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Perspectives on Casco Bay

 

 

8 miles of shoreline

200 square miles of water

8 official lighthouses and 8 historic forts

13 municipalities from Cape Elizabeth to Phippsburg, including Long Island and Chebeague Island, abut Casco Bay.

1 in 5 Mainers live in the 42 communities of the Casco Bay watershed, from Bethel to the Bay.

1989 Friends of Casco Bay was founded to improve and protect the environmental health of Casco Bay.

1990 Casco Bay was designated an Estuary of National Significance under the Clean Water Act.

 

With the arrival of spring, we hope you seize the Bay by getting outside to enjoy our 578 miles of shoreline, taking in that 200 square miles of water, and visiting those lighthouses and forts!

Climate Change, Ocean Acidification, and You

Climate Change Science and Data

  • The climate is changing faster than expected. Greenhouse gases, such as carbon dioxide and methane, are the culprits. The burning of fossil fuels for homes, industry, and transportation releases almost 10,000 million metric tons of carbon dioxide into the atmosphere every year. 1
  • Carbon dioxide is changing not only our climate, but also the chemistry of the ocean. About 30% of the carbon dioxide we release into the atmosphere is absorbed by the ocean. 2 In marine water, carbon dioxide decreases pH and increases acidity through a process known as ocean acidification.
  • Excess nitrogen from sewage treatment plants, polluted stormwater, and fertilizers, is also adding carbon dioxide into nearshore waters through a process known as coastal acidification. 3
  • Nitrogen can fertilize massive algal growth in our waters. When the algal blooms die, decomposition depletes the area of life-giving oxygen and releases carbon dioxide, acidifying the water.

The impacts of climate change are evident right here in Casco Bay

Warmer Waters

Friends of Casco Bay has been tracking water temperatures for over 25 years. On average, our data show a 2.5° F increase in water temperatures since 1993.

Sea Level Rise

As water warms, it expands, and the sea encroaches on our coastline. Coastal observers and property owners are reporting an increase in erosion.

Increasing Precipitation

Maine has seen a six-inch average increase in annual precipitation since 1895, further threatening coastal properties. 4

Threats to the Ocean Food Web

More carbon dioxide in our waters means there is less shell-building material (calcium carbonate) for clams, mussels and oysters, as well as for tiny critters at the base of the ocean food chain. The saturation state of calcium carbonate is a key measurement of shell-building material for many organisms. Shell formation becomes more difficult when the amount of available calcium carbonate falls below a 1.5 saturation state. 5 Our recent data indicate that for nearly half the year, levels of calcium carbonate in Casco Bay are not sufficient for shell-building.

What do these changes mean for Casco Bay?

  • Research Associate Mike Doan with our Continuous Monitoring Station. The Station houses a number of instruments that collect data on carbon dioxide, temperature, salinity, oxygen, chlorophyll, and pH, hourly, 365 days a year. This large quantity of data is necessary to accurately track changes in the Bay from climate change, including ocean and coastal acidification.

    As marine waters become more acidic, we can anticipate more pitting or dissolution of the shells of many commercially viable species in Casco Bay.

  • Rising water temperatures are linked with shell disease, directly impacting our lobster fishery and tourism industries.
  • Climate change is bad news for clams because green crabs — which eat juvenile shellfish — thrive in warming waters. 6
  • The distribution and populations of marine species in the Gulf of Maine are shifting. Scientists and lobstermen are documenting the shift in distribution of Maine’s iconic lobsters north and east.
  • Copepods are tiny crustaceans that are the main food source for juvenile lobsters. In laboratory experiments, copepods raised in conditions that simulate the climate changes occurring in the Gulf of Maine were less fatty. With a less healthful diet, young lobsters must divert energy from growth and resisting disease to finding enough food to survive. 7

What is Friends of Casco Bay doing?

