FALMOUTH — The appearance of several pockets of green algae at Town Landing is not too concerning – at least for now.

But Ivy Frignoca, baykeeper for Friends of Casco Bay, said she hopes residents will help the organization keep an eye on the area and alert her if the algae continues to spread and becomes what she called a nuisance bloom.

One way residents can do that is by volunteering to become a Water Reporter for the friends’ group. More information on the program and how to sign up is available online at www.cascobay.org.

Water Reporters help the Friends of Casco Bay get a better understanding of conditions in the bay. Their assistance is particularly important in looking out for nuisance algal blooms, water pollution, shoreline erosion, and marine wildlife sightings, the friends’ website says.

Frignoca said this week that the presence of some algae is actually helpful, because it provides habitat and food for a variety of marine life. However, she said an unchecked algal bloom can quickly become harmful.

That’s because a thick layer of algae can smother clams and other organisms. It can also use up the oxygen that lowers the pH level in the marine sediment, which makes it inhospitable to all types of critical marine creatures.

In addition, Frignoca said when the algae dies it releases carbon dioxide, which aggravates ocean and shoreline acidification.

She said a large algal bloom would be a sign of bad health, but what’s encouraging is that something can be done to both prevent and limit the impact.

Frignoca said algal blooms are caused by too much nitrogen, which particularly effects shallow water, such as at Town Landing or some of the other small coves in town.

Stormwater runoff is one of the biggest sources of nitrogen, she said. To prevent that issue, Frignoca said homeowners can limit their use of fertilizer, carefully choosing where and when it is applied, if it’s used at all.

Another way people can help combat the amount of nitrogen making its way into Casco Bay is to ensure that their septic systems are working, Frignoca said.

In general, she said nuisance algal blooms are becoming more and more of a problem around the bay. “For the last three summers we’ve seen more and more flats impacted,” Frignoca said.

“The problem seems to be increasing in relation to the changing climate,” she added. “Warmer temperatures and more sunlight seem to be aggravating the growth of these blooms.”

Frignoca said the nuisance blooms seem to be more of a problem in areas where there is “not a lot of circulation.” And, she said, once a bloom starts it can “sustain itself for months and months” at a time.

“We don’t have all the answers,” she said, but added she’s been particularly encouraged by the fact that when the Portland Water Treatment plant on Back Cove reduced its nitrogen output by over 70 percent, no algal bloom appeared there last summer.

“It shows great promise,” Frignoca said. “A lot depends on identifying the source, but the good news is it can be combatted.”

Kate Irish Collins can be reached at 780-9097 or kcollins@theforecaster.net. Follow Kate on Twitter: @KIrishCollins.

Algae can benefit marine life; it only becomes a concern when it spreads widely, according to Casco Baykeeper Ivy Frignoca. Right now she sees “nothing too concerning” at Falmouth Town Landing.

A nuisance algal bloom can cause problems for marine life and the underlying sediment, but the presence of some algae is actually helpful, according to Casco Baykeeper Ivy Frignoca.

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