Morphotraits vs. species: morphological composition and species structure of benthic lacustrine testate amoebae provide independent information for palaeoreconstructions

The aim of this study was to compare the variables influencing benthic testate amoebae assemblage species structure (SS) and morphotrait compositions (MC) along a depth gradient in two stratified freshwater lakes: Glubokoe and Valdayskoe, Russia. Redundancy and k-means analysis distinguished four groups for MC associated with the littoral, metalimnion and profundal zones common to both lakes, whereas for SS, six groups were associated with these zones separately in each lake. MC was found to reflect changes in a larger number of the hydrochemical variables studied compared to SS. The potential role of the oxygen-reduction potential (ORP), conductivity (COND), suspended solids and oxygen content in the formation of MC was demonstrated. The main factor influencing MC was ORP, whereas the main factor influencing SS was COND. The factors influencing MC and SS in the littoral and metalimnion zones were different, but were similar in profundal zone. Thus, the MC and SS of testate amoebae could provide independent information on environmental changes that should be taken into account when interpreting palaeoreconstructions.<br>