Effects of toxic and non-toxic cyanobacteria on the life history of tropical and temperate cladocerans

1. This study compares the effects of four toxic strains of Microcystis aeruginosa on tropical and temperate Cladocera. Survival was tested in acute toxicity experiments using Microcystis alone or in mixtures with the edible green algae Ankistrodesmus falcatus. The effect of chronic exposure on population growth was estimated in life-table experiments by varying the proportion of Microcystis and the green alga. Nutri-tional deficiency was assessed using a non-toxic cyanobacterium in a zooplankton growth experiment. Feeding inhibition was tested using a 14C-labelled green alga as a tracer in mixtures with toxic Microcystis. 2. Toxicity varied consistently between Microcystis strains, while sensitivity varied con-sistently between cladoceran species. However, no relationship was found between sensitivity and geographical origin or cladoceran body size. Two small-bodied clado-cerans from the same tropical lake, Ceriodaphnia cornuta and Moinodaphnia macleayi, were the least sensitive and most sensitive species, respectively. 3. Surprisingly, two small tropical cladocerans survived longer without food than did three large Daphnia species and a third small tropical species