

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8 Stress value < 0.10: Good representation, no real prospect of misinterpretation of

overall structure, but very fine detail may be misleading in compact subgroups.

Stress value C0.20: This provides a useful 2-d picture, but detail may be

misinterpreted particularly nearing 0.20.

Stress value 0.20 to 0.30: This should be viewed withscepticism, particularly in

the upper part of the range, and discarded for a small to moderate number of

points such as < 50.

Stress values > 0.30: The data points are close to being randomly distributed in

the 2-d ordination and not representative of the underlying similarity matrix.

.

8

8

. - 8

Each stress value must be interpreted both in terms of its absolute value and the number of

data points. In the case of this study, the moderate number of data points indicates that the stress

value can be interpreted more or less directly. While the above classification is arbitrary, it does

provide a framework that has proved effective in this type of analysis.

3.2.2 RI%SULTS

3.2.2.1 ORGANIC CARBON

Results for sedimentology and organic carbon analysis are presented in Table 3.2.2.1.

Organic carbon levels were very low throughout with all samples having values of 0.23% or lower. -

GRAVEL 56.1 24.1 323 25.1 ” 36.2 20.7 55 v.COARSESAND 2-1 7.4 9.1 COARSESAND 1 - 0.5 7.8 123

MEDIUMSAND 0.5 - 0.25 18.4 19.5 FINESAND 0.25 - 0.125 9.7 31.2 v. FINE SAND 0.125 - 62p 0.4 2.2 SILT ==62P 0.2 1.6

ORGANIC CARBON CAOV 0.13 0.06

8.4 93

9.5 10.5

14.7 15.9 31.7 35.6

2.1 2.4

1.4 1.3 0.12 0.23

9 4 9.1 10.4 5.3 7.1

15.3 20.1 15.6 26.1 46.5 12.3

1.7 2.1 0.6 1.1 1.4 0.3

0.11 0.04 0.12

Table 3.2.2.1: Sediment granulometry and organic carbon results for the seven subticlal core stations

surveyed north of Arklow, June, 2007.

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A reDort on a uroposed dredge disoosal site. Co. Wicklow JN899

3.2.2.2 SEDIMENT PARTICLE SIUE ANALYSIS

The results show that the core samples may be classified as either gravel or fine sand.

Stations 1,3,5 and 7 were dominated by gravel and stations 2,4 and 6 were dominated by fine sand.

Low levels of very fine sand, silt and organic carbon were observed at all stations (see Table

3.2.2.1). While sieving the samples, large numbers of old oyster shell where present and sometimes

in high numbers. Stations 2 to 6 are somewhat finer than Stations 1 and 7 (see Figure 3.2.2.2 for a

graphic representation of granulometry at the seven sites). Gravelhoarse fractions were found at all

of the stations sampled.

100

90 80

70 60 50

48

30

20 10

0

Silt

P' V. fine sand

Fine sand

Medium sand

Coarse sand

V. coarse sand

Gravel

Figure 3.2.2.2: Graphic representation of the granulometry results of sediments at each of the seven

sampling stations in June 2007 (see Figure 1 for core site locations).

3.2.2.3 BENTHIC FAUNAL hALYSKS

The taxonomic identification of the benthic infauna across all 7 stations sampled in the

survey yielded a total count of 51 species, ascribed to 7 phyla. A complete listing of these species

abundance is provided in Appendix I. Of the 5 1 species enumerated, 2 were anthozoans, there was 1

nemertean, 35 were polychaetes (segmented worms), 1 species was a sipunculid, 4 were crustaceans

(crabs, shrimps, prawns), 3 were molluscs (mussels, cockles, snails etc.) and 5 were echinoderms

(brittlestars, sea cucumbers). i

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UNIVARIATE ANAtYSES

Univariate statistical analyses were carried out on the station-by-statiodsample-by-sample

faunal data. The following parameters were calculated and can be seen in Table 3.2.2.3; species

numbers, number of individuals, richness, evenness and diversity. The numbers of species ranged

from 12 (Station 5) to 24 (Station 2). Number of individuals ranged from 34 (Station 7) to 67

(Station 2). Richness ranged from 2.63 (Station 5) to 5.47 (Station 2). Evenness ranged from 0.78

(Station 4) to 0.90 (Station 2). Diversity ranged from 2.88 (Station 4) to 4.13 (Station 2). The values

of the diversity indices and associated evenness indicate that the fahaa t the sites are well balanced

and there is not an over-dominance of one species over the others.

