Affiliation:
1. Fundação Estadual de Proteção Ambiental Henrique Luis Roessler, Brazil
Abstract
AIM: The Taquari River, a tributary of Guaíba Lake, is a major economic and environmental source for Rio Grande do Sul, a state located in the far south of Brazil; METHODS: This study evaluated the interference of sediment from this river in the reproduction and survival of 320 microcrustaceans (80 organisms per site) of the Daphnia magna species. Four sites between the middle course and the river mouth were monitored using eight samples from each site, between June/06 and April/10. Mortality higher than 20% suggested the acute action of the sample on the daphniids, while low reproduction indicated the presence of chronic toxicity. Sometimes an effect on survival was noted, but the number of individuals generated was always low. Semi-static chronic assays (21 day) were developed in 50 mL beakers using sediment and M4 culture medium at a ratio of 1:4 (v:v). Each beakers received a microcrustacean born from lots presenting LC50-24 hours = 0.98 mg K2Cr2O7 ± 0.04 mg totaling ten replicas per sample. The assays were developed under controlled light (16 hours light/day) and temperature (20 ºC ± 2 ºC) conditions; RESULTS: Duncan test showed a variation in reproduction (p < 0.05) with the presence of chronic toxicity. There was less reproductive activity in 91% of the samples, while for survival the reduction attained 9%. Spearman correlation identified the dependence between the rainfall index and reproduction in one of the samples and was absent when the rainfall index was compared to survival; CONCLUSIONS: Taquari River presented episodes of toxicity, and it is necessary to continue studies in the area and to inspect local sources of pollution, as already has been done. Chronic bioassays should be maintained when the purpose is to evaluate environmental quality, since reproduction proved more sensitive than survival.
Subject
Water Science and Technology,Ecology,Aquatic Science,Ecology, Evolution, Behavior and Systematics
Reference42 articles.
1. Standard methods for the examination of water and wastewater,1992
2. NBR 12713: Ecotoxicologia aquática - Toxicidade aguda - Método de ensaio com Daphnia spp (Cladocera, crustacea),2004
3. Mobilisation and transport of sediment: associated phosphorus by surface runoff;BALLANTINE D;Water Air and Soil Pollution,2009
4. Effects of an Organochlorine Pesticide on Different Levels of Biological Organization in Daphnia;BARRY MJ;Ecotoxicology and Environmental Safety,1996
5. Differential effects of phosphorus and fatty acidson Daphnia magna growth and reproduction;BECKER C;Limnology and Oceanography,2005
Cited by
5 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献