Quantifying spatial variation in the uptake of microplastic by mussels using biodeposit traps: A field-based study

Area of Science:

• Marine Biology
• Environmental Science
• Ecotoxicology

Background:

• Microplastic (MP) contamination is a pervasive environmental issue.
• Understanding MP uptake by marine organisms is crucial for assessing ecological risks.
• Spatial variations in MP uptake by marine species remain largely unquantified under field conditions.

Purpose of the Study:

• To investigate the spatial patterns of microplastic uptake and egestion by mussels in natural environments.
• To quantify microplastic accumulation in mussel biodeposits using a novel biodeposit trap.
• To compare microplastic uptake between wild and farmed mussels and across different environmental conditions.

Main Methods:

• Development and deployment of a novel "biodeposit trap" to measure microplastic uptake and egestion.
• Analysis of microplastic dimensional composition in mussel biodeposits and control traps.
• Field deployment of traps with wild mussels, farmed mussels, and empty shells at three sites with varying microplastic concentrations and water flow.

Main Results:

• Mussels preferentially accumulated smaller microplastics (0.02-0.05 mm) in their biodeposits.
• No significant difference in microplastic accumulation was observed between wild and farmed mussels.
• Microplastic uptake rates were 4-5 times higher at the site with the highest expected microplastic contamination and moderate water flow.
• Biodeposits contained smaller microplastics compared to control traps, which showed a higher dimensional range (0.05-5 mm).

Conclusions:

• Mussels effectively accumulate small microplastics, indicating their role as indicators of microplastic pollution.
• The biodeposit trap is an effective tool for assessing microplastic uptake and spatial variation in field conditions.
• Environmental factors such as microplastic concentration and water flow significantly influence microplastic uptake rates in mussels.