Table 3.2.2.3: Diversity indices €or the seven sampling stations sampled in June 2007.

MULTIVARIATE ANALYSES

The dendrogram and the M D S plot can be seen in Figures 3.2.2.1 and 3.2.2.2 respectively.

The faunal data for each of the 5 replicates at each of the seven sites were combined into one data set

and this .was used to generate a dendrogram and MDS.

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A reoort on a oromed dredge disoosal site. Co. Wicklow JN899

201 40

JN899 ARKLOW DUMPSITE GROUPED

I

Figure 3.2.2.1. Dendrogram showing the spatial relationship between the f a d data at the seven

stations sampled to the northeast of Arklow, June 2007.

The dendrogram shows that two sites to the east of the proposed disposal site are more like

one another than the 5 either within the disposal box or south of it. Within the proposed site, Stations

2 and 3 h e at a level of just over 60% similarity while Stations 4,5 and 6 separate fiom this latter

pair at a level of ca. 50% similarity. Stations 4 and 5 are most similar separating at a level of ca 70%

similarity.

ST. 3

Stress: D.01

ST. 7

ST. 2

ST. 1 ST. 6

Figure 3.2.2.2. M D S plot showing the spatial relationship between the faunal data at the'seven

stations sampled to the northeast of Arklow, June 2007.

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The MDS plot (Figure 3.2.2.2) had a stress level of 0.01, this represents an excellent

representation of the data with no prospect of misinterpretation. Stations1 and 7 lie on the right hand

side of the plot while all stations within the disposal site group to the left with Stations 4 and 5 being

most closely aligned.

3.2.3 DISCUSSION . *

The selection of reference sites can be problematic as the issue of similarity between the

areas being compared has to be taken into consideration. For this reason the two sites to the north

and to the south of the disposal area are termed “potential reference sites” in the introduction to this

section. No predictive model of the disposal site was available for examination to help select

potential reference sites. Water depth within the disposal site and to the north and south is all less

than 20 meters while to the east of the disposal site depth is greater than 20 meter; for this reason,

locating reference site to the east of the disposal site was not considered. As the Irish Sea in this area

is known to be quite turbid, the reference sites were located at distances that were considered to be

suf€iciently far from the proposed site to ensure that the heavier sediments would have settled out

and that only the finer sediments would still be in suspension.

The numbers of species and individuals returned were relatively poor and this is attributed to

the strong hydrodynamic regime that operates in the site causing organic-rich material to be exported

from the site and also giving rise to constant reworking of the sediment. Examination of the faunal data shows that only a small number (8 out of 5 1 taxa) were suspension feeders ; 21 species were

deposit feeders and the remainder being carnivores or microdetritivores. Organic material is the

basic food resource of many epi- and infaunal marine invertebrate taxa and if this resource is only

present in low percentages, there simply is not sufficient food to support a diverse and density-rich

benthic assemblage. This factor added to the fact that sediment is being continuously reworked gives

rise to low numbers of taxa and low individual species numbers. None of the taxa recorded are

considered as being rare or unusual and the habitat type is not listed in the EU Habitats Directive.

