6/05/2017  |   11:00 - 11:15   |  306A

LEAF LITTER PROCESSING IS PRIMED BY POND SEDIMENTS Leaf litter decomposition is a major pathway of material and energy processing in aquatic systems. The factors that control the breakdown of leaf litter in lentic systems remains incompletely described. In small man-made ponds leaf decomposition is mainly driven by microbial activity, thus may be sensitive local physical and chemical conditions. Our experiment evaluated the degree to which leaf litter processing is primed by contact with pond sediments. In 250 ml glass jars, we incubated 10, 1 cm leaf discs (Liriodendron tulipifera) with pond sediments that had been sieved to remove coarse particulate matter (> 1 mm), while simultaneously we incubated 10 additional leaf discs on a shelf 4 cm above the sediments. This design meant that the discs were exposed to similar conditions with the exception of those created locally by the contact with the sediment surface. After 4 months we found the leaves in contact with the sediments were less tough and had lost more mass than those incubated in the water column. Although the mechanism is unknown, our results indicate that pond sediments can accelerate leaf decomposition.

Jonathan Milisci (Primary Presenter/Author), Longwood University, jonathan.milisci@live.longwood.edu;


Jessica Hoak ( Co-Presenter/Co-Author), Virginia Tech, jessica.hoak@live.longwood.edu;


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6/05/2017  |   11:15 - 11:30   |  306A

CHARACTERIZING THE TRANSFORMATION OF SPECIFIC DISSOLVED ORGANIC CARBON COMPONENTS IN PRAIRIE STREAMS The dissolved organic carbon (DOC) pool within a stream can be an important energy source for stream heterotrophs and the biological use and transformation of this pool is an important aspect of stream nutrient dynamics. DOC uptake has typically been calculated for broad DOC lability classes or simply for total DOC, potentially missing important information about processing rates of individual DOC constituents. We used reach-scale tracer experiments to follow the transformation of multiple DOC components from leaf leachate within a tallgrass prairie stream. We calculated individual uptake parameters for three distinct fluorescent components (one protein-like and two humic-like components) using excitation-emission matrices and parallel factor analysis, corrected for potential photolysis in the stream. The fastest uptake rate was calculated for the protein-like component. The humic-like components were taken out of the water column more slowly and did not return to background levels simultaneously with the conservative tracer, indicating adsorption and re-release. This technique allows for closer examination of the fate of specific DOC components within streams, including biotic and abiotic processes.

Sophie A. Higgs (Primary Presenter/Author), Kansas State University, sahiggs@ksu.edu;


Walter Dodds ( Co-Presenter/Co-Author), Kansas State University, wkdodds@ksu.edu;


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6/05/2017  |   11:30 - 11:45   |  306A

RELATIONSHIPS BETWEEN INFLOWS, NUTRIENT LOADING, PHYTOPLANKTON AND DISSOLVED OXYGEN IN TWO BAY SYSTEMS OF THE WESTERN GULF OF MEXICO: A NUMERICAL MODELING STUDY A spatiotemporal analyses of relationships between inflows (river discharge), nutrient loading, phytoplankton and dissolved oxygen in San Antonio Bay (SAB) and the Copano and Aransas Bay System (CABS), located in the western Gulf of Mexico was performed using data collected from 1973 to 2014. The tools used for this study included coupled biological and physical numerical models (one for SAB and one for CABS). Statistical analyses of historical data for SAB and CABS were used to guide the structure of the biological modules nested within circulation models. The circulation aspect of the models was guided by TxBLEND, which was tailored to each bay. After development, calibration and validation, sensitivity analyses were performed on the models to determine which parameterizations had the most influence on simulation results. The models were then used in simulation analyses to identify inflow and nutrient loading thresholds where state water quality criteria were not met. As such, the products from this project will be used by state agency staff in the development of nutrient criteria options for SAB and CABS.

