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Friday, August 17, 2012

Watch the water

August 17 photo, click to enlarge
Since the Great Flood of 2010 freshwater lakes in Rhode Island have seen increased levels of algae. This is the time of year when algae multiplies prolifically (called a bloom) and may release toxins into the water.


There term algae applies to a very wide variety of organisms. The algae that people worry about because it sometimes produces neural-toxins is now considered a bacteria rather than a true algae and, in general, those are called cyanobacteria. The production of toxins by cyanobacteria is still not fully understood. The toxin is often released into the water when the cyanobacteria dies but often there is none. Even within cyanobacteria there are many species and only some even produce toxin.

DEM is currently surveying about a dozen Rhode Island lakes to measure the types of algae present. If some lakes are found to have high levels of cyanobacteria water samples will be sent off to Florida where a lab is equipped to estimate the toxin level. Unfortunately, any toxin in the water can vary substantially from day to day and by the time results are available any algae blooms may be over.

The best advice is to keep pets and children away from water that looks like that in the photo above or the one below. Though not likely to pose any real danger it is virtually impossible to tell whether it does.


The two photos here were taken on Pasquiset Pond during the morning of August 17. Just a few days earlier there was absolutely no "green scum" on the surface and very little visible in the water. I went swimming in the pond then without a thought. The effect was enhanced this morning where these photos were taken because a light breeze was blowing toward shore. But a lot of algae was visible in the water today, even in the middle of the pond.