The use of rotifers as test species in the aquatic effect assessment of pesticides in the tropics

The present study aimed at evaluating the suitability of rotifers as standard invertebrate test species for the aquatic effect assessments of pesticides, with special emphasis to tropical settings. This was done by weighing rotifers against the criteria that are traditionally used for this end. Rotifers are easy to maintain and culture in the laboratory and their (biological) response to chemical stressors like pesticides is well known. As abundant organisms in aquatic ecosystems, they play a key role in energy flow and nutrient cycling. Although they are often considered to have a low sensitivity to pesticides, a sensitivity analysis conducted in this study revealed that they may be more sensitive than the standard invertebrate test species Daphnia magna to fungicides. In addition, few toxicity data were available for rotifers other than Brachionus calyciflorus and these data were almost exclusively acute (EC50) toxicity values. Subsequently, the sensitivity of other rotifers as well as the chronic sensitivity, bioaccumulation potential, and possible role in biomagnification of pesticides in aquatic foodwebs remains largely unknown. Given their greater diversity and ecological role in tropical freshwaters as compared to temperate freshwaters, the use of rotifers in tropical risk assessments and immediate research needs are discussed.