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A report on a uromsed dredge disuosal site, Co. Wicklow JN899

4.0 POTENTIAL IMPACTS

Biological succession

Dredging and the disposal of spoil, by their very nature, affect the environment. Man-made

changes of this type are an interference with, and will have an effect on, the balance of nature (Bray

et al. 1997). Spoil disposal temporarily increases turbidity, influences . - .bottom-feeding communities at

and near the disposal site, and may affect the behaviour and physiology of fish and other marine

organisms. Toxic pollutants may be redistributed resulting in their increased availability to aquatic

life. One of the most obvious effects of spoil disposal is an increase in organic matter loadiig. This is

one of the most documented forms of disturbance to cause changes in redox chemistry, leading to

eutrophication and hypoxia (e.g. Rosenberg, 1976,1977; Rosenberg & Loo, 1988; Rosenberg et al. , 1992; Dim & Rosenberg, 1995). The excessive accumulation of dissolved and/or particulate organic

matter causes a parallel rise in the rate of oxygenic decomposition and mineralisation (i.e. biological

and chemical oxygen demand) that comprises the assimilative capacity of the system (Omori et al. , 1994). Under these conditions, benthic pore water oxygen is one of the first electron acceptors to

become exhausted (then NO3, M n 0 2 , FeOOH, SO4 and C02; Aller, 1982). This results in the

lowering of biologically available oxygen and, in turn, a reduction in the turnover rate of organic

decomposition (Delaune et al., 198 1 ; Fisher, 1982). Where the consumption of electron acceptors is

sufficient, the RPD‘ (Redox Potential Discontinuity; transition zone separathg a lower layer of

anaerobic sediment from an upper layer of surficial aerobic sediment) becomes shallower and in

cases of high impact the RPD can reach the sediment surface. With this, the resident aerobic

macrofauna are forced upwards in search of areas of higher oxygen levels (e.g. Rosenberg et al.,

1991; Nilsson, 1998) and to avoid the underlying toxic effect of reduced- compounds including

dissolved species of sulphide and precipitated metals (Theede et al., 1969; Fenchel & Reid, 1970). If these geochemical conditions persist beyond the physiological tolerance time of the resident infauna,

high mortality ensues and the community switches to one dominated by a limited number of species

(e.g. Bagge, 1969; Weston, 1990; Forbes et al., 1994). To accompany this progressive deterioration

of the sedimentary habitat the benthic faunal character (i.e. abundance, biomass, size, number of

species and trophic status) changes.

The faunal response may be characterised as a decrease in the density of the ips' 1

opportunistic families and a major increase in the density of families with the most opportunistic

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h lifestyle (Harvey et al., 1998). Both direct burial by dredge spoil discharged in large quantities within

a short time interval and an enhanced food supply are the two factors that may explain the changes in

density in various families. Pearson & Rosenberg (1 976) summarised these changes. They

highlighted that irrespective of boreal geographical location, benthic organic enrichment caused a

predictable and sequential change in the characteristics of the resident macrofauna and associated

sedimentary regime. Rhoads et al. (1 978) extended this to include changes in faunal composition

over time following a physical disturbance. In either case, the degree of disturbance encountered

along a perturbation gradient has been shown to differentially influence the biological structure of the

sediment (Gray et al., 1990). Most benthic habitats codorm to this successional paradigm and

therefore it has resulted in a formal, albeit qualitative, conceptual model (Fig 4.1) o f benthic

macrofaunal succession applicable to natural, physical and anthropogenic perturbations in space or

time (Pearson & Rosenberg, 1978). The effects of natural and anthropogenic disturbance on marine

ecosystems have been well documented in the scientific literature.

R

1 1 ’ . *

i

According to the Pearson-Rosenberg model, sediments threatened by ‘gross pollution’ (i.e.

