Algae danger is posed by bacteria

I SUBSCRIBE to an internet mailing list to do with boating on Ireland’s inland waterways.

Over the past couple of weeks, there have been a number of postings to the list expressing concern about blooms of blue-green algae in Lough Derg, on the lower Shannon.

The worry is based on the fact that many species of blue-green algae are poisonous. To my knowledge, one dog has already died this year after drinking from Lough Derg and a post mortem has shown algae to be the cause of death. Several other dogs and some farm animals have died in previous years.

Warning signs have been erected and swimming is banned. The risk to humans is less than the risk to animals. You would probably have to drink a litre or two of affected lake water before you were in danger of dying. But the stuff has killed people in China and even a small mouthful taken in accidentally by a swimmer can cause a nasty upset stomach. Some people also develop skin rashes after swimming.

Blooms occur at the end of the summer when the water temperature is highest. In a large lake like Lough Derg, maximum water temperatures usually lag four to six weeks behind maximum air temperatures. But the most dangerous season is probably already over.

The other factor needed before a bloom occurs is water with large amounts of phosphates and nitrates in solution. In other words, water that is mildly polluted by animal slurry, effluent from sewage treatment plants or domestic waste water. If the conditions are right the speed with which a bloom grows can be astonishing. These things can double their mass every 20 minutes.

I wanted to contribute to the thread on the mailing list, so I did a bit of research. My first discovery was amazing. Blue-green algae are not algae, at least not any more. Quite recently scientists have removed them from the algae and classified them in another Kingdom, the bacteria.

There are over 1,000 species and they are now called ‘cyanobacteria’. They used to be called ‘cyanophyta’. The reason for the change is something called Five Kingdoms classification which is all the rage in the world of biology today.

When scientists first started to classify living things they relied mainly on similarities and differences that they could see — either with the naked eye or through a microscope. But the science of genetics, as it progressed in the second half of the 20th century, gave them new and far more accurate tools. They could now examine the very DNA of living tissue. And they found that a lot of mistakes had been made in the past.

So everything was reorganised into five Kingdoms. The blue-green stuff from Lough Derg was put into the first Kingdom, the bacteria. The true algae, which include seaweeds, posed a bit of a problem. They didn’t fit with the bacteria or with the true plants. They were obviously not animals or fungi so the first four of the five Kingdoms were ruled out.

But these scientists are resourceful people. They created a fifth Kingdom called the Protoctista specifically as a bin into which they could toss all those awkward life forms that didn’t fit naturally into the other four. And the true algae have ended up in this fifth Kingdom.

The trouble is that if, like me, you’re of a certain age then quite a lot of the biology that you’ve learned over the years is now wrong.

I taught myself, because I was interested, and the learning process was often difficult and painful. Re-learning the stuff is even more difficult. I can no longer trust my books, I have to check on the internet, and the changes aren’t over yet.

It’s a bit depressing.

[e-mail]