Fioriture di alghe tossiche – Temperatura e Inquinanti


Rise In Toxic Algal Blooms Due To Climate And Nutrient Enrichment

October 25, 2013
Image Caption: Like pea soup, a thick mat of toxic microcystins cyanobacteria on Lake Taihu in China gets stirred up in the wake of a boat. Credit: Hans Paerl, courtesy University of North Carolina

Brett Smith for – Your Universe Online

Algae is probably best known for the green scum it forms on top of stagnant water, and in addition to looking unpleasant, some algal blooms host strains of cyanobacteria that are highly toxic.

According to a new study in the journal Science, nutrient enrichment and rising global temperatures are increasing the toxicity of some algal blooms in freshwater lakes, ponds and estuaries around the world. As these ‘eutrophic’ processes increase, so will the ratio of toxin-producing strains of cyanobacteria in harmful algal blooms.

The two study authors, from Oregon State University (OSU) and the University of North Carolina, emphasized the near-ubiquitous species Microcystis sp. cyanobacterium is of particular concern. The bacterium can regulate its position in the water column and produces microcystin, a toxin that causes liver damage.

In many environments, microcystin-producing cyanobacteria have a distinct advantage over non-toxic cyanobacteria. The poisonous strains can eventually out-compete the nontoxic strains, resulting in blooms that are increasingly toxic.

“Cyanobacteria are basically the cockroaches of the aquatic world, they’re the uninvited guest that just won’t leave,” said study author Timothy Otten, a postdoctoral scholar in the OSU College of Science and College of Agricultural Sciences.

“When one considers their evolutionary history and the fact that they’ve persisted even through ice ages and asteroid strikes, it’s not surprising they’re extremely difficult to remove once they’ve taken hold in a lake,” he added. “For the most part, the best we can do is to try to minimize the conditions that favor their proliferation.”

While the lack of an extensive historical record of algal toxicity prevents scientists from putting current observations into long-term context, Otten said, “If you go looking for toxin-producing cyanobacteria, chances are you won’t have to look very long until you find some.”


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