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Friends’ Volunteers Document Eelgrass Mystery

Volunteer Water Reporters and Friends of Casco Bay staff visited two Brunswick salt marshes in early September, where they shared observational insights and discussed local ecology.


Water Reporter Heather Osterfeld’s post from September 8 shows torn and uprooted eelgrass in Maquoit Bay. Water Reporters have noticed an increase of eelgrass adrift in the Bay since mid-August – from Brunswick west to Freeport, Yarmouth, Cumberland, and Falmouth.

Water Reporters up and down Casco Bay have been documenting an increase of torn and uprooted eelgrass washing ashore from mid-August through September. Falmouth Town Landing, Broad Cove, Wolfe’s Neck, and Maquoit Bay are among the locations where Water Reporters have encountered piles of this ecologically vital, ribbon-like seagrass.

Eelgrass (Zostera marina) grows underwater in the shallows of Casco Bay. Eelgrass meadows are recognized as critical nursery habitat for economically important fish and shellfish. Eelgrass helps to maintain water quality by absorbing nutrients and stabilizing sediments. These seagrass beds can also help the Bay be more resilient to climate change, serving as natural carbon sinks by absorbing carbon dioxide during photosynthesis and making our coastal waters less acidic.

In recent years, some eelgrass beds in Casco Bay have been decimated by rising populations of invasive green crabs. Scuttling through an eelgrass meadow along the bottom of the Bay, adult green crabs clip and uproot eelgrass as they search through bottom sediments for prey, while juvenile crabs may feed on the base of the plant itself. A particularly extreme example of this dynamic occurred between 2012 – 2013, when a boom in the green crab population coincided with the loss of nearly fifty percent of the eelgrass in Casco Bay.

When Casco Baykeeper Ivy Frignoca and Water Reporters take a closer look at the eelgrass that is washing ashore today, they often notice fraying at the stems indicative of green crab mandibles and claws. However, not all of the eelgrass displays this fraying, and Ivy and others speculate that the quantities of dead eelgrass are too large to be caused by green crabs alone.

“We are not sure why we are seeing so much eelgrass washing ashore,” said Ivy. “We have asked state officials to look into this and they are. Continuing to have Water Reporters track where and when eelgrass is coming ashore is key to figuring out what factors may be causing the problem.”

Sometimes being stewards of the Bay means following the clues just as Sherlock Holmes might.

Identifying the difference between the frayed stems of eelgrass clipped by green crabs from eelgrass that has been uprooted by a passing boat or other activity can require a discerning eye. The same kind of observational nuance applies to assessing the potential source of an algal bloom, or hypothesizing which factors are causing a specific stretch of salt marsh to erode. Ivy and Friends’ Community Engagement Coordinator Sarah Lyman met up with Water Reporters in early September, to hone observational skills while discussing questions and sharing insights.

“Many Water Reporters have an intimate familiarity with specific parts of the Bay. When we come together to share our knowledge and perspectives, we all leave knowing more about each other and the Bay,” said Sarah. “That’s what I love about Water Reporter: these folks that care about this place are learning alongside us and teaching us at the same time.”

Sarah and Ivy will be organizing more meetups for Water Reporters around the Bay in the coming months. To stay up to date on Water Reporter events and help us keep an eye on changing conditions in Casco Bay, join us.

June 2020 Water Reporter Post of the Month

As we celebrate two years of Water Reporter posts, we have chosen Trish Peterson’s photo of a lush eelgrass bed at the Punchbowl on Jewell Island as our June post of the month!

We wish all eelgrass beds looked this healthy! Eelgrass has been designated by the federal government as essential fish habitat and a habitat of particular concern. It is a terrific indicator of water quality. Eelgrass needs clean, clear water to grow, and this eelgrass bed is a poster child for good health!

You may see eelgrass (Zostera marina) at the water’s edge at low tide, when the tops of the blades can be seen floating at the surface.

Sometimes, we see eelgrass that has been ravaged by green crabs or made less healthy by too much nitrogen pollution—the same pollutant that causes nuisance algal blooms.

Trish’s post, besides being astoundingly beautiful, will help us compare healthy and less healthy eelgrass beds. Through our Baykeeping work, we advocate for solutions that lighten nitrogen loads to Casco Bay, and we are thinking hard about possible solutions to green crab degradation of eelgrass beds.

We thank Trish for her very active role as one of 229 Water Reporters who help us observe and track changes in and across Casco Bay. Trish has been a volunteer Water Reporter since February 2019. She has been taking photos all around the Bay, posting more than 100 observations about the Bay on the Water Reporter app since then.

“When I’m taking photos as a volunteer Water Reporter, it feels like I’m part photojournalist and part environmentalist!” says Trish. “By learning to identify things like algal blooms and eelgrass beds, I’m not only gaining a growing awareness of the marine environment, but also, in the larger picture, helping to improve the health of Casco Bay. In essence, Water Reporting has been fun, rewarding and educational. With the support of the staff at Friends of Casco Bay, it has been a good fit for me in retirement!”

If you are interested in becoming a Water Reporter like Trish, email Community Engagement Coordinator Sarah Lyman to find out how to get started.

