Gleyci Aparecida Oliveira Moser

Instantaneous transport of salt, nutrients, suspended matter and chlorophyll-a in the tropical estuarine system of Santos

The contribution of the polluted Sao Vicente and Santos estuarine channels to the eutrophication of Santos bay was assessed through the quantification of instantaneous transport of salt, dissolved inorganic nitrogen (DIN) and phosphate, organic and inorganic matter (OSM and ISM) and chlorophyll-a (Chl-a), during dry (austral winter- August/ 1999) and rainy (austral summer- January/2000) seasons. Samplings were carried out during spring and neap tides, in flood and ebb phases, in two transversal sections at the mouths of the Sao Vicente and Santos channels. Instantaneous transport values generally indicated importation of salt to the estuarine channels, exportation of DIN to the bay, mainly as N-NH4, at a maximum rate of 1155.1 g s-1 during the rainy season; importation of phosphate during the dry season (maximum of 385 g s-1) and exportation of ISM, OSM and Chl-a during periods of greater freshwater discharge. These results demonstrate the great contribution made by the Santos and Sao Vicente estuaries to the eutrophication of Santos bay, especially in the rainy season.

Short-term variability and transport of nutrients and Chlorophyll-a in Bertioga Channel, São Paulo State, Brazil

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.

SHORT-TERM PHYTOPLANKTON DYNAMICS IN RESPONSE TO TIDAL STIRRING IN A TROPICAL ESTUARY (SOUTHEASTERN BRAZIL)

Descriptors: Tropical estuary, Tidal stirring, Phytoplankton. Descritores: Estuario tropical, Movimento da mare, Fitoplâncton. The spatio-temporal distribution of phytoplankton assemblages can be highly affected by physical, chemical and biological processes (HANSSON, 1995; MACINTYRE; CULLEN, 1996; SEURONT et al., 2001). Estuaries are highly variable environments and the processes listed above can influence phytoplankton dynamics not only seasonally (MACEDO et al., 2001; IGNATIADES et al., 2002) but also during tidal cycles (GOOSEN et al., 1999; BRUNET; LIZON, 2003). Tidal stirring constitutes a relevant driving force affecting phytoplankton distribution, since it induces substantial horizontal and vertical mixing of the water column, as well as upstream and downstream displacement of water masses along the main longitudinal estuarine axis. While horizontal mixing has more mechanical effects on phytoplankton (LEGENDRE; DEMERS, 1984), vertical mixing can affect phytoplankton physiology and growth due to its strong impact on the availability of nutrients and light (DEMERS et al., 1979). Overall, tidal forcing is responsible for short-term changes in phytoplankton biomass, specific composition, growth and primary production (WETZ et al., 2006). These effects are especially important in shallow tidally-driven estuarine systems (CLOERN, 1991; WETZ et al., 2006) and different authors have been studying patterns of primary production on this time scale (JOUENNE et al., 2005; HELBLING et al., 2010), but it is also interesting to get some insights on changes in phytoplankton composition (BUCCI et al., 2012; MOSER et al., 2012). Due to its polyphyletic origin, phytoplankton show distinct physiological behavior as well as different abiotic requirements for growth (MARGALEF, 1978; SEIP; REYNOLDS., 1995; LICTHMAN; KLAUSMEIER, 2008). The phytoplankton community composition as well as the spatial and temporal distribution of the species would likely be better understood when considering the physiology as a reflex of their morphometric characteristics (REYNOLDS, 1988; REYNOLDS et al., 2002). Cell size (maximum linear dimension; MDL), surface/volume ratio (S/V) and cell shape are excellent tools to investigate such patterns (LEWIS, 1976; SOURNIA, 1982; MCGILL et al., 2006). REYNOLDS (1988, 2002) applied a functional classification for freshwater phytoplankton using morphological traits (MLD and S/V ratio), proposing the C-S-R strategies, based on Grime’s Competitors, Stress-tolerants and Ruderals (CSR) triangle model for terrestrial plants, and identified three strategies among phytoplankton species. In natural environments, the form and size selection can be the major force that drives phytoplankton communities under distinct

On the determination of a conversion factor from labelled thymidine incorporation by bacteria to cell production in a sub-tropical estuary: preliminary results

Faculdade de Ciencias Ambientais - Oceanografia. Centro Universitario Monte Serrat - UNIMONTE. (Campus Ponta da Praia, Av. Saldanha da Gama, 89, 11030-220, Santos, SP, Brasil) Bacterial carbon production has become a key parameter in quantifying carbon flows through aquatic food webs (Smith & Azam, 1992). Measurement of

Short-term response of phytoplankton community to over-enrichment of nutrients in a well-preserved sub-tropical estuary

At the interface between marine and fresh waters represented by estuaries, chemical changes in the body of water are reflected in the biological processes. Rivers, since humans usually use them as wastewater disposal systems, also play an important role in the nutrient enrichment of coastal waters and estuaries (SMITH, 2003). The first eutrophication associated processes that is focused on in almost all studies is the excess algal growth (YOSHIYAMA; SHARP, 2006). But, as estuarine system response to nutrient enrichment has been demonstrated not to be linear, as i.e. the high-nutrient and low-growth (HNLG) conditions described by (SHARP, 2001