104562723 Diatoms as Indicators of Water Pollution in Rivers

7/30/2019 104562723 Diatoms as Indicators of Water Pollution in Rivers

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DIATOMS AS INDICATORS OF WATER

POLLUTION IN RIVERS

Contents:

Abstract.2

Introduction...3

Aims..6

Methods.7

Sites description.7

Map of sites...9

Field sampling..10

Digestion..10

Preparation of permanent slides...11

TDI calculation.12

Biodiversity calculation13

Statistics description.13

Results..14

Testing for normality17

Testing for correlation..18

Testing for significant differences24

Independent Pooled T-test25

Discussion.26

Reference..29Appendix...30

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Abstract:

Benthic diatoms are used for assessment of eutrophication of water systems, but their

relationship to water quality is not always definite. This study assessed the correlation

of TDI to some physico-chemical factors of rivers.

Diatoms were sampled from eight sites of four different water qualities assigned by

the EPA, based on the Q-scheme value. Each site was tested for Dissolved Oxygen

(mg/L), Temperature (C), Conductivity (S/cm) and pH. TDI for each site was

calculated and assessed for correlation to these physico-chemical factors and to

calculated biodiversity (Shannon Wiener index) of each site. No relationship of TDI

to any of the above was found.

More samples would have to be obtained from the sites over longer period in order to

be able to assign representative TDI values. It is also highly recommended to assess

other communities (macrophytes, invertebrates, grazers pressure) and physical

factors (type of sediment, light intensity, flow, etc.) and take holistic approach of the

assessment.

Keywords:

Diatoms, TDI, Trophic Diatom Index, Physico-chemical factors,

River Eutrophication.

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Introduction:

Diatoms or Bacillariophyceae are Class of Division Heterokontrophyta (brown

algae). They are unicellular representatives of brown algae which can form colonies,

but are mainly attached to substrate by stalks or glide on mud with aid of mucilage

they produce. Their presence can be seen as thin biofilm layer present on surfaces of

stones, macrophytes or other macroalgae.

They are cosmopolitan species inhabiting freshwater or marine environment

and can occur in terrestrial habitat also. Around 12,000 species is known of more than

250 genera, but there may be over 100,000 species in total. In freshwaters, around 80

genera of diatoms are known. In oceans, diatoms form major part of photosynthetic

phytoplankton and it is estimated that themselves, they contribute about 25 35 % of

the worlds productivity in terms of carbon fixation (Kelly, 2005).

Diatom body consists of protoplasma enclosed in a cell wall (frustule) made of

silica. This consists of two overlapping, interlocking halves epitheca and hypotheca,

joined together by girdle bands. Girdle holds the two valves together by cementing

organic substance (Kumar & Singh, 1979). Identification of diatoms relies almost

exclusively on frustules visible in light microscope.

Figure 1: Exploded pennate diatom:(Kelly,200)

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Valves are usually identical for one species. They vary between species in shape and

symmetry, as well as in the type of arrangement of pores, slits and other features of

the silica wall. These differences formed the basis of diatom identification (Kelly,

2005).

Diatoms are divided into two major groups depending on the shape of the cell.

Centric diatoms are circular and pennate diatoms are elongated in valve view.

Some diatoms have a raphe paired longitudinal slit system associated with

motility. Raphe secretes mucilage which aids in locomotion or can be used for

attachment of diatoms. Mucilage can be also secreted by rimoportula, a tube-like slit

found in most centric diatoms and some pennales.

Diatoms can be prostrate Cocconeis sp. lying on substrate

stalked -Achnanthidium sp. attached on stalk

arborescent Gomphonema sp. on branched stalks

These different growth forms lead to different assemblages depending upon

the type of substrate (e.g. stable rock is preferred by Achnanthidium sp. and

Gomphonema sp. and fine sediments are favoured by motile species ( Nitzschia sp.)).

Silica wall of diatoms is relatively insoluble, their remains can accumulate and

preserve in sediments of rivers and lakes. These fossil records in conjunction with

knowledge of diatoms ecological specificity have been used to infer lake or ocean

histories, in particular pH changes and nutrient status as well as climate change

(Kelly, 2005).

