Abstract The Itapessoca estuary is part of the Itamaracá-Itapessoca Estuarine System, a ria-type estuary located on the northeast Brazilian shore, in the state of Pernambuco. Here we present an assessment of the estuarine circulation, suspended sediment dynamics, and its main transport mechanisms. We carried out a field survey where water level, currents, salinity, temperature, and suspended sediment concentration (SSC) were recorded at 10-minute intervals during two complete semi-diurnal tidal cycles under spring tide conditions. The field survey was conducted in September (2012), which is a transitional period between wet and dry seasons. The water level displayed symmetrical ebb-flood phases; however, currents were ebb-dominated. The freshwater contribution was negligible, and the mean salinity was ~35 g/kg, which is slightly lower than the adjacent shelf values (36.5 g/kg). The SSC transport was driven by the ebb-dominated tidal currents, with the highest values of ~30 mg/l occurring during the peak current during the ebb. The source of the suspended sediment was the erosion from the bottom, and the concentration was much lower than other similar estuaries (e.g., Caravelas). This observation suggests this system is a ‘sediment starved system’ in the sense that it presents a low concentration of suspended sediment.

As trocas de água e materiais através das desembocaduras de estuários são de difícil quantificação e são de fundamental importância para o entendimento do funcionamento de estuários e da zona costeira. A hidrodinâmica e transporte de sedimentos em suspensão no estuário do rio Camboriú foram estudados através da realização de duas campanhas de campo em 1998 cobrindo as condições de quadratura e sizígia. O período do levantamento foi anterior à obra de construção do molhe em 2003 que alterou a morfologia da desembocadura, fornecendo assim importantes informações base sobre o sistema. Cada experimento cobriu dois ciclos de maré com medições horárias de correntes, salinidade, concentrações de sedimentos em suspensão e nível de água. Os resultados mostram que o estuário é parcialmente misturado com estrutura vertical variando em função da amplitude e fase da maré. A estrutura dinâmica do estuário é balanceada entre os efeitos estabilizadores gerados pelo gradiente vertical de densidade, que permite produzir fluxo de empuxo e estratificação, e os efeitos turbulentos gerados pelo gradiente vertical de velocidade, que gera mistura vertical. A principal fonte de sedimentos para a coluna de água são os sedimentos de fundo, periodicamente resuspendidos pelas correntes de maré. O transporte advectivo de sal e sedimentos em suspensão foi diferente entre condições de quadratura e sizígia, sendo mais complexo durante a sizígia. A circulação gravitacional e a deriva de Stokes apresentam um papel secundário nos processos de transporte estuarinos.

Estuarine hydrodynamics is a key factor in the definition of the filtering capacity of an estuary and results from the interaction of the processes that control the inlet morphodynamics and those that are acting in the mixing of the water in the estuary. The hydrodynamics and suspended sediment transport in the Camboriú estuary were assessed by two field campaigns conducted in 1998 that covered both neap and spring tide conditions. The period measured represents the estuarine hydrodynamics and sediment transport prior to the construction of the jetty in 2003 and provides important background information for the Camboriú estuary. Each field campaign covered two complete tidal cycles with hourly measurements of currents, salinity, suspended sediment concentration and water level. Results show that the Camboriú estuary is partially mixed with the vertical structure varying as a function of the tidal range and tidal phase. The dynamic estuarine structure can be balanced between the stabilizing effects generated by the vertical density gradient, which produces buoyancy and stratification flows, and the turbulent effects generated by the vertical velocity gradient that generates vertical mixing. The main sediment source for the water column are the bottom sediments, periodically resuspended by the tidal currents. The advective salt and suspended sediment transport was different between neap and spring tides, being more complex at spring tide. The river discharge term was important under both tidal conditions. The tidal correlation term was also important, being dominant in the suspended sediment transport during the spring tide. The gravitational circulation and Stokes drift played a secondary role in the estuarine transport processes.

O cultivo de moluscos ao longo da costa de Santa Catarina tem crescido de forma acelerada nos últimos anos. Embora os benefícios sejam muitos, vários tipos de impactos ambientais podem ser decorrentes do cultivo de moluscos. Desta forma, o sucesso da atividade depende de fatores que envolvem a capacidade suporte do meio e do grau que o ambiente é impactado. Um dos mais evidentes impactos associados ao cultivo de moluscos marinhos é o aumento da taxa de fluxo vertical de partículas associado a redução da biomassa fitoplanctônica na coluna de água. O fluxo vertical de fitodetritos produzidos em uma área de cultivo foi avaliado por meio de análise por cromatografia líquida de alta eficiência (CLAE) de pigmentos fotossintéticos e produtos de degradação do material coletado por armadilhas de sedimento. Os resultados indicam que o cultivo de moluscos aumenta em média 5 vezes o fluxo vertical de fitodetritos, sendo que a maior parte da degradação da c1orofila-a ocorre na forma de feoforbideos. Dado o expressivo fluxo vertical de fitodetritos, comparado a pequena biomassa na coluna de água, sugere-se que o fitopl ncton a1OOono, trazido por processos advectivos, é importante para a manutenção do crescimento dos moluscos na área estudada.

Mussel culture is an expanding activity in shallow and sheltered bays along the coast of Santa Catarina, southern Brazil. Although mussel culture generates benefits, several environmental impacts are associated with this kind of activity. Its success depends on. factors which inc1ude the environmental impact and the carrying capacity of the system. One conspicuous effect of mussel culture is the enhancement of vertical particle flux to the bottom sediment and depletion of water column phytoplankton biomass. Phytodetritus vertical fluxes was evaluated in a mussel culture area by collecting partic1es with sediment traps and analysing plant pigment by high performance liquid chromatography (RF-HPLC). Results showed that mussel culture, in average, enhances almost 5 times the vertical phytodetritus flux as compared to the reference site. Pheophorbide like pigments were the main chlorophyll-a degradation products collected by the traps. Given the high phytodetritus production, compared to the low water column phytoplankton biomass observed, it is suggested that allocthonous phytoplankton advected to the cultured area is an important process to sustain the mussel growth in the area.