Zooplankton composition in aquatic systems of semi-arid Brazil: spatial variation and implications of water management

This study compares major taxa of zooplankton (Rotifera, Cladocera and Copepoda) between natural (intermittent streams) and artificial (reservoirs) aquatic systems in semi-arid Brazil to evaluate spatial variation of taxa abundance according to habitat type and the implications of water management on zooplankton composition. The zooplankton fauna recorded was composed of 42 species distributed across 21 families. Assemblage richness was dominated by Rotifera, which presented 13 families and 32 species. Brachionidae was the richest taxon (13 species), followed by Lecanidae (4 species) and Filiniidae (3 species). Cladocera were represented by 5 families and Chydoridae was the richest with 2 species. Copepoda presented three families with 4 species. Zooplankton composition did not vary between the study areas. However, segregation among sites (managed and natural) was observed within each study area. Results indicate that the modification of natural patterns of water flow and promotion of lentic conditions has the potential to interfere with zooplankton communities by favoring groups with slower growth rates such as Cladocera and Copepoda. Given the notion that factors affecting the structure and composition of the zooplankton community lie at several levels of the river watershed, decision-makers must identify the parts of the riverine ecosystems that are vital to maintaining its health, in order to propose (or re-evaluate) management and conservation policies for dryland streams. espacial e implicacoes do manejo. Este estudo compara a riqueza e densidade do zooplâncton (Rotifera, Cladocera e Copepoda) entre ambientes aquaticos naturais (rios intermitentes) e artificiais (reservatorios) do semiarido brasileiro com o objetivo de avaliar a variacao espacial dos taxa de acordo com o tipo de habitat e comentar as implicacoes do manejo desses sistemas na composicao do zooplâncton. A fauna foi composta por 42 especies distribuidas entre 21 familias. As comunidades foram dominadas, em termos de riqueza de especies, pelos Rotifera, que apresentaram 13 familias e 32 especies. Brachionidae foi o taxon mais rico com 13 especies, seguido por Lecanidae (4 especies) e Filiniidae (3 especies). Cladocera apresentou 5 familias dentre as quais Chydoridae foi a mais rica com 2 especies. Copepoda apresentou 3 familias e 4 especies. A composicao do zooplâncton nao variou entre as areas de estudo. Contudo, observou-se segregacao entre os locais de estudo (artificiais e naturais) dentro de cada area estudada. Os resultados do presente estudo indicam que modificacoes nos padroes naturais de fluxo pela implementacao de condicoes lenticas tem o potencial para interferir na composicao do zooplâncton e favorecer grupos com taxas de crescimento mais lentas como Cladocera e Copepoda. Tendo em vista que fatores que afetam a estrutura e composicao das comunidades de zooplâncton podem ser determinados em escalas diferentes da bacia hidrografica, deve-se identificar que partes dos sistemas ribeirinhos sao vitais para manutencao da integridade biologica antes de propor (ou reavaliar) as politicas de manejo de ecossistemas e conservacao de especies em ambientes aquaticos de areas secas.