Archive for October, 2008

Turbidity in the Chesapeake: Why so murky?

Wednesday, October 22nd, 2008

Why in the world is the Bay getting so cloudy?  That’s the question that’s puzzled so many of us.  Sure there is construction in the watershed and agriculture and stormwater runoff, and yet the cloudiness appears to be worse than one would expect, even with all that runoff. 

And especially strange, this haziness has been getting worse and worse every year, in a one-way slide.  This is disturbing, since even nutrients and dead zones are largely tied to changing conditions.  Wet years versus dry years.  More wind or less wind.  Hotter or cooler.  The Bay’s cloudiness, what scientists call turbidity, has been getting worse every year no matter what the weather.

That is downright weird.  And worrisome.

 When asked about what’s going on, most researchers would answer, “We just don’t know.”   Some even said, “It’s a mystery.”  Scientists don’t often use words like “mystery.”  This seemed out of the ordinary. 

Two scientists who have delved into this puzzle are Larry Sanford and Charles (Chuck) Gallegos.  Sanford (at the University of Maryland Center for Environmental Science) is an expert in sediment.  Gallegos (at the Smithsonian Environmental Research Center) is an expert in algae.  They think the turbidity question has remained a mystery largely because it falls between the cracks of different disciplines.  Between those who study sediment and those who study algae.  Between the inorganic and the organic.

 What is occurring in the Bay, if these two researchers are right, cannot be explained in terms of sediment alone or algae alone.  Instead, there appears to be an interaction in the Bay’s waters that results from an overload of both nutrients and certain kinds of sediment.  The organic matter fueled by nutrients and the fine sediment that now floats in the Bay are apparently sticking together in ways that cause a cumulative build-up, a worsening cloudiness.

The resulting haze reaches its peak during the summer, much like the haze of those hot humid days in the city.  Smog in the air.  Turbidity in the water. 

For more on the story see “Shadow on the Chesapeake.”