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What we have learned from 25 years of water quality data

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 scientists in assessing the environmental health of Casco Bay. This science is the foundation of much of our community engagement and advocacy efforts.

Volunteer Citizen Stewards measured dissolved oxygen, temperature, salinity, water clarity, and pH at nearly 40 shoreside sites on the same date and time on ten Saturdays from April through October, to create a simultaneous snapshot of surface conditions around the Bay.

Our staff scientists have monitored offshore at 10 stations, from surface to sea floor, aboard our research vessel, every month of the year.

The data allowed us to address these questions:

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

Volunteer Appreciation & Annual Member’s Meeting

Friends of Casco Bay’s 2016 Volunteer Appreciation Celebration & 2018 Annual Members Meeting

Volunteer Appreciation Celebration
& 2018 Annual Members Meeting

Join us as we recognize those who help us protect the health of Casco Bay. We will provide the updated Casco Bay Health Index based on data collected by volunteer Citizen Stewards over the past 25 years, and we will share new program directions.

When: Tuesday, January 23, 2018, 5:30-8 p.m.
[snow date: January 24, 2018]
5:30 Hors d’oeuvres, cash bar, Program begins at 6:30

WhereDiMillo’s On the Water, 25 Long Wharf, Portland, ME 04101
Free parking while at event.

Donation to attend is appreciated, not required. Suggested donation: $10 per person
If making a donation to attend this event, RSVP here

If you want to RSVP without making a donation, email Sarah Lyman at slyman [at] cascobay [dot] org or call our office at (207) 799-8574.

 

Continuous Monitoring Station

Monitoring a Changing Casco Bay 365 Days a Year

Continuous Monitoring Station
When we haul up the Continuous Monitoring Station to download data and recalibrate the equipment, we also track marine creatures that may have found a home on our “cage of science.”

Covered with sea squirts, sea stars, and other marine hitchhikers, the newest member of our monitoring team looks like an abandoned lobster trap. It may be homely, but we are pretty impressed with what it does, collecting water quality data hourly, 24 hours a day, 365 days a year. It is our Continuous Monitoring Station, which will help us answer the question “How are our coastal waters changing over time?” Research Associate Mike Doan calls it “the cage of science.”

It has been just over a year since we placed a carbon dioxide sensor and a data sonde—an electronic device that records temperature, pH, and other characteristics of water quality—inside this modified lobster trap and moored it in healthy waters near the center of Casco Bay off Cousins Island in Yarmouth.

After one full year, we have over 8,760 hours of data on oxygen levels, carbon dioxide, pH (the level of acidity of the water), salinity, temperature, chlorophyll fluorescence (estimated phytoplankton abundance), water clarity, and water depth.

Thanks to our 26-year data set on water quality in Casco Bay, we understand when and which areas of the Bay are likely to exhibit challenged water quality conditions that require further study. Armed with this baseline data, we can now consider how to address the question, How is the Bay changing?

The steady flow of data from the Station already is helping us detect and document how climate change and emerging coastal stressors may be affecting the Bay. Hourly data helps us identify daily, seasonal,
and annual trends to better understand the extent to which ocean acidification may be impacting the water chemistry of Casco Bay. In future years, we hope to deploy two more “cages of science,” one in challenged waters in Portland Harbor and one near Harpswell to help detect the influence the Kennebec River has on Eastern Casco Bay.

What is a data sonde?
A data sonde, such as the one being used by Research Associate Mike Doan, is an oceanographic
monitoring instrument that takes multiple measurements of water quality simultaneously. In
addition to being used as part of our Continuous Monitoring Station, data sondes are used by
staff scientists in other water quality monitoring efforts from shore and by boat. The data is
downloaded to a computer and analyzed to provide a long-term picture of water quality over
time. We thank Casco Bay Estuary Partnership and our generous members for helping fund
our Continuous Monitoring Station’s first year.

Nabbing Nitrogen results

Nabbing Nitrogen Flash Mob: What We Learned

Nabbing Nitrogen results
Nitrogen levels were high at every place we sampled. The highest levels of
nitrogen were found closer to land, in tidal creeks and near combined sewer
overflows. Lower nitrogen levels were found further from shore.