  • We helped form the Maine Ocean and Coastal Acidification Partnership (MOCA) to coordinate climate change research and policy change work. MOCA is a diverse coalition of researchers, policy experts, lawmakers, aquaculturalists, and seafood harvesters. We are working to create an action plan for Maine to protect the health of our coastal waters.
  • LD 1284 has been selected by the Environmental Priorities Coalition, a group of 34 environmental organizations, as one of its five priority bills to address climate change in Maine.
  • Our Water Reporter volunteers are recording observations of how the Bay is changing. These observations strengthen our advocacy efforts as these reports are shared with regulators, legislators, and other decision makers, alerting them to conditions in the Bay.

What can you do?

  • Tell your legislators to support LD 1284 to create a science and policy advisory council to address the impacts of climate change on Maine’s marine species.
  • Join Water Reporter. Your observations combined with those of other volunteers around the Bay will provide a better understanding of changing conditions.  

References

  1. T.A. Boden, R.J. Andres, G. Marland, Global, Regional, and National Fossil-Fuel CO2 Emissions, Research Institute for Environment, Energy, and Economics, Appalachian State University, 2017. https://cdiac.ess-dive.lbl.gov/trends/emis/overview_2014.html
  2. N. Gruber, D. Clement, R. Feely, et al., The oceanic sink for anthropogenic CO2 from 1994 to 2007, Science, 2019. http://science.sciencemag.org/content/363/6432/1193
  3. J. Weiss, Marine Pollution: What Everyone Needs to Know, Oxford University Press, 2015.
  4. I. Fernandez, C. Schmitt, E. Stancioff, et al., Maine’s Climate Future: 2015 Update, The University of Maine, 2015. https://mco.umaine.edu/pubs/pdf/mcf-2015.pdf
  5. J. Ekstrom, L. Suatoni, S. Cooley, et al., Vulnerability and adaptation of US shellfisheries to ocean acidification, Nature, 2015. http://pacshell.org/pdf/Ekstrom_etal2015.pdf
  6. E. Tan, B, Beal, Interactions between the invasive European green crab, Carcinus maenas, and juveniles of the soft-shell clam, Mya arenaria, in eastern Maine, USA, Journal of Experimental Marine Biology and Ecology, 2015. https://downeastinstitute.org/wp-content/uploads/2018/08/tan-beal-2015.pdf
  7. Copepods cope with acidification, Bigelow Laboratory for Ocean Sciences, 2018. https://www.bigelow.org/news/articles/2018-04-10.html

Your eyes on the Bay–new directions in citizen science

Casco Bay, like ocean waters around the world, is changing and changing quickly. We are evolving our water quality monitoring to stay on top of the science of how the Bay may be changing.

At our Volunteer Appreciation Celebration this week [click here for photos!], we announced that we are launching two pilot projects that will enable our volunteer citizen scientists to use new technologies to increase our knowledge of the changing conditions around Casco Bay.

We rely on people all around the Bay to relay to us changes they are observing. Our new initiatives are designed to engage more volunteer citizen scientists in collecting data and sharing their observations of a changing Casco Bay.

Initiative #1: Measuring the Color and Clarity of Casco Bay

We are launching a pilot program to enlist citizen scientists to help us measure the color and clarity of our waters.

For more than a century, marine scientists have used the Forel-Ule color scale to document the color of oceans and lakes. People often consider blue water to indicate healthy oceans and dirty-brown water to indicate polluted water. In fact, scientists attest to color being an excellent indicator of what is happening in our oceans.

We are putting a modern spin on an old way of assessing water quality. We will train volunteers to use a specific smartphone app, as well as a Secchi disk. On tide-specific days and times, we will ask volunteers all around the Bay to use the app to take a photo of the water against the Secchi disk. Each volunteer will then compare the color of the water to an electronic version of the Forel-Ule scale built into the app. The protocols for this data collection are easy to follow, and the data helps address a question we often hear: “How is the Bay changing?”

