Complex spatial and temporal patterns of littoral benthic communities interacting with water level fluctuations and wind exposure in the littoral zone of a large lake

Abstract

The spatial and temporal organisation of benthic invertebrate communities was studied in a large oligotrophic lake in central Europe. Three shallow littoral sites at 0.4 m depth were sampled monthly from May 2002 to April 2003. On a spatial scale, the benthic community composition at all sites and in all samplings significantly differed in both abundance and biomass. On a temporal scale, the benthic communities at all sites gradually changed each month; monthly samples always significantly differed, but samples from consecutive months were more similar to each other than to samples of non-consecutive months. The observed variability within benthic communities corresponded with changes in the abiotic parameters water level and wind exposure, but was best explained by short- and long-term fluctuations in the water level. Effects of wind exposure were most pronounced in the winter months, when high wind events most often occurred. However, wind effects were masked by stronger effects, such as water-level fluctuation within the shallow littoral zone, or diminished by parameters with opposite effects, e.g. slope vs. exposure. Wind-induced shear stress in the upper eulittoral zone directly influenced the abundance and biomass of the benthic community to a lesser extent. We conclude, however, that this stress alters habitats constantly (e.g. substrate composition, periphyton growth, resuspension vs. sedimentation) and is therefore the driving force for the reported permanent site differences. Furthermore, benthic communities were well adapted to frequent minor changes and also to regular major changes of their habitat, as bare substrates were rapidly recolonised within a month.