Numerical Modeling as Supporting Tool for Aquaculture of Oysters in a Subtropical Estuarine Ecosystem

Abstract

The Estuarine-Lagoon Complex of Cananeia-Iguape (ELCCI) is a large estuarine system dominated by mangroves, located on the southeast coast of Brazil (25° S, 48° W). Oyster farming is an important economic activity in Cananeia due to the natural abundance of oyster seeds originally found in its mangrove fields. The aim of this study was to describe the hydrodynamic aspects of the mangrove and oyster farming in the ELCCI by analyzing environmental scenarios using numerical simulations. Simulations allowed for the description of the distance of penetration of the salt wedge into the system as well as the direction and magnitude of the tidal currents. Higher values of river discharge corresponded to lower distances of penetration of the salt wedge, a feature which shows that the freshwater discharge and geomorphology together determine the variation in salinity within the estuary. Oysters are cultivated in regions of higher salinity and relatively stable conditions, with low speeds of tidal currents and little vertical variation in salinity. Under average river discharge conditions (450 m 3 .s -1 ), there is a confluence of tidal waves in Mar Pequeno, where velocity is lower. This change may lead to a higher sedimentation at restricted areas and thus to a higher deposition of organic matter derived from oyster cultivations during flood tides. MODELAGEM NUMÉRICA COMO INSTRUMENTO DE APOIO À AQUICULTURA DE OSTRAS EM UM ECOSSISTEMA ESTUARINO SUBTROPICAL RESUMO O Complexo Estuarino Lagunar de Cananeia-Iguape (CELCI) é um grande estuário dominado por sistemas de mangues, os quais são encontrados na costa sudeste do Brasil (25° S, 48° W).A ostreicultura é uma importante atividade econômica em Cananeia devido à abundância natural de sementes de ostras que são encontradas originalmente em seus campos de mangue. O objetivo deste estudo foi descrever os aspectos hidrodinâmicos do mangue e das áreas de cultivo de ostras no CELCI analisando-se cenários ambientais de simulações numéricas. As simulações permitiram a descrição da distância de penetração da cunha salina no sistema, assim como da direção e a magnitude das correntes de maré. Valores mais elevados da descarga dos rios corresponderam a uma menor distância de penetração da cunha salina, mostrando que a descarga de água doce e a geomorfologia juntos determinam a variação na salinidade dentro do estuário. As ostras são cultivadas em regiões de maior salinidade e condições relativamente estáveis, com baixas velocidades das correntes de maré e pouca variação vertical da salinidade. Sob condições de descarga média (450 m 3 .s -1 ), há um encontro de ondas de maré na localidade do Mar Pequeno, onde a velocidade de corrente é menor. Essa mudança pode levar a uma maior sedimentação em áreas restritas e, portanto, a uma maior deposição de matéria orgânica derivada de cultivo de ostra durante a maré enchente.

Microbiological quality of the water in collection areas and the tissue of Mytella falcata—Cananéia (SP, Brazil)

“…The bars represent the respective standard deviations. There was a statistical difference only in the summer for total coliforms (p < 0.05) Harari, 2017;Fontes et al, 2019;Freitas et al, 2017;Mignani et al, 2013;Salles et al, 2017). Analyses performed on the water samples collected for this work showed that there were variations in the density of TC and Ct throughout the year (temporal variation), in the water of the studied areas, as can be seen in Figure 2.…”

“…Salinity is an important environmental factor for determining estuarine oyster distribution (Fontes et al, 2019). These factors directly affect the environmental quality of water and aquatic organisms (Batista & Harari, 2017; Fontes et al, 2019; Freitas et al, 2017; Mignani et al, 2013; Salles et al, 2017).…”

“…357 (Brasil, 2005), but only 66.7% were below the stipulated criterion in relation to the percentile, indicating that the water was above allowed level microbiological contamination. Estuaries are highly dynamic environments and are subject to constant environmental changes, both natural and anthropogenic changes (Barros & Barbieri, 2012; Fontes et al, 2019). The changes in these systems are forced by factors such as solar radiation, tides, winds, precipitation, and river discharge (Moura & Nunes, 2016).…”

“…Altogether, tides, river runoff, stratification, and stirring processes are the factors that define the estuarine circulation patterns (Fontes et al, 2019; Miranda et al, 2002), as well as saltwater intrusion and the salt wedge positioning. Salinity is an important environmental factor for determining estuarine oyster distribution (Fontes et al, 2019). These factors directly affect the environmental quality of water and aquatic organisms (Batista & Harari, 2017; Fontes et al, 2019; Freitas et al, 2017; Mignani et al, 2013; Salles et al, 2017).…”

Plantas Do Manguezal: Uma Revisão Brasileira

“…Mapa da área de estudo indicando a localização da Baía de Trapandé, região onde situa-se o Baixio do Arrozal no Complexo Estuarino-Lagunar de Cananéia-Iguape-Ilha Comprida (Fontes et al, 2019)…”