Changes in phytoplankton composition in response to tides, wind-induced mixing conditions, and freshwater outflows in an urbanised estuarine complex

Abstract

Recent reports have shown an increase in potentially harmful phytoplankton in Santos bay (Southeastern Brazilian Coast), located in a highly urbanised estuarine complex. Prediction of blooms is, thus, essential but the phytoplankton community structure in very dynamic regions is difficult to determine. In the present work, we discriminate bloom forming microphytoplankton dominance and their relationship to physical and meteorological variables to look for patterns observed in different tides and seasons. Comparing 8 distinct situations, we found five scenarios of dominance that could be related to winds, tides and rainfall: i) Surfers, diatoms occurring during high surf zone energies; ii) Sinkers, represented by larger celled diatoms during spring tide, after periods of high precipitation rates; iii) Opportunistic mixers, composed of chain forming diatoms with small or elongate cells occurring during neap tides; iv) Local mixers, microplanktonic diatoms and dinoflagellates which occurred throughout the 298 sampling stations; and v) Mixotrophic dinoflagellates, after intense estuarine discharges. Results suggest alterations in the temporal patterns for some bloom-forming species, while others appeared in abundances above safe limits for public health. This approach can also illustrate possible impacts of changes in freshwater discharge in highly urbanised estuaries.Keywords: phytoplankton composition, winds, tides, Santos bay, rainfall.Variações na composição da comunidade fitoplanctônica em resposta às marés, à mistura induzida pelo vento e à descarga de água doce em um sistema estuarino urbanizado ResumoEstudos recentes na baía de Santos (sudeste do Brasil), localizada em um sistema estuarino altamente urbanizado, mostraram o aumento de espécies fitoplanctônicas potencialmente nocivas. Apesar da importância da previsão das florações algais nocivas, é difícil determinar a estrutura da comunidade fitoplanctônica em ambientes extremamente dinâmicos. O presente estudo analisa florações dominadas pelo microfitoplâncton e sua relação com variáveis físicas e meteorológicas, a fim de determinar padrões associados às marés e às estações do ano. Foram comparadas oito situações e obtidos cinco cenários de dominância relacionados aos ventos, marés e pluviosidade: i) Surfers, diatomáceas associadas à zona de surfe, de alta energia; ii) Sinkers, diatomáceas de tamanho grande que ocorrem nas marés de sizígia, depois de períodos de alta pluviosidade; iii) Opportunistic mixers, diatomáceas pequenas ou alongadas, formadoras de cadeia, que ocorrem durante períodos de quadratura; iv) Local mixers, diatomáceas e dinoflagelados microplanctônicos que foram abundantes em todas as 298 estações amostradas, e v) Mixotrophic dinoflagellates, que ocorrem após intensas descargas estuarinas. Os resultados sugerem uma alteração no padrão temporal de algumas espécies formadoras de florações, enquanto outras apresentaram abundâncias superiores aos valores seguros para a saúde publica. Esta abordagem ilustra também os possíveis impactos ...

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

“…Local CDOM produced by the degradation of algal estuarine species, and bacteria consumption will likely modify the characteristics of CDOM. Very high a cdom (443) was observed during the neap tide survey in September 2007, probably reflecting the susceptibility of the Santos Bay to periodic external contributions of CDOM (Moser et al, 2012). One possible source of this anomalous increase in CDOM could be freshwater released from the Henry Borden hydroelectric power plant (Gasparro et al, 2008) located in the city of Cubatão, 14 km uphill from Santos.…”

“…The resuspension of bottom sediments can occur episodically during strong tidal currents (Alfredini et al, 2008). Surveys have shown high ammonium, phosphate and chlorophyll concentrations in the Santos estuarine complex year round (Gianesella et al, 2000;Aguiar and Braga, 2007), and changes in the phytoplankton species composition and size structure (mainly diatoms, dinoflagellates and mixotrophic dinofalgellates) have been related to freshwater input, tides and wave action (Moser et al, 2012).…”

“…This indicates that mixing conditions (e.g., spring tides) tend to benefit the development of larger cells in Santos Bay. In fact, Moser et al (2012) showed the predominance of chain-forming diatoms with large cell sizes in association with spring tides and the consequent resuspension processes.…”

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

“…It was proposed that S. cf. costatum should be considered an indicator of the influence of riverine waters on estuarine systems (MOSER et al, 2012). In the light of this scene, we here evaluate how phytoplankton composition responds to nutrient over-enrichment in a well-preserved sub-tropical estuary by means of controlled bioassays using the natural community of the Cananéia-Iguape Estuarine-Lagoon System and submitting the microalgae to different levels of eutrophication.…”

Temporal variability of chlorophyll-a in the São Vicente estuary

“…costatum and Asterionellopsis glacialis (MOSER et al, 2012;VILLAC et al, 2008). Moser et al (2012) reviewed the dynamics of the phytoplankton in Santos bay and concluded that changes in microphytoplankton communities occur mainly in response to episodic changes in wind speed and direction and tides, but the results presented also give evidence of alterations in the temporal patterns of [Chl] and phytoplankton species composition during recent blooms. Despite the economic and ecological importance of the Santos estuarine complex, there is little systematic observation on phytoplankton dynamics available to date.…”