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Losing Sleep

Jeff Gunderson

Why don't we know the answer to many of Lake Superior's questions?

Sure, Lake Superior is broad, deep, and more like an inland sea than a freshwater lake, but I'm frequently surprised by what we don't know about it. Descriptive research and monitoring go back to the mid-1800s with the publishing of Louis Agassiz's Lake Superior: Its Physical Character, Vegetation and Animals, Compared with Those of Other and Similar Regions. Although scientific studies on Lake Superior didn't ramp up until the 1950s, after 60 years of study you might think we should fully grasp Lake Superior's physical, biological, and chemical processes — but we don't. It seems the more we study the lake, the more questions we generate.

On a light note, who knew Lake Superior had whale burps? One year ago we found out it did. Check out Sharon Moen's update in this issue. Not that whale burps are a big mystery, but why they were just recently discovered in Lake Superior and the exact mechanism of their formation are still not entirely known.

An intriguing question is raised in Lake Superior's Chemical Imbalance?, an article describing the research of Robert Sterner. In a recent journal article, Sterner examined the stoichiometry of carbon, nitrogen, and phosphorus in Lake Superior. Sterner compiled a database showing that nitrate levels have been rising in a nearly linear fashion for 100 years. According to Sterner, this may be one of Lake Superior's most unique and unusual features. So the big question is why is nitrate rising? We don't know the answer to that.

Another question that has remained a mystery is why annual estimates of carbon exports are larger than estimates of carbon inputs to Lake Superior; they should balance each other. Understanding the lake's carbon balance will help scientists and resource managers to better understand the dynamics of the upper trophic levels (important fisheries) of the Lake Superior food web. We have funded research in the past to address this question and will fund another study over the next two years. The new study should help to resolve the lake's carbon budget by identifying the source(s) of this unaccounted for carbon and ascertaining how important land-based contributions are to lake productivity.

How many fish are in the lake? At a recent meeting of the Lake Superior Technical Committee, it became clear how difficult it is to estimate that number. Most experts agree that siscowet lake trout have made an incredible recovery and are abundant throughout Lake Superior. However, an attempt to estimate the total biomass available for a potential new siscowet fishery (focused on omega-3 oils) produced two widely divergent estimates. One suggests that the lake contains 32.3-million pounds of siscowet; the other estimates 617.9-million pounds…just for the Michigan waters of Lake Superior! This huge discrepancy illustrates how difficult it is, even in this era of technology, to completely understand this gem of a lake.

These and other Lake Superior questions keep me awake at night. What sorts of questions are bugging you about Lake Superior? Send me an email. We'll see if we can find an answer.

By Jeff Gunderson
February 2012

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