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Category: Seasonal Sampling

Casco Bay Heats Up

30 years of temperature data show waters in Casco Bay are warming rapidly.

Casco Bay is warming rapidly, according to Friends of Casco Bay’s 30-year-and-growing data set. Temperatures in the Bay have warmed 3° Fahrenheit on average since 1993. At a rate of 1°F per decade, the warming trend suggests the nearshore environment in Maine’s most populated region will continue to see dramatic changes in the coming years.

“This rise in water temperature marks an enormous shift,” says Staff Scientist Mike Doan. “It’s a stark reminder that climate change is altering the Bay in a fundamental way. And not only is the temperature increasing, but the rate of increase has continued to rise, too.” 

30 years of seasonal temperature data show Casco Bay has warmed by approximately 3°F since 1993. These data are from Friends of Casco Bay’s three Sentinel Sites in the Bay, which are located offshore in Broad Sound, nearshore by Clapboard Island, and at the mouth of Portland Harbor. These are water column data, which are collected at regular intervals from the water’s surface to the bottom of the Bay.

We completed our 30th year of collecting seasonal water temperature data in October. Our full 30-year data set shows Casco Bay’s three warmest years on record have all occurred in the past five years, between 2018 and 2022. These data confirm that warming conditions in the Bay align with those observed in the Gulf of Maine and that the region’s waters are warming faster than global averages. 

Scientists have linked rising marine temperatures to shifts in species distribution. Valuable cold-water fisheries like lobster are migrating north. Green crabs, well-known for decimating softshell clam populations and ecologically critical eelgrass meadows, have grown in number in Casco Bay as waters have warmed. 

Staff Scientist Mike Doan collects water quality data from Friends’ research vessel, R/V Joseph E. Payne. Mike uses a data sonde – a scientific device that measures water quality characteristics – to measure temperature, salinity, dissolved oxygen, and other parameters.

“Rising water temperatures cause so many impacts,” says Casco Baykeeper Ivy Frignoca. “A significant rise in temperature can lower the amount of oxygen in the water, cause ill health for cold water plants and animals, and signal an end to a species’ ability to live here. How do we help the Bay adapt to these changes?” 

Slowing the rate that Casco Bay is warming will require accelerated regional and national efforts to reduce reliance on fossil fuels and turn to renewable energy. For many people living in the watershed however, changing energy policy to reduce carbon emissions can feel beyond their influence, says Executive Director Will Everitt. 

“Locally, we have a limited ability to control carbon emissions across the nation or beyond our borders. But we can control the pollution we put into the Bay,” says Will. “Everything we do now to improve the health of marine ecosystems can help buy us time in the face of the long-term impacts of climate change. Actions like limiting the use of pesticides and fertilizers, reducing stormwater pollution, and developing our towns in ways that do not harm water quality matter. Especially in highly populated areas like the shores of Casco Bay. ”

Listening to Casco Bay: the Clean Water Act, Climate Change, and More

We recently hosted an informative and thought provoking conversation at Listening to Casco Bay: the Clean Water Act, Climate Change, and More. 

Casco Baykeeper Ivy Frignoca and Staff Scientist Mike Doan walked us through our latest data on the health of the Bay and shared their observations from the 2022 field season. Here is a recording of the full event for those of you who were not able to attend or want to revisit the conversation.

If you don’t have time to watch the full recording, here are a few key moments you may want to check out:

In this 2 minute clip, Mike presents 30 years of watertemperature data that show Casco Bay is warming at a rapid rate. Casco Bay has warmed by more than 3 degrees fahrenheit over the past three decades. “This increase in temperature affects everything we do,” says Mike.

 

 

In this 5 minute clip, Mike shared temperature and dissolved oxygen data we collected from the Presumpscot River this summer. The Presumpscot is the largest river that flows into Casco Bay.

 

 

 

In this 4 minute clip, Ivy helps us understand how the Clean Water Act is structured to prevent pollution. “In essence, the Clean Water Act says: thou shall not pollute, unless you have a permit to do so,” says Ivy.

P.S. You can listen to the Bay yourself by checking out data from our Continuous Monitoring Stations.

Decades of Data: A Watershed Year for Science

This year we are marking two important milestones: our 30th season of monitoring the water quality of Casco Bay and the first full-year of having three Continuous Monitoring Stations in the water.

