Algae, Botulism, and Birds
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Posted by Rosemary Drisdelle Oct 10, 2007 |
About a year ago, I wrote about birds and type E botulism, an often fatal disease caused by a bacterial toxin. Type E botulism has been of particular concern in the Great Lakes in recent years and scientists have been trying to figure out why. Mussels, bacteria, and fish are part of the answer: introduced mussels filter the water depleting it of oxygen; anaerobic Clostridium bacteria grow, producing the toxin; introduced fish eat the mussels ingesting the toxin; and birds eat the fish, get botulism and die by the hundreds. It seems there’s another piece to the puzzle, however; which fits in between the mussels and the bacteria in the scenario above.
A report in the Associated Press turns the spotlight on cladophora, a type of algae. Cladophora thrives on phosphorus and sunlight: too much phosphorus, often originating from fertilizers, detergents, and other human pollution, allows cladophora to proliferate to unnatural amounts near the surface where there’s lots of light. Mussels filtering the water make it clear deeper down, letting in sunlight and allowing cladophora to grow there too. The algae deplete the water of oxygen, allowing Clostridium to grow, and once again, the toxin is produced.
Sadly, it all comes back to us: humans have introduced alien species and polluted the water, making wreckage of an ecosystem, and native species are suffering. Some face extinction. And we probably can’t undo it.
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