REFERENCE CONDITIONS AND EUTROPHICATION IMPACTS IN IRISH RIVERS: MEETING THE REQUIREMENTS OF THE WATER FRAMEWORK DIRECTIVE FINAL REPORT (Project 2000-FS-2-M1) Prepared for the Environmental Protection Agency Author: Aisling Walsh ENVIRONMENTAL PROTECTION AGENCY An Ghníomhaireacht um Chaomhnú Comhshaoil PO Box 3000, Johnstown Castle, Co.Wexford, Ireland © Environmental Protection Agency 2005 DISCLAIMER Although every effort has been made to ensure the accuracy of the material contained in this publication, complete accuracy cannot be guaranteed. Neither the Environmental Protection Agency nor the author(s) accept any responsibility whatsoever for loss or damage occasioned or claimed to have been occasioned, in part or in full, as a consequence of any person acting, or refraining from acting, as a result of a matter contained in this publication. All or part of this publication may be reproduced without further permission, provided the source is acknowledged. REFERENCE CONDITIONS AND EUTROPHICATION IMPACTS IN IRISH RIVERS: MEETING THE REQUIREMENTS OF THE WATER FRAMEWORK DIRECTIVE FINAL REPORT Published by the Environmental Protection Agency, Ireland Printed on Recycled paper ISBN:1-84095- to come 06/01/300 Price: €XX.XX Abstract An important objective of this project was to obtain an improved understanding of why ecological communities depart from reference conditions as pollution and eutrophication impacts on individual species and in particular indicator taxa such as Ecdyonurus . The effects of eutrophication on Ecdyonurus were studied using a novel split-stream experiment which involved artificially increasing the phosphorus concentrations in two oligotrophic rivers in the West of Ireland. Some of the nutrient manipulation experiments showed significant differences in algal biomass between the control and treated sections, but not all did so. Findings from this study appear to indicate that Ecdyonurus is not directly affected by the consequences of eutrophication. The experiments did reveal surprising results showing the importance of N- limitation in the rivers studied. On analysing the N:P ratios in a number of rivers in the West of Ireland it was found that approximately 4% of the samples were N-limited with low MRP concentrations (<0.05mg/l P). This implies that a small proportion of high status rivers are N-limited rather than P-limited. Thus, in terms of the Water Framework Directive, there may be a case for introducing tighter regulations on the limits of nitrogen emitted to water bodies as well as the need to control phosphorus. Results from these studies highlight the complexity of the in-stream processes driving these N- limited and P-limited high status rivers. It was hypothesised that the changes exhibited in the biomass in the split- stream experiment would be reflected in the gut contents of Ecdyonurus venosus , possibly showing a variation in algal taxa between both sections of the manipulation experiment. The split-stream experiment showed that Ecdyonurus did not demonstrate distinct preferences due to enrichment but neither were there any observed changes in the periphyton species community. On the basis of the findings from the study in the Castlebar River in 2003, Ecdyonurus venosus can be classified as both a herbivorous grazer and detritus feeder with a tendency towards opportunistic feeding. ii The food preference of these larvae appears to be strongly dependent on the food available in the environment at a given time and they seem to feed on particles that are most abundant during a particular season or those that are easily accessible during a feeding episode. The Ecydonurus gut contents consisted mainly of epilithic algal tissue, plant particulate matter (detritus), biofilm matrix and inorganic debris (mineral material). The life cycle of the Heptegeniidae was described for the first time in detail in five high status rivers in the West of Ireland. Of the three species of Ecdyonurus studied, Ecdyonurus venosus was the dominant species in all five high status rivers displaying a bivoltine life cycle with only a slight variation in emergence periods between sites. Findings show that one would expect to find this species when sampling during all seasons throughout the year. The life cycle of both Ecdyonurus insignis and Ecdyonurus dispar were found to be univoltine. The life cycle analyses in this study suggest that at least one species of Ecdyonurus should be present at all times of the year. The life cycle of Rhithrogena semicolorata was substantially easier to interpret and clearly displayed a univoltine life cycle. The Heptagenia specimens were identified to genus level only and were therefore described as a genus group that appeared to adopt a univoltine life cycle. Findings from our