5/19/2015  |   15:30 - 15:45   |  101B

TWO SIDES OF CROSS-ECOSYSTEM SUBSIDY FLUX IN AQUATIC AND TERRESTRIAL HABITATS Freshwater and terrestrial ecosystems are closely linked by flux of donor-controlled subsidies - the addition of nutrients and materials (detritus and prey), which not only can affect consumer abundance, but also explain variation in the strength of trophic cascades in food webs. However, while the flux supplies foods for recipient communities to subsidize primary producers and consumers and alter species interactions, harmful contaminants are also propagated to adjacent ecosystems through subsidy movement. In both donor and recipient ecosystems, contaminants cause considerable impacts on ecological processes through damaging ontogenetic development of focal species (e.g. aquatic insects, amphibians), decreasing subsidy quantity and quality, restricting population size of consumers. All of which may fuel a cascade effect and influence ecosystem functioning. Empirical studies have shown that the dynamics and effects of contaminants relating to subsidies can be affected by numerous factors. Future study to examine the influence of subsidies, including contaminant-specific flux, on trophic position of consumers should consider accessing direct and indirect effects of land-use change and global warming on food web structure in recipient habitats, as well as in source habitats.

Yixin Zhang (Primary Presenter/Author), Xi'an Jiaotong-Liverpool University, yixin.zhang@xjtlu.edu.cn;


Hongyong Xiang (Co-Presenter/Co-Author), Xi'an Jiaotong-Liverpool University, xianghy13@163.com;

5/19/2015  |   15:45 - 16:00   |  101B

CHEMICAL SPECIATION OF PHOSPHORUS IN THE WATER COLUMN AND SEDIMENT IN GREEN BAY Water and sediment samples were collected from Green Bay, Lake Michigan, during August 2014 to examine the dynamics of phosphorus (P) species and their transformation between dissolved and particulate, organic and inorganic phases. Particulate-P in suspended-particles and sediments were further fractionated into five phases using sequential extractions. Predominance and near-anthropogenic level (<1000 nM) of phosphate in the dissolved P pool was observed in the Fox River, while predominance of dissolved organic P and low DIP (22 ± 14 nM) were measured in Green Bay. Within the suspended particulate P, >50% was potentially bio-reactive P. Comparable bio-reactive P fraction was observed for particle-adsorbed P (32%) and phosphorus-bearing iron oxyhydroxides (29%). However, increased detrital-P and decreased bio-reactive P from surface waters to sediments were observed, indicating active particulate-P regeneration in the water column. Low abundance of iron-bound-P in sediments and higher phosphate in bottom waters likely reflected the influence of hypoxia conditions in Green Bay. Most of P was buried and accumulated in sediments mainly as iron-bound and authigenic-P in north of the Bay, but as organic-P off the Sturgeon Bay.

Peng Lin (Primary Presenter/Author), School of Freshwater Sciences, University of Wisconsin-Milwaukee, lin25@uwm.edu;


Val Klump (Co-Presenter/Co-Author), School of Freshwater Sciences, University of Wisconsin-Milwaukee, vklump@uwm.edu;


Laodong Guo (Co-Presenter/Co-Author), School of Freshwater Sciences, University of Wisconsin-Milwaukee, guol@uwm.edu;

