Microplastics in Shellfish at “Extremely Low” Levels Globally

A group of researchers at DMS joined together under Sandra Shumway and Evan Ward, critically reviewed 750+ publications on microplastics and molluscs in the field and laboratory. This incredible effort has resulted in a thoughtful review of the cluttered scientific literature. Many studies on suspension feeding molluscs and microplastics have perpetuated inaccurate findings based on inappropriate methodologies, poor animal husbandry, and misinterpreted results. All of these false conclusions have caused a damaging narrative for the shellfish industry, raising concerns about the safety of eating shellfish. While microplastics are ingested by shellfish, microplastics in molluscs are extremely low globally as these animals are capable of selective capture, ingestion, and egestion of particles. In reality, the number of microplastics inhaled and consumed by humans in everyday life far outweighs the number of microplastics found in shellfish. Recommendations were provided for future studies in both the field and laboratory that will prevent researchers from falling into the pitfalls discussed in this review. This review is presented from the perspective of experts on shellfish physiology and represents the opinions of, and assessments made by, the authors. The authors hope this review can be used as a starting point for those interested in furthering this field of research with thoughtful experimental questions. Link to the article.

Sampling freshwater mussel gut microbiomes in the Great Lakes

In June 2022, Hannah Collins and Tyler Griffin from the Ward Environmental Physiology Lab went to Buffalo, NY, to perform research on the gut microbiomes of freshwater quagga mussels (Dreissena bugensis). The three-day trip involved collecting these invasive mussels from Lake Erie with the help of Brian Haas at the Buffalo State Great Lakes Center field station. The goal of the project, funded by an NSF Emerging Frontiers in Research and Innovation grant, was to sample mussel gut microbes before and after defecation with the goal of distinguishing between microbes that live inside the mussels and other microbes that were simply passing through. This work serves as preliminary research for the larger goal of investigating the feasibility of using freshwater mussels to remove microplastics from freshwater systems and co-concentration them with plastic-degrading bacteria.

PhD student Hannah Collins taking samples of mussel guts for microbiome analyses (Photo: Tyler Griffin)

quagga mussels
Invasive Quagga mussels (Dreissena bugensis)

niagara river
View over the Niagara River in June 2022

DMS Kayla Mladinich shows that bivalves can reject microplastics

8 November 2022. DMS is happy to share the latest publication by PhD student Kayla Mladinich, showing the surprising but good news that blue mussels and oysters appear not to ingest all microplastic particles floating in the water.

By Kayla Mladinich.

Oysters and mussels are filter feeders that draw particles in from the surrounding water to be eaten. These animals can select which particles are eaten or rejected depending on factors such as particle size and surface properties. This study was performed to determine what kinds of microplastics will be consumed or rejected by oysters and mussels. Both species rejected larger microplastics more than smaller microplastics and did not differentiate between different types of plastic polymers. The results suggest that oysters and mussels will not ingest all microplastics that they are exposed to in the natural environment!

Kayla changing water and replenishing food for the animals.

An oyster being exposed to microplastics in the laboratory. Microplastics are gently pipetted over the inhalant aperture (where oysters draw particles in) which allows the oysters to choose between drawing the particles in or not (Photo: Kayla Mladinich).

Mladinich et al. ES&T (2022) Graphical abstract