Microplastics in bivalves and their habitat in relation to shellfish aquaculture proximity in coastal British Columbia, Canada

Abstract

Shellfish aquaculture often uses large amounts of plastic equipment and has been suggested as a potential source of microplastic contamination in the marine environment. To determine the influence of shellfish aquaculture on microplastic concentrations in bivalves and their environment, we compared microplastic particle (MP) concentrations in Manila clams Venerupis philippinarum and Pacific oysters Crassostrea gigas grown on commercial shellfish beaches with those in individuals of the same species grown on nearby non-aquaculture beaches in 6 regions of coastal British Columbia, Canada. MP concentrations did not differ between shellfish aquaculture and non-aquaculture sites for either bivalve species, sediment, or water samples. Plastic presence differed by site and oysters on sites with many synthetic anti-predator nets contained significantly, yet marginally, more MPs than those on sites without (0.05 vs. 0.03 g -1 dry-tissue weight on average). However, analysis of suspected MPs using Fourier-transform infrared spectroscopy in dicated a predominance of fibres from textiles (including nylon and polyester), which are not typically used in shellfish aquaculture, suggesting that this may be caused by the larger average body weight of oysters grown at non-aquaculture sites rather than by the degradation of aquaculture infrastructure.

Use of sediment dwelling bivalves to biomonitor plastic particle pollution in intertidal regions; A review and study

“…Our findings directly contradict a recent study of Covernton et al [40] and by doing so, provides a good example of how the inappropriate choice of a biomonitor as made by Covernton et al [40] can lead to erroneous conclusions. In a study partially funded by the British Columbia Shellfish Growers Association, Covernton et al [40] attempted to determine if shellfish aquaculture infrastructure contributed to MPs concentrations in bivalves. To do so, they compared MPs concentrations in Manila clams and Pacific oysters (Crassostrea gigas) transplanted onto commercial shellfish intertidal leases versus nearby non aquaculture intertidal sites.…”

“…To do so, they compared MPs concentrations in Manila clams and Pacific oysters (Crassostrea gigas) transplanted onto commercial shellfish intertidal leases versus nearby non aquaculture intertidal sites. Bivalves used in the study of Covernton et al [40] were transplanted from one source, a shellfish farm located within Baynes Sound. Oysters were placed on the surface sediments and Manila clams covered to a 2.5 cm depth within the surface sediment.…”

Microplastic concentrations in two Oregon bivalve species: Spatial, temporal, and species variability

“…Other potential seasonal factors include temperature‐associated influences on metabolic and feeding rates, which may be depressed during colder seasons, and life history events like spawning and associated physiological responses. Differences in aquaculture techniques, such as degree of plastic use by oyster growers, may contribute to variation in oyster microplastic burdens between sites and over time; however, grower‐specific culture techniques were not assessed in this study and previous studies in the PNW have failed to find a connection between aquaculture and microplastic burden in cultured Pacific oysters and manila clams when compared to wild‐grown organisms (Davidson and Dudas ; Covernton et al ). Temporal differences identified in this study indicate oysters may be able to clear microplastics from their system over time, as previously shown in laboratory studies where manila clams and blue mussels (29–40 mm in length) eliminated microplastics in feces and pseudofeces when depurated in clean water, with up to 60% of particles cleared from the body in as little as 9 h (Xu et al ; Woods et al ).…”

Microplastic Concentrations in Two Oregon Bivalve Species: Spatial, Temporal, and Species Variability

“…Other potential seasonal factors include temperature-associated influences on metabolic and feeding rates, which may be depressed during colder seasons, and life history events like spawning and associated physiological responses. Differences in aquaculture techniques, such as degree of plastic use by oyster growers, may contribute to variation in oyster microplastic burdens between sites and over time; however, grower-specific culture techniques were not assessed in this study and previous studies in the PNW have failed to find a connection between aquaculture and microplastic burden in cultured Pacific oysters and manila clams when compared to wild-grown organisms (Davidson and Dudas 2016;Covernton et al 2019). Temporal differences identified in this study indicate oysters may be able to clear microplastics from their system over time, as previously shown in laboratory studies where manila clams and blue mussels (29-40 mm in length) eliminated microplastics in feces and pseudofeces when depurated in clean water, with up to 60% of particles cleared from the body in as little as 9 h (Xu et al 2017;Woods et al 2018).…”