Assessing recent climatic and human influences on chironomid communities from two moderately impacted lakes in western Ireland

Abstract

This study assessed the influences of climate warming and human impacts on Irish lakes over the late nineteenth to early twenty-first centuries. High-resolution chironomid (Insecta: Diptera) stratigraphies were developed for two low- to mid-elevation lakes in northwest Ireland to determine if lakes with mild-to-moderate human impacts can be used to accurately reconstruct mean July air temperature. Application of an Ireland-based chironomid-inference model to quantitatively estimate July air temperature (\(r_{\text{jack}}^{2}\) = 0.60, RMSEP = 0.57°C) revealed that chironomids can reflect changes in Irish temperature, particularly post-1980 when warming accelerated, although this signal becomes compromised with intensified human impacts. A biotic response to nutrient enrichment and soil erosion from direct human activities was identified through a comparison of chironomid autecology with known catchment changes. Redundancy analysis and time series comparisons were used to identify when faunal turnover is a function of local (nutrient input, erosion) versus extra-regional (climate) drivers over the recent past, and identify any thresholds of human influence within the catchments. This study highlights the importance of careful site selection as moderately impacted sites do not follow a simple scheme, as well as multi-proxy analysis to assess catchment-based human activity for longer term chironomid-based temperature reconstructions in Ireland.