In situ filtering rates of Cladocera: Effect of body length, temperature, and food concentration

The individual filtering rates of the cladocerans in Créteil Lake were measured in the daytime with 14 C‐labeled Chlorella during a seasonal survey. This mesotrophic, shallow, polymictic lake is characterized by small algae (<25 µ m) and cladocerans (<1.3 mm). Multiple regression models were established for each genus and for all the cladocerans. Body length alone explained from 44 to 57% of the total variance in the filtering rates of Daphnia spp., Ceriodaphnia spp., and Diaphanosoma brachyurum . An additional 23–34% of the variance was attributable to temperature. The inclusion of the Chl a concentration finally yielded r 2 values ranging between 0.79 and 0.84. On the other hand, body length and temperature explained only 16% of the total variance in filtering rate of Bosmina longirostris . By taking into account the effect of factors other than length of the animal, the fit of the model established for all cladocerans improved considerably (from r 2 = 0.47 to r 2 = 0.83). Species‐specific responses and thermal effects in the lake show the difficulty of applying models based solely on body length to obtain sufficiently accurate estimates of cladoceran filtering rates.