A heterogeneidade ambiental em angiospermas marinhas e os efeitos sobre a variação espacial da macrofauna associada

Abstract

The study of environmental heterogeneity seeks to establish standards in the distribution and diversity of species based on biological and abiotic environmental characteristics. These studies are supported by the hypothesis of habitat heterogeneity, which assumes that most heterogeneous environments are more diverse and home to the largest number of species. The objective of this study was to evaluate the spatial heterogeneity in a meadow of seagrasses and their effects on the diversity of macrobenthos associated, in a tidal flat of Estuarine Complex Timonha-Ubatuba, State of Piaui. For this, they were marked three subareas A (downstream), B (middle) and C (upstream), following a horizontal environmental gradient from the mouth towards the upper estuary. In each area, in an environmental vertical gradient of air exposure time (beach towards the riverbed) were installed three transects with 30m in length parallel to the waterline, where two samples were taken, one in the dry season (November 2014) and another in the rainy season (April 2015). n each sampling, six previously drawn points were collected environmental data (soil temperature, salinity and sediment samples) and biological samples to quantify the percentage of cover, height of the canopy, morphometry of plants, density and biomass, as well as samples of macrofauna associated. rainfall data, air temperature, insolation and wind speed of obtained in INMET database for the region. Angiosperms and macroalgae were separated and identified. The plants were obtained morphometric data, density (hastes.m-²) and biomass (g.ps.m-²). And the fauna were determined as descriptors of the community (S - number of species, N - number of individuals, d - Margalef Wealth, J'- Pielou Equitability and H '- Shannon Diversity). Soil granulometry and percentage of organic matter and sediment carbonates. Multivariate statistical analyzes were employed to characterize the sub-areas, transects and study periods. The influence of environmental factors on changes in seagrass was analyzed by BIOENV. To describe the environmental heterogeneity were done we carried out a major component analysis (PCA) of prairie and variables were correlated using Spearman's test with the ecological descriptors associated macrofauna. The meadow was multi-species consist of the angiosperms Halodule wrightii, Halodule beaudettei, Halophila baillonis and Halophila decipiens, where only H. wrightii showed significant variance in the analysis of the percentage of coverage, density, biomass and morphological characters of plants, according to the period climate. The heterogeneity of the environment on the meadow was mainly determined by the density and biomass and showing a horizontal gradient in the distribution of macrofauna. The molluscs were the most common organisms in all subareas, representing 77.66% of individuals and 48 species. Crustaceans are represented by 16 species and polychaetes 25 species and these two groups representing 13.37% and 8.97% of individuals sampled, respectively the hypothesis of environmental heterogeneity was confirmed by the fauna of community descriptors in relation to different sub-areas of the meadow.