Scientists have noticed that certain diatom species thrive in certain environmentalconditions and reflect influence of physical and chemical factor of site. These

observations have been developed into indices used for routine water quality

monitoring. TDI (Trophic Diatom Index) was designed to monitor eutrophication in

rivers (Kelly, 2000).

Diatoms are being used in most EU Member States as cost-effective proxies for

phytobenthos one of the biological elements required by Water Framework

Directive from Member States to be included in ecological status assessment. Rapid

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To calculate TDI values of the sites to estimate the level of eutrophication.

To compare calculated TDI values to Q-scheme status of those sites

designated by EPA.

To assess difference between sites of poor/moderate status and good/excellentstatus.

To assess relationship between TDI and physico-chemical factors of the sites.

To estimate biodiversity of diatom populations in each site.

Methods:

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Diatom samples were obtained from following sites on following dates shown in

Figure 2:

Terryland 27

th

January 2010 Lough Kip River 27th January 2010

Grange - 10th February 2010

Abbert - 10th February 2010

Black - 12th March 2010

Ballycuirke 12th March 2010

Owenriff - 18th March 2010

Loughinch River - 18th March 2010

Sites description:

Terryland - Originates in Castlegar - Galway

Grid reference: M 31306 27263

EPA status: Poor (Q 2-3)

Water is derived mainly from calcareous material. Slower river, where sedimentation

can occur.

Its main part is in Galway city.

Lough Kip River - west of Lough Corrib, Co. Galway


EPA status: Good (Q 4) 2006, 2009 survey

High status (Q 4-5) from 1997 - 2003 surveysRiver flows from Lough Kip to Ballycuirke over acidic soil; relatively fast flowing

without sedimentation.

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Grange east of Lough Corrib, co. Galway


EPA status: Good (Q 4) - year 2000 onwards

Moderate (Q 3-4) measurement in 1997

Poor (Q 3) 1994

River is on calcareous, medium to high base soil. Farming is frequent in area.

Abbert east of Lough Corrib, co. Galway


EPA status: Good (Q4) from 2006 onwards

River flows over calcareous soil region; area highly farmed.

Black - east of Lough Corrib, co. Galway


EPA status: Moderate (Q3-4) 2003

Good (Q 4) 2000

Moderate (Q 3-4) 1989

River flows over calcareous stone and surrounding land is used for farming.

Ballycuirke sample was taken from river flowing from this lake, it is on west side of

Lough Corrib, co. Galway


EPA status: Mesotrophic Lake

Owenriff river on west side of Lough Corrib, co. Galway


EPA status: Good (Q 4) - 2006 and 2009 assessments

High status (Q 4-5) 2003, 2000

Moderate (Q 3-4) - 1997

River flowing from Glengowla area in Connemara through Oughterard, where the

sample was taken. River is fast flowing without much sedimentation. Quite large

number of freshwater mussels was noted at the site, implying good water quality.

Loughinch River west of Galway city

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EPA status: moderate (Q 3-4)

River flowing from Lough Inch over acidic soils into the sea near Furbogh town.

This water body was quite stagnant with plenty of sediment present.

Figure 2: Site map

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Field sampling:

Two samples were obtained from River Owenriff and Loughinch River. Other

samples were taken by other students as part of their fieldwork.

Five cobbles from across each river of about the same size were picked. Each was

gently swirled in the river to remove any macroinvertebrates and placed into white

tray with little of the river water and its top side was brushed with toothbrush until the

water was dark brown. Stone was returned to the river so as it was not picked again

for the sampling. This was repeated with other four cobbles. Water from the white

tray containing diatom samples was poured into plastic jar labelled accordingly.

Toothbrush was rinsed and cleaned against Wellingtons boots.

Physico chemical data were obtained. Dissolved oxygen using probe ORION

Model 810, pH was measured by Metter Toledo MP120 pH Meter together with

conductivity and temperature. On the return to lab, samples were preserved with few

drops of Lugols Iodine and stored in dark until needed.

Digestion:

Large pieces of material were removed from samples, jars shaken and

approximately 15 ml of the material were transferred into 30 ml centrifuge tube.

Calcareous material wasnt expected, but after previous experience, few drops of HCl

were added. Distilled water was added to bring the volume to 25ml. These were then

centrifuged until the material settled at the bottom of centrifuge tubes.

Supernatant was discarded into waste jar in fume hood and centrifuge tubes placed

into a rack submerged in cold water.

