Made available in DSpace on 2014-12-17T14:02:04Z (GMT). No. of bitstreams: 1 WanessaS.pdf: 455733 bytes, checksum: f1698247e4a0491cd094aa4ffa270c21 (MD5) Previous issue date: 2007-02-12 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The response of zooplankton assemblages to variations in the water quality of four man-made lakes, caused by eutrophication and siltation, was investigated by means of canonical correspondence analysis. Monte Carlo simulations using the CCA eingenvalues as test statistics revealed that changes in zooplankton species composition along the environmental gradients of trophic state and abiogenic turbidity were highly significant. The species Brachionus calyciflorus, Thermocyclops sp. and Argyrodiaptomus sp. were good indicators of eutrophic conditions while the species Brachionus dolabratus, Keratella tropica and Hexarthra sp. were good indicators of high turbidity due to suspended sediments. The rotifer genus Brachionus was the most species-rich taxon, comprising five species which were associated with different environmental conditions. Therefore, we tested whether this genus alone could potentially be a better biological indicator of these environmental gradients than the entire zooplankton assemblages or any other random set of five species. The ordination results show that the five Brachionus species alone did not explain better the observed pattern of environmental variation than most random sets of five species. Therefore, this genus could not be selected as a target taxon for more intensive environmental monitoring as has been previously suggested by Attayde and Bozelli (1998). Overall, our results show that changes in the water quality of man-made lakes in a tropical semi-arid region have significant effects on the structure of zooplankton assemblages that can potentially affect the functioning of these ecosystems / As respostas das assembl?ias zooplanct?nicas ?s varia??es na qualidade da ?gua de quatro reservat?rios, causadas por eutrofiza??o e assoreamento, foram investigadas por meio de uma an?lise de correspond?ncia can?nica. Simula??es de Monte Carlo utilizando os autovalores da CCA como estat?sticas teste revelaram que as mudan?as na composi??o de esp?cies zooplanct?nicas ao longo dos gradientes ambientais de estado tr?fico e turbidez abiog?nica foram altamente significativas. As esp?cies Brachionus calyciflorus, Thermocyclops sp. e Argyrodiaptomus sp. foram boas indicadoras de condi??es eutr?ficas enquanto que as esp?cies Brachionus dolabratus, Keratella tropica e Hexarthra sp. foram boas indicadoras de elevada turbidez por sedimentos em suspens?o. O g?nero de rot?feros Brachionus foi o mais rico em esp?cies, compreendendo cinco esp?cies que estiveram associadas a diferentes condi??es ambientais. Portanto, n?s testamos se esse g?nero sozinho poderia ser potencialmente um melhor indicador biol?gico desses gradientes ambientais do que toda a assembl?ia zooplanct?nica ou qualquer outro conjunto aleat?rio de cinco esp?cies. Os resultados da ordena??o demonstram que as cinco esp?cies de Brachionus quando sozinhas n?o explicaram melhor os padr?es observados de varia??o ambiental que a maioria dos conjuntos aleat?rios de cinco esp?cies. Portanto, este g?nero n?o pode ser selecionado como um t?xon alvo para um monitoramento ambiental mais intensivo conforme previamente sugerido por Attayde e Bozelli (1998). De um modo geral, nossos resultados mostram que mudan?as na qualidade da ?gua de reservat?rios em uma regi?o semi-?rida tropical t?m efeitos significativos sobre a estrutura das assembl?ias zooplanct?nicas, os quais podem afetar potencialmente o funcionamento desses ecossistemas