The Effects of Micro-plastics on Oyster Larvae in the Chesapeake Bay

Trash Free Maryland interviewed Christine Knauss, a PhD plastic pollution researcher at the University of Maryland Center for Environmental Science Horn Point Lab, about her research of the effects of micro-plastics on oyster larvae in the Chesapeake Bay.

About Christine

Christine Knauss recently finished her PhD at the University of Maryland Center for Environmental Science Horn Point Lab. She grew up in Baltimore. As a child Christine loved the ocean and playing in the environment. She used to play in a stream in the woods outside her house and continues to go to Bethany Beach almost every year. This is where her love for marine life began.

Christine earned her bachelor's degree with a double major in chemistry and biology from the University of Maryland, College Park. She also played on their NCAA Division 1 field hockey team.

“I was slightly late today because there was an overtime post-season game that is still going on.” - Christine.

Christine noticed as you move higher up in the environmental science field, it is male dominated. In order to change this, she is part of the diversity, equity, and inclusion group at her school.

“I am working on it and many other people are working very hard but it still is skewed once you get to higher positions.” -Christine

Her Research

Christine was inspired by the likes of Charles Moore, who discovered the Pacific Garbage Patch, and by an assignment for her scientific writing class. In this class she was asked to write to a fake boss about what to use in the office, cardboard or styrofoam cups. This led Christine to dive into the world of plastic pollution and micro-plastics. Noticing there was not much research in the field at the time, she decided this was what she wanted to do. These experiences inspired her to begin her research into micro-plastics and their effects on oyster larvae, and being a new field, method development was also a key part of the work.

Why Oysters?

In addition to being a keystone species in the Chesapeake Bay, they are also filter feeders. Oysters process upwards of 50 gallons of water a day! This means they interact with a lot of particles; not a lot of species do that. Also, they would appear to be the most vulnerable to plastic pollution because they will inevitably come into contact with large amounts of it.

Struggles with a New Field

Christine was amongst the first on the scene; hardly anyone was doing research on micro-plastics in the United States at the time. This made it hard to find funding and a program for graduate school.

“So I called and emailed any person that I could find associated with any papers here and there wasn’t anyone looking for a graduate student.” - Christine

So, she decided to create her own program and found someone to fund it, per advice from Dr. Chelsea Rockman, a prominent researcher in the field.

Parameters

The oyster larvae were exposed to micro-plastics in the form of micro-beads and microfibers for 1 to 6 days at various concentrations. Factors looked at were physiology such as growth, algal ingestion, carbon assimilation, and respiration. 

*Image on right of Oyster Larvae with fluorescent micro-beads*

Micro-beads

The results showed no effect on the physiology of oysters tested. Oyster larvae were able to ingest large concentrations of micro-beads that are not seen in the environment. The amount of food present did not change that. As the concentration of micro-beads went up so did the ingestion of the plastic. However the oyster larvae were able to get rid of lots of ingested micro-plastics from their digestive tract easily, most within 24 hours of ingestion.

Micro-fibers

Similarly, with microfibers results showed no effect on physiology, except at extreme concentrations not seen in the environment. In these extremes, there was a growth penalty.

Conclusion

Oyster larvae were not greatly affected by the presence of micro-plastics and can survive at very high concentrations, levels not seen in the environment,

“They seem to be pretty hardy.” - Christine

However, more research needs to be done to understand the full story. Things like ingestion might be affected by different types of plastic and different shapes, DNA might be damaged, changes in transcription of proteins, etc. Research has shown that adult reproduction is affected by the ingestion of micro-plastics but only at very high concentrations. As of right now, the biggest type of pollution affecting oysters in the Chesapeake Bay remains nutrient pollution.

What can Trash Free Maryland do?

When asked about what Trash Free Maryland can do Christine offered up her suggestions. She says we should continue grass roots projects and to educate the public on plastic pollution and micro-plastics. Christine also believes we should be pressuring the big companies creating all this plastic,

“Together we have a strong voice and can be powerful.”

She talked about how individually we have impacts, but emphasized that it is not really the individuals causing the problem, but companies producing products in the cheapest possible way and without a thoughtful packaging design process. She thinks it's time to pressure companies to make changes,

“For most products, there are no alternatives to plastic so a lot of the time we have little choice of the products we use everyday. By demanding companies think about the end of life for their products, we could make big leaps forward in reducing unnecessary plastic.” - Christine

Christine expressed interest in being involved in future Trash Free Maryland projects and endeavors. Thank you so much to Christine for meeting with us and for all the work you have done!

We look forward to working with you in the future to make Maryland Trash Free!

Post authored by Milan McWilliams, Social Media Intern