Efeitos do esgoto urbano nos Macrobentos e fauna visitante do Mangal da Costa do Sol, em comparação com o Mangal da Ponta Rasa e Mangal do Saco: um estudo isotópico duplo

Abstract

In September and October 2005, samples were taken in the polluted mangroves of Costa do Sol (areas CSA1 and CSA2) (Maputo city) and in the unpolluted mangroves of Ponta Rasa and Saco (both in Inhaca Island). The collected samples were used for a dual stable isotope study (carried out at a Belgian university) to compare the effects of sewage discharges into the mangrove and the use of mangroves as a latrine on the õ13C and õ15N of macrobenthic communities, visiting fauna and probable sources. of carbon and nitrogen (sediment, suspended particulate organic matter and plant material). The possible sources for each species in each mangrove were also compared and the trophic level was estimated only based on the õ15N of the species found. The nitrogen isotopic ratios of polluted and unpolluted mangroves in relation to faunal species and probable sources were, in general, different. However, the differences between the isotopic ratios of carbon of the two types of mangrove were less evident than among those of nitrogen, however, the faunal species showed differences between at least one polluted and unpolluted area. As it was not possible to identify the sources of C and N for the fauna visiting the polluted mangroves, a comparison was not made in relation to the probable sources, between the polluted and the unpolluted mangroves. The probable sources of carbon and nitrogen of the species common to both types of mangroves were different for the species P.catenata and U.annulipes and C.decollata. The amount of likely sources of C and N contributing to the diet of N. meinerti and P.guttatum were different between the polluted and unpolluted mangroves. The species, common to both types of mangroves, appeared to belong to the same trophic level in all mangroves, based only on õ15N (TRADUÇÃO NOSSA)