SFS Annual Meeting

5/21/2018  |   11:00 - 11:15   |  430 B

SPATIOTEMPORAL VARIATION IN TRIBUTARY NUTRIENT CONCENTRATIONS: A SEASONAL PERSPECTIVE FOR LAKE MICHIGAN Despite efforts to reduce nutrient loads to the Laurentian Great Lakes since the 1970’s, these inputs continue to cause coastal eutrophication and degrade ecosystem services. Tributaries are a key focus for managing nutrient loading, but controls on spatial and temporal variation in their nutrient concentrations have not been fully resolved. We circumnavigated Lake Michigan quarterly for 2 years to profile soluble reactive phosphorus (SRP), nitrate, and ammonium in ~100 tributaries that span the range of watershed size and land cover in the basin. Tributary nutrient concentrations were surprisingly dynamic across the seasonal cycle. SRP increases with urban and agricultural land cover, and the relationship is exacerbated during the summer. Nitrate concentrations increase with agriculture and watershed size, but were strongly attenuated by wetlands —especially in fall, winter, and spring. Our multi-year findings illustrate the challenges of limiting year-round nutrient loads to the Great Lakes, each of which has hundreds of time-varying tributaries.

Galen McKinley (Co-Presenter/Co-Author), Columbia University, mckinley@ldeo.columbia.edu;


Lucas Gloege (Co-Presenter/Co-Author), Columbia University, gloege@ldeo.columbia.edu;


Peter B. McIntyre (Co-Presenter/Co-Author), Cornell University, pbm3@cornell.ecu;


Robert J. Mooney (Primary Presenter/Author), Center for Limnology, University of Wisconsin - Madison, rjmooney@wisc.edu;


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5/21/2018  |   11:15 - 11:30   |  430 B

TEMPORAL AND SPATIAL VARIABILITY IN ORGANIC CARBON CONCENTRATION AND COMPOSITION IN LAKE MICHIGAN TRIBUTARIES The tributaries of the Great Lakes represent a major source of dissolved organic matter (DOM) loading. DOM contributes to numerous environmental processes including carbon transport, redox cycling, and interactions with environmental contaminants. However, little is known about the temporal and spatial variability in organic carbon composition and concentration in Great Lakes tributaries. We assessed seasonal DOM dynamics in >100 Lake Michigan tributaries over a period of one year, supplemented by monthly sampling of 30 tributaries during the frost-free period. Dissolved organic carbon (DOC) concentrations were used as a surrogate for DOM, while UV-visible spectroscopy was used to assess DOM composition. DOC concentrations are higher in northern tributaries, where wetlands make up a large portion of watershed area. Interestingly, low spatial variability in optical properties correlated with aromaticity and molecular weight indicate that the DOM being transported to Lake Michigan is primarily terrestrial in origin. However, seasonal fluctuations in the molecular weight of DOM suggest that the fraction of microbial contributions increase during winter and spring. Our extensive seasonal sampling reveals the dynamic role of tributary rivers in connecting watershed and lake carbon budgets.

Stephanie Berg (Co-Presenter/Co-Author), University of Wisconsin-Madison, stephanie.berg@wisc.edu;


Robert J. Mooney (Co-Presenter/Co-Author), Center for Limnology, University of Wisconsin - Madison, rjmooney@wisc.edu;


Megan B. McConville (Co-Presenter/Co-Author), University of Wisconsin-Madison, megan.mcconville@gmail.com;


Peter B. McIntyre (Co-Presenter/Co-Author), Center for Limnology, University of Wisconsin-Madison, pmcintyre@wisc.edu;


Christina K. Remucal (Primary Presenter/Author), University of Wisconsin - Madison, remucal@wisc.edu;


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5/21/2018  |   11:30 - 11:45   |  430 B

USE OF LOW-ORDER TRIBUTARIES BY LAKE SUPERIOR FISHES: IMPLICATIONS FOR CONSERVATION AND MANAGEMENT More than 200 small streams flow into Lake Superior that may provide seasonal habitat for lake fishes. Some Great Lakes fishes undertake reproductive migrations, but the patterns of these migrations into small tributaries are poorly documented. To characterize use of low-order tributaries by Lake Superior fishes, we captured in- and out-migrating fishes over 1.5 years during the ice-free season in three eastern tributaries. We collected >40 species and >14,000 individuals, of which 12 species and ~20% of all individuals were spawning migrants. We only collected two species of spawning migrants in common across all sites (introduced Steelhead and Coho Salmon), despite close geographic proximity and size. Migrations occurred predominantly in spring, and durations were condensed for species such as Rainbow Smelt and Longnose Suckers (<1 week) and protracted for Steelhead (>1 month). We also captured sub-adults of some species (e.g., White Suckers) moving downstream, but never collected spawners, which suggests temporal variability in tributary use by lake migratory fishes. Our detailed records of tributary use by migratory fishes offers additional context for conservation efforts regarding ecosystem subsidies, connectivity, and habitat protection.

