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ESB Power Stations

Lough Ree (Lanesborough)

Aquatic Ecological Monitoring

August 2016

Aquatic Services Unit (ASU) University College Cork (UCC) ERI Building, Lee Road, Cork P: +353 21 490 1935/ F: +353 21 490 1940

(October 2016)

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ESB Aquatic Surveys Aquatic Services Unit, UCC

Contents 1. Executive Summary ................................................................................................................. 3

2. Introduction ............................................................................................................................. 4

3. Methodology ........................................................................................................................... 5

3.1 Site Selection ..................................................................................................................................... 5

3.2 Macrophyte Survey ........................................................................................................................... 5

3.3 Diatom Sampling ............................................................................................................................... 7

3.4 Benthic Grab Sampling ...................................................................................................................... 7

3.5 Water Temperature .......................................................................................................................... 8

4. Results ...................................................................................................................................... 9

4.1 Macrophytes ..................................................................................................................................... 9

4.2 Diatoms ........................................................................................................................................... 10

4.3 Benthic fauna .................................................................................................................................. 14

5. Discussion .............................................................................................................................. 17

6. Conclusions ............................................................................................................................ 19

7. References ............................................................................................................................. 21

APPENDIX 1 Aquatic Macrophyte Data .................................................................................. 22

APPENDIX 2 Site photographs ................................................................................................ 25

APPENDIX 3 Diatom Species Lists ........................................................................................... 29

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1. Executive Summary

The Aquatic Services Unit (ASU) was commissioned to carry out aquatic surveys in relation to a thermal discharge to the River Shannon arising from ESB’s Lough Ree power station located at Lanesborough, Co. Longford. Surveys were conducted on August 19th 2016 and were a repeat of aquatic surveys conducted by ASU in August 2015. Water levels were similar during 2015 and 2016 surveys at the time of sampling i.e. mid-August in both years.

Aquatic communities were sampled at various distances upstream and downstream of the thermal discharge to allow for comparisons in relation to the thermal discharge. 2016 survey sites were identical those of 2015. The communities sampled and analysed for composition and abundance were: (i) aquatic macrophytes; (ii) diatoms, and; (iii) benthic macroinvertebrates.

There were some upstream/downstream differences detected in the aquatic macrophyte communities present in relation to the thermal discharge location, but the effects of hydromorphological impacts could not be separated from other pressures. There were no fundamental changes in the macrophyte species composition between 2016 and previous years. Factors such as depth; light; flow; turbidity and drainage/dredging seem likely the strongest determinant of species distribution at Lanesborough sites.

There was a clear relationship between increased water temperature downstream of the thermal discharge and decreased ecological status classification according to diatom communities. Ecological status declined from ‘High/Good’ at upstream sites, to ‘Moderate’ just downstream of the outfall, persisting ‘Moderate’ for up to 415m, then returning back to Good Status by 580m downstream of the discharge location.

There is no indication from the data that the thermal discharge is unequivocally impacting the distribution or densities of most macroinvertebrate species, which appear more affected by river hydromorphology. However, the presence of the Asian clam at higher densities at sites in the discharge canal experiencing on average elevated temperatures, suggests that this species is locally enhanced by the thermal discharge.

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2. Introduction

The Lough Ree Power Station generates a thermal discharge to the River Shannon at Lanesborough, Co. Longford. Aquatic surveys have previously been conducted in August 2014 and August 2015, upstream and downstream of the discharge. The current report presents results of surveys repeated in August 2016. Biotic communities sampled and analysed for composition and abundance were: (i) aquatic macrophytes; (ii) benthic diatoms; and (iii) benthic macroinvertebrates.

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3. Methodology

3.1 Site Selection

Sampling sites were chosen at distances upstream and downstream of the discharge having regard to: (i) results of thermal plume studies undertaken in 2014 at the station; (ii) the need to have more frequent sample points closer to the discharge, and (iii) specific morphology of the River Shannon downstream of the discharge, i.e., split main channel and transition between river and lake habitat.

Table 1 - Sampling sites showing the distance from the outfall and the parameters surveyed at each

Station Code 2015/2016

Station Code 2014

Distance from Outfall (m)

Diatoms Macrophytes Invertebrates

1 u/s LN2 (u/s) -229

2 u/s LN3 (u/s) -90

3 d/s +66

4 d/s +124

5 d/s LN5 (d/s) +160

6 d/s +315

7 d/s +316

8 d/s +415

9 d/s LN6 (d/s) +580

10 d/s LN7 (d/s) +1457

11 d/s LN 8 (d/s) +2112

Figures 1A and 1B show sample site locations for 2016. These are the same as those surveyed in 2015 for reasons discussed in the 2015 report. The sampling regime at each site consisted of a combination of the following: a transect along which macrophytes were recorded; a diatom sample taken from macrophytes; and a benthic dredge sample taken from the boat. Not all of these parameters were measured at every site. Table 1 presents the sampling programme that was undertaken at each site.

