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Volunteers sample Portland Harbor for nitrogen levels

A volunteer samples Portland Harbor for nitrogen on Sunday.
Carol Bousquet
Maine Public
A volunteer samples Portland Harbor for nitrogen on Sunday.

More than 170 volunteers collected water samples from Portland Harbor Sunday to determine nitrogen pollution levels. The nonprofit Friends of Casco Bay organized the sampling.

Casco Baykeeper Ivy Frignoca says the group did a large-scale "nitrogen nab" in 2016, but felt another large scale test was needed to better understand nitrogen sources. The data can help the state Department of Environmental Protection set new limits for discharge from wastewater treatment plants.

"We didn't feel there was enough data on the land-based loading. So we did the nab to help with that, set the nitrogen limits. Then that will impact permits and how much nitrogen can be released under the Clean Water Act permits that are issued to wastewater treatment plants," she says.

Frignoca says nitrogen is the primary fertilizer in salt water, and a healthy amount of nitrogen helps phytoplankton bloom and supports aquatic life.

"But when you get too much loaded in it creates too much growth," she says. "On the phytoplankton side it could spur algal blooms — some people call them Red Tide — that closes our aquaculture."

Frignoca says a bloom in 2017 that covered 14 acres of clam flats in Maquoit Bay killed every quahog under it, and the clam flat still hasn't recovered, and now another bloom is appearing.