May 22, 2018  
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Casco Bay slime sighting a week earlier than last year
Casco Bay slime sighting a week earlier than last year
The attack of the green slime is back. We’re not talking about a B-movie monster, but rather nuisance algal blooms that coat Casco Bay’s mudflats with green growth. Friends of Casco Bay’s staff, including Casco Baykeeper Ivy Frignoca, Research Associate Mike Doan, and Intern Emily Haggett, spotted bright green algal mats on Mill Cove and Antoine Creek in South Portland and Back Cove in Portland last week.

“We began monitoring these mud flats early this year because of the extensive blooms that occurred last year,” says Ivy. “The blooms this year are appearing a week earlier than last year in Back Cove, and weeks earlier on the South Portland side of the Harbor.”

“These blooms can smother clams and other critters in and on the mud. We wondered if the drought conditions last year combined with nitrogen levels in the water caused the blooms, but this year, we have a very different weather pattern because of all the rain. We hoped the blooms last year were an anomaly, yet here we are observing, once again, the rise of slime.”

Excess nitrogen is one factor that encourages such blooms (a lack of sea life that might consume the algae could also be a factor). All living things need nitrogen to grow, but an overdose can trigger excessive growth of nuisance algae, reduce water clarity, and lower oxygen levels. Possible sources of nitrogen include natural sources, as well as man-made sources, such as air pollution, sewage overflows, lawn care fertilizers, and other components of stormwater pollution.

We are not just seeing an increase in algae on the flats; we are seeing it in the water as well. Friends of Casco Bay maintains a Continuous Monitoring Station that collects data on water quality hourly, 24 hours a day. Our volunteers are monitoring 40 stations around the Bay, and we collect data while aboard our Casco Baykeeper boat. “Our monitoring data are showing that we have had phytoplankton blooms in the waters of the Bay since June 21st,” notes Mike. “We are keeping an eye on the health of the Bay. While phytoplankton blooms in water are expected this time of year, these are corresponding with the algae blooms on the mud flats—which we do not expect to see.”

Friends of Casco Bay works with state and local government officials and volunteers to identify nitrogen levels and sources. We are keeping an eye on the green slime growth and hope you will, too. Report excess green slime by emailing Take a photo and tell us the location, with coordinates and landmarks, if you can!

Friends of Casco Bay
43 Slocum Driv
South Portland, Maine 04106
Phone: (207) 799-8574

Posted on Wednesday, July 5, 2017 (Archive on Wednesday, July 26, 2017)
Posted by Jym St. Pierre   Contributed by Jym St. Pierre

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