Carcaças de peixes em rios intermitentes: fontes ou drenos de fósforo?

Abstract

Animals are directly and indirectly important in nutrient cycling. Fish represents steady poolsof nutrients in aquatic ecosystem recognized as nutrient sinks, accumulating over time morenutrients than is recycled by releasing. Nevertheless, considering fish as nutrient sink orsource depends on pool size, emigration and immigration, spatial and temporal biomasschanges, and fate of post mortem nutrients. Annual cease of flow in Intermittent rivers canpromotes fish kills that potentially causes sources of nutrients. The goal of this study is toinvestigate if fish carcasses represents a Phosphorus (P) source in intermittent rivers. Wequantified phosphorus composition of the most abundant fish species in a intermittent riverand temporal biomass change of these species to estimate P potentially released by fishmortality. Furthermore, we test whether fish carcasses were predated or not and identified fishscavengers in artificial river pools. The results shows a fish biomass temporal decrease in themiddle reach of the river only in the dry season very end. On the other hand, in the low riverreachs the overall fish biomass increase over time. Moreover, fish carcasses were highlypredated in artificial river pools. River intermittence can enhance the fish role as sink ofnutrients by different mecanisms that depends on the presence or absence of remanent pools.On the basis of these results, it can be concluded that fish carcasses in intermittent rivers arenutrient subsidies to terrestrial ecosystem in sites where total flow cease, whereas fish aresteady pool of Phosphorus capable to accumulate nutrients during dry season remanent riverpools sites.