Clarkson Integrator

Issue date: 11/16/09 Section: News

Media Credit: Chris Knox The biology seminar by Dr. Robert Michael McKay of Bowling Green State University on Friday, November 13, 2009 in Snell.

Last Friday, the thirteenth of November, Dr. Robert Michael McKay of Bowling Green State University introduced his research to the biology department in the biweekly biology department seminar.

His presentation was entitled, "Do Large Lakes Add Up? On the Chemical Stoichiometry of Nitrogen in Lake Superior," and described how current research has shown changes in the nitrate levels within Lake Superior may be occurring and what their impacts may be.

Dr. McKay began by explaining that nitrate levels in Lake Superior have been shown to be increasing exponentially over the past century. This is despite the fact that the Clean Air Act has resulted in stable or decreasing emissions.

The increasing nitrates in the water must therefore be due to other factors and the lake itself must not be assimilating the excess NO3- as efficiently as hypothesized.

In his study, Dr. McKay showed that the nitrate concentrations were no longer following the exponential trend, and had begun to level off, or at least slowed their increase significantly. His group did this by first compiling all historical data for nitrate levels in Lake Superior. This data set of ten thousand measurements was over-layed with a linear, quadratic and exponential regression. The exponential regression shot off higher than the data, showing that this model was no longer valid. However, the data still showed a lot of variability, due to both external conditions (such as season, temperature) and lab-collection differences between different studies.

In order to exclude a portion of the variability, Dr. McKay and his associates limited their data analysis to those collections that occurred under special circumstances, such as with deep water and in the spring season. With this data set, the linear regression explained approximately fifty-eight percent of the variability, and a quadratic regression explained about sixty-five percent of the variability.

From there, Dr. McKay explained some of the expected sources of variation. In the beginning, there had been some debate about whether the project was to measure nitrification of Lake Superior (by bacteria) or the nitrifying of Lake Superior (due to any circumstances).

The decision was to title the study, "The Nitrifying of Lake Superior," however, their result showed that mainly bacteria were altering the nitrate levels in the lake, so in reality, nitrification was taking place. Dr. McKay and associated found that the Redfield ratio (a standard ratio of nitrate to phosphate) was very high within Lake Superior. Through further investigation, they were able to target a species, the archaeon, as the possible source of nitrification within Lake Superior.

Dr. McKay received his BS in Biology at Queens University in New York, and his Ph.D. at McGill University in Canada. He is known for his research in oceanography, algal physiology and working within the Great Lakes.

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