Coincidence of sedimentation peaks with diatom blooms, wind, and calcite precipitation measured in high resolution by a multi-trap

Organisms and processes in the epilimnion of lakes determine the rate of sedimentation. To investigate the impact of phyto-and zooplankton on the sedimentation rate, we sampled the sedimenting material in Lake Stechlin. Sedimenting matter was collected using a high-resolution multi-trap in three-day intervals during the thermally stratified seasons in 2011 (at 65 m depth) and 2012 (at 20 m depth). Dry weight of the sedimented material was related to chemical, physical, and biological data collected from the water column, as well as to meteorological data. The high-resolution trap showed two mass sedimentation peaks in 2011 and one in 2012. We found that diatom blooms in spring were followed by the highest sedimentation rate in 2011, but not in 2012. The sedimentation rates significantly correlated to low wind speed, followed by a rapid formation of the thermocline, as well as to high calcite concentrations in 2011. Our results suggest that the presence of some aggregation factors like calcite crystal exopolymers or fecal pellets support the sinking process. Furthermore, the high resolution of the trap used here allowed for obtaining precise correlations between sedimentation and the measured parameters indicating relevance of temporal coincidence of multiple environmental variables.