5/19/2015  |   16:00 - 16:15   |  101B

FROM THE BENTHOS, BOTTOM-UP TO PHYTOPLANKTON: DECOMPOSITION HAS BEEN TRUMPED BY EXCRETION OF N AND P IN MODERN LAKE MICHIGAN In Lake Michigan, sedimentation and diagenesis resulted in diffuse flux through a sediment surface layer; a biogeochemical gauntlet for labile chemical species. Since Quagga Mussel benthification after 2003, and subsequent shift from diatoms to picocyanobacterial dominance, particles have been intercepted prior to burial and digestion-excretion is now a dominant benthic process. Its regeneration of phytoplankton growth nutrients is very rapid (1 (P) to 20 (N) nmol/animal/hr), and more importantly subverts biogeochemical speciation controls at the sediment-water interface. Excretion varies systematically with location in a seemingly resource-delivery proportionality. The mmol or more from 30,000 QM per square meter per day is a substantial return of resources to the water. As the flux is supplemented by autolysis in aging individuals, further return may now be coming to the ecosystem. Quagga mussel excretion rates were measured in transects across a seamount-like bathymetric feature in south-central Lake Michigan. On the upstream side of Northeast Reef, where freshly advected bottom water flows across mussel communities, excretion rates are about 0.8 and 31 nmol/animal/hr (SRP and NH4 respectively) for robust young adult mussels 15-20mm in length.

Carmen Aguilar (Primary Presenter/Author), UW-Milwaukee School of Freshwater Sciences, aguilar@uwm.edu;


Russell Cuhel (Co-Presenter/Co-Author), UW-Milwaukee School of Freshwater Sciences, rcuhel@uwm.edu;

5/19/2015  |   16:15 - 16:30   |  101B

TRANSPORT DYNAMICS OF DISSOLVED AND PARTICULATE NUTRIENTS IN RESPONSE TO WOOD ADDITIONS WITHIN AN AGRICULTURALLY IMPACTED STREAM Wood is a key component in forested streams, playing an important ecological and physical role in creating step-pool profiles, enhancing habitat heterogeneity, retaining organic matter, and changing water velocity. Wood additions can increase in-stream residence times by slowing water velocities and providing high depositional areas for fine particles (i.e. particulate nutrients C, N, P). Thus, wood additions may create biogeochemical hotspots in streams that allow greater potential for local nutrient cycling and processing. The objectives of this research were to determine if added wood enhances in-stream heterogeneity, results in more complex flow paths, increases natural retention of further organic matter and changes geomorphic characteristics of the stream reach. We conducted a conservative solute and fluorescent fine particle tracer injection study in an agriculturally impacted stream with wood additions in the Whatawhata catchment, North Island of New Zealand. Fine particles were analyzed within the surface water and in situ in sediment and biofilms on cobbles throughout the stream reach following the injection. We found that the addition of wood enhanced hydraulic complexity and increased the retention of solute and fine particles.

Jen Drummond (Primary Presenter/Author), Spanish National Research Council (CEAB-CSIC), j-drummond@u.northwestern.edu;


Aslan Wright-Stow (Co-Presenter/Co-Author), National Institute of Water and Atmospheric Research (NIWA), Aslan.Wright-Stow@niwa.co.nz ;


Paul Franklin (Co-Presenter/Co-Author), National Institute of Water and Atmospheric Research (NIWA), Paul.Franklin@niwa.co.nz;


John Quinn (Co-Presenter/Co-Author), National Institute of Water and Atmospheric Research (NIWA), John.Quinn@niwa.co.nz;


Aaron Packman (Co-Presenter/Co-Author), Northwestern University, a-packman@northwestern.edu;

5/19/2015  |   16:30 - 16:45   |  101B

WHAT IS FUELING THE “RING OF FIRE”? Benthic macro-invertebrates are often found in higher densities in the nearshore (shelf and slope) of the Laurentian Great Lakes. However, the flux and source of energy that supports this elevated population of invertebrates is not well defined. In this study, particulate phosphorus and organic carbon fluxes to the nearshore lakebed are measured using the naturally occurring radionuclides thorium-234 (half-life: 24.1 days) and yttrium-90 (half-life: 2.7 days). Large fluxes of P and C suggest that benthic macro-invertebrates in the nearshore are supported primarily by offshore pelagic production.

James Waples (Primary Presenter/Author), School of Freshwater Sciences, University of Wisconsin-Milwaukee, jwaples@uwm.edu;


Val Klump (Co-Presenter/Co-Author), School of Freshwater Sciences, University of Wisconsin-Milwaukee, vklump@uwm.edu;