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31 Years of Seasonal Sampling

Today, on World Ocean Day, we are celebrating our 31st year of collecting seasonal water quality data on the health of Casco Bay!

It also happens to be Casco Baykeeper Ivy Frignoca’s birthday – Happy Birthday, Ivy!

Every year, from May to October, Ivy and Staff Scientist Mike Doan take to our Baykeeper boat and truck to assess water quality at more than 20 locations in Casco Bay. This seasonal sampling includes measuring temperature, dissolved oxygen, pH, total nitrogen, water clarity, salinity, and chlorophyll fluorescence (an estimate of phytoplankton abundance). 

This year, for the first time, seasonal sampling will include testing for PFAS contamination in Casco Bay in collaboration with marine chemist Christoph Aeppli of Bigelow Laboratories for Ocean Sciences. PFAS are a class of widely-used, long-lasting chemicals and are an emerging pollutant of concern in Maine and around the world.

Staff Scientist Mike Doan collects water quality data from our Casco Baykeeper boat, R/V Joseph E. Payne. Mike uses a data sonde – a scientific device that measures water quality characteristics – to measure temperature, salinity, dissolved oxygen, and other parameters.

“There is an important gap in PFAS testing in Maine,” says Ivy. “Current monitoring for contamination in sources like drinking water, fish tissues, and wastewater appropriately focus on public health. However, we don’t know how PFAS pollution is affecting water quality and the environment more broadly, especially in tidal waters like Casco Bay.” 

Our collaboration with Bigelow this summer will help develop a baseline understanding of PFAS levels in Casco Bay, and lay the groundwork for testing in the marine environment moving forward. 

At Friends of Casco Bay, we use all of our seasonal sampling data to help assess the health of the Bay. Mike compares this seasonal work to a regular health check-up. “Like a doctor checking your blood pressure, if we find an anomaly or problem, we can do more thorough investigations,” says Mike. 

Seasonal sampling also enables us to assess water quality over a large area by visiting more than 20 different sites in the Bay. That’s a key difference from our Continuous Monitoring Stations, which collect data at a much higher frequency from three locations in Casco Bay.

Friends of Casco Bay conducts seasonal water quality monitoring at more than 20 locations in Casco Bay, marked by the blue dots. We also gather year-round data at their three Continuous Monitoring Stations, marked by the yellow stars.

The seasonal data we collect this year will add to our historic 30-year dataset, which has become one of the most long-term marine water quality datasets in the United States. Our data show that Casco Bay is warming at the same alarming rate observed in the greater Gulf of Maine. They have helped to designate Casco Bay as a federal No Discharge Area and strengthen legal protections for large areas of the Bay.

We share our data with other scientists as well as with state and federal agencies that use them to meet regulatory mandates. 

“For over three decades, Friends of Casco Bay’s monitoring efforts have provided scientists and regulators a crucial part of the data used to understand the condition of Casco Bay,” says Curtis Bohlen, Director of the Casco Bay Estuary Partnership, one of 28 federal National Estuary Programs. “The next thirty years will see unprecedented change in the Bay. Friends’ monitoring will undoubtedly be at the center of our efforts to witness and understand those changes.”