For more than 30 years, scientists have pointed toward phosphorus as the key to Lake Erie's Dead Zone. But new research from Ohio Sea Grant researchers Dr. Darren Bade and Dr. Bob Heath of Kent State University has found that a different nutrient-nitrogen-could be contributing as much as 80% of the oxygen loss.

The nitrification process that occurs in Lake Erie consumes four atoms of oxygen as certain kinds of bacteria break apart ammonium (NH4), first creating nitrite (NO2) and then nitrate (NO3). Since summer 2008, Bade and Heath have collected water and sediment samples in Sandusky Bay, hoping to find evidence of nitrification.

"Our studies to date show that nitrification can account for between 5% and 80% of the oxygen consumed," Bade says. "That seems to point to a great deal of nitrification, but we haven't been able to explain the variation. We thought it would be tied to the amount of ammonium available, but so far we haven't shown that to be the case."

Bade and Heath are currently testing bacteria in the collected samples to determine how many of them are genetically capable of performing nitrification. "We're measuring the numbers of those genes that you can find in a community, asking if there is a relationship between the numbers of nitrifying bacteria and the nitrification rate," Heath explains. The team will continue to collect samples seasonally through summer 2010 to strengthen their early observations.

"Finding this connection would conceivably mean having to completely recast the management strategies for Lake Erie," says Heath. "Until now, all of the plans have been based on phosphorus and focused on limiting phosphorus. This would change everything."

To read more about this Ohio Sea Grant-funded research, visit http://ohioseagrant.osu.edu/_documents/twineline/v31i3.pdf