Microplastics in Our Eelgrass Meadows


May 27, 2021 Annisquam, MA

The danger of mocroplastics invading seagrass meadows.

Imagine these pristine seagrass meadows like the photo above, but with blades that are sprinkled with tiny plastics. It is hard to imagine, especially when we can’t physically see these plastics in the water, sediments, or on the blades. On this beautiful spring morning in May, Cece Gerstenbacher, one of Alyssa Novak’s grad students from BU, shifted the way I think about plastics.  I had seen many images of plastic trash creating these huge debris islands called “Great Pacific Garbage Patch.” I had read research on how they are finding plastics in many of the fish we eat. So, I have become an avid beach cleaner whenever I see anything on the beaches I pick them up. However, on this morning at 6am in Annisquam, my whole way of thinking about plastics and marine life was about to change. Cece, a well-spoken, thoughtful and committed scientist shared 20 minutes with me as she busily harvested seagrass from the site we were at. During my interview, I was baffled to learn that this pristine looking seagrass meadows we were looking at had microplastics contamination. Since 2019, Cece has been studying these eelgrass blades under a microscope and has proof that these tiny plastics attached themselves to the blades.  What is even more concerning is that Cece is finding microplastics in eelgrass in unpopulated areas like the islands near Nantucket. Microplastics are evasive and are in our food chain. This thought provoking interview highlights the importance of building awareness, community outreach, and as consumers using our power to make more conscious decisions like investing in clothes that shed less microfiber(switch to natural fibers-away from synthetic) and a filter for your laundry machine. 

NA: How did you first get involved with microplastics?

CG: When I was an undergraduate junior- people in my lab accidentally stumbled on micro plastics while they were looking at tropical seagrass blades from Belize. They published a paper on it and it was a huge thing since nobody had looked at microplastics actually on seagrass before. 

There wasn’t many papers on micro plastics entering food chain, they didn’t think of it as a bioaccumulation things.  So I joined Alyssa’s class at BU, my advisor, and I chose this project to see if there was any micro plastics on seagrass blades in Massachusetts. We didn’t think that we would see so many or that it would become a big thing.

When we put the blades under the microscope we started to see them in 2019 and realized that this is going to be a big project not just for this class. So I applied for a grant and began studying  – what is influencing the  accumulation patterns of micro plastics and what is the mechanism of these micro plastics getting onto the blades? Then I applied for the masters program and here I am.

NA: Do you work with other local organizations?

CG: Yes, I’m working with the EPA and the National Park Service to understand when micro plastics entered to seagrass systems by looking at sediment-cores and looking at historic seagrass samples back to 2003. We are also looking at sites across with varying topographies and development. You can see this site we are at is in a residential area, we are comparing sites that are undeveloped like  the Islands off of Nantucket. We are still seeing the same about of micro plastic contamination on these seagrass blades too. 

NA: Wow- that’s weird. 

CG: Yes, it says to us that this is a ubiquitous issue and not just influencing the meadows that are close to human settlement proximity. It’s really a huge issue, I wish I had the answers for how to clean it up. Right now it’s most important for me to understand the how and why this accumulation is happening, and how to identify the sources. Hopefully to reduce the  amount micro-plastics that we put into the system.

NA: What are micro-plastics exactly?

CG: Micro-plastics are just pieces plastics that measure less than 5 mm in size, either on the length or width. They can either be made of primarily micro -plastics, like the cosmetic micro beads where they are manufactured to be micro-plastics.  Or they can arise from the breakdown of larger plastics like a water bottle, or anything that you can think of as plastic. It can enter the ocean and get eroded until it becomes micro-plastic. They can enter systems like seagrass meadows, especially near shore ecosystems like the site we are at. There is so much anthropogenic influence, so a lot of plastics can enter the meadow and they get trapped here.

Source: BU:https://www.bu.edu/articles/2019/microplastic-pollution-in-ocean-seagrasses/

NA: Wow on the surface we don’t see anything but clean pristine water and wild-life. It’s hard to imagine all the pollutants of plastics right here as we look at this meadow. How does this trapping occur?

