When algae go bad

Algae are like the teenagers of the botanical world. They really do lots of wonderful things - producing oxygen and taking up carbon dioxide for starters (algae, not teenagers) but do you ever hear about these things in the news? Oh no, all you ever hear about are those bad 'toxic' algae.....

Just in today's news there are reports of toxic algae in:
Merseyside, England
Florida
Canada
Nebraska

and the worst part is that most of these bad 'algae' aren't even algae - they are blue-green algae, which are actually bacteria.

This time last year: Beatrix versus the Botanists