3.2 Macrophyte Survey

Up to 5 macrophyte quadrats (size 1m x 1m) per transect were visually assessed on the river bed for macrophyte composition and relative abundance. The quadrats were selected along the transect line extending perpendicular from the shore to a maximum depth of 2m. Quadrat locations were selected on-site in order to assess the main community types encountered along each transect. Macrophyte surveys were carried out by snorkelling and the end position of each transect was recorded using handheld dGPS from a boat. A weighted float was used to mark the 2m depth end of each transect and a landmark was used at the other end.

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Figure 1A & 1B: Aerial photographs of 2016 sample site locations at Lanesborough

Fig 1B

Fig 1A

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3.3 Diatom Sampling

Diatom communities were assessed in accordance to the Diatoms for Assessing River Ecological Status (DARES) protocol including: (i) Identification of diatom community assemblage, and (ii) calculation of Trophic Diatom Index (TDI) and Ecological Quality Ratio (EQR). The TDI is a measure of the effect of nutrients on diatom assemblages (Kelly et al., 2008).

Table 2 - Status class boundaries for diatom EQR

Diatom EQR WFD Ecological

Status

≥0.93 High

≥0.78 – < 0.93 Good

≥0.52 – < 0.78 Moderate

≥0.26 - < 0.52 Poor

< 0.26 Bad

EQRs represent the relationship between the TDI observed for a given body of surface water and the expected TDI value for reference conditions applicable to that waterbody. “Expected TDI” (eTDI) is adjusted on a per site basis for alkalinity and season (Kelly et al., 2008). Table 2 shows how diatom EQR translates to Water Framework Directive (WFD) ecological status classifications of High, Good, Moderate, Poor and Bad. The EQR allows comparison of water quality status across the European Union as each member state has an EQR value for ‘High’; ‘Good’ etc., based on an intercalibration of boundaries between water quality categories (Kelly et al., 2008).

3.4 Benthic Grab Sampling

In 2014 samples were taken with Van-veen grab (0.045m2) however in 2015 and 2016 samples were obtained using a freshwater dredge (Figure 2) with an opening of 45cm x 18.5cm and a 1mm mesh net bag. The dredge proved to be marginally better than the grab, but at some sites required to be physically pressed into the substrate. The dredge samples were sieved on site through a 1mm sieve to extract biota. These were placed in a labelled container, preserved in formalin solution and transported back to the laboratory for identification and enumeration. Macroinvertebrates were classified according to the EPA Q-value biotic index system, even though actual Q-rating couldn’t be assigned to the sites owing to the unsuitability of the hydromorphology of the sampling locations for that purpose.

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Figure 2: Benthic freshwater dredge used in 2016 sampling

3.5 Water Temperature

Average monthly water temperature data was provided by Irish Hydrodata Ltd. arising from water temperature data loggers installed at locations upstream and downstream of the thermal discharge at Lanesborough. Loggers are deployed in broadly the same locations as ASU sampling sites, although the most downstream sites (10d/s and 11d/s) are not represented. The time period used to obtain monthly average temperatures was 7:00 on 16 July 2016 to 6.55 on 16 August 2016 (5 mins sampling rate). This covers the month preceding recent aquatic surveys of 19 August 2016.

For the purposes of comparing water temperature trends with biological metrics in the current report, a simple method of normalisation was used to convert per site average preceding monthly temperature data to a fraction of the site with the maximum average monthly water temperature. For example: maximum average monthly temperature (preceding August 19th 2016) occurred at Site 3d/s = 26.6oC; Site 1u/s = 18.4oC, therefore normalised water temp = 18.4/26.6 = 0.69. This allowed a 0-1 scale for average preceding monthly temperature data, which could be more practicably compared with, for example, diatom EQR, which also has a 0-1 scale.

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4. Results

4.1 Macrophytes

Appendix 1 shows composition and abundance data for macrophytes within quadrats assessed along transects. Appendix 2 shows photographs of transect locations. Transects varied in length depending on the profile of the river bed cross section. At some sites there was a gently sloping cross-section, while at others there was rapid descent to >2m within a few metres of the river bank. Transect lengths at Lanesborough study sites varied, from 7-30m. The number of quadrats assessed along each transect were determined by transitions in macrophyte community type, which was clearly influenced by depth along each transect. Between 2 and 5 quadrats per transect were required depending on river depth profile.

The Shannon River at Lanesborough has undergone a great level of hydromorphological alteration including drainage, canalisation and bank reinforcement. Once again in 2016, sites displayed a number of vegetation zones that depended on depth along each transect as it extended out from the river bank. The vegetation patterns were strongly influenced by hydromorphological alterations. Apart from reaches close to Ballyleague Bridge, fringing reeds and rushes comprised of a band of Common reed (Phragmites australis) towards the drier banks, with a band of emergent Branched Burr-reed (Sparganium erectum) and Club rush (Schoenoplectus lacustris) in the shallower littoral zone. In places there were other species associated with these emergents, including Equisetum fluviatile and Mentha aquatica. As in 2015, Nuphar lutea was most commonly recorded with Sagittaria sagittifolia; Sparganium emersum; Myriophyllum spicatum and some pondweeds (e.g., Potamogeton obtusifolia) dominated the aquatic plant community at a depth of between 0.5m and 1.6m. Cladophora was observed in close growing (Plate 1) and floating forms (Plate 2) at a number of sites, mainly downstream of the outfall. Tufts and felty layers of Blue-Green algae (Plate 3) were common at upstream and downstream sites. Freshwater sponges were most common in the thermal race, but were also recorded in small amounts at other sites. The specimens from the thermal race were long and branched (Plate 4). Similar to 2015, upstream sites (1u/s; 2u/s) were highly turbid, with very sparse vegetation at depths over 0.8m. Blue-green alga was more common at all sites in 2016 compared to previous years.