CG: Seagrass hydro dynamically trap stuff, that’s their job. If you look here, where the seagrass bed is its higher up than the regular sediment.  

NA: Yes, there is defiantly a height difference from the sand and the bed the seagrass is on. 

CG: So they are really good at trapping stuff, so they are going to trap the micro-plastics as well. 

NA: Why should we be concerned about the microplastics when we can’t see them or really touch them as objects?

CG: The concern is of course bioaccumulation, things eating these eelgrass blades, we are eating those things eventually. There is also a concern for how the microplastics may be affecting the epiphytes- the tiny organisms that live on the blades. Microplastics may be hurting the tiny organisms that are also embedded within them. Microplastics also have the ability to vector persistent organic pollutants ( toxic chemicals that adversely affect human health and the environment around the world) and other toxins and heavy metals, there is a concern that microplastics are harming the epiphytes ability to grow and photosynthesize. And in some cases epiphytes account for 50% of eelgrass photosynthesis. 

NA: So do epiphytes help transform sun energy into carbohydrates?

CG: Yes, they are not mutualistic with eelgrass, they are in competition with them for sunlight. However, they are still an important part of the ecosystem since they are sequestering sunlight  to nutrients. So there is a concern for how micro plastics might be impacting those epiphytes. 

NA: Are there other concerns in the ecosystem of these lush meadows?

CG: Yes, there is a concern about what microplastics are doing to the nitrogen cycle in sediments, because as they get sequestered on seagrass blades, they can also get sequestered in sediments. So there is a lot of concern about microplastics entering the seagrass ecosystem. We are trying to figure out how much they are impacting the natural ecosystems at the concentrations they are now. And what threshold there is for it going really south. At what concentrations of micro plastics in the system do we start seeing severe consequences.  

NA: Is there consequences in terms of seagrass loss, or epiphyte loss?

CG: Yes potentially, seagrass, epiphyte loss. There are so many other organisms that rely on this seagrass system. If there are a lot of micro plastic contamination in the ecosystem, There are so many organisms that will be eating it, like snails, and others. It’s likely they will eat the micro plastic too. Studies in coral reefs have shown that they have mistakenly eaten micro-plastics instead of brine shrimp eggs. 

NA: Can you explain the epiphytes and their relationship to seagrass again. Is algae an epiphyte? 

CG: It’s a blanket term for anything that grows on top of another organism. Like an orchid is an epiphyte on a tree. When you have seagrass the epiphytes can be really tiny. They can be algae. Right now we have snails on the blades, that are also epiphytes. These organisms are all competing with the blade for sunlight and nutrients. At the same time they sequester nutrients like carbon and nitrogen, and get consumed by organisms like fish and crabs. They are an active and important member of the ecosystem and it’s a healthy competition in an normal situation. 

NA: What’s not normal?

CG: You can have eutrophication which enhances the epiphytic load and messes up the water quality, the water gets murky and there is no light that can come through for photosynthesis.

NA: What have you found here in this meadow that seagrass ecosystem supports?

CG:  So much life-scallops, snails, yesterday I saw a skate, and a full lobster here . There are these huge snails, sand dollars, hermit crabs. A lot of shrimp in the water. Bivalves like mussels, clams, and oysters!

NA: So cool!

CG: Seagrass beds sustain so much life, If you look at a bare sediment you don’t see so much life. If you look at the eelgrass beds you see so much of the primary consumers of the ecosystem, which sustain the secondary and tertiary consumers. Then the top consumers are us. So this is where it all starts out for the coastal life in Massachusetts!

NA: What are some of the questions you are exploring thesis, and when do you graduate?

CG: I am graduation in December, I am gathering data to round up my studies. 

So one of my hypothesis is that “are epiphytes  influencing how many micro plastics are on the seagrass blade?” Which I found to be true, so the more epiphytes on a blade the more micro-plastics. They are like glue for the micro-plastics.

I had originally thought that population dense areas would have more micro-plastics but that is not true. Less settled areas also have micro-plastics. Micro-plastics are a global issue not just in ecosystems in developed areas, they have been found in the arctic, deep sea arctic systems. 

NA: It kind of makes sense, the oceans are all connected, and water and plastics just move right?

