Monday, May 18, 2015
15:30 - 17:00

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15:30 - 15:45: / 103AB COLONIZATION AND SURVIVORSHIP OF SHREDDER TAXA DURING A LONG-TERM ECOSYSTEM-LEVEL LITTER EXCLUSION, WOOD REMOVAL AND LEAF-ADDITION EXPERIMENT

5/18/2015  |   15:30 - 15:45   |  103AB

COLONIZATION AND SURVIVORSHIP OF SHREDDER TAXA DURING A LONG-TERM ECOSYSTEM-LEVEL LITTER EXCLUSION, WOOD REMOVAL AND LEAF-ADDITION EXPERIMENT We follow colonization and survivorship by eight dominant shredder taxa in a southern Appalachian stream through a series of ecosystem-level experiments, including: leaf litter exclusion (3-y), small wood removal (2-y), large wood removal (2-y), PVC addition (1-y), followed by 5-y of leaf additions while maintaining the exclusion canopy throughout the series of experiments. Compared with those of a nearby reference stream, populations of each shredder taxon were drastically reduced during organic matter exclusion and/or wood removal and PVC addition, but Pycnopsyche (Trichoptera: Limnephilidae) exhibited the most pronounced response to initial litter exclusion. Early to mid-size classes were most affected with little evidence of completion of life cycles during organic matter reduction. Survivorship curves were truncated in the organic matter reduction stream. With exception of Molophilus (Diptera: Tipulidae) survivorship curves were clearly Type III. Leaf addition resulted in shredder survivorship curves that were similar to those of the reference stream. Our study underscores the significance of detrital inputs, especially leaf litter as the main food base of headwater streams draining forested catchments.

J. Bruce Wallace (Primary Presenter/Author), Dept. Entomology and Odum School of Ecology, University of Georgia, bwallace@uga.edu;


Sue Eggert (Co-Presenter/Co-Author), USDA Forest Service, Northern Research Station, seggert@fs.fed.us;


Jackson R. Webster (Co-Presenter/Co-Author), Department of Biology, Virginia Tech, Blacksburg, VA, jwebster@VaTech.edu;


Judy L. Meyer (Co-Presenter/Co-Author), Odum School of Ecology, University of Georgia, jlmeyer@gmail.com;


15:45 - 16:00: / 103AB WEAK EFFECTS OF HOME-FIELD ADVANTAGE ON THE AQUATIC DECOMPOSITION AND COLONIZATION OF HIGH-QUALITY LEAF LITTER

5/18/2015  |   15:45 - 16:00   |  103AB

WEAK EFFECTS OF HOME-FIELD ADVANTAGE ON THE AQUATIC DECOMPOSITION AND COLONIZATION OF HIGH-QUALITY LEAF LITTER Terrestrial decomposers are often suggested to process locally derived plant materials more efficiently than foreign ones, thereby accelerating litter decay at their home relative to away region. This ‘home-field advantage’ (HFA) can even exist among streams as close as 5 km apart. HFA effects on decomposition were tested over a broad geographic scale using a reciprocal litter transplant experiment in Canadian headwater streams. Home-region litter collections of speckled alder (Alnus rugosa; Ontario) and red alder (A. rubra; British Columbia) were made, which were absent in the away regions. They were decomposed in both regions with contrasting riparian vegetation (Ontario: deciduous-dominated; British Columbia: coniferous-dominated). Coarse- and fine-mesh packs were used to investigate how HFA interacted with shredder- and microbe-mediated decomposition. Net HFA effects on decomposition were weak and not statistically different from zero (shredder-mediated: 7%; microbe-mediated: -0.7%). Fungal and algal colonization of litter were similar across regions. Nutrient-limited decomposers, particularly microbes, likely responded strongly to foreign high-quality litter, which enhanced the decomposition of A. rugosa in the coniferous-dominated away region. Inter-site differences in nutrient availability and hydrologic regime potentially also obscured HFA effects.

Alex Yeung (Primary Presenter/Author), Department of Forest and Conservation Sciences, University of British Columbia, Canada, yeungcheeyu@gmail.com;


John Richardson (Co-Presenter/Co-Author), Department of Forest and Conservation Sciences, University of British Columbia, john.richardson@ubc.ca;


16:00 - 16:15: / 103AB PATTERNS OF DISSOLVED ORGANIC NITROGEN (DON) PRODUCTION AND CONSUMPTION WITH THE ADDITION OF NITRATE (NO3): INSIGHTS INTO THE CONTROLS ON DON CYCLING

