Baseline water quality investigations on Lough Carra, western Ireland, with reference to water chemistry, phytoplankton and aquatic plants

Lough Carra is a shallow limestone lake in County Mayo in the west of Irela nd. It is situated in the Corrib catchment. The lake has been managed as a brown trout fishery since the 1950s, initially by the Inland Fisheries Trus t and more recently by the Western Regional Fisheries Board. The results fr om a number of studies carried out by the Inland Fisheries Trust and Fisher ies Boards are presented, including the findings of a 1972 bathymetric surv ey; data from long-term monitoring of mid-lake samples for chlorophyll and nutrients, ongoing since 1975; a four-year study on phytoplankton compositi on and biomass (1983-6) and vegetation surveys carried out in 1975 and 1996 , the latter as part of a study on littoral processes in the large western Irish lakes, funded by the Environmental Protection Agency. The findings sh ow the lake to be a very shallow hard-water system with low levels of photo plankton primary production. Diatoms dominated the algal crop in the autumn -spring period with genera of green algae and dinoflagellates present in su mmer. The submerged vegetation was dominated by species of the genus Chara. Extensive reed-beds, dominated by Phragmites australis (Cav.) Trin. ex Ste ud. grew on sheltered and on east-facing shores.