Concentrated sulphuric acid (5 ml) was added to each tube, then 2ml of saturated

solution of potassium permanganate were added and tubes were shaken gently to mix

the sample with chemicals.

Oxalic acid (10 ml) was added slowly to each sample, which caused effervescence. If

the mixture didnt become clear, 5 more ml were added.

After 10 minutes, all reactions in samples stopped and cooled down. Distilled

water was added to the neck of tubes and samples were centrifuged until they settled.

Supernatant was discarded into waste jar and material transferred into smaller test

tubes with distilled water. These were centrifuged until material settled and

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supernatant was discarded to waste jar. This was repeated until the sample reached

neutral pH.

As soon as the sample reached neutral pH, sample was transferred into clean, fully

labelled vial and stored.

Preparation of permanent slides - mounting:

Distilled water was added to the samples which were too concentrated until

slightly cloudy solutions were obtained.

Samples were shaken to obtain homogenous solution and few drops of one sample

were placed onto a glass cover slip with clean pipette. Cover slip was dried on low

heat on a hot plate.

A glass slide was labelled and placed onto heated hot plate placed in fume hood. One

drop of Naphrax was placed on the glass slide and cover slip placed onto it with the

side containing diatom film down. The slide was left on the hot plate until the

Naphrax stopped producing bubbles; cover slip was gently pressed onto slide, so as all

the left bubbles were pressed away and slide was taken off the hot plate and left in

fume hood to cool down.

Slide was then checked for the right diatom density under microscope.

This procedure was repeated for all samples.

Slides were examined and diatoms identified using identification key: Kelly, Martyn.

Identification of common benthic diatoms in rivers. 2000 AIDGAP, and Kelly M.G.,

Bennion H., Cox. E. J., Goldsmith B., Jamieson J., Juggins S., Mann D.G. + Telford

R.J. (2005). Common freshwater diatoms of Britain and Ireland: an interactive key.

Environment Agency, Bristol.

Slides were examined from right to left side with slide label being placed on the right

side. If the slide reached its end and 300 frustules count was not reached, slide moved

down one field view and counting continued from left to right.

TDI calculation:

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TDI index is based on the weighted average equation (Zelinka and Marvan 1961 cited

in Kelly, 2000):

where: aj = abundance (proportion) of valves of species

j in sample

sj = pollution sensitivity (optimum) of species

j in sample (values 1 5)

vj = indicator value (tolerance) of species j in

sample

Sensitivity scores: 1 = diatoms which favour very low nutrient concentrations

(sj) 2 = diatoms which favour low nutrient concentrations

3 = diatoms which favour intermediate nutrient concentrations

4 = diatoms which favour high concentrations of nutrients

5 = diatoms which favour very high nutrient concentrations

A few taxa have sensitivity values of zero. These include taxa relatively rare in

freshwaters and whose ecological preferences are not well defined (Lucid Diatom

Key).

This index calculates WMS (Weighed Mean Sensitivity) value, which is further used

in equation TDI = (WMS x 25) - 25 to calculate TDI.

TDI values range from 0- 100, with higher values indicating higher levels of nutrients

in the water system.

Biodiversity calculation:

12

=

== n

j

jj

n

j

jjj

va

vsa

index

1

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For estimation of biodiversity, Shannon Wiener index was used. Its formula is as

follows:

where: s = number of species

pi = relative abundance of species the

i-th species (calculated ni/N)

ni = no. of individuals of the i-th species

N = total number of individuals in the community

Statistical calculations:

All data were tested for normality, using Ryan-Joiner test for normality. If some data

were found not to be normal, they were log10-transformed and then worked on those.

Physico-chemical data, number of frustules and biodiversity data were tested for

correlation to TDI values using Correlation test in Minitab.

Poor and moderate status rivers data were joined and the same was done with good

and excellent rivers. These two groups were separately tested for normality with

Ryan-Joiner normality test. In order to test these two groups for significant difference

between them, they had to have proven equal variances and the independent pooled T-

test was then used.

Results:

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i

s

i

i ppH log1

'

=

=


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Within the eight sites 93 taxa were recorded belonging to 37 genera. The

composition of species in each site was different from site to site, even though there

were species found to be common and abundant for some sites. The most abundant

species for each site and their percentages are noted in Table 1 below.

