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Game On! New Research Begins

Photo by Chris J. Benson.

For the next two years Minnesota Sea Grant is pursuing the following investigations involving Lake Superior. The funding, which is provided by the National Sea Grant College Program and matched by the University of Minnesota, totals over $886,000.

What Fuels Lake Superior’s Food Webs?
Principal Investigator: Elizabeth Minor (University of Minn. Duluth)
With: J. Werne, D. Branstrator, T. Hrabik

Where do the elements of a lake trout's body come from? Are they derivative of algae, fallen leaves, and sunken logs on the bottom of Lake Superior or a combination thereof? To answer such a question, researchers will collect organic matter, zooplankton, and fish from off of Minnesota's north shore, a site along Wisconsin's nearshore, and a third offshore site in Lake Superior. They will collect samples from the sites in spring when the water is vertically mixing, in summer after stratification occurs, and when autumn leaves are floating into the lake. Back in the laboratory, the researchers will conduct isotopic analyses on the samples. The laboratory technique will allow the researchers to determine where these elements came from and whether the sources change over the seasons. If they discover that land-based sources of carbon and nutrients are important in Lake Superior's food webs, fisheries managers might want to include the watershed in management plans. If the researchers' preliminary data are correct and Lake Superior's food webs are predominantly founded on lake-based elements recently fixed by algae, managers could potentially use this information to anticipate how fish populations might respond to annual algae abundance.

Endocrine Mimics Disrupt Developing Bass
Principal Investigator: Patrick Schoff (University of Minn. Duluth)
With: J. Olker

When male fish start producing eggs (testicular oocytes), it’s time to ask questions. Sea Grant researchers are searching for the connection between this deformity that can be found in male smallmouth bass in some Minnesota lakes and rivers and chemicals that disrupt normal endocrine system functions. They are examining testicular tissue from smallmouth bass swimming in the St. Louis River, its estuary, and in inland lakes in Minnesota. The researchers will compare deformity rates among the sites relative to human influence, while simultaneously conducting laboratory studies to define how exposure to estrogen alters normal gonad development in male smallmouth bass. This study advances research into water quality challenges that could affect fisheries and coastal communities.

Low Light, Eyesight and Deepwater Foraging Success
Principal Investigator: Thomas Hrabik (University of Minn. Duluth)
With: A. Mensinger, B. Roth, O. Gorman

Despite living in dimly lit environments, deepwater sculpin, kiyi, and siscowet rely on visual cues to forage and to avoid predators. Sea Grant researchers will define the visual acuity of these native Lake Superior species by studying their physiological and behavioral responses to different light intensities in thermally controlled aquariums. The laboratory investigations will help the researchers to identify mechanisms that allow these species to thrive in low-light environments. These findings will be included in computer simulations to aid fisheries managers as they decide whether to open a siscowet fishery or not. The simulations will indicate the degree to which harvesting siscowet could affect Lake Superior’s food web. Understanding the relationship between the species and distinct light levels will help researchers consider how potential changes in Lake Superior’s temperatures and light regimes could alter the interactions between predatory siscowet and their prey.

Rusting Predictor: Understanding the Bacteria that Steals Port Steel
Principal Investigator: Randall Hicks (University of Minn. Duluth)
With: N. Johnson, A. Reed, B. Little

Steel corrosion in some areas of the Duluth-Superior Harbor is approaching the corrosion rates of saltwater. Now that iron-oxidizing and sulfate-reducing bacteria have been linked to infrastructure breakdown, Sea Grant researchers will examine the relationship between the microbial community and changes in oxygen, hydrogen, and sulfide concentrations within corrosion tubercles. Focusing on subtle changes occurring near the steel surface, the researchers suspect that water quality may boost the activity of some microbial communities and that microbial processes close to steel surfaces control corrosion rates. The researchers expect to uncover specific mechanisms that lead to corrosion through electron microscopy and molecular biology. Their discoveries will help them to refine a risk assessment tool for freshwater ports. The U.S. Army Corps of Engineers, port authorities, and companies could use this tool to more accurately assess conditions that accelerate corrosion rates.

Estuary Hotspots for Microbes Reflect Water Chemistry
Principal Investigators: Jacques Finlay (University of Minn. Twin Cities),
E. Stanley (University of Wisc.-Madison)
With: R. Sterner; Jointly funded by Minnesota and Wisconsin Sea Grant

The chemistry of the water within the St. Louis Estuary depends on its origin and its interactions. The upper estuary flows with river water and runoff from wetlands. As it moves toward Lake Superior, this water mixes with urban runoff and then nitrate-rich lake water. Microbial activity in the estuary reflects this range of water quality conditions and also seasonal variation in physical conditions such as temperature, light availability, residence time of water, and nutrient concentrations. In this study, Sea Grant researchers will identify hotspots of microbial activity in the estuary and determine the seasons in which nutrient and organic matter processing happens most quickly. Without microbes turning dead plants into next year’s building blocks, most nutrients would be unavailable for use in the food web. New information about the biogeochemical processes supporting the estuary will enhance water quality monitoring programs and guide strategies for improving estuarine health. This study complements the goals of the Lake Superior National Estuary Research Reserve, the Western Lake Superior Sanitary District, the U.S. Geological Survey, and other agencies.

By Sea Grant Staff
July 2012

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