SSS 2009-03-12（在线收听）

This is Scientific American's 60-Second Science. I'm Adam Hinterthuer. Got a minute?

Farmers fertilize their fields to get the maximum meal from their crops. But the effects of these loads of nitrogen and phosphorous extend beyond the field and past the growing season. According to a study published this week by the Proceedings of the National Academy of Sciences, these nutrients can also drive the evolution of aquatic organisms. 

Agricultural fertilizers often drain into aquatic ecosystems and spur a frenzy of growth. Eventually the growth peaks and crashes as oxygen is consumed faster than it can be replenished - a condition called eutrophication. 

Using samples from two European lakes, Swiss researchers studied a century’s worth of eggs buried deep in the sediment by two species of Daphnia, a tiny crustacean. They found that, during periods of high nutrient levels, genetically distinct hybrid species emerged. Those hybrids appeared better at surviving eutrophication and soon outnumbered the original species. 

What’s more, the hybrids remained the dominant Daphnia species decades after pollution control measures brought nutrient levels back to normal. The scientists say short-term human impacts can leave permanent changes in ecosystems and a species’ genetics. 

You could say we’ve got quite the ‘gene’ thumb.

Thanks for the minute for Scientific American's 60-Second Science. I'm Adam Hinterthuer.