Table 1: Four most abundant species from each river and percentage in which they

appear in that river with TDI of each site.

River Site SpeciesPercentage(%) TDI value

Abbert

Amphora pediculus 35.5

85.6Navicula lanceolata 17.9

Amphora lybica 10.2

Cocconeis placentula 7.7

Ballycurike

Nitzschia dissipata 32.2

66.6Encyonema silesiacum 18.8Achnanthidium minutissimum 13.4

Fragilaria capucina 6.1

Black

Navicula lanceolata 30.7

86.5

Achnanthidium minutissimum 10.4

Gomphonema parvulum 9.3

Navicula molestiformis 9.3

Gomphonema olivaceum 9.1

Grange

Amphora pediculus 42.5

88.4Navicula lanceolata 15.8

Nitzschia dissipata 10.2


Lough KipRiver


51.6Nitzschia dissipata 12.1

Achnanthes oblongella 8.8


Owenriff

Fragilaria capucina 36.6

49.6Gomphonema parvulum 11.6

Cymbella sp. 9.2


LoughinchRiver


41.5Sellaphora bacillum 10.6

Navicula oblonga 7.6

Rossithidium linearis 5.6

Terryland

Achnanthidium minutissimum 30

67.4Rhoicosphenia abbreviata 17.8

Gomphonema olivaceum 13.8

Navicula minima 7.4

Achnanthidium sp. was found on six sites and was also found in large proportions. In

Lough Kip River, it formed 27.1% of diatom community and in Loughinch River site,

it was found to take 47.5% of the community. Navicula sp. was found on five sites,

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being the most abundant in river Black with 30.7% (N. lanceolata) and 9.3%

(N.molestiformis). Cocconeis sp., Nitzschia sp and Gomphonema sp. were all found

on three sites all in relatively low numbers. Fragilaria sp. and Amphora sp. were

found on two sites only with Fragillaria sp. being the most abundant in river

Owenriff (36.6 %).Amphora sp. was the most abundant in River Grange (42.5 % of

species) and in River Abbert, two Amphora sp. were found - A. pediculus (35.5 %)

andA. lybica (10.2 %).

Table 2: Data collected for TDI analysis.

River SiteConducti

vity

(s/cm)

DO(mg O2

dm-3

)

pH TDIEPA

StatusNo.spp.

No. frustulesH'Identifi

ed

Non

- IDBallycuirke 194.0 9.60 7.73 66.6 poor 21 314 0 2.2

Terryland 653.0 6.35 7.07 67.4 poor 30 484 64 2.3

Abbert 648.0 11.50 7.75 85.6 moderate 19 352 45 2.1

Loughinch River 157.0 8.87 7.68 41.5 moderate 31 301 30 2.2

Grange 122.7 12.42 8.02 88.4 good 27 266 26 2.1

Lough Kip 148.6 11.40 6.83 51.6 good 31 306 73 2.7

Black 121.2 10.42 7.76 86.5 excellent 17 450 15 2.3

Owenriff 109.3 9.98 6.30 49.6 excellent 22 404 39 2.2

Conductivity (S/cm) had two outlier values in rivers Terryland and Abbert.

Conductivity is a measure of dissolved salts or dissolved ions in solution. It is

controlled by geology, watershed size and other sources of ions (e.g. pollution).

Therefore higher conductivity values ( > 500 S/cm) can indicate hard water, whilst

low conductivity values ( < 100 S/cm) can indicate soft water rivers.

DO (mg O2/dm3) was highest in rivers Grange, Abbert and Lough Kip.

The pH values were smallest at Owenriff (6.3) and Lough Kip River ( 6.83).

TDI values are mixed for different EPA status values, which were based on Q-scheme

system. Rivers described as excellent based on Q-scheme were found to have both

low and high TDI values. Same pattern can be seen in other sites of good and

moderate status. One site from each pair has much lower TDI value than the other site

of same Q-system status. Rivers Ballycuirke and Terryland are classified as poor

water quality sites and their TDI values are very close to each other of TDI 66.6 and

67.4 respectively.

TDI values around 60 are classified as moderately eutrophic and values around 80 are

fairly eutrophic (N Chathin 2008).

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Biodiversity indices of diatoms in each site were found to be quite high, 2.1 to 2.7

with the lowest value being of rivers Grange (2.1) and Abbert (2.1) and the highest of

Lough Kip River (2.7).

