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Assessment of contamination of the beach clam Tivela mactroides: implications for food safety of a recreational and subsistence marine resource in Caraguatatuba bay, Brazil

Grant number: 15/06339-5
Support type:Regular Research Grants - Publications - Scientific article
Duration: August 01, 2015 - January 31, 2016
Field of knowledge:Interdisciplinary Subjects
Principal Investigator:Alexander Turra
Grantee:Alexander Turra
Home Institution: Instituto Oceanográfico (IO). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The clam Tivela mactroides is an important sandy-beach resource along thewestern Atlantic coast, and is widely harvested by both tourists and residents forrecreational, subsistence and/or economic purposes. These clams are intensively exploitedin Caraguatatuba Bay on the southeastern Brazilian coast. Similarly to most coastal areasaround the world, this bay is subject to a variety of environmental threats derived fromhuman occupation (e.g., sewage) and economic activities (e.g., oil spills). Considering thehistory of changes in this area and current plans for development, environmental pressuresare expected to increase. This prospect raises concerns regarding food safety of membersof the public, including clam harvesters, who consume local seafood. In order to providebaseline information to compare with future situations, this study analyzed thecontamination of clam meat by microorganisms (fecal coliforms, Salmonella sp., Vibriocholerae, and Staphylococcus aureus) and Polycyclic Aromatic Hydrocarbons (PAHs).Preliminary evaluations revealed microorganism contamination levels above themaximum limits allowed under Brazilian legislation; with higher levels in the centralportion of the bay. Temporal evaluations at three sampling points in this area revealedyear-round contamination by all microorganisms, i.e., a continuous risk for clamconsumers. Although the effectiveness of thermal processing used by consumers could notbe formally tested in this study, it has the potential to reduce the contamination by fecalcoliforms, Salmonella sp., and S. aureus to safe levels, as demonstrated in the two samplesanalyzed. However, although S. aureus can be totally eliminated, its heat-tolerant toxinsmay still affect consumers. Concentrations of individual compounds (congeners) and totalPAHs were recorded, indicating contamination derived from oil spills. The results raise concerns regarding traditional small-scale fisheries, whichcan be threatened by the intensification of human activities in the coastal region, thusrequiring continuous monitoring of the quality of seafoods, in addition to effectivecommunication of the risks to consumers, and efficient measures to reduce both sewageand industrial pollution. (AU)