Nutrient distribution in a shallow subtropical lagoon, south Brazil, subjected to seasonal hypoxic and anoxic events

Abstract

Nutrient distribution in a shallow subtropical lagoon, south Brazil, subjected to seasonal hypoxic and anoxic eventsThe Conceição Lagoon, located in south Brazil, is a semi-enclosed coastal ecosystem that has seasonal hypoxic and anoxic conditions in its vertically stratified central region, characterized as a site of retention and mineralization of organic matter. This study investigates water column dynamics in the central region of the Conceição Lagoon (CCL) and its relation to physical and chemical variables, in order to understand the hypoxic and anoxic events. Surface, halocline and bottom waters were evaluated at three sampling sites along the CCL. The samples were collected in triplicate during the summer, fall and winter of 2014. Hypoxic and/or anoxic events occurred in the summer (1/21) at the halocline (3 m) and bottom (4 m) waters, and in the fall (2/5) in the bottom water (4.5 m). Positive values of apparent oxygen utilization showed mineralization processes in the halocline and bottom waters. The lowest vertical stratification index was recorded in August (southern winter), which was associated with wind speed (14.7 m.s -1 ) and direction (southern quadrant). Nutrient concentrations were higher in winter, related to increasing of water mixing. This was the first study to evaluate the dynamics of hypoxic and anoxic events in the CCL and how nutrients respond to the physical structure of the water column. ) e direção (quadrante sul) do vento. As concentrações de nutrientes foram maiores no inverno, devido ao aumento dos processos de mistura e remineralização da matéria orgânica. Este foi o primeiro estudo a avaliar a dinâmica dos eventos de hipoxia/anoxia na CLC em relação à distribuição dos nutrientes e estrutura física da coluna de água. AbstrAct resumoDescritores: Eutrofização, Estratificação, Zonas mortas, Mineralização.

Marine Heatwaves, Sewage and Eutrophication Combine to Trigger Deoxygenation and Biodiversity Loss: A SW Atlantic Case Study

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Assessment of the trophic status in a tropical estuarine system

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Spatial models of suitable sandy substrates for brittle star community conservation in Sancang Coast, West Java, Indonesia

“…Eutrophication originating from the land is a common problem among coastal ecosystems near river mouths that greatly affects the diversity of organisms, from fish to small benthic invertebrates (Brauko et al 2020). Eutrophications contribute to altering the pristine sandy beaches by creating drifting algae mats that induce episodic hypoxia (Barros et al 2017) that may affect brittle star species. Eutrophication processes in the form of increased phytoplankton production may increase the accumulation of organic pollutants in benthic sediment-ingesting fauna, including brittle stars.…”