Influência do entorno dos reservatórios no estado trófico e na distribuição de diatomáceas em sedimentos superficiais (bacia hidrográfica do Rio Mamanguape

Abstract

This study was to analyze the use and occupation of the land and its relation to water quality and to assess the distribution of diatoms in the surface sediment of five aquatic ecosystems and their trophic state (catchment area of the Mamanguape River - Paraíba, Brazil). For making the maps of land use and occupation was used buffer of 100 m in accordance with Law 12,651/2012 of the Forest Code. Between September and November 2012 water samples were collected and superficial sediment using an adapted sedimentary testemunhador. At the deepest point of the water column of each aquatic ecosystem were measured in situ abiotic variables: temperature, pH, dissolved oxygen, conductivity, total dissolved solids. In laboratory total organic carbon were analyzed in the sediment and total phosphorus in the water (PTA) and sediment. The land use classes (n = 5) and abiotic variables (n = 9) were related by Spearman correlation. The aquatic ecosystems of Arara I (AI), Dam Araçagi (BA) and Dam Matias (BM) had oligotrophic behavior due to the low PTA values (17.2 μg.l-1, 20.2 μg.l-1 ; 21.3 μg.l-1 respectively). However, P-high organic content in the sediment (93.7 μg.g-1; 156.9 μg.g-1; 123.9 μg.g-1 respectively), change in vegetation (59.61%; 57 , 20%, 78.30% respectively) and alkaline and clear water with high conductivity. The aquatic ecosystem of River Canto Dam (BRC) was classified as mesotrophic (PTA = 53.3 μg.l-1), turbid waters (STD = 229 mg / L), shrubby arboreal vegetation (30.28%) and climate limiting underwater light as the Lake of PAO (LP), eutrophic. Statistical analysis showed no significant correlation. They found 30 taxa, 18 genera and 14 families of diatoms in the sediment. In BM and BA the Aulacoseira gender contributed high absolute abundance. The greatest diversity of diatoms was observed in BRC and LP. The Navicula genus was widely distributed in aquatic ecosystems, the most frequent, indicative of turbulent environments. The trophic state index using as match allowance and bioindication of diatoms infer relevant information on water quality and provides management actions aiming at the recovery and conservation while also attend the fragility of aquatic ecosystems to eutrophication.