Reproductive inhibition in Daphnia magna Straus, 1820, exposed to sediment samples of an
area under impact from the petrochemical industry
TERRA1, N.R., FEIDEN2, I.R., MOREIRA3, J. de S. & NUNES4, E.A.
1 Fundação Estadual de Proteção Ambiental Henrique Luís Roessler (FEPAM). Av. Salvador França, 1707 - CEP 90960-000
Porto Alegre - Rio Grande do Sul - Brasil.
e-mail: 1 nara.terra@ufrgs.br; 2 ildafeiden@gmail.com; 3 julianomoreirabio@yahoo.com.br; 4 emilenenunes@aol.com
ABSTRACT: Bom Jardim is one of the streams that form the Caí river basin and it has been influenced by petrochemical industry wastes since 1982. Therefore we studied the effect of sediment on the cladoceran Daphnia magna Straus, 1820, in the stream to observe the impact so far caused by the industrial complex on the environment. Three stations in the stream were sampled to perform chronic tests on sediments. Long duration tests in semi-static flow were performed with D. magna. At the beginning of the observations, the microcrustaceans were 2 to 26 hours old. Each sampling station received ten individuals, placed individually in beakers containing one part of sediment to four parts of culture medium (v:v). We observed that reproduction at all sites was below the minimum expected limit to maintain the species (20 individuals/offspring), sometimes reaching zero at the site with the most impact, such as the one located next to the area where the treated effluents from the petrochemical complex were sprinkled. Both survival and reproduction data suggested that stream sediment quality decreases towards the mouth. Looking at reproduction and survival, we observed that the former was more sensitive to identify environmental quality in the assays performed.
Key-words: Chronic assay, Cladoceran, Epibenthic microcrustacean, Sediment.