Testing a Method for Quantifying Microplastic Content in Mytilus californianus

Abstract With the proliferation of microplastics within the environment, there has been an increased need to quantify them within organic tissues of aquatic species. Several studies have examined the potential role of mussels in filtering these contaminants, prompting interest in characterizing uptake and retention of microplastics in these species. There are a variety of methods to isolate and quantify microplastics, including density separation, enzymatic digestion, and filtration. The applicability of a combined digestion and ultrasonic bath methodology in isolating microplastics from the California mussel ( Mytilus californianus Conrad, 1837 ) was investigated. Microplastics were added to 20-gallon tanks at 0 g (control) 8 mg. Mussel tissues from each tank were digested using potassium hydroxide solutions. These digestions were subjected to vacuum filtration and a sonication bath, then treated with a mixture of sodium hypochlorite and nitric acid. It was found that this method successfully removed organic tissue from the mussels while leaving dyed microplastics intact. The latter were quantified using fluorescent microscopy. This proof-of-principle experiment indicates that this technique can be applied to further studies on environmental impact and retention of microplastics in mussels and may also have utility for other shellfish.