Home » Data on Casco Bay

Tag: Data on Casco Bay

What’s green, microscopic, and makes ½ our oxygen?

What’s green, microscopic, and makes half of the oxygen we breathe? Phytoplankton, the tiny algae at the base of the food chain, that’s what!

Measurements of chlorophyll — the green pigment that enables plants and algae to photosynthesize — provide an estimate of how much phytoplankton are in our coastal waters.

In this third edition of Mike’s Field Notes, Staff Scientist Mike Doan shares what he sees when he looks at our Continuous Monitoring Station’s most recent chlorophyll data. You can watch the three-minute video below.

In case you missed them, here are links to the first two videos of Mike’s Field Notes:

Mike gives a tour of our Continuous Monitoring Station.

Mike discusses how warm our winter and spring have been.

30 years of success protecting the Bay

We were delighted to have more than 80 Friends of the Bay join us for our 30th Anniversary Members Annual Meeting on June 16. As Executive Director Cathy Ramsdell said during the event, we only wish we could have held it in person.

If you missed the event — or if you want to re-watch your favorite parts — we are providing you with links to the following videos:

In this 8 minute video, the Casco Bay region’s Congressional Delegation, including Senators Susan Collins and Angus King and Congresswoman Chellie Pingree, share reflections on what 30 years of Friends of Casco Bay means to them and to our community.

In this 8 minute video, Cathy describes how our work to protect the health of the Bay continues. We may be socially distant from one another right now, but we remain connected to the Bay. Hear how our work continues.

Lastly, and perhaps most importantly, in this video Cathy shares our plans over the next decade and beyond to help our community address looming threats, and she announces the formation of the Climate Change and Casco Bay Fund for Technology, Science, and Community Engagement.

During the Annual Meeting portion of the event, Steve Bushey and Mark Green were elected to their first terms to the Board of Directors, Malcolm Poole was re-elected to his second term, and Joan Benoit Samuelson and Tollef Olson were elected to their third terms. You can find the complete list of our Board of Directors here.

Stay tuned. Soon we will announce how you can take part in our second 30th anniversary event, which will be held in late July.

Thank you for your support over the past 30 years and for joining us on our voyage toward a healthier, more protected Bay in the decades to come.

Take a tour of our Cage of Science

What is this Cage of Science that Friends of Casco Bay keeps talking about? We invite you to join Staff Scientist Mike Doan out on Casco Bay for a short tour of our Continuous Monitoring Station. In this 2 ½ minute video, Mike shows off the high-tech components of the station and shares why its stream of data is so important to our work.

Good Green vs. Bad Green

If you have ever tried to pick the right shade of green to paint your bedroom, you know there are soothing greens and greens you would never want to wake up to. The same holds true in the ocean.

Algae is one of those “greens” that can be a sign of a healthy ecosystem; but large areas of mudflats may become covered in a nightmarish bright green when algal growth is fueled by too much nitrogen in the water.

In 2019, as the water warmed from spring through fall, volunteers in our Water Reporter observing network tracked algal blooms that appeared in 18 different locations around Casco Bay. The photos they took on their smartphones documented changes throughout the summer, as the algal blooms expanded to worrisome levels in many coves from Cape Elizabeth to Harpswell and West Bath.

In 2017, we tracked algal growth at five sites. We do not have enough historical data to know whether nuisance algal blooms are expanding or simply that we are getting better at tracking more sites, thanks to our growing network of Water Reporters.

In any case, nuisance and harmful algal blooms are an increasing concern. Water Reporters are already discovering and tracking sightings in 2020!

Community Engagement Coordinator Sarah Lyman oversees our Water Reporter program. This year, Sarah hopes to recruit additional volunteers to our band of intrepid Water Reporters who track algal blooms. “Each volunteer will adopt a specific Bay location to observe weekly. Images of algae from the ‘good’ amounts to ‘concerning’ amounts are helpful because we can’t predict where and when a small patch of algae may become a nuisance algal bloom.”

Currently, there are 205 volunteers in our Water Reporter network. Together, they have recorded 991 observations about Casco Bay. If you are interested, learn more at cascobay.org/water-reporter.

Our Water Reporters tracked algal blooms at 18 locations around the Bay in 2019.