On Sunday morning, July 10th, 2016, at precisely 10:10 a.m., 97 people knelt down along the edge of Portland Harbor and scooped up small vials of water from Casco Bay. They were not praising Poseidon—they were Nabbing Nitrogen.

A recent heavy rain had flushed a surge of stormwater into the Fore River, so we were not surprised that
the analysis of their water samples found elevated levels of nitrogen. The most important takeaway of the event, though, was that there is an amazing Casco Bay community of volunteers ready and willing to get involved when we send out a call to action!

Interactive Casco Bay Health Index

Interactive Health Index

Friends of Casco Bay has developed the Casco Bay Health Index, an easy-to-interpret, visual guide to the health of the Bay. The Index allows us to integrate data from selected water quality parameters into a single value to compare and rank each site as Good, Fair, or Poor.

 

Now we have our new Interactive Health Index!

By clicking here, or the image below, you can see and interact with the Health Index. The Interactive Health Index will open in a new tab. By clicking on the dots you can see more about each sampling location.

Interactive Casco Bay Health Index

Overall, the water quality in Casco Bay is good, but there are instances when low oxygen, low pH, and murky waters are cause for concern. The 2016 Health Index reveals that over 31% of the sites are considered Poor, but more than 36% of the sites meet the Good standard.

The relative rankings were calculated by analyzing dissolved oxygen, water clarity, and pH data from shoreside sites that our volunteer Citizen Stewards monitored from 2012 to 2016. The values we chose to use were the 90th percentile of the dissolved oxygen percent saturation, the mean of the Secchi depth, and the mean of the diurnal differences in pH.

Commonly Asked Questions about the Casco Bay Health Index

 

What is the Casco Bay Health Index?

The Casco Bay Health Index was developed to provide a reliable, uncomplicated composite indicator of the Bay’s health, while also illustrating relative levels of eutrophication. The Index allows the scientifically-sound data collected through Friends of Casco Bay’s Water Quality Monitoring Program to be presented in a format that is easy to understand and to update.

 

What is the goal of the Index?

The goal of the Health Index is to present water quality information in an easy-to-understand visual format by condensing a large amount of existing data into a single score for each monitoring site. By summarizing a suite of environmental parameters into one score for each water quality monitoring site, each site can be ranked relative to one another, and trends—if there are any—can be more readily identified. This product, while quantitative in nature, should be considered a qualitative place to begin to determine environmental health. The sites are assigned colors—red, yellow or green, and are mapped to indicate the health of the waters around Casco Bay. Then we can ask: Which sites, based on the selected criteria, require a closer look? What is the relative condition of sites across a region? Are these conditions improving or degrading over time?

 

Where do the data for the Health Index come from?

The data used for the Health Index come from Friends of Casco Bay’s Citizen Stewards Water Quality Monitoring Program. Volunteers are well-trained using EPA-approved protocols developed by Friends of Casco Bay. They monitor specific sites and collect the data twice a day on 10 appointed Saturdays, between April and October. The Index incorporates the data for a 10-year span of time and can be updated annually by adding the most recent year’s data and eliminating the oldest. We can also look at the Index in five year increments to compare changes over time.

 

Which of the existing water quality parameters are most appropriate to use in the Index?

Friends of Casco Bay currently monitors five physical and chemical water quality parameters through our Citizen Stewards Water Quality Monitoring Program: temperature, salinity, dissolved oxygen (DO), Secchi depth, and pH. Of these, three have been selected for use in the Health Index—DO, Secchi depth, and pH.

 

Dissolved oxygen (DO) DO is expressed as Percent Saturation in order to incorporate temperature and salinity. When water holds all the oxygen it can at a given temperature and salinity, it is said to be 100% saturated. At a given site during a given sampling event, temperature and salinity are measured, and DO is measured in milligrams per liter (mg/l) and then compared with the mg/l for 100% saturation in those conditions. We look at the distribution of the Percent Saturation data; we consider the lowest 10th percentile as the worse-case conditions for a particular site. That 10th percentile threshold, expressed as a Percent Saturation number, becomes a component of the Health Index for that site.

 

Simply averaging all the DO data for a site might obscure the full extent of any challenged conditions. For example, if a site is eutrophic, wherein nitrogen pollution levels have resulted in a huge algal bloom, there will be large swings in DO levels between the morning and the afternoon; simply looking at the mean would obscure these swings.

