Diversidade de diatomáceas (Bacillariophyta) perifíticas no reservatório de Curuá-Una (Santarém, Amazônia, Brasil)

Abstract

The diatoms are main algae in the periphytic communities. In addition to the fundamental contribution to the trofic chain, they can also be used efficiently in the assessment of environmental conditions in rivers, streams, reservoirs and lakes. Aiming to investigate the composition (floristic survey) of the periphytic diatom community of the Curuá-Una reservoir (Santarém-PA), as well as analyzing the distribution of this community of periphytic algae in the river and Curuá-Una reservoir in relation to abiotic data. This study carried out collections between the months of May 2016 and April 2017 in six different sites, distributed over of the Curuá-Una reservoir (lake zone), mouth of the Moju and Mojui rivers (transiotinal zone/ influence lotic environment) in two periods (less rainy and rainy) totaling 24 samples. Measurements were taken in each sampling in situ of physical and chemical varieties of water. Periphytic diatoms were obtained using artificial substrates (samplers) type EDS (Epilithic Diatom Sampler) In total, 172 taxa were recorded throughout the sample, belonging to 34 genus and 21 families. The most representatives’ genus was Eunotia Ehrenberg, Gomphonema Ehrenberg, Frustulia Rabenhorst and Encyonema Kützing. The Shannon diversity ranged in the reservouir in the rainy season between from less rainy season. It was revealed the existence of a spatial pattern between the samplers, and that diatoms community is structured in three distinct groups. Canonical correspondence analysis showed that the composition of the periphytic diatoms is strongly associated by the environmental variables conductivity, pH, BOD, ammonium, silica, temperature and transparency. It was also possible to observe that most of the registered species were considered rare, some species stood out as sporadic and few were considered frequent or constant. The results observed in the present study showed a high diversity of taxa throughout the sample when compared with other studies carried out with EDS type samplers in Brazil, in addition, it provided a better understanding of the floristic composition of the periphery in Amazonian aquatic environments. The Curuá-Una reservoir is relatively preserved, however it shows signs of mild to moderate degree of anthropic influence, which are associated with the inadequate use of the soil around this aquatic environment.