Cladoceran community structure in three meso-eutrophic Polish lakes with varying thermal regimes

The effects of temperature on cladoceran community structure are not well understood. We assessed the dynamics of cladoceran communities in three meso-eutrophic Polish lakes within the same region but with different thermal regimes. In an artificially (power plant) heated lake, Daphnia were absent during the warmest period in July. In the two other lakes, one of which was secondarily heated and one that was non-heated, Daphnia accounted for 19-36 % of the total biomass of the cladoceran communities. Species richness was also higher in the non-heated and secondarily heated lakes than in the heated lake. Phytoplankton analysis suggested that cyanobacteria did not suppress Daphnia, as the highest relative abundance of Daphnia was observed in the non-heated lake, which also presented the highest relative abundance of cyanobacteria. Additionally, there was no indication that food depletion was greater in the heated lake than in the other two lakes. A contribution analysis to estimate bottom-up and top-down effects showed that predation was more important in controlling cladoceran birth rates in the non-heated lake compared to the other two lakes. Daphnia abundance declined with heating, while the abundance of smaller-bodied species, including Ceriodaphnia and Diaphanosoma, increased. We suggest that increased mortality due to the increased temperature in the heated lake may have been the cause of Daphnia suppression compared to the other two study lakes.Original Abstract: Evaluamos la dinamica de la comunidad de cladoceros en tres lagos meso-troficos de Polonia, de la misma region pero con diferentes regimenes de temperatura. En un lago calentado artificialmente (central termica) Daphnia estuvo ausente durante el periodo mas calido, en Julio. En los otros dos lagos, uno conectado con el anterior y por tanto, calentado indirectamente y otro que no lo fue, Daphnia represento el 19-36 % del total de la comunidad de cladoceros. La riqueza de especies fue tambien mas alta en el lago no calentado y el calentado secundariamente, que en el primero. El analisis del fitoplancton mostro que las cianobacterias no ejercieron ningun efecto negativo en la abundancia de Daphnia, ya que el lago no calentado presento la abundancia relativa mas alta de este genero y ademas la mayor abundancia relativa de cianobacterias. Adicionalmente, no hubo ningun indicio de que hubiera una mayor disminucion de alimento en el lago calentado artificialmente que en los otros dos lagos. Con un an