We are launching this initiative because our colleagues at Bigelow Laboratory for Ocean Sciences tell us that the waters of the Gulf of Maine have become increasingly yellow over the last century. We have seen heavy rains stain the surface waters of Casco Bay the color of tea. There is a lot of data on color and clarity for the Gulf of Maine, but not much has been collected in our nearshore areas.

Initiative #2: ON Casco Bay: Observing Network for Casco 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 year, we want to be on the lookout for green slime outbreaks, and Casco Bay needs more eyes looking out for its health! Friends of Casco Bay staff cannot be everywhere.

Photograph by Kevin Morris

We will enlist volunteers to help us observe and keep track of nuisance outbreaks. To do that, volunteers simply need a smartphone and a commitment to keep their eyes focused on our changing Bay.

We will train volunteers to use an innovative smartphone app that will enable them to document, catalogue, organize, and share their observations of the Bay. This information will be useful in our collaborations with other scientists, in expanding our community engagement by sharing observations on social media, and in our advocacy, to illustrate to regulators, legislators, and other policy makers changes happening around the Bay .

As this initiative evolves, we may ask volunteers to report any exciting, interesting or odd observations — from whales, osprey nests, or seals, to declines in eelgrass or mussel beds, clam die offs, jellyfish sightings, fish kills, invasive species outbreaks — you get the idea.

Stay Tuned

Be on the lookout for announcements regarding our training sessions on these pilot projects. We know that our longtime water quality monitors are eager to embark on a new adventure with us. We expect many new volunteers, who did not have the time to commit to our earlier water quality monitoring program, will jump aboard on one or both of these new efforts.

More eyes on the water and more advocates for its health are exactly what Casco Bay needs! In our experience, our volunteers are some of the most outspoken and well-spoken members of our community. We look forward to engaging more of you than ever. The commitment of volunteers will send ripple effects throughout towns around the Bay.

Volunteers do a great service to Casco Bay

Citizen Stewards received recognition for milestones in Water Quality Monitoring: John Todd, Michelle Brown, Debora Price, Sheila McDonald, Dick Stevens and Erno Bonebakker. Photograph by Kevin Morris

More than 125 volunteers and supporters of Friends of Casco Bay came to the Volunteer Appreciation Celebration on January 23, to recognize those who give their time to monitor the water quality of the Bay, clean up shorelines, stencil storm drains, participate in community outreach events, and serve on its Board.

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At the event, ten Citizen Stewards received recognition for milestones in Water Quality Monitoring. Sarah Lyman, Community Engagement Coordinator for Friends of Casco Bay, recognized each of the honorees, remarking, “There is so much power and synergy in being able to connect data and connect people.”

 

Those recognized for their milestones in service:

Erno Bonebakker (25 Years)

Erno has been volunteering since 1993, the first full year of the Friends of Casco Bay’s water quality monitoring program. He and his family moved here from California in 1988, and within a week, Erno attended a meeting about the health of Casco Bay. His passion for Casco Bay has only deepened as he continues to explore, study, and care for it. He divides his time between Chebeague Island and Portland.

 

Dick Stevens (15 Years)

Dick Stevens has been active in the Gulf of Maine Ocean Racing Association and the Portland Yacht Club–winning a few trophies along the way. Sailing the coast and kayaking the lakes and rivers of Maine has given Dick a closer appreciation of the delicate nature of this rugged environment. This inspired him to volunteer as a Citizen Steward for Friends of Casco Bay.

 

Sheila McDonald and Debora Price (10 Years)

Sheila MacDonald and Debora Price have shared a sampling site at Mere Point Boat Launch in Brunswick, where they have found enthusiastic support whenever they explained why they were sampling the water quality of Casco Bay. Sheila serves as deputy director of the Maine State Museum. Debora is retired after teaching, owning a local real estate business, and co-founding an eldercare service, Neighbors, Inc.

 

Michelle Brown (5 Years)

Michelle has a professional background in wildlife management and natural resource conservation. Throughout her career, she has witnessed the power of volunteers and volunteering, so when she and her husband moved to Peaks Island, she was delighted to find out about the Friends of Casco Bay Citizen Stewards Program and how the data that volunteers collect provide important information about the Bay.

