Macroinvertebrate assemblages of small upland peatland lakes in Ireland

Abstract

Blanket bogs are an important habitat in Ireland and are listed for their conservation value by the European Union. Despite this little is known about the invertebrate fauna of freshwater habitats and environmental factors that structure these in blanket bogs, particularly in small upland lakes. This study addressed this topic by sampling twelve small lakes (<0.21km2) at altitudes greater than 300 meters above sea level. Macroinvertebrates were sampled by standard kick-sweeps (five per lake) and Chironomidae were sampled by collecting foam samples, both in spring and late summer in 2005. A total of 202 taxa were identified, largely dominated by the insect orders Diptera, Trichoptera, Heteroptera and Coleoptera. Some were notable as either rare, new records for an area or typical of either upland or acidic water conditions. The chironomids alone contributed 100 species, five of which were confirmed new Irish records, one had not been recorded in the UK at the time of sampling. There were significant differences in both the macroinvertebrate and chironomid assemblages recorded in the twelve lakes. About 78% of the variation was attributed to differences in pH, elevation and nutrients (total phosphorus, nitrates and/or ammonia). Species turnover between the two seasons sampled was high for chironomids but low for the rest of the macroinvertebrates. Significant seasonal changes in the macroinvertebrate community composition occurred, particularly in lakes with a pH of less than 6. Lakes situated on either igneous or sedimentary geologies grouped together, indicating that the surrounding peaty soils usually had a greater influence on water chemistry. Small lakes in upland blanket bog have characteristic invertebrate communities, in part, similar to other aquatic peatland habitats. More such studies are required to document the species present and to determine how susceptible these lakes are to anthropogenic impacts such as climate change.