A Reference Based Typology and Ecological Assessment System for Irish Lakes - Preliminary Investigation - Final Report

Information on the ecology of 201 lakes was successfully collected. The resulting dataset is the most extensive on lake ecology in the Republic of Ireland. The typology is to be used as the reporting typology for Ireland. Comparison of the typologies developed at the individual element level indicated that they were at least as successful as the default typology system of the WFD (system A). The relative benefits of using the typologies developed at individual element level versus the overall typology level should be further considered. Owing to the uncertainty associated with background (reference) nutrient concentration estimates, it may be preferable to apply a correction factor based on background nutrient status after the application of an ecological assessment metric. This would also be likely to improve transparency. The biological elements: fish and phytobenthos were not considered in this study but should be incorporated at the earliest opportunity. The success of the ecological assessment metrics developed was found to vary with the biological elements. Some elements such as phytoplankton and macrophytes were clearly more useful in detecting pressure. The performance of the invertebrate trophic score for littoral macroinvertebrates had limited success (r2 = 0.43) and needs further development. The response of littoral macroinvertebrates to eutrophication pressure may be complex, perhaps owing to the non-uniform substrate, diverse communities or complex food web. The relationship between profundal invertebrates and eutrophication pressure was also concluded to require further work. The complicating influence of depth and stratification on the effects of eutrophication may make it difficult to develop an assessment system that can be used in all situations. Focusing on a limited depth range such as the sub-littoral as well as the profundal zone may help extract the influence of stratification and depth from that of eutrophication. Most ecological change was found to take place at an early stage of nutrient enrichment; generally between 10 and 20 ug l-1 TP. Ecological status boundaries need to reflect this. Ecological assessment metrics were developed for eutrophication only. It is recommended to complement current data with a separate study whose site selection is stratified across a range of known acidification and hydromorophological pressures in Ireland. Further chemical and physical characterisation of lakes is necessary and should be carried out by the River Basin Districts. Reference conditions were unavailable or poorly represented for certain lake types; mainly in the 20 to 100 mg l-1 CaCO3 alkalinity band. A palaeolimnological project focusing on biological elements such as phytoplankton, chironomids and macrophytes would help to characterise reference conditions for these types. This would complement ongoing work by the EPA funded project INSIGHT, which aims to test the validity of many of the reference lakes selected by this project using palaeolimnological techniques. Fundamental research into the functioning of aquatic ecosystems at third level should be supported to provide a basis for continued refinement of ecological assessment techniques. Work should be immediately carried out to refine metrics, develop estimates of uncertainty in assessment and an excerise on integrating assessment, based on all biological elements should be performed.

FREE Gary;  LITTLE Ruth;  TIERNEY Deirdre;  DONNELLY Karol;  CARONI Rossana; 

2007-06-12

Environmental Protection Agency

JRC37478

1-84095-215-6,   

https://publications.jrc.ec.europa.eu/repository/handle/JRC37478,