Cyanobacteria and Microcystins
Recently nearly half a million people using Lake Erie for drinking water were warned not to use it. The reason for this is increasingly common in Lake Erie and other surface waters. By the time fall and late summer have rolled around, enough excess nutrients have washed into our waterways that the natural balance can be upset.
In particular, cyanobacteria – also known as “blue green algae” – are given the ideal opportunity (temperature, sunlight, and nutrients) to outcompete other waterborne organisms to create a vast, green soup that can be dangerous to drink or even bathe in. Harmful algal blooms have also been associated with the death of pets and livestock. In the case of that corner of Lake Erie which serves Toledo and the surrounding communities, toxins called microcystins were found to be present in the water going to people’s homes even after going through the treatment plant. There are many kinds of cyanobacteria that produce at least 80 different microcystins. Other cyanobacteria produce different toxins, such as anatoxins, saxitoxins, and cylindrospermopsin. Microcystins are held in the cell wall of the cyanobacteria, and when the cells break open, the toxins are released. While the US EPA still has no official limit, the World Health Organization recommends just 1 part per billion for microcystins in drinking water. People who consume the water can have rapid liver damage and risk cancer from long term use. Microcystins may also irritate the skin and eyes of people who bathe in just a few parts per billion.
Public water providers are normally very good at dealing with the seasonal challenges of these blooms. Municipalities at risk test regularly, but this year weather conditions may have conspired to catch them off guard. Recent news reports advise that NASA will now use its satellites to help monitor the lake.
NOAA Great Lakes CoastWatch Lake Erie 8-4-2014
It has been found that certain oxidants, such as potassium permanganate (KMnO4), are very useful to not only destroy the cell, but break down the microcystin molecules themselves. In addition, powdered activated carbon may be used since its high surface area and high adsorbency allows it to rapidly soak up the toxins. Microcystins have a molecular weight around 1,000 Daltons, which is probably why reverse osmosis membranes have been shown to be effective. Laboratory testing is critical to ensure that the treatment of any cyanotoxin is effective.
Although lawns and leaky septic tanks can contribute to this extremely serious problem, there is very strong evidence attributing algal blooms mainly to agricultural fertilizers, perhaps because they are applied at the wrong times or in too great amounts. Life has a natural balance and the cause of harmful algal blooms is preventable. Is it worth getting this extremely important problem under control? Just ask the half million people who spent a few days unable to drink from their faucets, yet live next to the greatest fresh water resource on earth.
- Ohio EPA – Harmful Algal Blooms in Ohio Waters
- NOAA – Harmful Algal Blooms