 

Secchi depth Secchi depth is a measure of water clarity. The Index uses a mean of the data to characterize each site. Sites with more organic matter and sediments in the water will be murkier and will exhibit reduced clarity, resulting in shallower (lower) Secchi depth measurements.

 

pH pH is a measure of the acidity of the water. pH data exhibit tremendous variability—diurnal differences through the day and seasonal shifts through the year. The Water Quality Monitoring Program requires that measurements be collected at 7:00 a.m. and then again at 3:00 p.m. on each monitoring day. This allows for a look at the change in conditions over the course of a day. The pH at a site is influenced heavily by respiration and photosynthesis. Respiration by algae, both seaweeds and phytoplankton, adds carbon dioxide to the water, which lowers pH. Measurements collected in the early morning, at 7:00 a.m., reflect the conditions found after a night of respiration and no photosynthesis. Photosynthesis of course requires sunlight and removes carbon dioxide from the water, raising pH. By afternoon, at 3:00 p.m., pH measurements will reflect the result of photosynthesis. The change between the morning and afternoon measurements, termed the diurnal swing, can be indicative of the magnitude of respiration and photosynthesis, and, indirectly, the amount of algae in the water. Since an excessive bloom of algae is one symptom of nitrogen pollution, a large diurnal swing in pH can serve as an indicator of excess nitrogen. A small change in pH is expected in a healthy, productive coastal system, but a relatively large swing can indicate a challenged site. We calculate the difference between the morning and afternoon readings, the diurnal swing, then amass that dataset to calculate the mean for the Health Index for that site.

 

What ranges are most appropriate for the component parameters?

For each of the three components of the Health Index, we have defined ranges, between which we would expect to see worse-case and best-case conditions. These ranges have been defined by looking not only at data for Casco Bay, but also data from other regions, state and federal guidelines, and relevant scientific literature.

 

Parameter: 0 point value 100 point value
Percent Saturation of Dissolved Oxygen 65% 95%
Secchi Depth (meters) 0.2 m 3.0 m
pH (diurnal swing) 0.4 0.1

 

How is the Health Index score calculated?

Each of the components calculated for a given site is plotted along the scale for that parameter. We use a natural logarithm formula to determine where on the scale of 0 to 100 a particular component falls. For example, a site’s calculated 10th percentile threshold for the Percent Saturation parameter will fall between 65% and 95% at a specific point on the scale between 0 and 100. The same is done for the Secchi depth component and the diurnal swing in pH. Now we have three numbers which fall between 0 and 100. These are added together and divided by 3 to obtain the mean, which is the Health Index score for that site.

 

How are the final Health Index scores presented?

After each site has a Health Index score associated with it, it can be classified as Good, Fair, and Poor, determined by score thresholds. A score of 85 and above is considered “Good”, a score of 70 to 84 is “Fair”, and anything below 70 falls into the “Poor” category.

 

What is eutrophication?

Eutrophication occurs when too many nutrients (and occasionally other factors) fuel explosive plant growth. While nitrogen is an essential nutrient in marine systems, too much nitrogen can become a pollutant when it triggers excessive algal growth. This growth can result in low DO measurements, shallow Secchi depth readings, and wide variations in pH.

Mac Richardson Nabbing Nitrogen Photo credit: Dave Dostie

Did we Nab Nitrogen? We sure did!

Mike Doan at Friends of Casco Bay’s Annual Members Meeting. Photo credit: Kevin Morris.
Mike Doan at Friends of Casco Bay’s Annual Members Meeting. Photo credit: Kevin Morris.

On January 24, 2017, Research Associate Mike Doan stood before an audience of volunteers and supporters at Friends of Casco Bay’s Annual Members Meeting. He reminded them, “A year ago at this volunteer celebration, we proposed the idea of Nabbing Nitrogen, to get people involved in water quality monitoring on one day, at one moment in time. If we’d recruited 50 volunteers, we would have considered it a success. More than 170 people signed up to volunteer to sample for nitrogen!”

Volunteers lined docks and other access points to Nab Nitrogen on Sunday, July 10, 2016. Photo credit Dave Dostie.
Volunteers lined docks and other access points to Nab Nitrogen on Sunday, July 10, 2016. Photo credit Dave Dostie.

