Cladoceran and chironomid assemblages as qualitative indicators of water depth in subarctic Fennoscandian lakes

The relationship between surface-sediment cladoceran and chironomid communi ties to lake depth was analysed in 53 lakes distributed across timberline i n northern Fennoscandia using multivariate statistical approaches. The stud y sites are small and bathymerically simple, with water depth ranging from 0.85-27.0 m (mean 6.36 m). Maximum lake depth was the most important factor in explaining the cladoceran distributions and the second most important f actor in explaining the chironomid distributions in these subarctic lakes, as assessed on the basis of a series of constrained RDAs, Monte Carlo permu tation tests, and variance partitioning. Quantitative inference models for maximum lake depth were created for both groups of animals. Well-performing calibration functions for predicting lake depth were obtained in each case using linear partial least squares (PLS) regression and calibration, weigh ted averaging (WA) with an 'inverse' deshrinking regression, and weighted a veraging partial least squares (WA-PLS). Quantitative reconstructions of la ke level fluctuations should be possible from cladoceran and chironomid cor e data with a root mean squared error of prediction (RMSEP), as estimated b y jack-knifing, of about 1.6-3.0 m.