Overall, there has tended to be minor differences year to year in some cover values for the main submerged species, but there have been no fundamental differences in species composition year to year. As in previous surveys, the depth of 2m appeared to be the limit of the photic zone for submerged macrophyte species, and there was generally no vegetation at this depth, only bare benthic substrates that varied, including cobble and zebra mussel shell/gravel with silt and mud. In the thermal race peaty detritus was common along with numerous live Asian clams. Clams were so abundant in places that they formed the entire benthic substrate.

Similar to previous surveys, the main upstream/downstream difference in aquatic macrophyte community was in that the half of the river that has formed a thermal race downstream of the outfall (represented by sites 3d/s, 5d/s, 7d/s and 8d/s) there was a shallow water (0.2-1.5m) plant community with low diversity. It consisted of abundant water lily (Nuphar lutea) with some Myriophyllum spicatum, Sparganium emersum, Cladophora and some freshwater sponge. This was somewhat different to the communities found upstream of the outfall at similar depth, which comprised sparse coverage of

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Nuphar lutea, Sparganium emersum and Fontanalis antipyretica moss. Overall, however, there were no conclusive differences that could be attributed to the thermal discharge alone.

Plate 1: Close growing mats of Cladophora were quite common at Lanesborough sites in the thermal race (3d/s, 5d/s, 7d/s).

Plate 2: Floating mats of Cladophora in the thermal race near site 5d/s.

Plate 3: Blue-green algae (Cyanobacteria) – common upstream and downstream of the thermal outfall.

Plate 4: Sponges growing in the thermal race were not as prolific as in 2015, but had equally long branched structures.

4.2 Diatoms

Appendix 3 contains lists of diatom species found at each sampling location. Table 3 summarises TDI, EQR and WFD ecological status classifications. Figures 3 and 4 show the trends in TDI and EQR, respectively.

Table 3 - Diatom metric summary 2014, 2015 and 2016

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Site TDI EQR Ecological Status

2014 2015/2016 2014 2015 2016 2014 2015 2016 2014 2015 2016

2u/s 1u/s 46.51 46.00 41.59 0.80 0.85 0.96 G G H

3/us 2u/s 45.21 32.83 47.58 0.82 1.00 0.87 G H G

3d/s 56.33 62.32

0.69 0.63

M M

4d/s 4d/s 41.67 52.40

0.92 0.79

G G

5d/s 5d/s 50.94 52.52 63.45 0.74 0.75 0.61 M M M

7d/s 57.69 60.44

0.67 0.67

M M

8d/s 59.03 56.31

0.65 0.73

M M

6d/s 9d/s 56.15 40.33 51.04 0.66 0.94 0.81 M H G

7d/s 10d/s 49.52 48.41 63.18 0.76 0.81 0.61 M G M

8d/s 11d/s 44.88 42.00 47.78 0.83 0.92 0.87 G G G

In 2016, as in 2015, there was a significant increase in TDI (and decrease in EQR) downstream of the thermal discharge compared to sites upstream of the outfall. In general, a change of +/- 7 TDI points signifies a significant difference between sites (Dr M. Kelly, pers. comm.).

This equates to a decline in ecological quality from High/Good status upstream (1u/s; 2u/s) to Moderate status downstream (3d/s). Moderate status then persisted along the thermal race at sites 5, 7 and 8d/s. Similar to 2015, status was restored to upstream levels, i.e., ‘Good’ status in 2016, at site 9d/s. Status was also ‘Good’ at the most downstream site (11d/s). Site 10d/s, at the head of the navigation channel on the south side of the upper Lough Ree basin, recorded Moderate status in 2016, as it did in 2014.

Figure 3 - TDI trend in relation to the thermal discharge (green dashed line)

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Figure 4 - Diatom EQR trend in relation to the thermal discharge (green dashed line)

It is important to note that whilst site 4d/s is geographically downstream of the thermal discharge, the site is located in the navigation channel side of the river and not in the thermal race that has formed on one half of the river downstream of the outfall. Average preceding monthly water temperature at 4d/s was 18.5⁰C in August 2016, compared to 26.6⁰C at 3d/s. This is an 8.1⁰C difference, even though the two sites are at virtually the same distance south of the thermal outfall. Figure 5 illustrates the relationship between average preceding monthly water temperature (normalised) and Diatom EQR. This indicates that higher water temperatures correspond with lower EQRs, while cooler sites have higher EQRs.