Our Nabbing Nitrogen event became a flash mob, where volunteers scooped up jars of seawater at precisely 10:10 a.m. on July 10, 2016. The weather was awful, so we had to cancel plans for boaters to sample out on the water. Though limited to land-based sites, volunteers would not be deterred. They lined the shoreline of Portland and South Portland on both sides of the Fore River. Mike championed, “It was the volunteers and their enthusiasm and energy, despite the rain, that made the event such a success.”

Lindsay Wold and Chaz Wilcoxen with their Nabbing Nitrogen sample
Lindsay Wold and Chaz Wilcoxen with their Nabbing Nitrogen sample

On that particular morning, we experienced a heavy rain that followed a long dry spell. This made for ideal conditions for collecting data on a storm event. We collected and analyzed 90 samples, which Mike used to construct a map of nitrogen levels around Portland Harbor at this one point in time. He wasn’t surprised to find that nitrogen levels were higher than normal.

Why do we worry about too much nitrogen in Casco Bay?
Nitrogen is an essential plant nutrient, critical for growing. In the ocean, nitrogen nurtures plant growth, from single-celled phytoplankton to large seaweeds. But too much nitrogen triggers excessive algae growth that can turn the Bay green. When the plants die, decomposing bacteria remove the oxygen from the water and release carbon dioxide, making the water more acidic.

Over the last 100 years, the amount of nitrogen available for plant growth has more than doubled, thanks to the invention of commercial fertilizers and the increase in the burning of fossil fuels. Human sewage, air pollution, and rainwater washing fertilizers and animal wastes off yards and farms add excess nitrogen to our coastal waters.

Mike said, “Do you remember last summer, when we saw large mats of green algae in Back Cove in Portland and Mill Cove in South Portland? Those carpets of ‘green slime’ smothered anything trying to live underneath them. In South Portland, we also found that the mud beneath the algal mats was highly acidic.”

Too much nitrogen in the water can impact the nursery of the sea. “Phytoplankton and seaweeds can make the water murky, limiting sunlight to eelgrass,” explained Mike. “We are fortunate that Casco Bay has a lot of eelgrass. Eelgrass is our ‘rain forest.’ It serves a number of purposes: it holds sediments in place, helping to prevent erosion, dampens wave action, which protects the shoreline, and most importantly, provides hiding places for juvenile marine animals.”

Mac Richardson Nabbing Nitrogen Photo credit: Dave Dostie
Mac Richardson Nabbing Nitrogen
Photo credit: Dave Dostie

We will meet with sewage treatment plant operators and stormwater managers to discuss what all the data means.

Already, with the help of our volunteers and great media coverage of our event, people know that there is a lot we each can do to reduce the flow of nitrogen into the Bay. Casco Baykeeper Ivy Frignoca told the audience at our Annual Meeting that they can help by:

  • Not using fertilizer on their yards and practicing BayScaping to minimize the need for lawn chemicals
  • Keep rainwater from running off our driveways and yards
  • Replacing lawns with rain gardens or permeable pavement
  • Support efforts by local municipalities to reduce nitrogen-laden sewage overflows into the Bay
  • Support our work with the Maine Department of Environmental Protection to set responsible limits on nitrogen discharges into coastal waters
Mac Richardson Nabbing Nitrogen
Mac Richardson Nabbing Nitrogen
Photo credit: Dave Dostie

WMTW Meteorologist Sarah Long was one of the many volunteers that participated in this sampling event. You can see her coverage of the event here: http://www.wmtw.com/article/citizen-scientists-help-keep-casco-bay-healthy/8972719.

 

2016 Casco Bay Health Index

Casco Bay Health Index – Updated with 2016 data

2016 Casco Bay Health Index

 

Friends of Casco Bay has developed the Casco Bay Health Index, an easy-to-interpret, visual guide to the health of the Bay. The Index allows us to integrate data from selected water quality parameters into a single value to compare and rank each site as Good, Fair, or Poor.

Overall, the water quality in Casco Bay is good, but there are instances when low oxygen, low pH, and murky waters are cause for concern. The 2016 Health Index reveals that over 31% of the sites are considered Poor, but more than 36% of the sites meet the Good standard.