‘GP’, Figure 1.1) are characterised by high levels of labile organic matter, an absent or shallow RPD, a high microbial oxygen demand (Yamamoto & Lopez, 1985; Berman et al., 1994), and a milieu o f

reduced toxicants. Ifthese conditions persist over time, total defamation of the sediment occurs, and

the surface layers may become laminated through the lack o f infaunal mixing and the accumulation

of bacterial mats and decomposing ‘floc’ (Rumohr, 199Ob; Tyson & Pearson, 1991; Rosenberg &

Dim, 1993; Rumohr et al., 1996). At some distance in space or time, a transition takes place fiom

being ‘grossly polluted‘ to being ‘polluted’ (i.e. ‘P’, Figure 4.1). By this stage, the sediment content

of labile organic matter has declined and the formerly anoxic or hypoxic sediment has being replaced

by oxic conditions in the uppermost layers of the profile. This allows small ‘opportunistic’ species

r F I

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1 (e.g. polychaetes Capitella spp. and PoZydoru spp.) that have a physiological requirement for

sediment containing high levels of organic matter to colonise the surface layer (Gray, 1981; Forbes &

Lopez, 1990; Tsutsumi et al., 1990; Forbes et. al., 1994). These species have the ability to respond

rapidly to environmental perturbation by switching fiom a planktonic mode of reproduction to

benthic lecithotrophy when low oxygen and high sulphide levels are encountered (Gray, 1980;

Forbes et al., 1994). Few organisms follow this life style strategy so there is a tendency for a limited

number of species to reach extremely high densities in the presence o f pollutants. The bioturbatory

activities of these infauna start to significantly modi@ the physical, chemical and biological nature of the deposit (see, inter alia, Gray, 1974,1979; Rhoads, 1974; Rhoads et al., 1977; A1

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Rhoads & Boyer, 1982; Krantzberg, 1985; Snelgrove & Butman, 1994). These bioturbatory activities

form holes, tubes and burrows in the sediment and the biologically mediated circulation and

incorporation of oxygenated water into the sediment stimulate aerobic microbial decomposition of

organic material and increase the depth of oxygen penetration into the sediment (Lyons et al., 1979;

Yingst & Rhoads, 1980). The macrofaunal assemblage enters a ‘transitory’ phase of succession (i.e.

‘T’, Figure 4.1) when the sedimentary changes allow further colonization of a larger variety of

species. This stage is unfavorable for the ‘pioneer’ population to persist. Species that characterise the

transitory sere (e.g. Mirza & Gray, 198 1) include suspension and deposit feeding bivalves (e.g.

riyusiru spp., CorbuZa spp.), ‘conveyor belt’ polychaetes (e.g. ScoZopZos spp., Amphictene spp.,

CZymeneZZa spp.), and relatively immobile holothurians (e.g. Leptosynaptu spp., Leptopentuctu spp.,

riyone spp.). Here again the physical and chemical properties of the sediment are further modified

by the new infaunal dominants making way for additional species to take hold. A more complicated

and persistent faunal assemblage now forms and evolves towards an ‘equilibrium’ or ‘climax’

community status (= ‘normal’; ‘N7, Figure 4.1). Sediments at the ‘equilibrium’ stage are

characterised by ‘‘burrow complexes of large species such as Nephrops nowegicus, Brissopsis Zyveru

and ScuZibregmu inflaturn intermingled with smaller tube dwelling and burrowing species” that

together depress and maintain the RPD at depths in excess of lOcm (Pearson & Rosenberg, 1978).

The taxa inhabiting this sere are characterised by large body size, long life spans, a large assimilative

capacity and a wider range of functional types than exhibited by taxa in the earlier successional

series.

Fig 4 1 : Diagrammatic representation of the predictable and sequential changes in makrofaunal

structure and sedimentary characteristics that accompany a change in the level of organic enrichment

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or that follow a natural or anthropogenic perturbation event. Oxidised sediment (OS) is separated

from the reduced sediment (RS) by the redox potential discontinuity (RPD). Spatial and temporal

phases; GP, grossly polluted; P, polluted; T, transitory; N, normal. Modified fkom Pearson and

Rosenberg (1 976,1978).

Effects of Dredging & Dumping

Marine soft bottom macrobenthic communities occupy one of the most extensive open water

habitats in coastal ecosystems (Thorson, 1957; Peres, 1982). Within these communities, analysis of

differences in benthic community structure is one of the mainstays of detecting and monitoring the

biological effects of marine pollution and habitat disturbance (Warwick & Clarke, 1993).

