The distribution of littoral chironomids along an altitudinal gradient in High Tatra Mountain lakes: Could they be used as indicators of climate change?

Abstract

We studied assemblages of littoral chironomids from three alpine lakes in the High Tatra Mountains (Slovakia) along an altitude range of 1725-2157 m. The study sites were selected in order to em- phasize differences in their thermal regimes. Littoral samples were taken quantitatively in the ice-free seasons of 2000 and 2001. In total, 3468 chironomid larvae and pupae were collected and 29 taxa were identified. Some parameters of the littoral chironomid assemblages showed clear patterns along the altitude gradient. The number of taxa and Shannon diversity increased markedly with decreasing altitude. Density, however, did not show any correlation with altitude. Even though gatherers highly dominated in all sites, their relative abundance decreased with decreasing altitude. The ratio of scrapers and predators correlated negatively with altitude. According to the results of a Detrended Correspondence Analysis, Pseudodiamesa arctica and Micropsectra radialis were chosen as indicator species for alpine lakes > 2000 m a.s.l. Typical subalpine lake inhabitants are Zavrelimyia sp., Prodiamesa olivacea, Corynoneura scutellata group, Cricotopus polaris, Micropsectra bavarica and Paratanytarsus austriacus. A single species, Micropsectra junci, seemed to be char- acteristic of alpine lakes < 2000 m a.s.l. This gradient lake concept could be used to predict changes in mountain lake fauna under expected climate change scenarios. Generally, an upward shift of subalpine species would be expected. The thermal regime of lakes, however, also depends on several local factors. Consequently, the schemes outlined here would not be valid for the entire Tatra lake district.