Water Quality Monitoring

Citizen Stewards Water Quality Monitoring Program

Citizen Stewards David Brenneman and Lauren Leclerc (Photo by Kevin Morris)

Citizen Stewards David Brenneman and Lauren Leclerc (Photo by Kevin Morris)

Each year, dozens of volunteers collect data on water quality in Casco Bay. Our monitoring program is now in its 26th season! Trained in EPA-approved techniques, our Citizen Stewards collect samples at 40 sites around Casco Bay.  Our volunteer program was the first in the state to obtain EPA certification, which allows our data to be used by local, state and federal agencies. In fact our data is submitted to Congress to report on the environmental health of Casco Bay. This data is critical as Friends of Casco Bay works with businesses, municipalities, and decision-makers around the Bay to find effective ways to curb pollution.

We combine all the data collected through this program into our  Health Index, an easy-to-interpret, visual guide to the health of the Bay. Over the past 25 years of monitoring the health of the Bay we’ve identified areas in good shape and some with challenged water quality. In order to improve our understanding of the health of the Bay we’ve designed our program to collect samples throughout the Bay at the same time. Our Citizen Stewards, collect water quality samples at 40 sites along the Bay at 7:00 AM & 3:00 PM on 10 specific Saturdays from April to October. Sampling is completed once per month in April, May, June, and October. In July, August and September, we collect samples twice a month.

What does the data tell us?

Research Associate Mike Doan analyzes the data that Friends of Casco Bay has amassed. “I know of no other program in the country that asks its volunteers to sample twice a day. This provides a unique opportunity to assess daily fluctuations in dissolved oxygen, temperature, salinity, and pH. Our data shows that water chemistry is clearly impacted by the cycle of photosynthesis, respiration, and decomposition of the microscopic plants called phytoplankton.”

Throughout the day, phytoplankton absorb sunlight and photosynthesize, releasing oxygen into the water. At night, the process is reversed; phytoplankton absorb oxygen from the water. Peter Milholland says, “This work is groundbreaking. We never knew until we started testing twice a day how all the parameters would change from morning to afternoon. Water quality typically changes from a ‘worst case’ to a ‘best case’ scenario as the day progresses. Knowing that helps us better understand the rhythm of the Bay.” In a general sense, the water quality of the Bay is lower in the morning and higher in the afternoon as oxygen levels in the water increase, pH rises, and nitrogen content decreases.

Some areas of the Bay experience dramatic daily swings in oxygen, pH, and nitrogen levels. Often these regions, such as narrow embayments in eastern Casco Bay, are where we find substantial crops of phytoplankton thriving in the water column. When these phytoplankton die and decay, the bacteria that break them down consume oxygen from the water, which other marine life needs. Decomposition of these marine plants can also release more carbon dioxide, raising the acidity of the sea water. This makes it harder for baby clams and other shellfish to build their protective shells.


Join Our Team!

Interested in joining the ranks of our volunteers who sample water quality at sites around the Bay? Volunteers are trained in rigorous EPA-approved sampling methods and collect samples twice per day on 10 selected Saturdays. To get involved, fill out our volunteer application. If you have questions, please call 207-799-8574.

Fill out our volunteer application

What are our volunteers like? Each year, we recognize those Citizen Stewards who have reached milestones in water quality monitoring for 5, 10, 15, and 20 years of service.


Video About Our Monitoring Work:

Learn more about our Water Quality Monitoring work  and our efforts to improve and protect Casco Bay.

Help Support our Water Quality Monitoring Program

Your donation will support our staff and volunteers’ work to sample water quality around the Bay. Donate here and choose “Citizen Stewards Water Quality Monitoring Fund” in the designation box. Thank you!