Nitrogen fertilizes the ocean, too

Nitrogen encourages the growth of plants on land and in the ocean, where it stimulates the growth of algae, from microscopic phytoplankton to sinuous seaweeds, the base of the ocean food web.

Excess nitrogen can stimulate algal growth beyond what marine life can absorb. Nuisance algal blooms can cover tidal flats with a thick carpet of “green slime,” smothering animals below the mat and preventing juvenile clams from settling into the mud. Large phytoplankton blooms can reduce water clarity. When these blooms die, decomposition sucks life-giving oxygen out of the seawater and releases carbon dioxide, creating acidic conditions that make it harder for clams and mussels to build and maintain their shells.

Boom and Bust: How phytoplankton influence pH

When we look at our water quality data, we can see that some characteristics of the Bay influence other characteristics. In this example, large phytoplankton blooms have a big impact on the chemistry of Casco Bay.

Ready for some Marine Science 101?

In the graph below, we compare two types of data we collect at our Continuous Monitoring Station: chlorophyll and pH.


We measure chlorophyll to understand how much phytoplankton is in the water. Phytoplankton are microscopic plants that are the base of the food chain. Chlorophyll is the green pigment in phytoplankton (and all plants) that traps the energy of the sun for photosynthesis. Higher levels of chlorophyll indicate an abundance of phytoplankton. Graphs of chlorophyll show when populations of phytoplankton are on the rise and when they crash.

pH is a measure of acidity. The lower the pH, the more acidic the solution. The pH measurement decreases as acidity increases. That is because pH is an inverse measure of the concentration of hydrogen ions in a solution, measured on a scale of 0 to 14. The scale is logarithmic, and each number is an order of magnitude different. For example, a pH of 7 is ten times more acidic than a pH of 8, and one hundred times more acidic than a pH of 9. pH is an abbreviation for “power of hydrogen.” Any solution with a pH lower than 7 has more hydrogen ions than hydroxide ions. Data from our Continuous Monitoring Station show that pH is around 8.0 on average, but changes hourly, daily, and seasonally.

What is this graph telling us?

The graph above compares chlorophyll and pH data from our station. The two lines track the daily means of that data calculated from July 2016 through mid-March 2020.

You can see the variability in both chlorophyll and pH over time, moving from left to right.

When chlorophyll spikes, there is generally an uptick in pH, and then a decrease in pH as chlorophyll levels drop.

Why does this happen?

Whenever carbon dioxide (CO2) is added to water, the water becomes more acidic (pH goes down). The opposite is true as well. Acidity decreases (pH goes up) as CO2 is removed from the water.

This image of phytoplankton is courtesy of Southern Maine Community College.

When phytoplankton photosynthesize, they convert carbon dioxide (CO2) from the water to carbohydrates and oxygen. This reduces the amount of CO2 in the water, lowering the acidity. The larger the bloom of phytoplankton, and the longer the daylight hours, the lower the acidity (and the higher the pH). Other factors influence pH as well, but the amount of phytoplankton is a primary driver.

As the bloom ends, much of the phytoplankton die and decompose. The process of decomposition releases CO2 to the water and pH levels go down (more acidic water).

Compare changes in chlorophyll and changes in acidity throughout the year here.

We’re still monitoring the health of Casco Bay, and you can too

It is lonely out on the pier where Staff Scientist Mike Doan is collecting data on the health of Casco Bay — and he is playing it safe, taking his own selfie as seen here.

We are continuing to monitor the health of Casco Bay. Our Continuous Monitoring Station is still collecting data every hour, 24 hours a day, 365 days a year. Mike services the station every two weeks, making sure the equipment is clean and well-calibrated.

Mike has seen some unusual readings over the past few months — a large phytoplankton bloom in December, a smaller one in February, and warmer-than-usual water temperatures in January and February. He is anxious to compare data from March.

“This has been an unusual winter, and I’m curious to see how conditions change as we move into spring,” Mike reflects.

You can take a look at the data on our website. We also encourage you to get out along the Bay — while maintaining social distancing — and record your own observations on your smartphone. You can find out how on our Water Reporter page.

The Bay Is Blooming

What are the signs of spring for you? Chirping chickadees? Street sweeping? Longer daylight? Changing the clocks? (March 8th is the start of Daylight Savings Time!)

The lengthening daylight jumpstarts the growth of phytoplankton, the single-celled plants that are the foundation of the ocean food web. Like plants on land, they respond to increasing sunlight by bursting into bloom.

