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Monitoring by Land

Monitoring by Land—Seasonal Spatial Surface Sampling

Collecting surface water quality data by land from docks and piers at 13 sites around the Bay provides us with spatial coverage over a broad range of conditions around the shoreline of the Bay,  from South Portland to Harpswell and Brunswick. We visit these sites every two weeks from May to October.

This provides our scientists and other staff the opportunity to get a frequent look at conditions around the Bay. In addition to collecting data on water quality, we also record observations of weather, sea state, wildlife, and unusual sightings and conditions.

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 surface 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.

The data were collected by volunteer citizen scientists, whom we trained to rigorous specifications (using a Quality Assurance Project Plan [link]). These stewards used a Secchi disk and water quality test kits specifically designed by us as “Casco Bay kits” with the help of LaMotte Company.

After pulling up buckets of seawater at their shoreside sites, volunteers carefully mixed chemicals, titrated, and flocculated to get measurements for dissolved oxygen, salinity, pH, temperature, and water clarity. They would devote more than an hour at a time to monitor their assigned stations, at appointed times in both the morning and afternoon, on ten Saturdays from April through October.

Their data enabled us to identify when and where we are most likely to find water quality variations throughout the sampling season. These data, along with other staff collected data, helped us address our early questions, “How healthy is the Bay?” and “Where are the most challenged regions of the Bay?”

The stations that were representative of different regions and where water quality ranges from “healthy” to “challenged,” are now monitored in only seconds by staff using a data sonde, continuing this important long-term data set.


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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