Bio-Optical Properties of the Inner Continental Shelf off Santos Estuarine System, Southeastern Brazil, and their Implications for Ocean Color Algorithm Performance

Abstract

Optical characterizations of coastal water masses are important tools for a better understanding of physical and biochemical processes and aid the optimization of ocean color algorithms. In this study we present three optical classes of water observed during October/2005 and March/2006 on the inner continental shelf adjacent to Santos Bay (Brazil), based on remote sensing reflectance. ANOVA indicated a crescent estuarine influence in classes 1 to 3. Class 3 presented the highest chlorophyll-a and nutrient concentration and highest light absorption coefficients. Colored dissolved organic matter (CDOM) dominated the light absorption in all classes and was strongly correlated to salinity in October/2005 due to the influence of the La Plata plume. The results indicated that CDOM dynamics in the Santos inner shelf are very complex. The performance of global chlorophyll algorithms was significantly smaller for October/2005 than for March/2006. As inconsistent changes in light absorption spectra by phytoplankton were detected between samplings, the results show that future bio-optical algorithms for this region must be optimized preferentially considering CDOM optical parameters.

Variability in the light absorption coefficients of phytoplankton, non-algal particles, and colored dissolved organic matter in a subtropical bay (Brazil)

“…Although a cdom (443) showed a significant negative dependence on salinity during all conditions, as generally reported for coastal regions, the correlation was only robust (R ¼ À0.94) for CM (lower precipitation). This is consistent with recent findings on the contribution of inner shelf waters with low salinity to SB during winter (Carvalho et al, 2014). The expected inverse dependence of S cdom (index of CDOM composition) on a cdom (443) was not observed during the monthly sampling, but was robust for the tidal sampling (R ¼ À0.86 in NT and R ¼ À0.63 in ST).…”

“…In Santos Bay, the inverse dependence of a cdom (443) on salinity during all conditions investigated indicates terrestrial runoff as a source of CDOM to Santos Bay. Nevertheless, the most robust relationship (R ¼ À0.94) was found during cold months suggesting the influence of the adjacent inner shelf waters (Carvalho et al, 2014). A contribution to CDOM by sediment resuspension (e.g., Menon et al, 2011) was ruled out, as no correlation was found between TSM and a cdom (443).…”

Comparação da variação da diversidade taxonômica e de traços funcionais em comunidades fitoplanctônicas em duas enseadas do litoral norte de São Paulo

“…(Odebrecht et al, 1995;Franco et al, 2016). Outro gênero que se destacou por suas densidades foi Trichodesmium que é encontrado em águas oceânicas ao longo da quebra de plataforma do Brasil (Detoni et al, 2016), mas devido a sua flutuabilidade natural, pode ser deslocado para regiões mais próximas da costa pela ação de ventos (Capone et al, 1997), e de fato, possui registros de florações no litoral de São Paulo (Carvalho et al, 2014).…”