The relative rankings were calculated by analyzing dissolved oxygen, water clarity, and pH data from shoreside sites that our volunteer Citizen Stewards monitored from 2012 to 2016. The values we chose to use were the 90th percentile of the dissolved oxygen percent saturation, the mean of the Secchi depth, and the mean of the diurnal differences in pH.

Commonly Asked Questions about the Casco Bay Health Index

 

What is the Casco Bay Health Index?

The Casco Bay Health Index was developed to provide a reliable, uncomplicated composite indicator of the Bay’s health, while also illustrating relative levels of eutrophication. The Index allows the scientifically-sound data collected through Friends of Casco Bay’s Water Quality Monitoring Program to be presented in a format that is easy to understand and to update.

 

What is the goal of the Index?

The goal of the Health Index is to present water quality information in an easy-to-understand visual format by condensing a large amount of existing data into a single score for each monitoring site. By summarizing a suite of environmental parameters into one score for each water quality monitoring site, each site can be ranked relative to one another, and trends—if there are any—can be more readily identified. This product, while quantitative in nature, should be considered a qualitative place to begin to determine environmental health. The sites are assigned colors—red, yellow or green, and are mapped to indicate the health of the waters around Casco Bay. Then we can ask: Which sites, based on the selected criteria, require a closer look? What is the relative condition of sites across a region? Are these conditions improving or degrading over time?

 

Where do the data for the Health Index come from?

The data used for the Health Index come from Friends of Casco Bay’s Citizen Stewards Water Quality Monitoring Program. Volunteers are well-trained using EPA-approved protocols developed by Friends of Casco Bay. They monitor specific sites and collect the data twice a day on 10 appointed Saturdays, between April and October. The Index incorporates the data for a 10-year span of time and can be updated annually by adding the most recent year’s data and eliminating the oldest. We can also look at the Index in five year increments to compare changes over time.

 

Which of the existing water quality parameters are most appropriate to use in the Index?

Friends of Casco Bay currently monitors five physical and chemical water quality parameters through our Citizen Stewards Water Quality Monitoring Program: temperature, salinity, dissolved oxygen (DO), Secchi depth, and pH. Of these, three have been selected for use in the Health Index—DO, Secchi depth, and pH.

 

Dissolved oxygen (DO) DO is expressed as Percent Saturation in order to incorporate temperature and salinity. When water holds all the oxygen it can at a given temperature and salinity, it is said to be 100% saturated. At a given site during a given sampling event, temperature and salinity are measured, and DO is measured in milligrams per liter (mg/l) and then compared with the mg/l for 100% saturation in those conditions. We look at the distribution of the Percent Saturation data; we consider the lowest 10th percentile as the worse-case conditions for a particular site. That 10th percentile threshold, expressed as a Percent Saturation number, becomes a component of the Health Index for that site.

 

Simply averaging all the DO data for a site might obscure the full extent of any challenged conditions. For example, if a site is eutrophic, wherein nitrogen pollution levels have resulted in a huge algal bloom, there will be large swings in DO levels between the morning and the afternoon; simply looking at the mean would obscure these swings.

 

Secchi depth Secchi depth is a measure of water clarity. The Index uses a mean of the data to characterize each site. Sites with more organic matter and sediments in the water will be murkier and will exhibit reduced clarity, resulting in shallower (lower) Secchi depth measurements.

 

pH pH is a measure of the acidity of the water. pH data exhibit tremendous variability—diurnal differences through the day and seasonal shifts through the year. The Water Quality Monitoring Program requires that measurements be collected at 7:00 a.m. and then again at 3:00 p.m. on each monitoring day. This allows for a look at the change in conditions over the course of a day. The pH at a site is influenced heavily by respiration and photosynthesis. Respiration by algae, both seaweeds and phytoplankton, adds carbon dioxide to the water, which lowers pH. Measurements collected in the early morning, at 7:00 a.m., reflect the conditions found after a night of respiration and no photosynthesis. Photosynthesis of course requires sunlight and removes carbon dioxide from the water, raising pH. By afternoon, at 3:00 p.m., pH measurements will reflect the result of photosynthesis. The change between the morning and afternoon measurements, termed the diurnal swing, can be indicative of the magnitude of respiration and photosynthesis, and, indirectly, the amount of algae in the water. Since an excessive bloom of algae is one symptom of nitrogen pollution, a large diurnal swing in pH can serve as an indicator of excess nitrogen. A small change in pH is expected in a healthy, productive coastal system, but a relatively large swing can indicate a challenged site. We calculate the difference between the morning and afternoon readings, the diurnal swing, then amass that dataset to calculate the mean for the Health Index for that site.