Figure 5 - Water temperature (normalised) vs Diatom EQR (thermal discharge = green dashed line)

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Strong upstream/downstream differences in % Achnanthidium minutissimum were evident in 2016 as illustrated by Figure 6, below. Relative abundance of A. minutissimum, a species that usually dominates in waters of ≥Good Ecological Status, was markedly reduced at sites downstream of the outfall where water temperature was on average much warmer (3d/s; 5d/s; 7d/s; 8d/s) compared to upstream sites (1u/s;2u/s).

Figure 6- Relative abundance of A. minutissimum (thermal discharge = green dashed line)

Note that site 4d/s, although geographically downstream of the thermal discharge is on the navigation channel side of the river and considerably cooler than downstream sites located within the thermal race side of the river at similar latitudes (3d/s, 5d/s, 7d/s and 8d/s).

Figure 7 - Diatom species richness trend (thermal discharge = green dashed line)

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In 2014, there was a suggestion of a relationship between diatom species richness and water temperature at Lanesborough sites, but the relationship has proven weak in subsequent years (2015/2016). Figure 7 illustrates the 2016 trend in this analysis, which shows no obvious upstream/downstream pattern.

4.3 Benthic fauna

The benthic fauna collected at each of the sites in 2016 (Table 4) was characterised by a moderate range of less sensitive as well as tolerant macroinvertebrates mainly from the EPA Quality groups C, D and E. There were no highly sensitive group A species and only small numbers of Group B taxa (cased caddis larvae and Aphelocheirus). It isn’t possible to give a Q-rating for these sites because their hydromorphology was generally unsuitable for the normal kick-sample based Q-value system, the study reach being mainly too deep. The nearest EPA monitoring point is at Ballyleague Bridge Lanesboro, i.e., within the study area and when that was last sampled in 2014 it was assigned Q3 / Poor Ecological Status under the WFD (moderately polluted). This rating is not incompatible with the current results. The only concentration of more sensitive species was that of the cased caddis of the genus Ceraclea, most of which were C. nigronervosa a species usually associated with freshwater sponges. It was present in relatively high densities at 6d/s: on the cooler western side of the channel. However, whether this is a substrate (sponge) distribution effect or a temperature effect, cannot be said with certainty due to the overall sporadic occurrence in samples.

All of the same dominant taxa present in 2015 were also present in 2016 namely the crustaceans Gammarus, Asellus and Chelicorophium curvipinum, the molluscs Dreissena polymorpha (Zebra mussel) and Corbicula fluminia (Asian clam). Other taxa frequently encountered, but usually in smaller numbers included molluscs Theodoxus fluviatilis (the river nerite), Bithynia tentaculata, flat worms Dugesia spp and Dendrocoelum lacteum and Chironomid midge larvae.

Patterns of distribution of some of the species listed superficially show a negative or positive association with warmer sites at Lough Ree Power. Asian clam for example was most commonly found at site 3 d/s, 5d/s and 7d/s, all within the discharge canal and with higher average temperatures, while, Chelicorophium curvispinum and zebra mussels were most dense at site 1u/s, 2u/s, 4d/s and 6d/s all with lower average temperatures and all outside of the discharge canal. However, Lucy et al. (2004) notes that Chelicorophium curvispinum appears to be strongly associated with zebra mussels in Ireland. It is also know to attach its tubes to solid substrates (wood, stones, shells, water plants). Its distribution therefore seems to be dependent more on the availability of suitable substrate for its tubes, in this case zebra mussels colonies, than any particular temperature preferences. Zebra mussels themselves tend to prefer hard substrates on which to attach, as well as more sluggish flows, which in turn may also be the greater determining factors in its observed distribution. This is borne out to an extent by the fact that the Asian clam prefers sand and silty substrates and was never present in high numbers where zebra mussels were present in high densities in our samples. However, given that the Asian clam comes from naturally warmer waters than occur in Ireland, would suggest that they would be favoured by elevated temperatures in the Lough Ree Power thermal discharge. An intensive survey undertaken in Lanesborough by IFI in 2014 (Caffrey & Millane, 2014) showed that the species were present in much higher densities and were composed of far greater numbers of larger individuals in the discharge canal than in paired sites in the main river channel, where the temperatures were cooler. These surveys suggest that while the distribution of the species may not be influenced by temperature (as they were

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also noted at sites upstream of Lanesborough), elevated temperatures favour their growth rates and probably also enhance reproductive success and survival as they occurred in overwhelmingly higher densities in the discharge canal (thousands per m2) compared to sites in the adjoining main channel (few per m2). The only reference to substrate in the report was the observation that they occurred in ‘coarse substrate’ in the discharge canal, referred to in the IFI report as the ‘hot water stretch’.

None of the less dominant species showed any discernible or consistent distribution pattern that could be attributed to temperature effects. It is possible that with continued annual sampling at the same sites over several years that a pattern might emerge in some cases. However, given that the numbers of these less common species tend to be low, there is no guarantee that such a pattern would emerge and its value in any case would arguably be of lesser ecological significance, given the lower densities involved.

