Influência de fatores ambientais na estruturação da comunidade de macrófitas aquáticas em um sistema de reservatórios em região tropical

Abstract

This study aimed to analyze which environmental factors are more significant for the structuring of the macrophytes community, in a system of reservoirs located in urban areas. For this the hypotheses were that: In reservoirs cascade structure of aquatic plants is affected by seasonality, competition with phytoplankton, measured by chlorophyll a and nutrients. The composition of various biological types in the community of aquatic weeds is subject to varying degrees of trophic. The study was developed in an area of remaining forest, from October 2014 to July 2015, in quarterly collections in four urban reservoirs inserted in the State Park of Dois Irmãos, Pernambuco - Brazil. In each reservoir were demarcated two installments, one in the mouth and another in the mouth, with a width of 5 meters and length equal to the ecosystem (between 108 and 350 m). For visual analysis of coverage were employed methods Braun Blanquet and Volume Plants Infestation (PVI). In the center of each transect water samples were collected for analysis of chlorophyll a, ammonia, nitrite, nitrate and total phosphorus, and water transparency measurements with the Secchi disk depth and with the adapted measuring tape. The hypotheses were tested by Bray-Curtis similarity analysis, PERMANOVA and Canonical Correspondence Analysis (CCA). All tests were run in the program R. were inventoried 56 species, where 90% of the taxa were present in the reservoir Dois Irmãos (49) Dentro, Meio and Prata had 34, 19:17 ratio, respectively. Ecosystems showed a different composition, as seen in the analysis of similarity; Our results rejected part of the initial hypothesis, that the structure of the aquatic plants is affected by the seasonality and the phytoplankton and hence the structure of macroflora more strongly influenced by the nutrients. The second hypothesis was confirmed by the existence of different biological types according to trophic. Therefore, our results reinforce the reservoir cascade theory, the nutrient factor was one of the main factors that influenced the pattern of vegetation cover with submerged in oligotrophic environments (upstream) and floating in eutrophic downstream environments.