Pollution makes crustaceans adapt rapidly

Rapid evolution can influence the environmental effects of pollution, say biologists from Cornell University and Germany's Max Planck Institute for Limnology.

The discovery, reported in the September 30 issue of the journal Nature, shows that environmental degradation can be reduced when the affected animals evolve quickly. “It appears that ecological events that we think of as occurring relatively quickly — such as nutrient enrichment of a lake — can be influenced by the rapid evolution of the animals that are affected,” says Cornell biologist Nelson G. Hairston Jr.

In less than 30 years, as Germany’s Lake Constance suffered environmental degradation from phosphorus pollution, populations of tiny crustaceans called Daphnia found more and more toxic cyanobacteria (also called “blue-green algae”) mixed with their favourite food, a more edible type of algae. So the crustaceans adapted to handle a less nutritious food that would have seriously stunted the growth of their ancestors, and they became one of the important, natural controls for toxic cyanobacteria in the lake.

The research, carried out at the Germany institute, documented the crustaceans’ express-style evolution by hatching a series of dormant Daphnia eggs that were found, level by level, in lake-bottom sediments in a state of “diapause.” Diapausing animals, such as certain insects and crustaceans, can suspend their growth and development for years or even centuries during periods of unfavorable conditions.

DNA tests of Daphnia grown from eggs that were deposited over the years revealed that crustaceans that couldn’t cope easily with cyanobacteria were virtually eliminated from the population; all that remain today are cyanobacteria eaters, even though the toxic bacteria still aren’t particularly nutritious.

“Strong natural selection can lead to rapid changes in organisms, which can, in turn, influence ecosystem processes,” the biologists concluded in their article.

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