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Testing for Algal Toxins

Updated: Aug 17, 2020

Photo credit: Pine Tree Camp

The most frequent question we are getting asked by residents of North Pond (and downstream residents of Great Pond) is:

Is the water safe?

The Maine DEP considers any bloom where the water transparency is less than 3 ft to be potentially harmful. This is because cyanobacteria (blue-green algae), the typical culprit in blooms at this time of year, can sometimes produce toxins. Cyanobacteria have been on Earth for over a billion years – in all that time they have developed evolutionary adaptations that allow them to thrive in many environments. One of these adaptations is the production of cyanotoxins to help them compete.

Cyanobacteria produce a range of toxins, some of which can pose a health risk to humans and animals. But when and why they produce various toxins is still quite hard to predict! We often use water transparency as an imperfect proxy for when there might be a risk. Toxin production is almost always associated with blooms, but not all blooms produce toxins.

Last week, the water transparency of North Pond became less than three feet and we warned the North Pond community not to swim in the lake until a toxin test could be performed. The 7 Lakes Alliance has begun a toxin monitoring program in North Pond and the Great Meadow Stream. We are currently testing for a liver toxin called microcystin, which previous work by the DEP indicates is the most likely toxin to be produced in our lakes. Microcystin is a slow acting toxin; in other words, most people and animals won’t have an acute response to it. Instead the health risk lies in the toxin building up in your system, leading to liver damage.

7 Lakes Alliance has purchased eurofins-Abraxis rapid microcystin test kits to enable us to quickly know if the microcystin levels are high. We have also purchased Envirologix ELISA test kits (to be run at Colby through our water quality partnership) which can better estimate microcystin concentrations if we detect its presence.

On August 5th, we collected samples at 4 locations and tested them for microcystin.

Sample locations of microcystin testing: north shore of North Pond (NS), Pine Tree Camps (PT), rt. 225 bridge on the Great Meadow Stream (225), and North Bay of Great Pond (NB).

The good news is that they all came back negative!

Photograph of microcystin test results. Each test strip has a control line (marked C) and sample line. A negative test is indicated when the sample and control lines are both red. All of these samples were negative for the toxin microcystin.

North Pond is still experiencing a significant cyanobacteria bloom and the situation can change quickly, so we reiterate DEP guidance that you should avoid areas with surface scums and limit exposure to lakes with significant blooms:

We will be continuing to monitor toxin levels weekly and will report results on this blog. The North Pond Association is helping with the purchase of additional test kits so that we can continue to monitor through the end of the summer.

Photo credit: Karen Ashton


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