Figure 3: Graphical representation of collected data on different sites.

Physico-chemical factors and TDI of rive

0

100

200

300

400

500

600

700

Ballyqurike

Terryland

Abbert

Spiddal

Grange

Loughkip

Black

Owenriff

River site

Value

Conductivity (s/cm) DO (mg O2 dm-3) pH TDI No. spp.

Apart from two conductivity measurements outliers, it seems that when conductivity

is lower (sites Grange and Black), TDI values are higher and in raised conductivity

values (sites Loughinch River and Lough Kip River) the TDI is lower. These factorsdont appear to be in correlation with any other physico-chemical properties or

biodiversity.

All samples were tested for normality by performing Ryan-Joiner test for normality.

Conductivity data were found to be not normal, therefore had to be log- transformed.

All other data were found to be normal.

Testing for normality

H0: Data do not deviate from straight line (Data are normal).

HA: Data do deviate from straight line (Data are not normal).

Accept H0 if RJcrit< RJcalc. or if p-value >/=0.05 (p=0.05, n-2df); n=8

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Conductivity

RJ calc. = 0.819 p-value < 0.010

RJ crit. = 0.8804

RJ crit. > RJ calc. also p value < 0.05

Accept HA - Data are not normal.

Log-transformed conductivity

RJ calc. = 0.881 p-value = 0.028

RJ crit. = 0.8804

RJ crit. < RJ calc, also p value > 0.05

Accept H0- Log-transformed conductivity data are normal.

DO

RJ calc. = 0.965 p-value > 1.000

RJ crit. = 0.8804


Accept H0- DO data are normal.

pH

RJ calc. = 0.928 p-value > 1.000

RJ crit. = 0.8804


Accept H0- pH data are normal.

TDI

RJ calc. = 0.958 p-value > 1.000

RJ crit. = 0.8804


Accept H0- TDI data are normal.

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No. of Frustules

RJ calc. = 0.965 p-value > 1.000

RJ crit. = 0.8804


Accept H0- frustule count data are normal.

In calculation of biodiversity normality p-value was calculated 0.045 therefore less

than probability of 0.05, but after calculating critical RJ and calculated RJ it was

decided the data are normal also.

Correlation of separate physico-chemical data to TDI was tested both by generating

plots and by hypothesis testing.

Biodiversity

RJcalc. = 0.900

RJcrit. = 0.8804

RJcrit. < RJcalc. p - value > 0.045

Accept H0- Biodiversity data are normal.

Testing for correlation:

H0: There is no association between TDI and conductivity.

HA: There is association between TDI and conductivity.

rcritical at p=0.05; n-2 df

Decision: Accept H0 if rcalculated < rcritical also if p value > or = 0.05

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2.92.82.72.62.52.42.32.22.12.0

90

80

70

60

50

40

Figure 4: Exploration of correlation of TDI to conductivity (S/cm).

rcalculated = 0.247

pvalue = 0.556

rcritical = 0.707

n = 8

rcalculated < rcritical

Accept H0 there is no association between TDI and conductivity.

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131211109876

90

80

70

60

50

40

Figure 5: Exploration of correlation of TDI to DO (mg O2/L).

H0: There is no association between TDI and DO.

HA: There is association between TDI and DO.

rcalculated = 0.386

pvalue = 0.344

rcritical = 0.707

n = 8


Accept H0 there is no association between TDI and DO.

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8.07.57.06.5

90

80

70

60

50

40

Figure 6: Exploration of correlation of TDI to pH.

H0: There is no association between TDI and pH.

HA: There is association between TDI and pH.

rcalculated = 0.618

pvalue = 0.102

rcritical = 0.707

n = 8


Accept H0 there is no statistically significant association between TDI and pH.

From the plot, we could say that there is some positive correlation between TDI and

pH, even though it is not statistically significant correlation.

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500450400350300

90

80

70

60

50

40

Figure 7: Exploration of correlation of TDI to number of frustules counted.

H0: There is no association between TDI and No. of frustules counted.

HA: There is association between TDI and No. of frustules counted.

rcalculated = 0.122

pvalue = 0.773

rcritical = 0.707

n = 8


Accept H0 there is no association between TDI and no. of frustules.

