Lacustrine, profundal meiobenthic oligochaetes as indicators of trophy and organic loading

Abstract

Meiobenthic and macrobenthic oligochaetes were collected from two depths in Lake Päjänne and examined together with environmental data in which two environmental gradients can be seen. Numbers of Piguetiella blanci, Aeolosoma quaternarium and Aeolosoma hemprichi were positively correlated with oxygen saturation and negatively correlated with total phosphorus and COD suggesting that these species are indicators of oligotrophic conditions. Numbers of Amphichaeta leydigii, Specaria josinae and Vejdovskyella comata were positively correlated with total phosphorus which implies that these species prefer eutrophic conditions. The last three species and Dero digitata showed positive correlations with COD and organic sedimentation, which suggests that they also indicate organic loading. A decrease in aeolosomatid biomass was seen with increasing phosphorus and organic loading. The average body size of detritus-feeding naidids in the upper part of the profundal zone was reduced by organic loading, and more clearly eutrophication, which emphasizes the importance of including meiobenthic oligochaetes in pollution investigations. Of the naidid and aeolosomatid species, Chaetogaster langi preferred the greatest depths of the profundal zone while most of the other species were more abundant at 20 m rather than at the maximum depth. Clustering of the oligochaete taxa supported these observations and clustering of sampling stations based on oligochaete variables generally corresponded to clustering based on environmental data.