Faecal bacteria in Perna perna (Linnaeus, 1758) (Mollusca: Bivalvia) for biomonitoring coastal waters and seafood quality

Abstract

A B S T R A C TUrban development in coastal areas is intense and leads to the increase of sewage outfall and other negative impacts as consequences. Thus, stringent regulations establishing limits to the microbiological contamination of water and seafood are needed. The objective of this study is to evaluate the usefulness of Enterococci and Thermotolerant Coliform densities in the flesh of mussels Perna perna as an alternative tool for monitoring the microbiological quality of coastal waters. The study also considers allometric relations applied to clearance rates to understand rates of bacterial concentration. Bacterial loads obtained in mussels' flesh were from 50 to 4,300 times greater than in the water sampled in the vicinity of the mussels and some were considered inappropriate for consumption even when the water presented no restrictions. The mean clearance rate obtained for Enterococci retention was 317.7 ml h -1 and this rate (CR) is related to the mussels´ size (L) by the equation CR = 28.3229L1.6421 . The results showed that bacterial densities in the mussels' tissues may reflect chronic contamination of the environment and that clearance rates are important for taking the best decision in situations where, for example, it is desired to introduce mussels for aquaculture and the evaluation of the water concerned is required. R E S U M OO desenvolvimento urbano em áreas costeiras é intenso e o aumento das descargas de esgoto é uma das conseqüências. Assim, leis específicas que regulem limites para a contaminação microbiológica das águas e de alimentos de origem marinha são necessárias. O objetivo deste estudo é avaliar a utilização de Enterococos e coliformes termotolerantes na carne de mexilhões Perna perna como alternativa para o monitoramento da qualidade microbiológica de águas costeiras. O estudo também considera relações alométricas aplicadas às taxas de "clearance" para entender a concentração de bactérias pelo molusco. As densidades bacterianas obtidas no molusco foram de 50 a 4300 vezes maiores do que nas amostras de água coletadas próximas dos moluscos e alguns foram considerados impróprios para consumo, mesmo quando as águas não mostraram restrições. A taxa de "clearance" média obtida para retenção de Enterococos foi 317.7 ml h -1 e essas taxas (CR) puderam ser relacionadas com o tamanho dos mexilhões (L) pela equação CR = 28.3229L 1.6421 . Os resultados mostram que as densidades bacterianas nos tecidos dos mexilhões podem refletir a contaminação crônica do ambiente e que as taxas de "clearance" devem ser consideradas para a tomada de decisão em situações onde, por exemplo, se deseja implantar mexilhões para cultivo.

Evaluación de las concentraciones de <i>Escherichia coli</i> en <i>Crassostrea gigas</i> y agua de mar en dos zonas de cultivo de ostras ubicadas en el Golfo de Nicoya, Costa Rica

“…The same seasonal trend was found in the Thau Lagoon in France (Derolez et al 2013). Levels of thermotolerant coliforms in bivalve molluscs may differ with fecal contamination in the surrounding water (Martínez & Oliviera, 2010) and may change from one time period to another (Campos et al 2013a;Soegianto & Supriyanto, 2008). Derolez et al (2013) noted an inverse relationship between E. coli concentrations in seawater and in C. gigas oysters.…”

Coliform density in oyster culture waters and its relationship with environmental factors

“…However, a study by Martinez & Oliveira (2010) obtained bacterial densities in mussel flesh from 50 to 4,300 times greater than in water sampled in the vicinity of the mussels, which indicated that the relationship between the number of bacteria in the water and the bacteria accumulated by the mollusks is not straightforward and depends on many, difficult to evaluate, factors. Bacterial densities found in mussels are the result of complex interactions related to their physiology and morphology, such as size, filtering, excretion, and metabolic rates (Solé et al, 2000), and also depend on prey characteristics, such as size, specific composition and density of bacteria in the water.…”

Bioaccumulation and persistence of faecal bacterial and viral indicators in Mytilus edulis and Crassostrea gigas

“…Many authors have highlighted the effect of temperature and salinity on physiological indicators (such as clearance and absorption efficiency) in shellfish species 10,23 . Another study observed that the clearance rate and absorption efficiency in mussels (Perna perna)…”