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Table 4 – Benthic macroinvertebrates taken in dredge samples

EPA WQ

Class 1 u/s 2 u/s 3 d/s 4 d/s 5 d/s 6 d/s 7 d/s 8 d/s d/s 10

Trichoptera - Caddisfly

Polycentropus kingi C 1 1

Polycentropus sp C 1

Hydropsyche C 1

Neuroclepsis bimaculata C 1 4 2 2

Pschomyidae C 1

Ceraclea spp. B 1 25 11

Lempdostoma hirtum B 1

Limnephilidae C

Diptera -True Flies

Chironomidae C 2 1 1 12 20 16 2

Simulium C 2 1

Hemiptera (Water bugs)

Aphelocheirus aestivalis B 1 2

Crustacea - FW Shrimps

Gammarus C 1 1 130 5 38 9 18 29

Asellus D 2 4 10 1 1 7 11 10

Chelicorophium curvispinum

-

15 158 23 1087 13 1420 4 6

Mollusca - Snails and Bivalves

Corbicula fluminea - 38 1 213 23 2 20

Dreissena polymorpha - 154 171 80 2 100 2 545

Acroloxus lacustris C

Bithynia tentaculata C 3 1 1

Potamopyrgus C 4 12

Lymnaea peregra D 1

Theodoxus fluviatilis C 1 1 2 2

Hirudinae - Leeches

Glossiphonia D 1

Erpobdellidae D 1

Annelida -Segmented worms

Oligochaeta spp E 2 20 3 9 5 5 4

Turbelaria - Flat worms

Dugesia spp C 3 1 5 1 2 11

Dendrocoelum lacteum C 1 1 3 2 1

Freshwater Sponge - + + +

Taxa Total 9 10 13

14 9 12 5 10 12

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5. Discussion

As in previous years, there were upstream/downstream differences in the aquatic macrophyte communities at Lanesborough in 2016, but the relative impacts of temperature and/or hydromorphological pressures cannot be delineated in terms of minor differences observed in aquatic macrophyte communities. The river is canalised in the discharge reach; split into two channels and forming a warm water race on the True Left bank downstream of the outfall in which mainly Nuphar lutea was flourishing. The community was broadly similar in species composition upstream and downstream, but tended to have greater coverage (abundance) at sites in the warm waters downstream of the outfall. However, sites in the thermal race were also shallower and less turbid than many other sites so these differences are not necessarily temperature related. In general, macrophyte species recorded at all sites were typical of large, slow flowing, slight-to-moderately enriched waters (Holmes et al., 1999). In 2016 occurrence of freshwater sponge was less compared to previous years, but blue-green alga was more common.

There were clear upstream/downstream differences in the 2016 diatom metrics in relation to the thermal discharge, with ecological quality declining immediately downstream of the outfall from ‘High/Good’ down to ‘Moderate’; persisting ‘Moderate’ for 415m; then returning to ‘Good’ status by 580m downstream of the outfall.

Site 10d/s is a slight anomaly, being less affected by the thermal plume, but recording low % A. minutissimum and some of the poorer TDI and diatom EQR results in both 2015 and 2016. During the 2015 study the site was only 0.4oC warmer than ambient and thermal plume studies concur that it is far less affected by elevated temperature. There is no temperature logger at this site (monthly average temperature was inferred as a percentage of 2016 ambient average temperatures, based on 2015 data). It may be useful to have a long term temperature record from this site given the apparent anomalies in ecological metrics to date. At present, based on the limited temperature data available, it doesn’t appear the thermal plume is the cause of slightly impaired water quality at this site.

Once again, the marked decline in relative abundance of the diatom species Achnanthidium minutissimum downstream of the outfall appears strongly related to upstream/downstream temperature differences. The suggestion that A. minutissimum is a cool water species and is affected by elevated temperature (Smith & Manoylov, 2013) has been discussed in previous reports. The 2016 results, once again, strongly concur with this finding. Sites closest to the thermal outfall (3d/s, 5d/s, 7d/s and 8d/s) showed markedly decreased % A. minutissimum compared to upstream sites (1u/s and 2u/s), with % A. minutissimum generally increasing as distance downstream of the outfall increases, returning to upstream levels by 580m downstream.

The macroinvertebrate faunal community upstream and downstream of the thermal discharge at Lanesborough was again dominated in 2016 by species tolerant of degraded water quality and the near absence of any sensitive species. Moreover the most abundant invertebrates, as in 2015, belonged to 3 highly invasive species, whose distribution patterns appear to be more influenced by the availability of suitable substrate than to any clear effect of elevated temperature associated with the thermal discharge. However, there is evidence within the data, supported by another study in the area (Caffrey

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& Millane, 2004), that Corbicula densities and population size distribution is enhanced at sites with higher temperatures, i.e., within the discharge canal.

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6. Conclusions

Overview

There were some upstream/downstream changes in the aquatic macrophyte communities detected in relation to the thermal discharge location, but the effects of hydromorphological alterations could not be separated from other pressures.