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2.72.62.52.42.32.22.1

90

80

70

60

50

40

Figure 8: Exploration of correlation of TDI to diversity (H).

H0: There is no association between TDI and diversity.

HA: There is association between TDI and diversity.

rcalculated = -0.395

pvalue = 0.333

rcritical = 0.707

n = 8


Accept H0 there is no association between TDI and biodiversity.

There was no significant correlation found between any of the physical factors to TDI.

Number of frustules counted was found not to be significantly correlated to TDI

either. There is no statistically significant correlation of TDI to biodiversity.

The strongest relationship was found between TDI and pH. TDI and no. of frustules

had the smallest correlation. All relationships were positive except TDI against

biodiversity, which was quite strong, but negative.

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Test for significant difference between poor/moderate status rivers and good/excellent

status rivers:

Ryan-Joiner test for normality was performed with positive result. In order to assess

significance in difference between the sites, F-test for equal variances was also done

as follows:

Test for equal variances:

H0: There is no difference in group variances.

HA: There is difference in the two group variances.

Fcritical at p=0.05; (n1 - 1 df; n2 1 df)

Decision: Accept H0 if Fcalculated < Fcritical also if p value > or =0.05

Fcalculated = 1.38

pvalue = 0.796

Fcritical = 9.2766

n = 4

Fcalculated < Fcritical

Accept H0 there is no significant difference in variances between poor/moderate and

good/excellent rivers.

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Independent pooled T test:

Performed for two independent, random, small samples which are normal and their

variances are equal.

H0- there's no difference between the two samples of different water qualities.

HA - there's a difference between the two samples of different water qualities.

Accept H0 if t-calc < t-crit. (p = 0.05, n1+n2 -2df)

good/excellpoor/moderate

90

80

70

60

50

40

Figure 9: Boxplot to explore relationship and similarity of poor/moderate and

good/excellent rivers.

Estimate for difference: -3.8

95% CI for difference: (-38.0, 30.5)TValue = -0.27 p-Value = 0.798 DF = 6

CIs span 0 therefore there is no difference between the two sample means. Also p-

value > 0.05 also accept H0.

Therefore the TDI values for poor/moderate rivers are not significantly different from

good/excellent rivers TDI values.

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Discussion

During the diatom identification, ninety-three taxa belonging to thirty-three

genera were found. The most abundant species within all sites was Achnanthidium

minutissimum and the next most abundant were motileNavicula sp.

TDI calculated from sites at given dates were 66.6 for Ballycuirke river, 67.4 for

Terryland both being classified as poor status rivers. For Abbert and Loughinch rivers

both of moderate status, the TDIs were 85.6 and 41.5 respectively. Good status rivers

Grange and Lough Kip River had TDI 88.4 and 52.6 respectively and the excellent

rivers Black and Owenriff had TDIs calculated to be 86.5.and 49.6 respectively. TDI

values greatly vary between sites of the same water quality status based upon the Q-

scheme index.

Dissolved oxygen (mg O2/L) had highest values in rivers Grange, Lough Kip River

both being good status rivers and river Abbert, being classed as moderate water

quality site. Correlation of this factor to TDI wasnt proven in statistical testing.

Conductivity readings were also found not to be correlated to TDI and also included

two outlier data of higher values if compared to the rest (653 S/cm and 648 S/cm in

rivers Terryland and Abbert respectively). Figure 3 in results section suggests some

relationship between TDI and conductivity, e.g. when TDI is low, conductivity values

raise (Loughinch River and Lough Kip River) and the opposite when the TDI values

are higher, conductivity readings are lower (rivers Grange and Black). pH data were

found not to have statistically significant correlation to TDI, but after visual

exploration of the result (Figure 6) it seems that there is some positive relationship.

The pH correlation suggests possible correlation of pH to TDI, but the sample size is

too small to confirm this theory with statistical significance.

