<P> Limnologist Dr. David Schindler, whose research at the Experimental Lakes Area led to the banning of harmful phosphates in detergents, warned about algal blooms and dead zones, </P> <P> "The fish - killing blooms that devastated the Great Lakes in the 1960s and 1970s haven't gone away; they've moved west into an arid world in which people, industry, and agriculture are increasingly taxing the quality of what little freshwater there is to be had here...This isn't just a prairie problem . Global expansion of dead zones caused by algal blooms is rising rapidly ." </P> <P> The major groups of algae are Cyanobacteria, green algae, Dinoflagellates, Coccolithophores and Diatom algae . Increase in input of nitrogen and phosphorus generally causes Cyanobacteria to bloom and this causes dead zones . Cyanobacteria are not good food for zooplankton and fish and hence accumulate in water, die, and then decompose . Other algae are consumed and hence do not accumulate to the same extent as Cyanobacteria . Dead zones can be caused by natural and by anthropogenic factors . Use of chemical fertilizers is considered the major human - related cause of dead zones around the world . Natural causes include coastal upwelling and changes in wind and water circulation patterns . Runoff from sewage, urban land use, and fertilizers can also contribute to eutrophication . </P> <P> Notable dead zones in the United States include the northern Gulf of Mexico region, surrounding the outfall of the Mississippi River, the coastal regions of the Pacific Northwest, and the Elizabeth River in Virginia Beach, all of which have been shown to be recurring events over the last several years . </P>

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