There was a clear relationship between increased water temperature as a result of the thermal discharge and decreased Ecological Status classification according to diatom communities. Ecological status declined from Good/High at upstream sites, to Moderate just downstream of the outfall, returning back to Good Status by 580m (9d/s) downstream of the discharge location.

The inclusion of average monthly water temperature measurements allowed for a strong relationship between temperature and diatom metrics to be demonstrated. The inclusion of samples from both sides of the split channel downstream of the thermal discharge (i.e., 3d/s, 5d/s, 7d/s & 8d/s compared to 4d/s) tend to clearly show that ecological status is negatively affected by increased water temperature according to diatom communities.

Site 10d/s appears to be a slight outlier as it is apparently less affected by the thermal plume, but recorded some of the poorer diatom metrics in both 2015 and 2016. There is no long term temperature data for this site, but on the basis of information available the thermal plume does not appear to be the reason for slightly impaired water quality at this location.

Macrophytes

The evidence suggests that depth, light and hydromorphological pressures were strong determinants of distribution of summer macrophyte communities at Lanesborough, but it is not possible to say what role, if any, water temperature plays in this.

Diatoms

There were clear upstream/downstream differences in the 2016 diatom metrics in relation to the thermal discharge, with ecological quality declining immediately downstream of the outfall from ‘High/Good’ down to ‘Moderate’; persisting ‘Moderate’ for 415m; then returning to ‘Good’ status by 580m downstream of the outfall.

Benthic fauna

In general the benthic invertebrate fauna comprised a range of species typical of more enriched conditions although a definite Q-rating could not be assigned due to the unsuitability of the depositing habitats encountered.

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In general, macroinvertebrates at the Lanesborough sites didn’t reveal any clear trends which could unequivocally point to an influence from the thermal discharge. The only exception to this was in the case of the Asian clam, which was present in highest densities in the discharge canal. This effect however, is spatially confined.

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7. References

Caffrey, J. and Millane, M. (2004) Status of the Asian clam in the mid- River Shannon and recommendations for its management. Inland Fisheries Ireland, City West Business Campus. Dublin 14, Ireland

Holmes, N. T. R., Newman J. R., Chadd, S., Rouen, K. J., Saint, L. and Dawson F. H. (1999) Mean Trophic Rank: A User’s Manual. R&D Technical Report E38. Environment Agency , Rio House, Waterside Drive, Aztec West, Almondsbury, Bristol, BS32 4UD.

Kelly, M., Juggins, S., Guthrie, R., Pritchard, S., Jamieson, J., Rippey, B., Hirst, H. and Yallop, M. 2008. Assessment of ecological status in U.K. rivers using diatoms. Freshwater Biology, 53, 403–422.

Lucy, F., Minchin, D and M. Sullivan (2004) First record of the Ponto-Caspian amphipod Chelicorophium curvispinum (Sars 1895) in Ireland. The Irish Naturalists Journal, 27 pp 461-464.

Smith, M. E., Kalina M. Manoylov, K. M. (2013) Changes in Diatom Biodiversity in Lake Sinclair, Baldwin County, Georgia, USA. Journal of Water Resource and Protection, 2013 (5): 732-742.

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APPENDIX 1 Aquatic Macrophyte Data

LANESBOROUGH (Downstream sites - Quadrat = Q) Q1 Q2 Q3 Q4 Q5

Approx. Depth 0-0.3m 0.3 - 0.5m 0.5 -1.6m 1.6- 1.8m 2m

Site

Distance from outfall (m)

Transect Length (m) Irish Grid X Y

11d/s (-)2112 N/A M 99291 67984 19

92

91

26

79

84

Diatom sample only

10d/s (-)1457 8 M 99779 68353 19

97

79

26

83

53

Phragmites australis 100%

Phragmites australis 100% Clay bank

Nuphar lutea 3%; Sagittaria sagittifolia 5%; FW sponge +.

FW sponge +; mussel shell/gravel with mud.

9d/s (-)580 30 N 00419 69005 20

04

19

26

90

05

Band of Phragmites australis (80% cover) with Fontanalis antipyretica 5% ; Cladophora sp. 30%; + boulders/silt.

Schoenoplectus lacustris 60%; Cladophora sp. 35%; Lemna trisulca 5%; Potamogeton obtusifolius 1%

Sagittaria sagittifolia 20%; Potamogeton lucens 3%; Myriophyllum spicatum 3%. Nuphar lutea 2%; Sparganium emersum 10%; Phragmites australis 5%; Cladophora sp. 10%; Elodea nutallii <1%; Potamogeton obtusifolius <1%; + cobble / boulder /silt.

Cladophora sp. 50%; Sagittaria sagittifolia 10%; Bare mud.

