Pop quiz: Can you figure out which of these photos is of Casco Bay?
The correct answer is B—but on any given day or part of the Bay, Casco Bay could look like any of these three pictures.
Why does it matter? Water color can be an important indicator of the environmental health of our waters.
For example, the bluish-green water from Casco Bay in the middle photo above was measured as 6 on the Forel-Ule scale. This tells us that the water color is dominated by phytoplankton, but also that some dissolved matter and some sediment may be present, which is typical for areas towards the open sea.
Image A is of water in the Caribbean and is a 2 on the scale—indigo blue with high light penetration. These waters have often low nutrient levels and low production of biomass.
Image C is from Lake Michigan and is a 18 on the scale. Brownish green to cola brown colors indicate waters with an extremely high concentrations of organic and inorganic compounds, which are typical for rivers and estuaries.
You and Friends of Casco Bay have joined a worldwide effort to better understand how our waters may be changing—by observing water color. The images above are photos taken by volunteers like you and have become part of a worldwide catalog of water color.
Since we launched our Color by Numbers pilot project using the EyeOnWater app three months ago, 178 people have signed up to measure the color of Casco Bay. The map of Casco Bay below shows where volunteers have taken 387 color measurements on their smartphones and tablets.
You are helping us learn more about the environmental health of Casco Bay. The data you collect, using the EyeOnWater app on your smartphone, will become part of a worldwide catalog of water color. The more measurements collected, the more our understanding of the Bay improves.
We look forward to keeping you posted about what we are learning.
Want to get outside, take photos that may help protect the health of Casco Bay, and connect with other community members?
We invite you to join our new volunteer Observing Network, Water Reporter, an exciting way to share what yousee around the Bay.
In 2016 and 2017, we saw a concerning increase in the number and extent of nuisance and harmful algal blooms in Casco Bay. Large mats of algae covered tidal flats, smothering animals underneath the mats, preventing juvenile clams from settling, and increasing the acidity of the sediment.
This summer and fall, we continue to be on the lookout for nuisance, green algal outbreaks—and we need your help!
For this project we are asking you to take photos of the Bay to document algal bloom events, water pollution and trash, shoreline erosion, and marine wildlife sightings. Through the Water Reporter app, your photos will be shared with Friends of Casco Bay, as well as with other observers. You will be able to see and comment on others’ posts and get an idea of what is going on around the Bay.
Each submission is displayed on a map and posted to individual, organization, and watershed feeds. To keep you in the loop, you will receive email notifications every time someone comments or takes action on your report.
In order to be a Water Reporter volunteer:
You will need a smartphone (iPhone or Android) or a tablet (iPad or Android tablet).
Create an account on the Water Reporter app and join the Friends of Casco Bay group.
Be willing to take photos of the Bay and share them on the app along with their location.
What you need to know:
Each photo you submit will provide a better understanding of conditions in the Bay.
Friends of Casco Bay is especially interested in tracking algal blooms as they occur, so if you come across one, be sure to share a photo along with the hashtag #algae.
For other reports please use hashtags like #trash #erosion #pollutionreport or #wildlife in the photo caption to improve search and categorization of your report for the community and Friends of Casco Bay.
What’s the big deal with green algae?
In the marine environment, nitrogen jumpstarts the growth of algae and phytoplankton, tiny plants that form the base of the ocean food chain, which in turn nurture zooplankton, clams, oysters, crabs, lobsters, fish, and whales. But too much nitrogen may trigger large blooms of nuisance algae or “green slime,” which can reduce water clarity and lower oxygen levels, making life harder for marine organisms. These nuisance algal blooms may be triggered by excess nitrogen from fertilizers, sewage, pet wastes, and emissions from tailpipes and smokestacks. For more information on excess nitrogen and green algae visit https://www.cascobay.org/our-work/science/nuisance-algal-bloom-tracking/.
Rick Frantz and Jennifer Fox are part of Portland’s vibrant waterfront scene. They own Andy’s Old Port Pub on Commercial Street, and they take the ferry home each night to Great Diamond Island. Casco Bay is literally their backyard.
On January 23, as more than 125 volunteers and supporters of Friends of Casco Bay watched, the waterfront business owners and Casco Bay islanders were recognized for their work on behalf of the Bay. Executive Director Cathy Ramsdell presented them with the Friend of Casco Bay Award at the organization’s Annual Members Meeting and Volunteer Appreciation Celebration.
Jennifer was formerly a fundraiser for nonprofits and Rick a graphic designer before they purchased the pub in 2007. Jennifer and Rick have made their tavern a popular gathering spot for waterfront business people and tourists, as well as island residents, many of whom contribute to the pub’s nightly music scene. They strongly support local harvesters and promote our regional seafood to customers from Maine and “away.”
They are a fitting choice for the Friend of Casco Bay Award because of the many ways in which they have fostered a sense of community among those who live, work, or play on Casco Bay, reminding friends, neighbors, and newcomers that we all have a responsibility for protecting the environmental health of the Bay.
The Friend of Casco Bay Award was created in 1992 to recognize those who have excelled in their commitment to protecting the Bay. The award is not given annually, but only when an individual or group is identified whose efforts have provided significant, long-term benefits to Casco Bay. Friends of Casco Bay, based in South Portland, is a conservation organization that uses science, advocacy, and community engagement to improve and protect the environmental health of Casco Bay.
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.
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.
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.
0 point value
100 point value
Percent Saturation of Dissolved Oxygen
Secchi Depth (meters)
pH (diurnal swing)
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.
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!”
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.”
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.”
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