Staff Scientist Mike Doan says that both our Seasonal Sampling and Continuous Monitoring efforts are crucial to our mission to protect the health of the Bay. “Casco Bay covers more than 200 square miles of water,” he explains. “Our monitoring programs are designed to efficiently measure how healthy various parts of the Bay are while tracking how our waters are changing over time.”

“We are proud to say that we have stuck with science for the long-haul,” says Will Everitt, Executive Director of Friends of Casco Bay. “It takes tenacity to stick with any long-term project. It takes committed supporters and donors to ensure that we have the resources to continue this work year in and year out. If you are one of those supporters, thank you. You’ve helped us reach these milestones.”

The Casco Bay Estuary Partnership (CBEP), one of 28 federal National Estuary Programs, is among the many entities that put our data to use. “For three decades, Friends of Casco Bay’s monitoring efforts have provided a crucial part of the data used to understand the condition of Casco Bay,” says Curtis Bohlen, Director of CBEP. “The data are relied on by scientists and regulators alike. Friends’ thirty year history of monitoring the Bay provides a long term perspective crucial for understanding how the Bay is — and is not — changing.”

30 Years of Seasonal Sampling

Our Seasonal Sampling program continues to add to one of the most-important and long-term marine water quality data sets in New England. Data from this program helped to designate Casco Bay as a Federal No Discharge Area and upgrade Clean Water Act classifications for large areas of the Bay, ensuring our waters are better protected for years to come.

From May to October, Staff Scientist Mike Doan and Casco Baykeeper Ivy Frignoca take to our Baykeeper boat or truck and travel to 22 sites across the Bay.

“We are providing a health check-up for the Bay each day we are out there,” Mike explains. “Like a doctor checking your blood pressure, if we find an anomaly or problem, we can do more thorough investigations.”

365 Days of Continuous Data

Mike and Ivy use a scientific device that measures water quality characteristics called a data sonde to measure temperature, dissolved oxygen, pH, salinity, chlorophyll, turbidity, and water depth. They also collect water samples that we send to a laboratory to measure total nitrogen.

As of May 20, 2022, Friends has a full year of around-the-clock data from all three of our Continuous Monitoring Stations. In May 2021, we launched two new Continuous Monitoring Stations in Casco Bay, located off Harpswell to the east and in Portland Harbor to the west. These two Stations joined our original station off the coast of Yarmouth, near the coastal center of the Bay, first launched in 2016.

Mike designed our Continuous Monitoring Stations, which combine a data sonde with a sensor that collects carbon dioxide data. “We launched the stations to measure how the Bay is changing,” says Mike. “By looking at data collected every hour on the hour, we can better see through the noise of daily and seasonal changes, and understand how climate change may be impacting our waters. Having three stations up and running for more than a year now is giving us a clearer picture of what is happening in very different regions of the Bay.”

Our Continuous Monitoring Stations are maintained thanks to the generous support of the Casco Bay Estuary Partnership and the more than 700 Friends of the Bay who gave to our Climate Change and Casco Bay Fund.

Bay temperatures rise as oxygen levels dip

Friends of Casco Bay has been collecting water quality data on the health of the Bay for 29 years. A recent analysis of our seasonal long term dataset shows that water temperatures are on the rise in Casco Bay.

 

On average, water temperatures in Casco Bay are increasing at an approximate rate of 1°F every decade.*

“It’s alarming to see we’re going in the wrong direction,” said Staff Scientist Mike Doan. “There are so many ways that warmer water can impact the Bay. A primary concern is that warm water species are moving in and cold water species are moving out. Invasive green crabs, for example, thrive when the Bay is warmer. On top of species shifting, we are also looking at a system that is increasingly susceptible to nitrogen pollution. And that’s only the tip of the iceberg.”

When Mike says warmer waters make the Bay more susceptible to nitrogen pollution, he is thinking about how excess nitrogen can lead to lower levels of oxygen in the water. Nitrogen pollution comes from sources such as stormwater and wastewater treatment facilities. When excess nitrogen enters the Bay, it can spur the rapid growth of plant life and algae. When these plants inevitably decompose, they can consume so much of the oxygen in the water that aquatic animals like fish and shellfish struggle to breathe, and can even die.