8d/s

(-)415 (in outfall

channel) 8 N 00443 69166 20

04

43

26

91

66

LHS: Octodiceras fontanum 5%; Fontinalis antipyretica 30%; Cladophora 2%; Blue-Green Algae <1% RHS: Phragmites australis 100%

Nuphar lutea 1%; Sagittaria sagittifolia 1%; Myriophyllum spicatum 1%; Cladophora 1% + cobble/sand/silt substrates and BG patches <1% + mussel shell gravel (Very turbid)

(Max. depth = 1.6m) Nuphar lutea <1% + Bare mussel shell gravel

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7d/s

(+)316 (in outfall

channel) 14 N 00496 69254 20

04

96

26

92

54

LHS: Octodiceras fontanum 2%; Fontinalis antipyretica 1%; Cladophora 5%; Blue-Green Algae <1%; RHS: Sparganium erectum 100%

(Max. depth = 0.9m) Nuphar lutea 80%; Nymphoides peltata <1%; Myriophyllum spicatum 1%; FW sponge <1%; BG algae 5%; Fontanalis antipyretica 2.5% (at margins) + cobble/sand/silt substrates.

5d/s

(+)160 (in outfall

channel) 14 N 00586 69369 20

05

86

26

93

69

LHS: Octodiceras fontanum 2.5%; Fontinalis antipyretica 1%; Blue-Green; Cladophora 5%; Algae <1%; RHS: Sparganium erectum 100%; Phalaris arundinacea +

(Max. depth = 1.3m) - Quadrat (a): Nuphar lutea 80%; Myriophyllum spicatum 5%; Sagittaria sagittifolia 1%; BG algae 2%; FW sponge <1%; Quadrat (b): FW sponge 5%; Sparganium emersum 10%; Cladophora 1%; Lemna minor +; Fontanalis antipyretica 2% (towards LHS) + cobble/sand/silt/ shell/ clam substrates.

3d/s

(+)66 (in outfall

channel) 16 N 00638 69458 20

06

38

26

94

58

RHS: Phalaris arundinacea 1%; Mentha aquatica 1%. LHS: Cladophora 15%.

(Max. depth = 1.0m) Nuphar lutea 5%; BG algae 7%; FW sponge <1%; FW sponge <1%; Phormidium sp. 3% + Bare mussel shell/gravel /cobble/sand/silt substrates.

4d/s

(+) 124 (in navigation channel) 20 N 00596 69448 2

00

59

6

26

94

48

Schoenoplectus lacustris 40%: Sparganium erectum 40%.

Fontanalis antipyretica 5%; Nuphar lutea 1%; Sagittaria sagittifolia 1%; Elodea Canadensis <1%; Phormidium sp. ; Lemna trisulca <1%; Cladophora 1%; BG algae 15%

Fontanalis antipyretica 2%; Nuphar lutea <1%.

Bare + zebra mussel shell/gravel/ cobble

Outfall N 00619 69519 20

06

19

26

95

19

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LANESBOROUGH (Upstream sites) Q1 Q2 Q3 Q4 Q5

Approx. Depth 0-0.3m 0.2 - 0.5m 0.5 -1.6m 1.6- 1.8m 2m

Site

Distance from outfall (m)

Transect Length (m) Irish Grid X Y

2u/s (-)90 16 N 00661 69572 20

06

61

26

95

72


Phragmites australis 20%: Schoenoplectus lacustris 80% + bare mud.

Nuphar lutea 3%; Sagittaria sagittifolia 3%; Potamogeton obtusifolius <1%; Elodea nuttalii <1%; Fontinalis antipyretica +; plus zebra mussel shell/gravel/silt. (Note: Very turbid with very little vegetation below 0.8m)

Bare, embedded cobble with mussel shell/gravel/silt. No vegetation.

Bare, embedded cobble with mussel shell/gravel/silt. No vegetation.

1u/s (+)229 10 N 00797 69614 20

07

97

26

96

14


Schoenoplectus lacustris 10%; Phragmites australis 40%; Equisetum fluviatile 1%;Sparganium erectum 40%

Nuphar lutea 1%; Elodea nuttalii 1%; (Note: Very turbid, sparse, with very little vegetation below 0.8m)

Bare, embedded cobble with mussel shell gravel/silt. No vegetation.

Bare, embedded cobble with mussel shell gravel/silt. No vegetation.

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APPENDIX 2 Site photographs

ESB Lough Ree Station –Lanesborough (19/8/15)

11d/s (19/8/16) LHS approx. 2km downstream of outfall. Diatom sample only.

10d/s LHS approx.1.5km downstream of outfall (19/8/16)

9d/s (19/8/16) LHS approx.500m downstream of outfall channel

8d/s (19/8/16) RHS of thermal outfall channel

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7d/s (19/8/16) Across outfall channel 5d/s (19/8/16) Across outfall channel

3d/s (19/8/16) Across shallow outfall channel 4d/s (19/8/16) LHS

2u/s (19/8/16) LHS 1u/s (19/8/16) LHS

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1u/s (19/8/16) Benthic substrate. Note Zebra mussel.

3d/s (19/8/16) Benthic substrate - note peaty debris and Asian clam.

4d/s (19/8/16) Benthic substrate. 6d/s (19/8/16) Benthic substrate.

7d/s (19/8/16) Benthic substrate - note Asian clam.

8d/s (19/8/16) Benthic substrate - note peaty debris and Asian clam.