studies support the hypothesis put forward that the various species of Ecdyonurus emerge in overlapping phases such that during the summer months larvae of at least one Ecdyonurus species will be present in the benthic riffle fauna of Irish rivers Ecdyonurus is a good indicator of pollution and the water chemistry results appear to support the hypothesis that the presence of Ecdyonurus is associated with good water quality. The presence/absence of Ecdyonurus in the high status versus impacted sites supports its use as a significant bioindicator of water quality. A selection of indices and metrics were examined and the results revealed that the most significant differences between the high status and impacted sites were found using Margalef’s index, total number of taxa and % EPT. Results from feeding and iii microhabitat investigations suggest that as eutrophication and the impacts of organic pollution progress, a change in the feeding guilds and microhabitat preferences among the macroinvertebrate communities occurs. iv ACKNOWLEDGEMENTS This report has been prepared as part of the Environmental Research Technological Development and Innovation Programme under the Productive Sector Operational Programme 2000-2006. The programme is financed by the Irish Government under the National Development Plan 2000-2006. It is administered on behalf of the Department of the Environment and Local Government by the Environmental Protection Agency which has the statutory function of co-ordinating and promoting environmental research. My sincere thanks to my supervisor Dr. Mary Kelly-Quinn for her advice and guidance throughout the course of this study. I would like to thank Professors John Bracken and Tom Bolger for the use of departmental facilities, and my committee members Dr. Bret Danilowicz and Dr. Tom Hayden for their helpful suggestions and comments. This project was funded by the Irish Environmental Protection Agency under the ERDTI programme 2000-2006, their sponsorship is gratefully appreciated. I wish to convey a special thanks to Mr. Martin McGarrigle, EPA, Castlebar for his knowledge, assistance and advice during the course of the last five years. I would like to thank the chemistry laboratory in the EPA Regional Inspectorate in Castlebar for processing the water samples, to Hugh McGinley and Pat Durkin from the EPA Hydrometric Office, Castlebar, for the help with constructing the split-stream experiment and to Noriana Kennedy and Eli Mulvey for assistance with the laboratory and fieldwork. Many thanks to Berine Ni Chathain for providing invaluable assistance with diatom identifications and to Dr. Robin Raine in the Martin Ryan Marine Institute in NUI, Galway for the use of a fluorescent microscope. I would like to thank the staff and postgraduates in the Limnology unit in UCDs’ Zoology Department, especially Wayne Trodd. The help provided v by Fiona Kelly for assistance with the sediment analysis is gratefully acknowledged. To my colleagues in the EPA in Castlebar, particularly Karol Donnelly and Ruth Little for their help, good humour and encouragement over the years. vi TABLE OF CONTENTS ____________________________________________________________________ Title page i Abstract ii Acknowledgements v Table of Contents vii Chapter 1. Introduction 1 ____________________________________________________________________ 1.1 Introduction 1 1.2 Thesis outline 4 1.3 Project context 6 1.4 The Water Framework Directive 9 1.4.1 Background 9 1.4.2 Ecological boundaries 9 1.4.3 The Reference condition 10 1.4.4 Classifying ecological status 12 1.4.5 Benthic macroinvertebrates 13 1.4.6 Conclusions 14 1.5 Eutrophication 15 1.5.1 Background 15 1.5.2 Nutrient sources 15 1.5.3 Eutrophication Trends in Ireland 16 1.5.4 Effect of eutrophication on macroinvertebrates 17 1.5.5 Diurnal dissolved (DO) variation 18 1.6 Research Objectives 20 1.7 Study locations 21 1.7.1 Site 1: The Owengarve River 24 1.7.2 Site 2: The Castlebar River 26 1.7.3 Site 3: The Brusna River 28 1.7.4 Site 4: The Dunneill River 30 vii 1.7.5 Site 5: Callow Loughs Stream 32 1.7.6 Site 6: The Cartron River 34 1.7.7 Site 7: Lough na Corralea Stream 36 1.7.8 Site 8: The Robe River 38 1.7.9 Site 9: The Mullaghanoe River 40 1.7.10 Site 10: The Mad River 42 Chapter 2. Experimental enrichment of a high status river in the West of Ireland: Effects of nutrient manipulation on the genus Ecdyonurus and benthic chlorophyll levels 44 _____________________________________________________________________ 2.1 Introduction 44 2.2 Study outline 47 2.3 Materials and Methods 48 2.3.1 Site 1: The Clydagh River 48 2.3.2 Site 2: The Castlebar River 48 2.3.3 Preliminary investigations 49 2.3.4 Experimental design and nutrient addition 50 2.3.4.1 Split-stream construction 50 2.3.4.2 Nutrient