The world is your oyster: low-dose, long-term microplastic exposure of juvenile oysters

Maes Thomas; Barry Jon; Stenton Craig; Roberts Edward; Hicks Ruth; Bignell John; Vethaak A Dick; Leslie A Heather; Sanders Matthew

doi:10.1016/j.heliyon.2019.e03103

The world is your oyster: low-dose, long-term microplastic exposure of juvenile oysters

Heliyon. 2019 Dec 27;6(1):e03103. doi: 10.1016/j.heliyon.2019.e03103. eCollection 2020 Jan.

Authors

Maes Thomas¹, Barry Jon¹, Stenton Craig^{2

3

4}, Roberts Edward², Hicks Ruth², Bignell John², Vethaak A Dick^{5

6}, Leslie A Heather⁵, Sanders Matthew²

Affiliations

¹ Cefas, Centre for Environment, Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, NR33 0HT, UK.
² Cefas, Centre for Environment, Fisheries and Aquaculture Science, Barrack Road, The Nothe, Weymouth, DT4 8UB, UK.
³ Edinburgh Napier University, School of Applied Science, Sighthill Campus, 9 Sighthill Court, Edinburgh, EH11 4BN, UK.
⁴ St Abbs Marine Station, The Harbour, St Abbs, Berwickshire, TD14 5PW, UK.
⁵ Deltares, Department of Marine and Coastal Systems, P.O. Box 177, Delft, 2600 MH, The Netherlands.
⁶ Vrije Universiteit, Department of Environment and Health, De Boelelaan 1085, Amsterdam, 1081 HV, The Netherlands.

Abstract

Bivalve filter feeders, such as oysters, filter large volumes of water and are particularly exposed to microplastics (MP). Consequently, these animals digest and assimilate high levels of MP in their bodies that may likely impact their physiology, and potentially affect shellfish stocks, benthic habitats and, indirectly, the health status of the marine ecosystem and human consumers. In this study we exposed juvenile oysters, Crassostrea gigas, to 3 different MP concentrations (10⁴, 10⁵ and 10⁶ particles L^-1), represented by 6μm Polystyrene (PS) microbeads, compared to a control treatment receiving no MP. The study ran for a period of 80 days to test for the impacts of MP on growth, Condition Index and Lysosomal Stability. From histological analysis, microbeads were detected in the intestines of exposed oysters and in the digestive tubules, but no cellular inflammatory features were observed over time. Weight and shell length remained comparable between the different treatments and control. We found that Condition Index in the highest concentration increased initially but significantly reduced over time. The oysters in the highest MP exposure also showed the lowest mean Lysosomal Stability score throughout the experiment. Lysosomes play a vital role in the cells defense mechanisms and breakdown of constituents, crucial for the oysters' wellbeing. Most importantly, we detected an increased mortality in those oysters who were chronically exposed to the highest loads of MP.

Keywords: Aquaculture; Aquatic ecology; Condition index; Ecological health; Environmental hazard; Environmental health; Environmental science; Environmental toxicology; Histology; Long term exposure; Lysosomal stability; Microplastics; Pacific oyster; Polystyrene microbeads; Wastewater management; Water pollution.