Did you see this eelgrass post on Water Reporter from Angela (Angie) Brewer, Biologist III at Maine Department of Environmental Protection?

Angie posted a photo of an eelgrass blade shredded by a green crab and asked us to keep an eye out for similar damage.

She also asked fellow Water Reporters to keep an eye out for white brown discolorations or brown discolorations in the water around the Bay, especially in the Brunswick area. Please post photos on Water Reporter if you see these discolorations. Water Reporters can also comment on Angie’s post to update her on what you are seeing.

Cousins Island View

Blue Carbon: Could eelgrass help save the Bay?

Research Associate Mike Doan loves to explore eelgrass meadows from above and below the water.

When you ask people if they have a favorite sea creature, they may name a winsome harbor seal or an imposing great white shark. If you ask that question of Mike Doan, Friends of Casco Bay’s Research Associate, he’ll say, “Eelgrass.”


Mike says, “Eelgrass beds are Casco Bay’s rainforest. They are one of the most productive and biologically diverse habitats on the planet. When I am diving or drifting over an eelgrass meadow, it just makes me feel relaxed and peaceful.”

Mike is not alone in his appreciation of this exceptional plant. It is one of the few true marine flowering plants, with roots, stems, and leaves. Many sea creatures look to eelgrass for foraging, hiding places, and something to grab on to in the shifting tides of the estuary. The long, flowing leaves dampen wave action, and the roots anchor the mud, inhibiting shoreline erosion.

Now some scientists, including Mike, suspect that eelgrass beds may provide an even bigger benefit to the marine ecosystem: perhaps eelgrass can help temper the effects of acidifying seawater. Coastal acidification is caused by the increase in carbon dioxide (CO2 ), both from the absorption of CO2 released into the atmosphere by burning fossil fuels and from nitrogen flushed into the ocean by rainwater runoff.

Because eelgrass extracts huge amounts of nitrogen and carbon from seawater, eelgrass may well have a role in mitigating coastal acidification. A new area of research termed Blue Carbon is investigating the way that sea grasses, salt marshes, and mangroves take up and hold carbon in the tissues of the plants. Much of that carbon is transferred into the sediments, “sequestering” the carbon from circulation for many years. Scientists have found that sea grasses and salt marshes absorb and hold up to ten times more carbon than forests on land.

Seaweeds such as kelp also take up nitrogen and carbon. How can they be helpful? Mike says that if we promote seaweed aquaculture, we can later harvest the plants, effectively taking away the carbon and nitrogen they absorb from coastal waters. “Cultivating and cutting algae for biofuel or for food would help remove excess nitrogen and carbon dioxide from the ocean, which in turn would help neutralize the water chemistry to nurture the growth of shellfish such as clams and mussels.”

[box] Coding carbon by color What is Blue Carbon? The National Oceanic and Atmospheric Administration defines blue carbon as the fraction of carbon taken up and stored in ocean and coastal ecosystems, such as mangroves, sea grasses, and salt marshes. Green carbon is the carbon that is taken up by terrestrial ecosystems, such as forests and fields. Black carbon is the carbon that’s released in the production and burning of coal, oil, and gas.[/box]

Restoring Nature’s Nurseries of the Sea

Restoring Nature’s Nurseries of the Sea

Restoring Nature’s Nurseries of the SeaIn parts of Casco Bay, long blades of eelgrass still sway hypnotically in clear water, their tips just tickling the surface. It’s easy to imagine the multitudes of marine creatures hiding among the sheltering fronds.

At one time, the Bay had the largest and densest beds of eelgrass along the coast of Maine. In the mid-1990s, Casco Bay had approximately 8,700 acres of eelgrass beds. Today, nearly 60% of those beds have disappeared, mostly from Middle and Maquoit bays.

That is why Friends of Casco Bay Research Associate Mike Doan is excited to be helping with a project to replant eelgrass lost to marauding invasive green crabs. Mike is gathering critical data on water quality conditions at the replanting sites.

Restoring eelgrass benefits fish and wildlife populations. It also improves water quality, inhibits shoreline erosion, and removes nitrogen and carbon dioxide from seawater, reducing coastal acidification.

“Friends of Casco Bay is collaborating on a multi-organizational project to test the feasibility of restoring eelgrass to upper Casco Bay,” explains lead investigator Hilary Neckles of the US Geological Survey. Our Baykeeper boat picked up eelgrass harvested from a healthy site in Cumberland and transported it to Southern Maine Community College. There, volunteers cleaned and prepped the eelgrass for transplanting. The next morning, we delivered the shoots to the experimental site, where volunteers anchored the eelgrass using four different techniques.

The work complements our studies on coastal acidification. “It’s an exciting overlap with Friends of Casco Bay’s investigations of sediment pH in the area’s clam flats,” notes Dr. Neckles. “Mike is monitoring sediment pH of some intertidal flats that could be potential eelgrass restoration areas. This project will provide information about the role of eelgrass in mitigating coastal acidification.” She adds, “The results of our pilot project will inform decisions about the potential for large-scale restoration efforts in upper Casco Bay.”