A comunidade de amebas testáce testáceas as e o gradiente de carbono orgânico dissolvido em ambientes aquáticos de restinga

Abstract

Dissolved organic carbon (DOC) has long been recognized as an important factor shaping aquatic ecosystems as it influences physical, chemical and biological processes. The DOC is mainly composed of humic substances (HS), up to 90%, which gives a brownish-reddish color to the water. Allochthonous DOC has different effects on the biological communities, i.e. the testate amoebae (TA). The relationship between the DOC gradient and the TA community is yet poorly understood, especially in the restinga aquatic environments. The present work objectives are: i) map and investigate the restinga aquatic environments along a DOC concentration gradient; ii) gather knowledge about the TA community (composition, richness and density) in aquatic environments and iii) find possible biological indicator species for the DOC gradient and other environmental variables. We sampled 32 environments in the restinga of the North of the Rio de Janeiro state, they were of freshwater and small, like ponds. The TA community was studied from a single sampling period - January of 2017 - and analysed for its composition, richness and density. Physical and chemical variables were analysed along the gradient. We did not find any direct relationship between density of TA and the DOC gradient, instead, our results show a relation between the composition of TA and the DOC gradient, with an alternation of the dominant genera. In low DOC concentrations TA community was dominated by the genera Centropyxis followed by Difflugia, while Arcella dominated in high DOC concentrations. The genera Lesquereusia was dominant in just one site with low concentration, while the genera Armipyxis occurred in higher density in the site with the highest concentration of DOC.