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Monitoring the Bay: science that helps keep Casco Bay blue

We keep an eye on the health of Casco Bay.

It may be hard to believe today, but in the late 1980s, a report entitled “Troubled Waters” labeled Casco Bay as one of the most polluted estuaries in the nation. That report inspired a group of concerned citizens to form Friends of Casco Bay in 1989, to improve and protect the environmental health of Casco Bay.

When we were founded, pollution was widespread, but the truth was that no one had a handle on the environmental health of the Bay. So Casco Baykeeper Joe Payne, our first employee, launched our Water Quality Monitoring Program, enlisting staff and volunteer Citizen Stewards to “take the pulse” of Casco Bay using proven scientific methods. 

Monitoring the water allows us to look at what’s beneath the beautiful view. We have been collecting data on the water quality of Casco Bay since 1992. For over 25 years, we have maintained and added to one of the largest and most important long-term data sets on marine water quality in New England.

The data allowed us to address these questions:

  • How healthy is the Bay?
  • Where are problem areas?
  • What influences the health of the Bay?

Over that time, we have learned much about the Bay. 

What we have learned

  • Casco Bay is generally healthy, compared with other estuaries.
  • Year after year, our data has identified Portland Harbor, the New Meadows embayment, and the mouth of the Harraseeket River as the most environmentally challenged areas in Casco Bay.
  • The healthiest regions of the Bay are Broad Sound, Maquoit and Middle bays, and the offshore waters near Halfway Rock.
  • By sampling both along the shore and offshore, we determined that land-based origins contribute significant sources of excess nitrogen.
  • The bottom water of the Bay has become more acidic, a worrying trend that mirrors what is happening worldwide.
  • Summer is lasting longer beneath Casco Bay. Water temperatures are staying warmer into the fall.
  • In order to better understand how the Bay is changing, we are increasing the frequency of data collection.

Based on what we understand about the health of our waters, and the technology available to us, the questions we are asking about the health of the Bay have changed, as have the ways we collect data. Today, we are not just asking about the Bay’s health at specific sites, we are collecting data to see how the Bay is changing and what effects the changing climate may be having on our waters.

We see water as fundamental habitat. Improving water quality is the focus of our work. Clean water makes the difference for all species living in and on the Bay—including us! The challenges to water quality range from the effects of pollutants entering the Bay, to the impacts of climate change—increasing temperatures, lower oxygen levels, and dips in pH. 

We do not collect data merely for the sake of collecting data. Our monitoring efforts are used to inform advocacy and education efforts. We are making science and information accessible to encourage better decision-making and to inspire communities around the Bay to help protect the health of our coastal waters. These efforts have led to the reduction of pollution into the Bay from point sources, such as industrial facilities, overboard discharges, and other straight pipes into the Bay. 

As the threats to our coastal waters change, we will continue to keep an eye on the health of the Bay.

Our staff is collecting data and observing changes to health of the Bay through the following projects:

Continuous Monitoring Station

Photography by Kevin Morris

Our Continuous Monitoring Station is using the latest technology to collect data every hour, 24 hours a day, 365 days a year. This station will help us better understand the changing chemistry of our coastal waters and track trends over time.

From Land

Photograph by Kevin Morris

Our staff scientists are collecting snapshots on the health of our waters at 12 shore side sites around the Bay, May through October.

By Sea

Friends of Casco Bay Water Quality Sampling on the Baykeeper Boat.
Photography by Kevin Morris

Our staff are out in our Baykeeper boat, collecting data from the surface to the sea bottom, giving us a profile of the Bay’s water quality. 

Microplastics Pilot Project

Photograph by Kevin Morris

We are looking at whether and what types of microplastics are in the Bay. Learn more about the impact of these tiny plastics.

Nuisance Algal Bloom Observations

Over the past two years, more of our coves are becoming covered by nuisance algal blooms. We are noting the extent and longevity of these blooms. 

Protecting Eelgrass Habitat

Restoring Nature’s Nurseries of the Sea

We are working with Maine Department of Environmental Protection, Casco Bay Estuary Partnership, and others to protect this important habitat.

Our volunteer Citizen Stewards are helping us collect data and observe changes to the health of the Bay through the following projects:

Citizen Stewards Program

The Citizen Stewards Program educates local residents about marine protection issues while harnessing the energy of volunteers to collect much-needed data and observations on the health of Casco Bay.

Slimewatchers Project

 Photograph by Deb Dawson

Volunteers help us track outbreaks of nuisance algal blooms by reporting the excessive green algae you see.

For more about our science work, you can see our past projects page.

What is our science telling us?

Overall, the Bay is a healthy and productive system. However, our coastal waters face a myriad of threats, including nitrogen pollution, ocean and coastal acidification, climate change, and stormwater pollution.

You can learn more about the health of specific areas of Casco Bay by using our Interactive Casco Bay Health Index. The Casco Bay Health Index is an easy-to-interpret, visual guide to the health of the Bay based on data collected by our Citizen Steward volunteers. You can compare 37 sampling sites around the Bay and learn more about what affects water quality at each site.

Our data is telling us that nitrogen levels are high close to shore, likely due to an excess of this nutrient flowing from our lawns, fields, and sewage systems. The “rise of slime” caused by nitrogen pollution results in shorelines smothered by mats of bright green algae, clam flats closed to harvesters by red tides, and murky waters choking out eelgrass beds. We are observing an increase in nuisance and harmful algal blooms, which may be linked to excess nitrogen.

Our data is telling us that the chemistry of Casco Bay is changing. Our waters are becoming more acidic. This is bad news for clams, mussels, and oysters—and those who make their livelihoods from these resources.

How our data has been used

Our science is essential to our advocacy and community engagement. Our data has been used for many purposes, large and small, by our staff and other organizations, agencies, researchers, and individuals. Our data has been used to:

  • Identify challenged conditions in areas of the Bay
  • Create our Health Index for Casco Bay
  • Inform our community engagement
  • Ensure better long-term protections for the Bay
  • Regulate and reduce pollution through State-issued discharge permits
  • Influence legislation
  • Advance science in Maine
  • Assist in the education of our future oceanographers and marine scientists
  • Enable government to document health of Maine’s coastal waters
  • Assist others in innovative ways

Learn more about our data and how it is used here.

You can help us tackle the biggest threats to the Bay!

Read more about our science work:

Plastics Pollution in Casco Bay

March 29, 2018

The good news is that fewer discarded plastic bags have been showing up in our coastal cleanups lately; however, plastic litter we cannot see continues… Read more

Spring starts early in Casco Bay!

February 15, 2018

  It may be hard to believe if you have spent any time outside this chilly winter, but spring likely has sprung in the waters… Read more

Volunteers do a great service to Casco Bay

January 25, 2018

More than 125 volunteers and supporters of Friends of Casco Bay came to the Volunteer Appreciation Celebration on January 23, to recognize those who give their… Read more

Keeping you up to date as we keep an eye on the Bay

January 19, 2018

Casco Bay, like ocean water around the world, is changing and changing quickly. We want you to know that we have changed our volunteer Citizen… Read more

What we have learned from 25 years of water quality data

December 6, 2017

Since 1992, more than 650 volunteers have gotten their hands wet in our Citizen Stewards Water Quality Monitoring Program, complementing the work of our staff… Read more

Back Cove August 2nd, 2017

Our “Slime Watchers” Are Keeping an Eye on the Bay

October 12, 2017

If you have ever thought about buying a drone but could not figure out what to use it for, take a lesson from Deb Dawson,… Read more