CG: Yes, there is this huge dispersal, anything that is floating in the ocean can go thousands of miles. Right now I’m trying to think about how microplastics are fluxing between the blades, water column and sediment. So I’ve been taking samples from each to see if  the concentrations align with each other. For example is a meadow with high microplastics on the blades going to have a lot of micro plastics in the water column and the sediment? Or is it entirely influenced by the epiphytes and doesn’t matter how much there is in the water column.

NA: I love it,  science at work you are asking and analyzing  some amazing questions!

CG: Yes, I’d like to find out what are the mechanisms these microplastics are accumulating so we can start thinking about clean up that we haven’t developed yet. We can take the steps toward clean up. 

NA: This could take up to 10 years or so right?

CG: Yes, there is no quick fix, that microplastics aren’t going to quickly leave this system. That is why it is important to study the impacts of it. Microplastics are probably going to increase in this ecosystem. So we need to understand where that threshold is, at what point does the microplastics become detrimental. They are a part of our current ecosystem whether we like it or not. 

NA: If you were to promote microplastic awareness what are some of the things you would say to your family for example?

CG: An important thing you can do to reduce microplastics in marine environments would be to get a filter on your washing machine. A lot of microplastics that come into the oceans is from our washing machines. Our machine right now don’t have a filter that is tiny enough to filter microplastics. So they end up in a waste water plant, which also doesn’t have a filter for micro plastics so they end up in the oceans. A lot of microplastics come from washing machines. 

NA: Do you have a filter in your washing machine?

CG: At home I do

NA: Where can we get these filters?

CG: There is a variety of products out there, you can google it and many come up. These would help reduce microfibers that end up in the oceans.

NA: So are we essentially wearing microplastics? 

CG: Yes, what I am wearing is probably made of Polyester .or some combination of a synthetic material. (Synthetic materials do not biodegrade like natural materials)So when it goes in the wash, some of the microfibers get released. The water drains to a waste water treatment plant. It goes through the treatment plant, which also usually does not have filters for tiny microplastics so it ends up in the oceans. 

NA: This is a great idea, if you think about all the households we have and if they used a better filter.

CG: Yes, there would be a lot of reduction in microfibers. Also it would be great to get manufactures to have the filters built into the machines. There needs to be legislation that says these are needed. Consumers have a lot of power for change. A lot of people don’t know these filters even exist.

NA: Like me, I didn’t know. Now I’m going to go get me a filter!

CG: Spreading awareness about our backyard, how these beaches you swim in are contaminated and that they are your microplastics is important. 

NA: As powerful consumers, what other conscious choices should we be making to help our oceans?

CG: Some cleansers have microbeads so stay away from them.  We also need a whole culture shift for sustainable fashion. Shop wool & cotton where you can. Shop second hand. Stay away from single use plastic. Push for legislation at local levels, for example going plastic free. 

Reuse and recycle. 

DO what you can when you can- be sustainable as best as you can. 

NA: Wonderful, thank you for you hard work and enthusiasm for tackling this project!

Resources ETC:

If you are interested in ocean clean up, sign up to volunteer with Robin Lacey at Coastsweep with Massachusetts Office of Coastal Zone Management: 




For more info on Microfibers and filter options check out this link:


BBC also has some interesting news:




Other Words I had to look up:

POPs: persistent organic pollutants-are toxic chemicals that adversely affect human health and the environment around the world


PCPs: Polychlorinated biphenyls (PCBs) were developed in the 1940’s and were used extensively in the manufacture of transformers, capacitors, and other heat transfer devices through the late 1970’s. PCBs are a group of chemicals that have extremely high boiling points and are practically nonflammable. Because of this, they were used extensively as heat transfer fluids in transformers and capacitors. In 1979 their manufacture and importation was banned in the United States, based on mounting evidence that they were toxic to humans and wildlife. Today they are classified as probable human carcinogens and are listed in the top 10% of EPA’s most toxic chemicals.



Excessive richness of nutrients in a lake or other body of water, frequently due to runoff from the land, which causes a dense growth of plant life and death of animal life from lack of oxygen. For more info on this check out: nature.com