The differences in TDIs within the sites of same Q-value could have been

caused by myriads of factors which act upon any river community. These factors are

temperature, amount of light received, nature of substrate, nutrient availability

(nitrates and phosphates), competition for space, natural succession processes, grazing

pressure and hydromorphological regime (Kelly & Bennion, 2009). Assessments of

water quality based on Q-scheme system of TDI should also take these factors into an

account and assess the site as a whole. Q-scheme Index is based on macroinvertebrate

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communities, which may not react to physico-chemical changes as fast as diatoms. Q-

scheme Index is also assessing level of organic pollution of water body, not

eutrophication as TDI does. Taking only one sample for the water quality analysis

cant represent accurately the ecological status of the water system, because diatom

assemblages are dynamic. For example Achnanthidium minutissimum is usually the

dominant species during early succession, but as its resources become limiting in the

biofilm, longer stalked taxa such as Gomphonema acuminatum and loosely attached

and tangled taxa asFragilaria capucina (Kelly & King, 2009). Based on this pattern,

Rivers Lough Kip and Lough Inch river communities are quite new, river Black has

these two species abundant also, together with motile diatom Navicula sp. River

Owenriff has most abundant taxon Fragilaria capucina and Cymbella sp. is also

present, which suggests that this community is older than the previous rivers.

Also higher percentage of motile species indicates that factors other than water

quality, such as sedimentation, may be influencing the diatom assemblages (N

Chathin, 2008). Again many factors are affecting the community structure and

therefore the TDI value.

In statistical analyses, Q-scheme based poor/moderate and good/excellent sites didnt

show significant difference in TDI values because both high and low TDI values

occur in rivers assigned same Q-value; again more samples would be needed to

confirm this result.

There was no correlation of TDI of sampled sites to any of the physico-

chemical factors. Leira and Sabater (2004) study confirms this as follows: Chemical

analyses of water is a good indicator of the chemical quality of the aquatic systems,

but do not integrate ecological factors and dont necessarily reflect the ecological state

of the system.

Although not significant, there was some correlation found of TDI to pH. pH was

used in several analyses of sediment cores of diatom fossils. These were used as

estimation of previous conditions on Earth and ocean acidity. Based upon this, I

would agree with the association of pH to TDI values and diatom community

structure, and would suggest that bigger, more representative samples were taken in

future analyses. Samples should be taken repeatedly at same sites for two to three

years, with three samples spread over a year to obtain consistent data. I would also

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suggest that sampling of nutrients (phosphates and nitrates) are added to the analyses,

as they play an important role in phytoplankton growth and their biodiversity.

A holistic view on the assessment of communities in sites should be developed

rather than focusing on the biological elements separately (Kelly, Haig 2009), because

the stream ecosystem assemblages closely interact within.

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Reference:

Atazadeh I., Sharifi M., Kelly M.G. 2007Evaluation of the Trophic Diatom Index for assessing water

quality in River Gharasou, western Iran. Springer Science + Business Media B.V.

Kelly M., Bennion H., Burgess A., Ellis J., Juggins S., Gurthie R., Jamieason J., Adriaenssens V.,

Yallop M. 2009 Uncertainty in ecological status assessments of lakes and rivers using diatoms.

Springer Science + Business Media B.V.

Kelly M.G., Bennion H., Cox. E. J., Goldsmith B., Jamieson J., Juggins S., Mann D.G. + Telford R.J.

(2005). Common freshwater diatoms of Britain and Ireland: an interactive key. Environment Agency,

Bristol.

Kelly M. G., Haigh A., Colette J. & Zgrundo A. 2009. Effect of environmental improvements on the

diatoms of the River Axe, southern England.

Kelly M., King L., N Chathin B. 2009. The Conceptual Basis of Ecological-Status Assessments using

Diatoms. Biology and Environment: Proceedings of the Royal Irish Academy.

Kelly Martyn;Identification of common benthic diatoms in rivers. 2000, by AIDGAP

Kumar H.D. and Singh H. N.; 1979 A Textbook on Algae. Macmillan Tropical Biology Series;

Macmillan International College Editions.

Leira M., Sabater S. 2004Diatom assemblages distribution in catalan rivers, NE Spain, in relation to

chemical and physiographical factors. Elsevier Ltd.

N Chathin B. and Harrington T. J. 2008 Benthic Diatoms of the River Deel: Diversity and

Community Structure. Royal Irish Academy.

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Appendix:

Examples of diatoms present in sites sampled

Achnanthes oblongella Achnanthidium minutissimum

Amphora lybica Amphora pediculus

Cocconeis placentula Cymbella sp.

