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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.

 

You can help

Casco Bay belongs to all of us, and it takes a community of champions to protect the Bay!

You can help Friends of Casco Bay improve and protect the environmental health of our coastal waters by being informed about the issues we are working on. Our Bay Papers make it easy!

Each Bay Paper is written to help you:

  • Understand the issue at a glance
  • Get the background information you need to explain the issue to others
  • Take action to reduce bad impacts on the health of the Bay
  • Learn how Friends of Casco Bay is attacking the problem

By reaching out to your neighbors, colleagues, friends, and family, you can be a Champion for the health of the Bay.

 

You Can Make a Difference Bay Paper

Friends of Casco Bay is showing you how you can make a difference in the health of Casco Bay

Confronting the consequences of climate change and the changing chemistry of our oceans—specifically, the carbon dioxide that threatens our coastal waters—may seem daunting, but Maine has many advantages to help it meet the challenge. Even if you adopt only one or two of the suggestions below, you will be helping to improve the health of Casco Bay.

Learn more in our You Can Make a Difference Bay Paper.

 

[button link=”https://cascobay.org/wp-content/uploads/2013/01/You-Can-Make-A-Difference-Bay-Paper-Friends-of-Casco-Bay-2014.pdf” newwindow=”yes”] Download our You Can Make a Difference Bay Paper[/button]

 

 

Nitrogen Bay Paper

Friends of Casco Bay is fighting nitrogen pollution

footprintsHave you noticed that more and more of our coves and inlets are carpeted with green slime?

  • Nitrogen pollution is a problem in parts of Casco Bay.
  • Nitrogen runoff makes the water less healthy for marine life.
  • Nitrogen fertilizes algae blooms that choke out clams and other intertidal creatures.

Learn more in our Nitrogen Bay Paper.

 

[button link=”https://cascobay.org/wp-content/uploads/2013/01/Nitrogen-Bay-Paper-Friends-of-Casco-Bay-20141.pdf” newwindow=”yes”] Download our Nitrogen Bay Paper[/button]

 

 

Ocean Acidification Bay Paper

Friends of Casco Bay is sounding the alarm on ocean acidification

Acidic Mud

Did you know that acidic mud could wipe out clam harvesting in Casco Bay?

Why? Sea water is becoming more acidic, which weakens or simply dissolves the shells of small clams, oysters, and other shellfish. Learn more in our Ocean Acidification Bay Paper.

 

[button link=”https://cascobay.org/wp-content/uploads/2013/01/Ocean-Acidification-Bay-Paper-Friends-of-Casco-Bay-20141.pdf” newwindow=”yes”] Download our Ocean Acid Bay Paper[/button]

 

 

Sewage Bay Paper

Friends of Casco Bay is working to stop sewage from polluting Casco Bay

CSO discharge

Did you know that when it rains, raw sewage, polluted rainwater, and industrial wastewater pour into Casco Bay?

This toxic soup can sicken swimmers, make seafood unsafe to eat, and harm marine life.

Learn more in our Sewage Bay Paper.

 

[button link=”https://cascobay.org/wp-content/uploads/2013/01/CSO-Bay-Paper-Friends-of-Casco-Bay-20141.pdf” newwindow=”yes”] Download our Sewage Bay Paper[/button]

 

 

Snow Dump Bay Paper

Friends of Casco Bay says, “Keep plowed snow away from our coastal waters.”

Bayside Snow pile (Chris MilNeil)

 

Did you know that “pure as the driven snow” is anything but?

Learn more about how plowed snow impacts Casco Bay by reading our Snow Bay Paper.

 

[button link=”https://cascobay.org/wp-content/uploads/2013/01/Snow-Dump-Bay-Paper-Friends-of-Casco-Bay-20141.pdf” newwindow=”yes”] Download our Snow Bay Paper[/button]

 

BayScaping

Tips for green yards to keep Casco Bay blue

Did you know that the fertilizers and pesticides that are applied to your lawn may end up in Casco Bay?

Learn more about how to care for your lawn by downloading BayScaping: Tips for green yards to keep Casco Bay blue and Does your lawn care professional BayScape?

[button link=”https://cascobay.org/wp-content/uploads/2013/01/BayScaping-tips-to-keep-Casco-Bay-Blue-compressed.pdf” newwindow=”yes”] Download BayScaping: Tips to keep Casco Bay Blue[/button]

[button link=”https://cascobay.org/wp-content/uploads/2013/01/Does-your-lawn-care-professional-BayScape-compressed.pdf” newwindow=”yes”] Download Does your lawn care professional BayScape?[/button]

Be a champion and make a difference in the health of Casco Bay

Casco Bay belongs to all of us, and it takes a community of champions to protect the Bay!

