Assessing the threat of microplastics to commercial oysters, particularly those of the genus Crassostrea

• Main Author: Brettell, D
• Other Authors: Lewis, C, Galloway, TS, Leung, KMY
• Format: Master Thesis
• Language: English
• Published: University of Exeter 2018
• Subjects: Crassostrea gigas
• Online Access: http://hdl.handle.net/10871/35321

Current statistics show that China is the largest producer of plastics in the world, contributing to almost 30% of production worldwide (Plastics Europe, 2017). In particular, mega-cities in China connected with the Pearl River Estuary contribute to much of this production, and locations in the Estuary’s proximity are potential sites for plastic pollution. In this thesis, the hypothesis that Crassostrea hongkongensis oysters cultured in Deep Bay, Hong Kong would be susceptible to microplastic uptake was tested. Extensive sampling was conducted across the bay through the collection of oysters, water and sediment from five selected sites (rafts). Follow up analysis of samples revealed that an average of 15.1 ± 6.1 microplastics per individual were present within the oysters, and oysters situated in the outer part of the bay took up more microplastics compared to those situated in the inner part of the bay. The numbers and types of microplastics quantified in sediment and water samples across sites did not correspond to the number of microplastics quantified in Crassostrea hongkongensis specimens across sites, suggesting that there was an element of selection during the biological uptake of these particles, and this was potentially influenced by particles’ properties such as size, shape and polymer type. Having established that wild Crassostrea hongkongensis in Deep Bay were taking up microplastics, an experiment was set up to investigate whether a genetically similar oyster species, Crassostrea gigas, would exhibit selective uptake up microplastics according to plastics’ size, shape or polymer type, and whether microplastic exposure would induce biological responses within the oysters. Eight microplastic types of various polymers, sizes and shapes were supplied in equal concentrations to Crassostrea gigas oysters at a final concentration of 100 microplastics mL-1, where they were exposed for a 24 hour period. Findings revealed that microplastic polymer type and size did indeed influence uptake (Pr ...