On the whole, Casco Bay contains healthy levels of oxygen. However, water temperature and oxygen have an inverse relationship. Warm water holds less oxygen than cold water, and as water temperatures in the Bay rise, Mike has observed a corresponding decline in dissolved oxygen (a measure of how much oxygen is in the Bay).

 

On average, levels of dissolved oxygen are healthy in Casco Bay but are slowly decreasing at an approximate rate of 0.1 mg/L every decade.*

“There’s a very healthy amount of oxygen in the Bay right now, and the decline we’re observing is moving at a slow pace,” said Mike. “However, it’s important to keep our eye on this trend. As climate change causes the Bay to warm, oxygen levels will continue to decrease. With it, the impacts of nitrogen pollution and associated drops in oxygen will grow.”

Scientists up and down the New England coastline are reporting similar trends in temperature and dissolved oxygen. At Friends of Casco Bay, these trends are based on Mike’s analysis of a subset of 29 years of our seasonal sampling data. Specifically, Mike looked at data from three locations in the Bay that we access by boat near Fort Gorges, Clapboard Island, and in Broad Sound. At each of these sites we collect data at the water’s surface, and then every two meters down to the bottom of the Bay, to create a “profile” of the water column. Every one of these data points is included in Mike’s analysis, making him confident that these trends accurately reflect changing conditions in Casco Bay.

 

* The exact rates: water temperatures are rising at 0.99°F per decade and dissolved oxygen levels are decreasing at 0.091mg/L per decade.

What did we see on the Bay this summer?

Last week over 165 Friends of the Bay joined Casco Baykeeper Ivy Frignoca and Staff Scientist Mike Doan online at our latest Casco Bay Matters Event: What Casco Bay Is Telling Us.

Here is a recording of the event for those of you who were unable to attend or would like to revisit the conversation.

Every year, Ivy and Mike traverse the Bay by land and boat from May through October, collecting water quality samples and speaking with those who live, work, and play on the water. At last week’s Casco Bay Matters event, Ivy and Mike shared their observations from this past field season, what our data are telling us about the health of the Bay, and what we all need to do moving forward to keep Casco Bay blue.

If you don’t have time to watch the whole recording, here are a few clips of key moments you may find interesting:

CLIP #1: In this 90-second clip, Staff Scientist Mike Doan breaks down what he sees in the salinity data (the saltiness of seawater) from our Continuous Monitoring Station in Yarmouth. This year the Bay was particularly salty and Mike has thoughts as to why.

CLIP #2: What does the construction project surrounding Portland’s Back Cove have to do with the health of Casco BayIn this 2 minute clip, Casco Baykeeper Ivy Frignoca explains how the big construction project that you can see from I295 reduces pollution while accounting for the impacts of climate change.

CLIP #3: In this 90-second clip, Casco Baykeeper Ivy Frignoca explains how Volunteer Water Reporters are informing our advocacy and helping us track changing conditions seen on Casco Bay.

Want to watch the full 60-minute eventHere it is!

Data from our seasonal sampling program and our three Continuous Monitoring Stations can be viewed at cascobay.org/our-work/science/.

A View from the Hill: The Bay Rests

Friends of Casco Bay Board President Sandy Marsters recently wrote an ode to the Bay in fall, for his regular column with the Portland Phoenix. “There is calm as the Bay breathes with the tides,” writes Sandy, “great inhales and exhales that roll the stones round onshore, polish the sea glass, break in long whispers along the sand.” You can read Sandy’s full column about the beauty of the Bay in autumn, here.

You’re invited: What Casco Bay is Telling Us

Casco Baykeeper boat on the water at dawn

Casco Bay is changing and changing quickly. Join Casco Baykeeper Ivy Frignoca and Staff Scientist Mike Doan for a conversation about what Casco Bay is telling us and what we, as a community, need to do moving forward. On Wednesday, October 27, grab your lunch, log on to Zoom, and join the conversation. Ivy and Mike will be sharing with us their observations and experiences from this field season, what our data are telling us, and how you can help as we work to improve and protect the health of Casco Bay.

You must register to join this event. We would love for you to join us.

Register

What: What Casco Bay Is Telling Us: A Casco Bay Matters Event

When: Wednesday, October 27, Noon to 1 p.m. 

This event will take place via Zoom. We will send you instructions for joining the event after you register.