You can help Friends of Casco Bay improve and protect the environmental health of our coastal waters by being informed about the issues we are working on. Our Bay Papers make it easy!

Each Bay Paper is written to help you:

  • Understand the issue at a glance
  • Get the background information you need to explain the issue to others
  • Take action to reduce bad impacts on the health of the Bay
  • Learn how Friends of Casco Bay is attacking the problem

By reaching out to your neighbors, colleagues, friends, and family, you can be a Champion for the health of the Bay.

 

You Can Make a Difference Bay Paper

Friends of Casco Bay is showing you how you can make a difference in the health of Casco Bay

Confronting the consequences of climate change and the changing chemistry of our oceans—specifically, the carbon dioxide that threatens our coastal waters—may seem daunting, but Maine has many advantages to help it meet the challenge. Even if you adopt only one or two of the suggestions below, you will be helping to improve the health of Casco Bay.

Learn more in our You Can Make a Difference Bay Paper.

 

[button link=”https://cascobay.org/wp-content/uploads/2013/01/You-Can-Make-A-Difference-Bay-Paper-Friends-of-Casco-Bay-2014.pdf” newwindow=”yes”] Download our You Can Make a Difference Bay Paper[/button]

 

 

Nitrogen Bay Paper

Joe’s footprints in green slime at a cove in Falmouth
Joe’s footprints in green slime at a cove in Falmouth

Friends of Casco Bay is fighting nitrogen pollution

Have you noticed that more and more of our coves and inlets are carpeted with green slime?

  • Nitrogen pollution is a problem in parts of Casco Bay.
  • Nitrogen runoff makes the water less healthy for marine life.
  • Nitrogen fertilizes algae blooms that choke out clams and other intertidal creatures.

Learn more in our Nitrogen Bay Paper.

 

[button link=”https://cascobay.org/wp-content/uploads/2013/01/Nitrogen-Bay-Paper-Friends-of-Casco-Bay-20141.pdf” newwindow=”yes”] Download our Nitrogen Bay Paper[/button]

 

 

Ocean Acidification Bay Paper

Acidic MudFriends of Casco Bay is sounding the alarm on ocean acidification

 

Did you know that acidic mud could wipe out clam harvesting in Casco Bay?

Why? Sea water is becoming more acidic, which weakens or simply dissolves the shells of small clams, oysters, and other shellfish. Learn more in our Ocean Acidification Bay Paper.

 

[button link=”https://cascobay.org/wp-content/uploads/2013/01/Ocean-Acidification-Bay-Paper-Friends-of-Casco-Bay-20141.pdf” newwindow=”yes”] Download our Ocean Acid Bay Paper[/button]

 

 

Sewage Bay Paper

Combined Sewer Overflow on Commercial At in Portland discharges excess
Combined Sewer Overflow on Commercial At in Portland discharges excess

Friends of Casco Bay is working to stop sewage from polluting Casco Bay

 

Did you know that when it rains, raw sewage, polluted rainwater, and industrial wastewater pour into Casco Bay?

This toxic soup can sicken swimmers, make seafood unsafe to eat, and harm marine life.

Learn more in our Sewage Bay Paper.

 

[button link=”https://cascobay.org/wp-content/uploads/2013/01/CSO-Bay-Paper-Friends-of-Casco-Bay-20141.pdf” newwindow=”yes”] Download our Sewage Bay Paper[/button]

 

 

Snow Dump Bay Paper

Snow Pile

Friends of Casco Bay says, “Keep plowed snow away from our coastal waters.”

 

 

Did you know that “pure as the driven snow” is anything but?

Learn more about how plowed snow impacts Casco Bay by reading our Snow Bay Paper.

 

[button link=”https://cascobay.org/wp-content/uploads/2013/01/Snow-Dump-Bay-Paper-Friends-of-Casco-Bay-20141.pdf” newwindow=”yes”] Download our Snow Bay Paper[/button]

 

BayScaping

Tips for green yards to keep Casco Bay blue

Did you know that the fertilizers and pesticides that are applied to your lawn may end up in Casco Bay?

Learn more about how to care for your lawn by downloading BayScaping: Tips for green yards to keep Casco Bay blue and Does your lawn care professional BayScape?

[button link=”https://cascobay.org/wp-content/uploads/2012/03/BayScaping-tips-to-keep-Casco-Bay-Blue-for-website.pdf” newwindow=”yes”] Download BayScaping: Tips to keep Casco Bay Blue[/button]

[button link=”https://cascobay.org/wp-content/uploads/2012/03/Does-your-lawn-care-professional-BayScape-for-website.pdf” newwindow=”yes”] Download Does your lawn care professional BayScape?[/button]