Ashley Moerke (Primary Presenter/Author), Center for Freshwater Research and Education, Lake Superior State University, amoerke@lssu.edu;


Kevin Kapuscinski (Co-Presenter/Co-Author), Lake Superior State University, kkapuscinski@lssu.edu;


John Milan (Co-Presenter/Co-Author), Lake Superior State University, jmilan@lssu.edu;


Paul Ripple (Co-Presenter/Co-Author), Bay Mills Indian Community, pripple@baymills.org;


Frank Zomer (Co-Presenter/Co-Author), Bay Mills Indian Community, fzomer@baymills.org;


Ian Harding (Co-Presenter/Co-Author), Bay Mills Indian Community, icharding@baymills.org;


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5/21/2018  |   11:45 - 12:00   |  430 B

VARIABILITY IN PHYSICAL AND BIOLOGICAL EXCHANGE AMONG COASTAL WETLANDS AND THEIR ADJACENT GREAT LAKES Hydrology is a major governor of physically-driven exchange among coastal wetlands and the adjacent Great Lake, whereas fish movement is a major governor of biologically-driven exchange. We use data describing coastal wetland morphology, hydrology, water quality, and fish tissue stable isotopes to examine variability among wetlands in the strength and nature of these exchanges. Water quality patterns were characterized for lake and tributary end-members and 5-plus wetland locations, and fish use of habitats along the wetland-nearshore continuum was characterized by targeted sampling of resident and migrant species and their potential food sources. The interplay between tributary-water and seiche-water inputs – which derives from geomorphic setting -- influenced nutrient and suspended matter concentrations and ratios, with implications for how the wetlands process and transmit watershed-derived materials. The degree to which coastal fishes derived nutritional support – and thus translocated materials – from wetlands was influenced by a combination of geomorphology and species-specific behaviors. At all sites, wetland- and nearshore-captured fishes obtained substantial nutrition from adjacent habitats. Wetland-nearshore exchanges thus vary along multiple dimensions of landscape setting that should be considered in coastal wetland protection, restoration, and management.

Mike Sierszen (Co-Presenter/Co-Author), USEPA/NHEERL/MED, Duluth, MN, Sierszen.Michael@epa.gov;


Joel Hoffman (Co-Presenter/Co-Author), U.S. Environmental Protection Agency, hoffman.joel@epa.gov;


Anne Cotter (Co-Presenter/Co-Author), USEPA/NHEERL/MED, Duluth, MN, Cotter.Anne@epa.gov;


Anett Trebitz (Primary Presenter/Author), U.S. Environmental Protection Agency, Trebitz.Anett@epa.gov;


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5/21/2018  |   12:00 - 12:15   |  430 B

YOU ARE WHERE YOU EAT: ESTIMATING COASTAL WETLAND-DERIVED RESOURCE USE BY LAKE MICHIGAN SPORT FISH USING STABLE ISOTOPES Great Lakes coastal wetlands are highly productive ecosystems at the terrestrial-aquatic boundary that support diverse biological communities and provide critical habitat for many economically-important fish species. Open-water nearshore lake habitats are linked to coastal wetlands via the exchange of materials (e.g., organisms, nutrients, organic matter) through both abiotic (e.g., waves, seiches) and biotic (e.g., fish movement) mechanisms. The magnitude of these fluxes likely varies in part due to differing levels of hydrologic connection between the wetland and the nearshore. We estimated wetland-derived resource contributions to nearshore Lake Michigan sport fish among three coastal wetland hydrogeomorphic types (riverine, lacustrine, and barrier-protected) using stable carbon and nitrogen isotope mixing models. In general, both coastal wetland water dissolved inorganic carbon (DIC) and prey are significantly depleted in 13C relative to the nearshore across all wetland types, but these isotopic differences are more pronounced in systems with less hydrologic connectivity (i.e., barrier-protected wetlands in southern Lake Michigan). Quantifying the importance of coastal wetlands in supporting coastal fisheries will help managers prioritize the conservation and restoration of these areas, many of which have been degraded due to land use conversion, invasive species, and pollution.

Katherine O'Reilly (Primary Presenter/Author), Illinois-Indiana Sea Grant, keo@illinois.edu;


Jeremiah Shrovnal (Co-Presenter/Co-Author), University of Wisconsin - Green Bay, shroj01@uwgb.edu;


Christopher Houghton (Co-Presenter/Co-Author), University of Wisconsin - Green Bay, houghtoc@uwgb.edu;


Patrick Forsythe (Co-Presenter/Co-Author), University of Wisconsin - Green Bay, forsythp@uwgb.edu;


Gary Lamberti (Co-Presenter/Co-Author), University of Notre Dame, glambert@nd.edu;


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