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Spring Blooms in Casco Bay

What signs tell you that spring has arrived? Grass turning green? A robin in your yard? Ospreys returning to their nests?

What about huge blooms of phytoplankton in Casco Bay?

The chlorophyll fluorescence measurements in the graph above were recorded by our Continuous Monitoring Station, which has been in place for almost two years.

Chlorophyll fluorescence is a measure that provides an estimate of phytoplankton abundance. Chlorophyll is the green pigment in plants that traps the energy of the sun for photosynthesis.

The graph tells us that this year’s spring bloom of phytoplankton started around the same time as last year, but was bigger in magnitude this year than in 2017.

Why do we care about chlorophyll levels? Phytoplankton are the single-celled plants that make up the foundation of the ocean food web. Phytoplankton also provide half of all the oxygen we breath—so thank phytoplankton for every other breathe you take. You can read more about phytoplankton and chlorophyll in our recent post.

Photography by Kevin Morris

Every hour and every day, the Continuous Monitoring Station—a.k.a our “Cage of Science”—is building a more complete picture of the seasons beneath the Bay. Thanks to support from Casco Bay Estuary Partnership and generous donors, the Station collects measurements of temperature, salinity, pH, dissolved oxygen, carbon dioxide, and chlorophyll fluorescence year-round. Every other week, Research Associate Mike Doan cleans and calibrates the equipment, and downloads and graphs the data to track conditions in the Bay.