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10d/s benthic substrate. Note live Asian Mussel and dead and live Zebra Mussel (19/8/16)

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APPENDIX 3 Diatom Species Lists

Site Genus Species Infraspecific taxon N

1u/s Rhoicosphenia abbreviata 1

Navicula antonii 3

Caloneis bacillum 2

Encyonema caespitosum 3

Navicula capitatoradiata 2

Navicula cryptocephala 1

Navicula cryptotenella 14

Nitzschia dissipata 1

Cocconeis euglypta 20

Gomphonema exilissimum 6

Nitzschia fonticola 5

Gomphonema gracile 1

Fragilaria gracilis 2

Cocconeis lineata 18

Eolimna minima 27

Achnanthidium minutissimum 156

Nitzschia paleacea 6

Gomphonema parvulum parvulum 2

Amphora pediculus 2

Ctenophora pulchella 1


Gomphonema pumilum 11

Achnanthidium pyrenaicum 4

Encyonema silesiacum 7

Achnanthidium subatomus 2

Navicula tripunctata 13

Navicula trophicatrix 1

Melosira varians 1

2u/s Rhoicosphenia abbreviata 3

Ulnaria acus 1

Mayamaea atomus permitis 1

Eunotia bilunaris 2



Fragilaria capucina capucina 1




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Tabellaria flocculosa 1




Eolimna minima 2


Nitzschia palea 1



Fragilaria pectinalis 2

Amphora pediculus 2




Navicula reichardtiana 1


Nitzschia soratensis 1

Fallacia subhamulata 1

Gomphonema tergestinum 1


Melosira varians 6

3d/s Rhoicosphenia abbreviata 1

Navicula antonii 1

Eunotia bilunaris 1

Pseudostaurosira brevistriata 1

Navicula capitata capitata 1



Nitzschia dissipata media 1



Achnanthes exigua 2




Planothidium frequentissimum 2


Nitzschia lacuum 1

Navicula lanceolata 1


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Fragilaria mesolepta 7

Eolimna minima 10


Staurosira oldenburgiana 1

Gomphonema olivaeum 2



Amphora pediculus 1

Staurosirella pinnata 4

Kolbesia ploenensis 2

Diatoma problematica 1

Cocconeis pseudolineata 2


Sellaphora pupula 1




Nitzschia sociabiis 2

Cyclotella sp 1

Stephanodiscus sp 1

Staurosira subsalina 11


Melosira varians 8

Diatoma vulgare 1


Ulnaria acus 1

Navicula antonii 1

Caloneis bacillum 1

Eunotia bilunaris 2

Gomphonema brebissonii 1


Achnanthidium caledonicum cf 1










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Lemnicola hungarica 1

Nitzschia lacuum 1

Cymbella lanceolata 2

Planothidium lanceolatum 1


Eolimna minima 11




Amphora pediculus 7



Navicula radiosa 1



Eunotia sp 1

Gomphonema sp 6

Nitzschia sp 1


pennate undifferentiated 1

Melosira varians 3

Diatoma vulgare 2

5d/s Navicula antonii 2





Navicula cryptotenelloides 2



Achnanthes exigua 3





Eolimna minima 7


Gomphonema minutum 1

Craticula molestiformis 1

Staurosira oldenburgiana 1

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Amphora pediculus 1





Achnanthidium saprophilum 14




Navicula antonii 4

Nitzschia archibaldii 1





Achnanthes exigua 5





Gomphonema gracile 1


Eolimna minima 17


Nitzschia palea debilis 2


Amphora pediculus 1




Planothidium rostratum 2



Fallacia subhamulata 2


Melosira varians 11


Navicula antonii 2

Eunotia bilunaris 1

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Achnanthes exigua 15


Tabellaria fasiculata 2



Gomphosphenia grovei lingulatiformis 1

Lemnicola hungarica 1

Amphora libyca 1



Eolimna minima 8



Cocconeis pediculus 1


Cocconeis placentula placentula 6

Cocconeis placentula 2



Fragilaria radians 2




Cyclotella sp 1

Eolimna subminuscula 1



Cymbella tumida 1

pennate undifferentiated 4


Ulnaria acus 1

Navicula antonii 16


Gyrosigma attenuatum 1



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Achnanthes exigua 1


Tabularia fasiculata 1


Eunotia formica 1



Cymbella lanceolata 1

Amphora libyca 1




Eolimna minima 19

Eunotia minor 1








Cocconeis placentula placentula 4









Cymbella tumida 3

Melosira varians 6

Diatoma vulgare 1


Navicula antonii 4



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Nitzschia capitellata 1


Navicula costulata 1



Navicula cryptotenelloides 2

Nitzschia dissipata media 1




Tabularia fasiculata 1





Navicula lanceolata 1



Eolimna minima 22




Amphora pediculus 5

Amphipleura pellucida 1





Rossithidium pusillum 1



Diploneis sp 1



Cymbella tumida 1

Melosira varians 4

Diatoma vulgare 1




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Kareyvia clevei 1









Eolimna minima 1


Encyonema minutum 1





Amphora pediculus 1


Amphipleura pellucida 1






Gomphonema tergestinum 1


Melosira varians 1

Diatoma vulgare 1

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