Ecotoxicological assessment in a pond of freshwater shrimp farming, using the cladocera Ceriodaphnia dubia as test-organism

Abstract

Aquaculture has risen considerably in the last years due to an increase in consumption and to the reduction in the natural fishery stocks. The production of the freshwater prawn Macrobrachium rosenbergii has increased due to the use of intensive systems, generating more organic matter in the natural environment, and possibly, causing its eutrophication. Presently, for this activity to be sustainable, it must be economically, socially and environmentally supported. Therefore, the proposition of the 2005 CONAMA states the use of ecotoxicological analysis for controlling effluents. The aim of this study was to carry out ecotoxicological analysis, with the test-organism Ceriodaphnia dubia, in order to evaluate the water quality from an enterprise of fresh water shrimp culture. Samples were collected monthly, for six months, in a pond of fresh water shrimp Macrobrachium rosenbergii farm. Sites for sampling were set up in order to cover the complete water flow, i.e., from water supply in the system (affluent), passing through shrimp pond, then through effluent and its disposal into the natural environment (water receiver). Results showed that all sites were classified as toxic (acute or chronic). The average of the effluent dilution in all samples reveled NOEC of 50%, LOEC of 100% and IC₅₀:168h of 56.62%. In addition, the physical and chemical variables were analyzed and compared with the results of toxicity.