 

Craig Burnell (5 Years)

Craig always knew he wanted to become involved in the sciences, studying and learning about our environment. He works at Bigelow Laboratory for Ocean Sciences as a Research Associate in the Bigelow Analytical Services facility. When not working, he is likely to be training for his next bike race, which will include a race across the country this summer.

 

John Todd (5 Years)

John and his wife Cathie have summered in Phippsburg since the 1960s. They finally moved there full time in 2005 after John retired from a career in international development. They love living on The Basin, where they enjoy swimming and kayaking, especially with their grandchildren.

 

Jan Flinterman (5 Years)

Jan has shared coverage of a water quality site at The Basin, a saltwater inlet on the New Meadows River in Phippsburg, with John Todd and Jim Sidel. Data collected by Citizen Stewards helped convince the Maine Legislature to upgrade this popular anchorage to the highest level of water quality protection, Class SA.

 

Rob Sellin and Natalie West (5 Years)

Rob and Natalie spent many years sailing the world before arriving in Maine in 2011 aboard S/V Wilhelm, their 44-foot steel cutter. They settled in South Portland and have been sampling water quality at the pier at Southern Maine Community College since 2012. They sail the coast of Maine every summer, exploring the extraordinary bays and offshore islands of our state, often accompanied by their adult children and their grandchildren.

Keeping you up to date as we keep an eye on the Bay

Photograph by Kevin Morris

Casco Bay, like ocean water around the world, is changing and changing quickly.

We want you to know that we have changed our volunteer Citizen Stewards Program and our staff-led Water Quality Monitoring efforts in order to stay on top of the science of how the Bay may be changing.

When our organization started in 1989, no one knew the health of the Bay. That was the question we were asked—“How healthy is Casco Bay”—and that is what our first quarter-century of monitoring has enabled us to address.

Thanks to the data that hundreds of our volunteer Citizen Stewards have helped us collect over the past 25 years, in addition to data collected by our staff, we can identify where regions of the Bay are challenged, and where, generally speaking, the Bay is healthy. The snapshots of data volunteers collected are a key aspect of our Casco Bay Health Index and have been vital to our advocacy efforts. This 25-year data set has provided us with a solid foundation from which to launch this next phase of data collection.

Looking forward, our monitoring goals are to:

  • Understand how Casco Bay is changing with respect to climate change, ocean and coastal acidification, sea level rise, and other stressors
  • Conduct more intense data collection efforts in challenged regions of the Bay to try to understand why water quality is so poor, in places such as Portland Harbor and the mouth of the Harraseeket River
  • Involve more volunteers in our efforts to keep Casco Bay blue. While we are utilizing more technology to help us achieve our first two goals, technology will never replace the connections, energy, visibility, and goodwill that volunteers like you provide as ambassadors for the Bay.

In order to meet these goals, we are now monitoring Casco Bay through these four ways:

  1. Our Continuous Monitoring Station collects hourly data to help us address the question “How is Casco Bay changing?” We launched this station more than a year ago, and we are excited about how much we have learned about the Bay in a short time. We intend to keep this Station operating in perpetuity.
  2. Using data sonde technology, our staff will continue to collect data at 12 legacy volunteer Citizen Steward sites—these sites were chosen as representative of regions around the Bay and include healthy sites, challenged sites, and those in between. We think of this monitoring as “the Bay getting a checkup.” How are regions of the Bay doing? Are healthy areas remaining healthy? Are challenged areas continuing to show problems, or might they be improving?
  3. Using our Baykeeper boat, our staff will conduct more intensive efforts in challenged regions of the Bay. If you have seen our Health Index, you have seen that there are “red dot” areas. We are looking closer at those red dot areas and asking, “what may be causing the trouble?” We began this work in 2017, as we conducted transects, from surface to bottom, and across regions, in Portland Harbor and in the Harraseeket River. We will continue to look intensively at these regions.
  4. Using volunteer citizen scientists, we will engage the community to help us collect data and observations on a changing Casco Bay. Our volunteer program is going through a large transition. We are significantly changing the time commitments required to become a citizen scientist, and we are changing the parameters that volunteers collect. We will be asking Citizen Steward Volunteers to collect new kinds of data and record observations on changes in Casco Bay.

