YARMOUTH — Environmentalists say excess nitrogen in the Royal River – deemed “impaired” by the Department of Environmental Protection – is a cause for concern. 

The Royal River Conservation Trust and Royal River Alliance on March 26 hosted a panel discussion on the river’s water quality. On hand to present data were representatives from the DEP, University of Maine, Friends of Casco Bay and Casco Bay Estuary Partnership.

According to the trust’s executive director, Alan Stearns, 12 towns in Maine have a piece of the river’s watershed from Auburn to Casco Bay.

“What comes down the river is one reason there’s an amazing habitat at the mouth of the river (in Casco Bay),” Stearns said. “The Royal River connects … two amazing resources: the woods up river and the wildlife down river.”

Friends of Casco Bay has been continuously monitoring three sites in Casco Bay for water quality: one near Yankee Marina, one in the Cousins River behind the Muddy Rudder, and one at the mouth of the river.

Five years of data, from 2008 to 2012, has shown levels of nitrogen in the site near the Yankee Marina are much higher than levels closer to the mouth of the Royal River. 

A significant concern with too much nitrogen is the effect it has on dissolved oxygen, the experts said. 

Low dissolved oxygen levels are often the result of excessive algae growth caused by phosphorus or nitrogen. Too much nitrogen can cause over-stimulation of growth of aquatic plants and algae which, in turn, can clog water intakes, use up dissolved oxygen as they decompose, and block light to deeper waters. 

Angela Brewer, of DEP’s Bureau of Water Quality, said the Royal River has been on the department’s list of impaired waters since the mid-1990s due to its level of dissolved oxygen, which is under 85 percent saturation and implies negative impacts on dissolved oxygen levels and marine life.

Friends of Casco Bay Baykeeper Ivy Frignoca said nitrogen levels in parts of the bay are among the highest observed in Maine marine waters. And in both the Royal and Cousins rivers, the nitrogen levels are higher than they should be, according to Frignoca. 

University of Maine professor Damian Brady presented graduate student Whitley Gray’s findings on nitrogen levels in the Royal River, and comparisons to other Casco Bay tributaries.

“We talk a lot about carbon and climate change, but for the previous eight decades before that, most of understanding around water quality in estuaries was around nitrogen,” Brady said. “It’s still a really important number.” 

With 3,500 miles of tidal shoreline, there are more estuaries per mile of coastline in Maine than anywhere else in the country. 

Brady said in most of the country, the vast majority of nitrogen in estuaries is coming from the land, but in many of the estuaries in Maine that he’s studied, nitrogen is coming from the Gulf of Maine. 

Nitrogen can also come from wastewater treatment plants, septic tanks, industrial wastewater, acid rain, and fertilizer runoff from agricultural, residential and urban areas.

The DEP estimates the town’s treatment facility is the only significant “point source” to the river; precipitation and land cover are the primary influences on “non-point source” loadings.

To look at nitrogen loads, or “quantitative estimates of an exposure to pollutants,” Gray compared the Presumpscot River, the Royal River, and the Capisic Brook in Portland. 

Although the Presumpscot River is twice as large, the Royal River has about twice the amount of concentrated nitrogen, but still has less than the Capisic Brook. 

“Even though (the Royal River) is a smaller watershed, it’s got a similar load to the Presumpscot,” Brady said. 

Brady stressed that the goal isn’t to completely eliminate nitrogen from the watershed.

“(Nitrogen is) the engine that keeps every ecosystem on the planet alive, so having some nitrogen is always really important,” Brady said. 

As far as next steps, Brady said he and his team at UMaine hope to take more samples this spring. 

“We still have a lot of analysis to do on this data but it gives you a picture of what we’re seeing so far,” he added. “Trying to figure out why we’re seeing what we’re seeing is the next step.”

Bill Gregory,  a member of the Royal River Alliance, said the panel discussion was the beginning in the alliance’s “desire to explore, with the entire community, the state and needs of the watershed for optimal environmental health.”

Two follow-up discussions hosted by the alliance and RRCT are planned for the spring, on April 25 at Yarmouth First Parish Church and on May 12 at the Royal River Park. 

Jocelyn Van Saun can be reached at 781-3661, ext. 183 or jvansaun@theforecaster.net. Follow her on Twitter @JocelynVanSaun.

Robert Mohlar, of the DEP’s Bureau of Water Quality, presents findings on nitrogen levels in the Royal River during a March 26 panel discussion in Yarmouth.