 

What ranges are most appropriate for the component parameters?

For each of the three components of the Health Index, we have defined ranges, between which we would expect to see worse-case and best-case conditions. These ranges have been defined by looking not only at data for Casco Bay, but also data from other regions, state and federal guidelines, and relevant scientific literature.

 

Parameter: 0 point value 100 point value
Percent Saturation of Dissolved Oxygen 65% 95%
Secchi Depth (meters) 0.2 m 3.0 m
pH (diurnal swing) 0.4 0.1

 

How is the Health Index score calculated?

Each of the components calculated for a given site is plotted along the scale for that parameter. We use a natural logarithm formula to determine where on the scale of 0 to 100 a particular component falls. For example, a site’s calculated 10th percentile threshold for the Percent Saturation parameter will fall between 65% and 95% at a specific point on the scale between 0 and 100. The same is done for the Secchi depth component and the diurnal swing in pH. Now we have three numbers which fall between 0 and 100. These are added together and divided by 3 to obtain the mean, which is the Health Index score for that site.

 

How are the final Health Index scores presented?

After each site has a Health Index score associated with it, it can be classified as Good, Fair, and Poor, determined by score thresholds. A score of 85 and above is considered “Good”, a score of 70 to 84 is “Fair”, and anything below 70 falls into the “Poor” category.

 

What is eutrophication?

Eutrophication occurs when too many nutrients (and occasionally other factors) fuel explosive plant growth. While nitrogen is an essential nutrient in marine systems, too much nitrogen can become a pollutant when it triggers excessive algal growth. This growth can result in low DO measurements, shallow Secchi depth readings, and wide variations in pH.

Seastars on Continuos Monitoring Station

Keeping an eye on the Bay 24/7

Seastars on Continuos Monitoring StationImagine working 8,760 hours a year. Friends of Casco Bay has two water quality monitors that do just that: a datasonde, an instrument that can measure several properties of water at once, and a specialized device that only measures carbon dioxide. They are anchored together on the ocean floor in Yarmouth to collect data once an hour, every hour, year round. Appropriately, these high tech tools comprise our new Continuous Monitoring Station. These hard workers have been in place since July 2016.

 

Why is this hourly data vital?

 

The steady flow of data our Continuous Monitoring Station collects will help us detect and document how climate change and other emerging coastal stressors may (or may not) be affecting the Bay. Hourly data will help us identify daily, seasonal, and annual trends and better understand the extent to which ocean acidification may be impacting the water chemistry of Casco Bay. The station may also help us assess sea level rise. The station collects data on oxygen levels, carbon dioxide (CO2), pH (the level of acidity of the water), salinity, temperature, chlorophyll, and water depth.

 

In order to ensure continuous data, we have two datasondes which are swapped and refreshed every two weeks. When he arrives at the dock in Yarmouth, Research Associate Mike Doan has less than an hour to reposition the alternate datasonde so that we don’t miss any of those 8,760 hours of information.

 

Mike hauls up the anchored devices, uploads data from the CO2 sensor to his laptop, and scrapes off marine hitchhikers such as sea stars, tunicates, and algae. “It’s amazing how fast sea creatures occupy any available surface, including our instruments!” says Mike. Before he leaves, he replaces the datasonde with one freshly calibrated and lowers the entire Continuous Monitoring Station back onto the ocean floor. Such attention to detail provides quality assurance that the data is accurate.

 

While this station is busy year around, we continue to enlist volunteers to help us understand the overall health of our marine waters and to identify troubled areas of the Bay. From April to October each year, more than 90 volunteer Citizen Stewards monitor scores of shoreside sites where they measure five parameters of the surface water: pH, salinity, water temperature, water clarity, and oxygen level. If you are interested in becoming a water quality monitoring volunteer, you can learn more about the program here or email Peter at pmilholland [at] cascobay [dot] org.