5/18/2015  |   16:00 - 16:15   |  103AB

PATTERNS OF DISSOLVED ORGANIC NITROGEN (DON) PRODUCTION AND CONSUMPTION WITH THE ADDITION OF NITRATE (NO3): INSIGHTS INTO THE CONTROLS ON DON CYCLING Despite decades of research documenting the quantitative significance of dissolved organic nitrogen (DON) in the nitrogen cycle of forests, tundra, and streams, the drivers controlling its production and consumption remain elusive. One hypothesized control on DON in streams is nitrate (NO3) availability; however, the majority of work examining this relationship has been via synoptic surveys which has produced inconsistent spatial and temporal patterns. The objective of this research was to provide direct experimental evidence documenting ways in which NO3 availability controls DON concentrations in streams. Using the framework for solute analysis provided by Tracer Additions for Spiraling Curve Characterization (TASCC), we performed a series of experiments in New Hampshire headwater streams that manipulated NO3 and measured the response of the manipulated solute and ambient DON. Although results indicate that DON is primarily used as a nutrient source in these streams (net DON accumulation with added NO3), strong underlying seasonal patterns are discernible when the data are analyzed at the monthly scale. Evidence overall suggests that DON can be used as both a nutrient source and as an energy source.

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

Bianca Rodriguez-Cardona (Co-Presenter/Co-Author), University of New Hampshire, bianca.rodz.pr@gmail.com;


William H McDowell (Co-Presenter/Co-Author), University of New Hampshire, bill.mcdowell@unh.edu;


16:15 - 16:30: / 103AB STABLE ISOTOPE ANALYSIS OF FOOD AVAILABILITY FOR FRESHWATER MUSSELS IN A REGULATED RIVER

5/18/2015  |   16:15 - 16:30   |  103AB

STABLE ISOTOPE ANALYSIS OF FOOD AVAILABILITY FOR FRESHWATER MUSSELS IN A REGULATED RIVER Dams are often cited as a primary cause of imperilment for freshwater fauna. Although many of the effects of dams on lotic systems are well understood, little is known about their influence on food availability for freshwater mussels. We selected six sites in the Green River, Kentucky: one reference site upstream of Green River Lake and five sites distributed along a 128-km reach downstream of Green River Dam. Mussel foot tissue (N=498) and food resource (N=218) samples were collected June-October, 2012-2013. We used stable isotope mixing models and water chemistry analysis to examine variation in the quality and quantity of benthic and suspended food items. Food resources varied among sites, but did not present a downstream gradient. The Green River Dam limits transport of phytoplankton early in the growing season (June-August); however, surface releases from the reservoir supplement phytoplankton concentrations immediately downstream of the dam in September and October. Within-site analysis showed differences in the assimilation of food items among mussel species. This study will help identify areas with food resources suitable for reintroducing or augmenting mussel populations.

Mieko Camp (Primary Presenter/Author), Tennessee Cooperative Fishery Research Unit, mcamp@tntech.edu;


Jim Layzer (Co-Presenter/Co-Author), Tennessee Technological University, jim_layzer@tntech.edu;


16:30 - 16:45: / 103AB FUNGAL CONTRIBUTIONS TO CARBON FLOW AND NUTRIENT CYCLING DURING STANDING TYPHA LEAF DECOMPOSITION: A TALE FROM TWO CLIMATES

5/18/2015  |   16:30 - 16:45   |  103AB

FUNGAL CONTRIBUTIONS TO CARBON FLOW AND NUTRIENT CYCLING DURING STANDING TYPHA LEAF DECOMPOSITION: A TALE FROM TWO CLIMATES We examined the contribution of fungi to standing leaf decomposition in Typha domingensis and Typha angustifolia in a subtropical and temperate freshwater marsh, respectively. Typha leaves were collected while living and then periodically during senescence and standing-dead decomposition for one year. Fungal biomass and production rates and losses in leaf carbon were quantified and used to construct a partial decay budget estimating carbon flow into fungi. Significant losses in T. domingensis (37%) and T. angustifolia (55%) leaf carbon were observed during litter decomposition along with concomitant increases in fungal biomass, which reached a maximum of 37±4 and 106±7 mgC/g detrital C in T. domingensis and T. angustifolia, respectively. Cumulative fungal production totaled 39 mgC/g initial detrital C in T. domingensis and 123 mgC/g initial detrital C in T. angustifolia, indicating that 11% and 22% of the Typha leaf C was converted into fungal biomass, respectively. Observed differences in the performance and contribution of fungi to Typha decomposition between the subtropical and temperate marsh sites may be reflected in the differing litter quality observed between these two Typha species.