Macrobenthic organisms are very often used as biological foci in these analyses, as the majority have

limited powers of locomotion, thereby acting as natural biological indicators of environmental stress.

The relationship of marine macrobenthic community structure to environmental disturbance is

complicated because these communities are often patchy in distribution and variable in time

(Carriker, 1967; Pearson & Rosenberg, 1978).

Many species have adapted strategies to survive the fkequent natural disturbances, which they

are subjected to, i.e. storms, currents (Rhoads, 1974). The sudden deposition of significant quantities

of spoil material on the shallow seafloor buries and often kills the benthic fauna. The impact of water

column turbidityhelease of toxins caused by disposal of spoil material is for the most part

insignificant (Saucier et al., 1978); however it may affect benthic processes by reducing light

intensity and increasing sedimentation rates (Toumazis, 1995). Survival and subsequent repopulation

primarily depends on depth of burial, properties of the deposited materid and natural sediment and

functional groupings of indigenous faunas (Young & Richardson, 1998).

Laboratory and field studies have shown that mobile deposit feeders can often survive burial

of up to 5Ocm of spoil material and reach the new sediment surface in a few hours to days (Nichols

et al., 1978; Mauer et al., 1978). Less mobile surface deposit feeders and suspension feeders,

especially sessile forms have very limited abilities to migrate to the sediment-water interface

resulting from such a depositional event. Harvey et al., (1 998) reported a faunal response as being

characterised by a decrease in the density of the less opportunistic families and a majbr increase in

the densities of families with the most opportunistic lifestyle. Both direct burial by spoil material, in

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A report on a Drowsed dredge disposal site.'&. Wicklow JN899

large quantities over a short time interval and an enhanced food supply were said to be the two

factors which might explain the changes in densities in the various families. Survival rates are

greatest when the spoil material is similar in nature to the natural sediment, i.e. sand on sand, mud on

mud (Kranz, 1974; Saucier et al., 1978).

Repopulation of defaunated sites occurs by larval recruitment and by adult migration from

adjacent undisturbed benthic communities (Santos & Simon, 1980). The spatial and temporal scales

of successional change resulting fiom waste deposition have been measured for shallow water

marine benthos (Rosenberg, 1976; Pearson & Rosenberg, 1978, Rhoads et al, 1978; Arntz &

Rumohr, 1982). Benthic recolonisation of dredge spoil sites may be as rapid as 3 months for fine-

grained sediments but may require up to 3 years for coarse-grained sediments (Saucier et al., 1978).

Harvey et al. (1 998) reported a recovery time of more than 2 years for a disturbed area to re-establish

a sediment composition and a macrobenthic community structure similar to undisturbed background

levels. A new deposit is subjected to biogenic reworking, i.e. bioturbation, and is thereby changed in

. *

terms of its physical properties and attendant dominant geochemistry processes (Rhoads, 1974). The

first species to repopulate disturbed sites are pioneering species, often short lived, tube dwelling

polychaetes and amphipods, which tend to stabilize the sediment sufface (Rhoads & Young, 1970).

Over time longer lived, deeper dwelling deposit feeders and carnivores repopulate the deposit,

species diversity increases and an equilibrium assemblage is established (Rhoads & Gennano, 1982).

This site has been used in the past as a dredge spoil disposal site. The last time it was used

was ca. 1 1 years ago. From the findings of this survey, there are no signs of this previous disposal

event.

In conclusion, the disposal of ca 100,000 m3 of material at the disposal site will result in the

smothering and destruction of the existing biological community present. The local oceanographic

conditions at the site will cause the deposited material to be redistributed over the area and this will

also cause the disposed sediment to be fully oxidised. Recolonisation of this sediment will therefore

be fast and may even allow later stage colonisers to establish themselves without requiring the usual

pioneering stages.

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A reDort on a Droposed dredge disposal site. Co. Wicklow JN899

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