 

Our volunteers, staff scientists, and now our automated partners, all play a role in helping us to better understand what is going on in Casco Bay.

 

 

Thank you to funders of this project, including Casco Bay Estuary Partnership, Davis Conservation Foundation, Horizon Foundation, Schwartz Family Fund of the New Hampshire Charitable Foundation, and WEX. We also thank our Members and the many donors, local businesses, and foundations that give us operational support to do our work each year.

 

 

Althea McGirr at LIttle Diamond Island

Althea Bennett McGirr says, “It shucks to be a clam!”

Althea McGirr at LIttle Diamond Island
Althea Bennett McGirr, a Board member since 2011, doesn’t need Friends of Casco Bay to tell her that the chemistry of Casco Bay is changing. She has seen the effects of Coastal Acidification firsthand.

At the annual Labor Day clambake on Little Diamond Island, Althea and her sister Priscilla help out at the end-of-the-season event that draws the community together for a farewell to summer. While the lobsters, sweet potatoes, sausages, and corn are roasting in a fire pit outside the hundred year-old Casino, their job is to wash and de-sand freshly harvested Casco Bay clams.

Althea recalls scooping huge handfuls of clams into 8 heavy kettles to steam them for the feast. Nowadays, they have to place the clams into the pot delicately, or else the shells may end up chipped or even shattered. Althea says that the clams they buy now are smaller and more fragile than the ones she
recalls from years back.

Althea’s observations seem to correspond to observations Friends of Casco Bay has been making over the years. We are studying Coastal Acidification, the problem of increasing acidity from the ocean absorbing carbon dioxide released by the burning of fossil fuels, and, we believe, from excess nitrogen washing into coastal waters by stormwater runoff. Fertilizers, sewage discharges, and pet wastes trigger algae blooms that add excess carbon dioxide to coastal waters.

Pitted Clam
The pitted shell shows that life can be tough for a clam spat in acidic mud.

Our data shows that the acidity of Casco Bay has increased since we began our water quality monitoring program nearly 25 years ago. In 2011, we began sampling the pH (acidity) of mudflat sediments, where soft-shell clams live. We found that the mud nearest to shore was more acidic (had lower pH) than sediments further away from sources of land-based pollution. Higher acidity makes it harder for shellfish to extract calcium carbonate from their environment, the material that clams, mussels, and other mollusks need to build and strengthen their shells.

In the summer of 2014, Friends of Casco Bay installed several clam “condos” in the intertidal mudflats of Recompense Bay in Freeport. Our goal was to see what would happen when we exposed juvenile clams to acidic mud. Research Associate Mike Doan caged baby clams inside PVC tubes and left them in the mud for several days. Microscope photographs of the tiny clam spat showed that after just one week, their shells had become pitted, showing signs of dissolving.

Mac Richardson Nabbing Nitrogen Photo credit: Dave Dostie

Nabbing Nitrogen: A water sampling “flash mob”

Too much nitrogen can turn Casco Bay from a healthy blue to an unhealthly green.

Mac Richardson Nabbing Nitrogen Photo credit: Dave Dostie
Mac Richardson Nabbing Nitrogen
Photo credit: Dave Dostie

On a rainy July 10, at precisely 10:10 a.m., 97 volunteers for Friends of Casco Bay hung out over docks or trudged through mud to collect jars of seawater. The analysis of their samples from sites along the Fore River in Portland and South Portland will increase our understanding of nitrogen levels in Portland Harbor. When we receive the lab results, our science staff will construct a map to show nitrogen concentrations at various sites around the harbor.

Already, these efforts have accomplished one of the main goals of the project: to explain to the public that excess nitrogen is one of the factors responsible for turning our mudflats an unhealthy green. All living things need nitrogen to grow, but an overdose can trigger excessive growth of nuisance algae, reduce water clarity, and lower oxygen levels. Sources of excess nitrogen in coastal waters include sewage, pet wastes, decaying plants and animals, and burning fossil fuels.

We partnered with Maine Department of Environmental Protection and the City of South Portland, and we raised funding for the project from Maine Outdoor Heritage Fund, RBC Blue Water Project, Casco Bay Estuary Partnership, Bowdoin College Common Good Grant, and our generous members.