The graph of chlorophyll fluorescence shows the increase and decrease in phytoplankton abundance in Casco Bay throughout the year at our Continuous Monitoring Station in Yarmouth.

How can we know what is happening in the ocean? Our Continuous Monitoring Station indicates the abundance of phytoplankton in Casco Bay by measuring chlorophyll fluorescence. Chlorophyll is the green pigment in plants that traps the energy of the sun for photosynthesis.

Our long-term monitoring station, anchored just above the sea floor off Cousins Island in Yarmouth, collects measurements of temperature, salinity, pH, dissolved oxygen, carbon dioxide, and chlorophyll fluorescence, every hour, year-round.

Staff Scientist Mike Doan observes, “Our Continuous Monitoring Station is going into its fifth year of data collection. During the first two springs [2017 and 2018], the chlorophyll levels peaked, as expected, around March, which would be consistent with seasonal phytoplankton bloom cycles. Last year, we experienced a winter bloom that peaked in January, much earlier than we would have expected. So far this winter we have experienced a similar situation, with a moderate bloom over the winter. We are very interested in seeing what the February and March data tell us.”

We update our website each month, so come back often to see if these early blooms continue to occur in Casco Bay, yet another signal that things may be changing in the Bay.

A warm winter, even in Casco Bay

If you are thinking this past January was unusually warm, you would not be wrong. January 2020 was Earth’s warmest January in 141 years of temperature records, according to NOAA’s National Centers for Environmental Information. According to WCSH6 meteorologist Keith Carson, Portland’s average temperature from December 1, 2019, to February 12, 2020, was 30.2 degrees Fahrenheit. So far, 2020 ranks as the 3rd warmest winter on record in Portland and the 6th warmest in Bangor.

Friends of Casco Bay’s Continuous Monitoring Station in Yarmouth confirms that water temperatures in Casco Bay were also especially warm. Our station has been amassing hourly data on the health of the Bay for nearly four years. This graph compares water temperatures from 2016 to date. Staff Scientist Mike Doan says “It is too soon to claim a trend, but the data are concerning. January 2020 water temperatures were on average the warmest we have seen at the station.”

We are celebrating our 30th—the “pearl anniversary”

  • Pearls are gemstones that mark a 30th anniversary. Pearls are symbolic of wisdom gained through experience. We have learned a lot in 30 years!
  • A pearl is created by an oyster in response to an irritant. A pearl can form over time as an oyster secretes layer upon layer of aragonite, a form of calcium carbonate, around a particle of sand. Friends of Casco Bay was created in 1989 in response to a report that claimed Casco Bay was polluted. We continue to respond to many issues that aggravate the health of the Bay.
  • Oysters thrive in estuaries like Casco Bay. Sea farmers in Casco Bay raise the American and European species of oysters. These sea creatures can tolerate a broad range of temperatures and salinities. Our data document a wide range of water quality conditions around our estuary, where fresh water and salt water meet.
  • Oysters help clean the ocean. One oyster can pump up to 50 gallons of water through its body each day, filtering pollutants from the sea water. Our pumpout boat can remove 650 gallons (or more) of raw sewage from marine toilets in a day.
  • Oysters are vulnerable to ocean acidification. Like other creatures whose shells are made of aragonite, oysters, mussels, and clams have a harder time building and maintaining their shells in acidic conditions. We use data from our Continuous Monitoring Station to calculate the amount of aragonite in seawater (“omega aragonite”) to determine if there is enough raw material for an oyster to build its shell—or make a pearl.
  • Oysters remove nitrogen from the water. An oyster uses nitrogen from seawater for its growth. Excess nitrogen is deposited in the mud as pseudofeces (fake poop), taking that nitrogen out of circulation. Friends of Casco Bay works to reduce excess nitrogen in coastal waters from fertilizers, polluted stormwater, and sewage outfalls.
  • Friends of Casco Bay is the thread connecting the string of pearls. Our community of staff, board, volunteers, supporters, and concerned citizens are bound together by the common goal of improving and protecting the environmental health of Casco Bay.

Save the date for our 30th Anniversary Event

As we look ahead in 2020, we invite you to our 30th anniversary celebration on April 29, 2020, at Ocean Gateway in Portland. Mark your calendar and save the date! More details to come here: 30th Anniversary Event.