Kevin A. Kuehn (Primary Presenter/Author), University of Southern Mississippi, kevin.kuehn@usm.edu;


Rong Su (Co-Presenter/Co-Author), Department of Biological Sciences, The University of Southern Mississippi, RONG SU ;


Brian Ohsowski (Co-Presenter/Co-Author), Biology Department, Eastern Michigan University, bohsowski@luc.edu;


Steve Francoeur (Co-Presenter/Co-Author), Biology Department, Eastern Michigan University, steve.francoeur@emich.edu;


Scott Phipps (Co-Presenter/Co-Author), Weeks Bay National Estuarine Research Reserve (NERR), scott.phipps@dcnr.alabama.gov;


Robert Neely (Co-Presenter/Co-Author), Provost & Vice President for Academic Affairs, Texas Women’s University., rneely@mail.twu.edu;


16:45 - 17:00: / 103AB INVESTIGATING FINE PARTICLE TRANSPORT AND SUBSTRATE HETEROGENEITY USING THE NOTRE DAME LINKED EXPERIMENTAL ECOSYSTEM FACILITY (ND-LEEF)

5/18/2015  |   16:45 - 17:00   |  103AB

INVESTIGATING FINE PARTICLE TRANSPORT AND SUBSTRATE HETEROGENEITY USING THE NOTRE DAME LINKED EXPERIMENTAL ECOSYSTEM FACILITY (ND-LEEF) Transport and retention of fine particles in streams represents a critical link between upstream to downstream systems, especially in headwaters where particles play a significant role in organic-matter budgets and processing. However, the influence of benthic substrate on particle retention has not been well documented, likely due to inherent heterogeneity of natural systems. To improve understanding, we conducted experimental releases and modeled the impact of benthic substrate heterogeneity and particle size on transport and retention in streams using yeast cells (5um) and corn-pollen (70um). Using the pulse addition technique, we estimated transport distances in four 50m experimental streams (discharge=2L/sec) with varying substrate size (1cm pea-gravel vs. 10cm small cobble) and complexity (homogenous 50/50 mix vs. alternating sections) at ND-LEEF. Transport distances (Sw) ranged from 4-19m for yeast, and 8-41m for pollen under similar flow. Benthic substrate complexity influenced particle retention: particles traveled furthest in cobble, moderate distances in mixed and alternating, and shortest in pea-gravel reaches. Differential retention of particles confirms that the linkage between particulate organic-matter dynamics in flowing waters is not necessarily constant along a spatial continuum.

Arial Shogren (Primary Presenter/Author,Co-Presenter/Co-Author), University of Alabama, ashogren@ua.edu;
Assistant Professor, Department of Biological Sciences, University of Alabama

Jennifer L. Tank (Co-Presenter/Co-Author), University of Notre Dame, tank.1@nd.edu;


Joseph Mueller (Co-Presenter/Co-Author), University of Notre Dame, jmuell10@nd.edu;


Christopher Jerde (Co-Presenter/Co-Author), University of Nevada, cjerde@unr.edu;


Diogo Bolster (Co-Presenter/Co-Author), University of Notre Dame, diogo.bolster.5@nd.edu;


17:00 - 17:15: / 103AB SPATIOTEMPORAL VARIATION IN ECOSYSTEM HETEROTROPHY IN CARBONATE SUBTROPICAL WETLANDS IS DRIVEN BY FLOCCULENT ORGANIC MATTER

5/18/2015  |   17:00 - 17:15   |  103AB

SPATIOTEMPORAL VARIATION IN ECOSYSTEM HETEROTROPHY IN CARBONATE SUBTROPICAL WETLANDS IS DRIVEN BY FLOCCULENT ORGANIC MATTER Variation in carbon (C) quantity and quality drive processes affecting ecosystem trophic state (net autotrophy or heterotrophy). Labile flocculent organic matter (floc) derived from algae and detritus is an abundant C source in carbonate subtropical wetlands, but the spatiotemporal patterns of floc and its effects on ecosystem trophic state are poorly quantified. We estimated net aquatic ecosystem productivity (NAP) during wet and dry seasons from continuous measurements of depth-integrated water column dissolved oxygen (mg O2 m-2 d-1) and floc metabolism (gross primary productivity, GPP; ecosystem respiration, ER; mg O2 g AFDM-1 h-1) in ridge and slough wetlands in the Florida Everglades. Estimates of NAP were modeled from light, temperature, and reaeration (derived from wind speed). Wet-season NAP was 3× greater (-71.0 ± 22.2 > -213.5 ± 103.1) and dry-season NAP was 1.5× greater (-75.7 ± 13.9 > -113.9 ± 60.2) in ridges than sloughs. Temperature-corrected, floc-derived GPP (11.50 ± 0.28, 11.02 ± 0.38) and ER (25.22 ± 0.27, 25.70 ± 0.26) were similar in ridge and slough. Enhanced ecosystem heterotrophy likely occurs through biogeochemical priming with increased dry-season floc densities.

John S. Kominoski (Primary Presenter/Author), Florida International University, jkominoski@gmail.com;


Jim Brock (Co-Presenter/Co-Author), Desert Research Institute, Jim.Brock@dri.edu;


Christopher McVoy (Co-Presenter/Co-Author), Independent Scientist, cmcvoy@gmail.com;