Toxic Algae in Casco Bay!

Wednesday, October 11, 2017 by Julia

A few week ago the LabVenture! team began observing a mysterious green phytoplankton, also know as algae, in our daily plankton samples. The phytoplankton was to small to identify with our microscope, but we could tell there was a lot of it. Eager to solve the mystery, we decided to get a closer look at the unknown phytoplankton. We brought our samples to Zack, a scientist at the Gulf of Maine Research Institute, who has a very powerful microscope. 

We used some phytoplankton identification guides to try to determine what type it was. We sent our suggestions and some photos of the mystery plankton to the Department of Marine Resources’ (DMR) Biotoxin Monitoring Program to see if our identification was correct. We were! DMR had been seeing high counts of this same species throughout Casco Bay. When a phytoplankton species increases rapidly in numbers in a certain area that is called a “bloom”. Our observations confirmed that this phytoplankton bloom extended all the way into Portland Harbor where we collect our plankton samples.

The mystery doesn’t end there! There is a type of phytoplankton called dinoflagellates and some species of dinoflagellates produce biotoxins that can harm fish, shellfish, and even humans that eat contaminated fish or shellfish. Have you ever hear of the “red tide”? The red tide is actually a bloom of dinoflagellates that produce a biotoxin. Shellfish like mussels can take in this biotoxin, which can make humans who eat the mussels sick.

The phytoplankton we saw was a type of dinoflagellate, but DMR wasn’t sure what species it was. It is important to be able to determine the exact species because some types of dinoflagellates can look very similar but one species may be toxic while another is harmless. After a whole bunch of tests, including a DNA test, they found that it was a species called Karenia mikimotoi. This species is usually found in the Gulf of Mexico and produces a biotoxin that is harmful to fish and shellfish, but not humans. The bloom has since died off, but our observations during LabVenture! helped to solve the mystery!


Check out this article about a clam die off in Brunswick as a result of the bloom:

Check out this clip of our very own Andy Pershing discussing the bloom:

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