Potential of the water flea Daphnia magna to control phytoplankton population in eutrophic waters

Abstract

Water enrichment has become a national problem that needs to be resolved. This study examined the ability of water fleas Daphnia magna to grow and to control phytoplankton populations in the waters from eutrophic ponds Situ Cikaret and Situ Gunung Putri in Bogor Regency, West Java. Water samples from these water bodies were used to grow the daphnid populations in the styrofoam aquariums without artificial feeding with an initial density of 3.3 individuals/L. The experiment was carried out with three replications. Daphnid population was counted every 4-5 days to observe its growth and development. The chlorophyll content that reflects the phytoplankton biomass at the beginning of the study in the water of Situ Cikaret and Situ Gunung Putri were 52 and 22 μg/L, respectively. The water from fertile ponds allowed the development of phytoplankton populations and be utilized by daphnids to support their growth and reproduction. The results indicated that daphnids showed a preference for some phytoplankton genera more than other genera because not all phytoplankton populations were consumed. Following an increase in chlorophyll content, the daphnid density also increased to reach a maximum of 197 individuals/L in the water of Situ Cikaret and 169 individuals/L in the water of Situ Gunung Putri on day 15. The chlorophyll content decreased significantly towards the end of the experiment indicating the phytoplankton population is almost depleted. Hence, this study showed the potential of water flea Daphnia magna as bio-resources to utilize eutrophic pond waters and to control the phytoplankton population to improve water quality.