Encyonema silesiacum Fragilaria capucina

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http://openwin%28%27kelly_fracaprad_1%27%2C%27800%27%2C%27308%27%2C%27fragilaria%20capucina%27%2C%27../images/Kelly_fracaprad_1.jpg','Phase%20contrast%20var.%20radians.%20%20Goodie%20Water,%20Scotland.','Image:%20M.G.%20Kelly%20Copyright:%20M.G.%20Kelly.');http://openwin%28%27000275b%27%2C%27482%27%2C%27306%27%2C%27encyonema%20silesiacum%27%2C%27../images/000275b.jpg','valve%20view%20brightfield%20','Image:%20M.%20Bayer%20Copyright:%20RBGE.');http://openwin%28%27uk000418%27%2C%27800%27%2C%27401%27%2C%27cymbella%20spp.%27%2C%27../images/uk000418.jpg','valve%20view%20brightfield%20Cymbella%20tumida','Image:%20D.G.%20Mann.');http://openwin%28%27000363b%27%2C%27430%27%2C%27269%27%2C%27cocconeis%20placentula%27%2C%27../images/000363B.jpg','Raphe%20valve%20view%20Brightfield%20','Image:%20M.%20Bayer%20Copyright:%20RBGE.');http://openwin%28%27000104b%27%2C%27346%27%2C%27237%27%2C%27amphora%20libyca%27%2C%27../images/000104b.jpg','valve%20view%20brightfield%20','Image:%20ADIAC%20Copyright:%20RBGE.');


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Gomphonema olivaceum Gomphonema parvulum

Navicula lanceolata Navicula minima

Navicula molestiformis Navicula oblonga

Nitzschia dissipata Rhoicosphenia abbreviata

Rossithidium sp. Sellaphora bacillum

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http://openwin%28%27000125b%27%2C%27584%27%2C%27269%27%2C%27sellaphora%20bacillum%27%2C%27../images/000125b.jpg','','Image:%20ADIAC%20Copyright:%20RBGE.');http://openwin%28%27uk000750%27%2C%27614%27%2C%27444%27%2C%27rossithidium%20spp.%27%2C%27../images/uk000750.jpg','Rapheless%20valve%20view%20brightfield%20R.%20linearis%20/%20pusillum;%20black%20spot%20focus','Image:%20D.G.%20Mann.');http://openwin%28%27uk000634%27%2C%27784%27%2C%27469%27%2C%27rhoicosphenia%20abbreviata%27%2C%27../images/uk000634.jpg','Valve%20view%20Brightfield%20focussed%20on%20pseudosepta','Image:%20D.G.%20Mann.');http://openwin%28%27000589bb%27%2C%27514%27%2C%27226%27%2C%27nitzschia%20dissipata%27%2C%27../images/000589BB.jpg','valve%20view%20brightfield%20','Image:%20M.%20Bayer%20Copyright:%20RBGE.');http://openwin%28%27000151b%27%2C%27756%27%2C%27234%27%2C%27navicula%20oblonga%27%2C%27../images/000151b.jpg','','Image:%20ADIAC%20Copyright:%20RBGE.');http://openwin%28%27uk000715%27%2C%27618%27%2C%27503%27%2C%27navicula%20molestiformis%27%2C%27../images/uk000715.jpg','Valve%20view%20brightfield%20black%20spot%20focus','Image:%20D.G.%20Mann.');http://openwin%28%27000586ab%27%2C%27370%27%2C%27223%27%2C%27navicula%20minima%27%2C%27../images/000586AB.jpg','valve%20view%20brightfield%20','Image:%20M.%20Bayer%20Copyright:%20RBGE.');http://openwin%28%27000332b%27%2C%27753%27%2C%27249%27%2C%27navicula%20lanceolata%27%2C%27../images/000332b.jpg','','Image:%20ADIAC%20Copyright:%20RBGE.');http://openwin%28%27001193ab%27%2C%27374%27%2C%27194%27%2C%27gomphonema%20parvulum%27%2C%27../images/001193ab.jpg','valve%20view%20brightfield%20','Image:%20M.%20Bayer%20Copyright:%20RBGE.');http://openwin%28%27000285b%27%2C%27481%27%2C%27272%27%2C%27gomphonema%20olivaceum%27%2C%27../images/000285b.jpg','','Image:%20ADIAC%20Copyright:%20RBGE.');


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104562723 Diatoms as Indicators of Water Pollution in Rivers

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