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Monitoring By Sea

Monitoring by Sea from the Baykeeper Boat—Profile Sampling

Our staff scientists collect water quality data using a data sonde, from the deck of the Baykeeper boat.

Once each month during July, August, and September, our staff are on the Bay collecting data at nine different sites. Data are collected at two meter intervals from the surface to the seafloor, to create a “profile” of the water column.

The sampling is conducted in five regions.

Three are individual profile sites, which we have been monitoring for over 25 years, and we continue to add to this long term data set. We call these the Sentinel Sites. The locations of these sites are:

  • Broad Sound, our deepwater site
  • Clapboard Island, Falmouth, our “suburban” site
  • Fort Gorges, our “urban” site in Portland Harbor

Our historical surface sampling helped identify the Harraseeket and Fore River regions as challenged areas of the Bay. Currently, we are gathering data in both of these regions in the warm months of July, August, and September. We collect data using three profile sites along transect lines, in each region. 

The Harraseeket and Fore River regions often have low dissolved oxygen, high chlorophyll, high nitrogen, low pH or some combination, indicating challenged water quality. We are looking deeper for hints as to what causes these areas to have poor water quality. The transects provide better insight into water quality dynamics in the area.

What information is collected?

We use a data sonde to collect information on water quality. A sonde is an electronic monitoring device that can collect several parameters of water quality at once. The data are downloaded to computer and analyzed.

What do we measure at these profile sites? Temperature, Salinity, Dissolved Oxygen, pH and Chlorophyll fluorescence (all from the sonde); water clarity (using a Secchi disk); and samples of water collected for Total Nitrogen and Dissolved Inorganic Nutrients.

How our data has been used

Our science is essential to our advocacy and community engagement. Our data has been used for many purposes, large and small, by our staff and other organizations, agencies, researchers, and individuals. Our data has been used to:

  • Identify challenged conditions in areas of the Bay
  • Create our Health Index for Casco Bay
  • Inform our community engagement
  • Ensure better long-term protections for the Bay
  • Regulate and reduce pollution through State-issued discharge permits
  • Influence legislation
  • Advance science in Maine
  • Assist in the education of our future oceanographers and marine scientists
  • Enable government to document health of Maine’s coastal waters
  • Assist others in innovative ways

Learn more about our data and how it is used here.

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