Algae Blooms Impacting Harwich Ponds

By: William F. Galvin

Topics: Waterways

Harwich news.

HARWICH — Over the past couple of years the number of algae blooms in local ponds seem to be on the rise. Skinequit Pond in South Harwich has experienced two blooms just in the past two weeks, and for the second year in a row the West Reservoir in West Harwich had the blue-green shade that is emblematic of cyanobacteria.

The town had a decade-long battle with algae blooms and fish kills in Hinckley’s Pond before spending nearly $400,000 on alum and sodium aluminate treatment to reduce the excess phosphorous nutrients that cause the blooms. Fourteen years ago Long Pond was also treated with alum.

Several year ago the board of health closed Hinckley’s Pond to human access and strongly urged residents not to allow pets to be exposed to the water. The toxins in cyanobacteria can be lethal to animals and fish and cause gastrointestinal and serious skin irritations in humans. Cyanobacteria, also known as blue-green algae, has been responsible for several fish kills in local ponds over the years.

Conservation Commission Chairman Brad Chase, a state division of marine fisheries biologist, told the commission last week that his agency is studying the impacts of the toxic algae on herring in the Stony Brook herring run in Brewster. Research shows the existence of blue-green algae in the guts of juvenile herring, he said. The agency is looking at growth and survival as part of the study. Chase said it is thought the algae is ingested accidentally when herring are feeding on zooplankton. He said he would see if the researchers can add more locations to the study.

Several of the ponds which have had the algae blooms and fish kills are along the rivers through which herring migrate to spawn, including Hinckley’s Pond, Long Pond and the West Reservoir. Commission member John Ketchum said Skinequit Pond is also a spawning body for the anadromous fish. Conservation Administrator Amy Usowski said last week’s bloom did not cover the entire pond. The town posted a notice of the presence of the algae at the public access to the pond, she said.

Ketchum said he’d like to see the town supporting toxic algae testing. The town of Barnstable has a biologist on staff who conducts such testing, he said. The Association to Preserve Cape Cod has a testing program, but they would charge the town for the service, Usowski said. (The APCC this week released a report detailing pond water quality throughout the region; read about the report here.)

Usowski said the town health and natural resources departments may have a testing kit soon. The town does have microscopes, she said. Ketchum wanted to know if the town has an employee who can work with microscopes and determine results. Usowski said she did that work when employed in Eastham nearly a decade ago. Under a microscope, she said, the toxic algae looks like a string of blue-green pearls.

“This is going to become a bigger issue” moving forward, Ketchum said.