Qualidade da água e distribuição espacial de foraminíferos bentônicos em estuários das Baías Norte e Sul da Ilha de Santa Catarina (Brasil)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Watersheds with different characteristics lead to different rates of biogeochemical elements that contribute in estuarine systems. Thus, this study investigated the contribution of drainage on the nutrients as well as the responses of benthic foraminifera, with focus on estuarine region of six major systems that discharge in the North and South bays of Santa Catarina, SC, Brazil. The estuaries of rivers: Cubatão do Sul, Biguaçu, Maciambu were mainly fluvial inputs on the West side (continental side) to the bays and the estuaries of rivers Ratones, Tavares and Itacorubi on the East side (insular side). Among the three estuaries on the continental side that contribute the least impacted by the urbanization and with lower basin (71 km2) is the estuary of the Rio Maciambu, located at a Conservation Unit Area. The estuary of the Rio Cubatão do Sul (743 km2) and Rio Biguaçu (383 km2) have consistently higher anthropogenic contributions from agricultural activities and domestic sewage. On the island bring estuaries with lower basins: Ratones with 91km2, Tavares with 50 km2 and Itacorubi with 28 km2, the latter being the most impacted by urbanization. Ratones is located at the Ecological Station of Carijós and Tavares at the Extractive Reserve of Pirajubaé. The descriptors analyzed to assess the spatial variability of water quality were: salinity, pH, dissolved oxygen, temperature, turbidity, dissolved inorganic nutrients (nitrite, nitrate, ammonium, orthophosphate and silicon reactive), nitrogen and total phosphorus, chlorophyll-a, total and fecal coliforms. At 2007 and 2008 were performed 4 samplings in each study the area in order to obtain data under different conditions of river flow and tide. From the data of salinity and dissolved inorganic nutrients (nitrogen and phosphorus), biogeochemical balances have been prepared using the methodological guidelines of Land-Ocean Interactions in Coastal Zone (LOICZ) approach. The sediments were analyzed in relation to their distribution, abundance and composition of benthic foraminifera and grain size (sand and mud fraction). The Hydrochemistry results showed that the estuaries of rivers with greater urbanization in the surrounding area, with emphasis on Itacorubi would be similar and sometimes even higher than those found in polluted estuarine systems. The estuaries of rivers Ratones and Tavares, despite being in conservation units, also had some values above the reference limits established by CONAMA 357/05 law, emphasizing the values in excess of fecal coliform and phosphate, suggesting the contribution of domestic sewage. Hydrochemistry best conditions were found in the estuary of the River Maciambu. The estuaries showed pattern of nutrients consumption on the dissolved inorganic phosphorus (DIP) mass balance, except the estuary of the Rio Ratones which showed positive variations indicating exportation of water from the bottom of the estuary to the North Bay. For the dissolved inorganic nitrogen (DIN), all estuaries were estimated such internal removal in the estuary, before leaving the water for the Bays. The results obtained in the benthic compartment suggests that the estuaries of rivers Cubatão do Sul e Biguaçu are most unfavorable to benthic colonization. The low density of benthic foraminifera probably reflects the anthropogenic impacts related to the increased amount of particulate material in suspension and remobilization of sediments from bottom despite the deforestation of the margins and the constant dredging of the bed. The estuary of the Rio Maciambu highlighted by the higher density of living foraminifera, suggesting its higher benthic productivity. The estuary of the Rio Itacorubi showed high concentrations of nutrients and turbidity, besides the higher percentages of mud and also organic indicators of stress in benthic compartment (high dominance of Ammonia tepida with reduced diameter). Comparatively, the estuaries on the continental side were characterized by higher residual flows, river flows of DIN and DIP, higher concentrations of reactive silicon and dissolved oxygen and the highest densities of tecamebas (protozoa indicators of river contribution). The estuaries on the island side were characterized by the greatest number of fecal coliforms and higher concentrations of chlorophyll-a, especially in Itacorubi and Tavares estuaries. The estuary of the River Ratones and Maciambu showed higher salinity and, consequently, greater flows of salt water leaving the surface and entering from bottom waters.

ASSUNTO(S)

agua - biguaçu, rio (sc) - qualidade agua - - analise estuarios - baia norte (florianópolis, sc) - baía sul (florianópolis, sc) agua - ratones, rio (ilha de santa catarina, sc) - qualidade agua - maciambu, rio (ilha de santa catarina, sc) - qualidade geografia agua - cubatão sul, rio (sc) - qualidade agua - tavares, rio (ilha de santa catarina, sc) - qualidade geografia agua - itacorubi, rio (ilha de santa catarina, sc) - qualidade

ACESSO AO ARTIGO

Documentos Relacionados