Antonietta Quigg (Primary Presenter/Author), Texas A&M, quigga@tamug.edu;


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6/05/2017  |   11:45 - 12:00   |  306A

GLOBAL-SCALE PATTERNS AND DRIVERS OF ORGANIC-MATTER DECOMPOSITION IN STREAMS AND RIPARIAN ZONES Organic-matter decomposition is a central process in streams and riparian ecosystems. However, global-scale patterns of decomposition rates and the environmental drivers of this process are poorly known. We present decomposition data based on the research project titled CELLulose Decomposition EXperiment (CELLDEX). Using a crowdsourcing approach with researchers from over 40 countries, CELLDEX involved the deployment of a highly standardized decomposition assay (based on measurements of cotton-strip tensile strength) in approximately 400 streams and their riparian zones. The locations represent Earth’s major biomes and span 140 degrees of latitude. We observed global-scale decomposition patterns in both streams and riparian zones, including negative relationships with latitude, and stark differences in decomposition rates among biomes. The ratio of in-stream to riparian decomposition rates showed a hump-shaped relationship with latitude, peaking at mid-latitudes. As a complement to these findings, we will estimate the mean global temperature of streams and evaluate whether background variation limits the use of decomposition assays to assess stream condition. Our findings bear relevance that ranges from establishing global baseline data and tracking global change, to providing basic information about ecosystems functioning in some of the least-studied regions of the planet.

Scott Tiegs (Primary Presenter/Author), Oakland University, tiegs@oakland.edu;


David Costello ( Co-Presenter/Co-Author), Kent State University, dcostel3@kent.edu;


David Szlag ( Co-Presenter/Co-Author), Oakland University, szlag@oakland.edu;


Diana Ethaiya ( Co-Presenter/Co-Author), Oakland University, dethaiya@oakland.edu ;


Mark Isken ( Co-Presenter/Co-Author), Dept. of Decision and Information Sciences, School of Business Administration, Oakland University, isken@oakland.edu;


the CELLDEX Consortium ( Co-Presenter/Co-Author), Multiple Institutions, CELLDEX.consortium@gmail.com;


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6/05/2017  |   12:15 - 12:30   |  306A

LITTER QUALITY AND STREAM FOOD WEBS: A NEW PARADIGM FOR UNDERSTANDING ELEMENT CYCLING. Leaf litter quality comprises a suite of chemical and physical traits that influence organic matter cycling through aquatic ecosystems. Differences in litter quality are reflected in decomposition rates with faster decomposing leaves often considered a “higher quality” resource. Decomposition rate, however, provides no information of the pathways of C and N transport from leaves into aquatic food webs. Our experimental findings support a new paradigm for understanding how litter quality affects stream food webs, challenging the view that faster decomposing organic matter is a better food resource. Using labeled leaves (13C and 15N) we demonstrate that leaf types that decompose more slowly (Oak and Sycamore) transfer more of their carbon and nitrogen to insects, whereas faster decomposing leaf types (Broadleaf Cottonwood and Ash) lose significantly more C and N through leaching and microbial processing. Using litter from distinct genotypes of cottonwood trees, we were able to decouple the effects of tannin and lignin on C and N assimilation. Element assimilation correlated positively with lignin concentrations but negatively with tannin concentrations. Across these experiments, the community composition of insects did not differ among leaf types, despite significant differences in biogeochemical pathways.

Jane Marks (Primary Presenter/Author), Northern Arizona University, jane.marks@nau.edu;


Adam Siders ( Co-Presenter/Co-Author), University of Florida, asiders@ufl.edu;


Adam Wymore ( Co-Presenter/Co-Author), University of New Hampshire, adam.wymore@unh.edu;
Dr. Adam Wymore is a Research Assistant Professor at University of New Hampshire.

Zacchaeus Compson ( Co-Presenter/Co-Author), University of North Texas, zacchaeus.compson@unt.edu;


Bruce Hungate ( Co-Presenter/Co-Author), Northern Arizona University, bruce.hungate@nau.edu;


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