In 2016, you may remember that we organized a citizen science “flash mob to Nab Nitrogen.” The event was an incredible success, signaling that there is a huge reservoir of goodwill from people who want to help protect the health of the Bay and are willing to do that in short bursts of data collection efforts. We learned that we can count on our community to help us grab vast amounts of data if we make sampling easier and reduce the time commitment.

For example, we are piloting having volunteers measure the color of our waters as a biological indicator. The general public often considers blue water to indicate healthy oceans and dirty-brown water to indicate polluted water. In fact, scientists attest to color being an excellent indicator of what is happening in our oceans. For more than a century, marine scientists have used the Forel-Ule scale to document the color of oceans and lakes.

The color of our water, measured by this scale, can be an excellent environmental indicator. By using a specially designed smartphone app and a secchi disk, volunteers can help us collect scientific data on the color and clarity of our waters. The protocols for this data collection are easy to follow, and the data helps address a question we often hear: “How is the Bay changing?”

We will also ask volunteers to help us observe and keep track of nuisance and harmful algal outbreaks, which have plagued our waters these past two summers.

By revamping our volunteer monitoring efforts, we have the opportunity to broaden our network of knowledgeable ambassadors for our coastal waters—and make strides in our understanding of the Bay.

In our experience, our volunteers are some of the most active, outspoken, and well-spoken members of our community. We look forward to engaging more volunteers than ever this year. The commitment of these volunteers will send ripple effects through towns around the Bay.

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

Thank you all for a great event! You can see more about our Citizen Steward awardees and the photos here: https://www.cascobay.org/2018/01/25/volunteers-great-service-casco-bay/

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.
5:30 Hors d’oeuvres, cash bar, Program begins at 6:30

Our event is on for Tuesday, January 23! We have been watching the weather closely—the messy wintery mix will turn into rain and 40 degree weather by midday on Tuesday, January 23, and temps will stay in the 40s until well past our event.

Parking is easy and FREE at DiMillo’s—if you are driving with guests, you can drop your passengers off right at the ramp under the drive-thru overhang leading to the floating restaurant.

Where: DiMillo’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.

 

Back Cove August 2nd, 2017

Our “Slime Watchers” Are Keeping an Eye on the Bay

Back Cove August 2nd, 2017
Friends of Casco Bay volunteer Deb Dawson took this algal bloom photo over Portland’s Back Cove this summer to document how much the green slime had spread.

If you have ever thought about buying a drone but could not figure out what to use it for, take a lesson from Deb Dawson, a professional photographer and one of our volunteer water quality monitors. This past summer, Deb took her talents to even greater heights—right over Back Cove in Portland with her new drone outfitted with a video camera.

Executive Director Cathy Ramsdell, who regularly walks Baxter Boulevard, had reported seeing green algae growth spreading across Back Cove. She says, “We know that nitrogen fertilizes green plants in the ocean just as it does on land. It would be great if we could determine what is causing this bloom – excess fertilizer? – stormwater runoff? – sewage discharges? – a lack of predators? – car and factory emissions? – or all of the above!”

Before launching her drone, Deb checked with the Portland Jetport to make sure the route she had scouted out would not interfere with the traffic pattern of landing and departing planes.

Deb’s images confirmed what Cathy had feared: the Cove was quickly becoming carpeted in green slime. An email alert went out to Friends of Casco Bay members and the news media.

Other “green slime” reports have come in from other parts of Casco Bay. Report excess green slime by emailing slimewatchers@cascobay. org. Take a photo and tell us the location, with coordinates and landmarks, if you can.

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!

When you check 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.