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vol.53 issue3-4Seasonal changes in the mixed and barrier layers in the western Equatorial AtlanticInstantaneous transport of salt, nutrients, suspended matter and chlorophyll-a in the tropical estuarine system of Santos author indexsubject indexarticles search
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Brazilian Journal of Oceanography

Print version ISSN 1679-8759On-line version ISSN 1982-436X

Abstract

GIANESELLA, Sônia Maria Flores et al. Short-term variability and transport of nutrients and Chlorophyll-a in Bertioga Channel, São Paulo State, Brazil. Braz. j. oceanogr. [online]. 2005, vol.53, n.3-4, pp.99-114. ISSN 1982-436X.  http://dx.doi.org/10.1590/S1679-87592005000200002.

Short-term variability of nutrients, chlorophyll-a (Chl-a) and seston (TSS) concentrations were followed up at a fixed station in the Bertioga Channel (BC), Southeastern Brazil, over two full tidal cycles of neap and spring tides, during the winter of 1991. Simultaneous data on hydrographic structure, tidal level and currents allowed the computation of the net transport of those properties. Tidal advection and freshwater flow were the main forcing agents on the water column structure, nutrient availability and Chl-a distribution. Dissolved inorganic nitrogen and phosphate average values were high (16.88 and 0.98 ¼M, respectively, at neap tide and 10.18 and 0.77¼M at spring tide). Despite N and P availability, Chl-a average values were low: 1.13 in the neap and 3.11 mg m-3 in the spring tide, suggesting that the renovation rate of BC waters limits phytoplankton accumulation inside the estuary. The highest Chl-a was associated with the entrance of saltier waters, while the high nutrient concentrations were associated with brackish waters. Nutrients were exported on both tides, TSS and Chl-a were exported on the spring tide and Chl-a was imported on the neap tide. The study of the main transport components indicated that this system is susceptible to the occasional introduction of pollutants from the coastal area, thus presenting a facet of potential fragility.

Keywords : Inorganic nutrients; Chlorophyll-a; Séston; Tidal cycle; Transport components; Outwelling; Bertioga Channel; Estuary.

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