Lago Erie e fioriture algali


Lago Eire in Ohio, Stati Uniti

Lake Eire

An image of the Lake Erie algae bloom acquired by the Landsat-5 satellite on October 5, 2011.  NASA EARTH OBSERVATORY / USGS

Lake Erie is under attack from noxious algae blooms, and the problem only looks likely to get worse if something isn’t done to reverse the trend, new research suggests.

In the summer of 2011, western Lake Erie turned a noxious green, as a massive algae bloom coated the surface and lapped up in mats along the shore. At its peak, the bloom covered an area 2.5 times larger than that of any Erie bloom on record, according to a study published today (April 1) in the Proceedings of the National Academy of Sciences.

Several factors converged to cause the bloom and may increasingly do so in the future, said Anna Michalak, a study co-author and researcher at the Carnegie Institution for Science at Stanford University.

Fertilizing the algae

First, agricultural practices have changed in the past few years, allowing for more fertilizer to run off from fields in the surrounding region and end up in the lake, Michalak said. There, the fertilizer feeds the growth of algal blooms. The practices include increased use of fertilizer, earlier application of the nutrients on bare ground and less use of tillage, in which fertilizer or manure is worked into the soil.

The first technique was intended to deliver fertilizer before spring storms, so farmers would not have to pick a time to apply fertilizer between rains, Michalak told OurAmazingPlanet. However, the method hasn’t worked as intended, due in part to larger than expected storms. The second practice, avoiding tillage of the soil, helps preserve nutrients in the earth, but may increase the amount of fertilizer lost in large spring rains, she said….

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