SFS Annual Meeting

5/21/2018  |   09:00 - 09:15   |  420 A

IMPACT OF LOST FLOODS ON FOOD WEBS AND FISH IN A REGULATED RIVER-FLOODPLAIN In river-floodplains, spatial heterogeneity creates and maintains a food web mosaic that sustains fishes across different life stages, but losses of natural fluvial dynamics due to river regulation may potentially alter these processes. During 2015-2016, we investigated how decreased hydrologic connectivity due to regulation affected food webs in a river-floodplain of the Snake River, Idaho, USA, by generating flow food webs and estimating trophic basis of fish production within a range of floodplain habitats. Here, we compare two of these habitats: one springbrook reach scoured by periodic connection to the Snake River and another not scoured since 1997 that possesses deep silt deposits and dense macrophytes. We observed that overall, there is a larger flow of energy through the food web in the connected, scoured reach when compared to the disconnected reach, and the trophic basis of trout production in the connected reach was sustained by a greater proportion of aquatic insects, as opposed to more non-insect taxa in the disconnected reach. The loss of hydrologic connectivity appears to be altering the food web mosaic of the Snake River floodplain, with potential implications for the life histories of fishes.

James Paris (Primary Presenter/Author), Stream Ecology Center, Dept. Biological Sciences, Idaho State University, parijame@isu.edu;


Colden Baxter (Co-Presenter/Co-Author), Idaho State University, baxtcold@isu.edu;


Rachel Brinkley (Co-Presenter/Co-Author), Idaho State University, Brinrach@isu.edu;


Hunter Osborne (Co-Presenter/Co-Author), Resident Fisheries Project, Shoshone-Bannock Tribes Fish and Wildlife Department., hosborne@sbtribes.com;


Zachary Wadsworth (Co-Presenter/Co-Author), Resident Fisheries Project, Shoshone-Bannock Tribes Fish and Wildlife Department., zwadsworth@sbtribes.com;


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5/21/2018  |   09:30 - 09:45   |  420 A

TROPHIC NICHE WIDTH AND DIFFERENTIATION WITHIN UNIONID MUSSEL COMMUNITIES As inhabitants of the sediment-water interface, unionid mussels link benthic and pelagic systems. Through filter feeding, unionids redistribute pelagic nutrients into the benthos, altering benthic nutrient cycles. Currently, North America unionid diversity is in dramatic decline. To understand the impacts of these declines we need to better understand the trophic structure of unionid communities. We investigated trophic niches and potential partitioning in a speciose mussel community using stable isotopes (?13C, ?15N). Further, we determined whether isotopic niche space patterns were consistent among communities, and if variation in gill structure explained these differences. Individuals were collected from 8 sites along the Sipsey River, AL, along with seston and benthic organic matter samples for each site. Gill tissue was also collected from 4 of these sites, and cilia density was determined using scanning electron microscopy. Unionids were found to partition into trophic niches within communities, though there is significant variation between communities. This variation is likely due to fluctuation in seston composition available to communities, suggesting that while unionids form niches they are flexible in these niches depending on food availability.

Brian van Ee (Primary Presenter/Author), University of Alabama, bcvanee@gmail.com;


Carla L. Atkinson (Co-Presenter/Co-Author), University of Alabama, carlalatkinson@gmail.com;


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5/21/2018  |   09:45 - 10:00   |  420 A

BRIDGING GREEN TO BROWN FOOD WEBS: PRODUCTION AND DECOMPOSITION OF DISSOLVED ORGANIC CARBON IN OVERLAPPING CONSUMER HOTSPOTS Transfer of energy and nutrients from green to brown food webs is regulated by consumer activity. Dense aggregations of consumers may alter the abundance and stoichiometry of inorganic nutrients available to green and brown food webs and organic resources available to brown food webs. Overlap of consumer groups with different life histories and tissue element requirements may have further interactive effects on resource dynamics. We sought to understand the direct and indirect effects of overlapping consumer hotspots on the abundance and bioavailability of dissolved organic carbon (DOC). We used a mesocosm experiment crossing three levels of fish (Campostoma anomalum) and mussel (Amblema plicata and Actinonaias ligamentina) biomass and measured DOC and bioavailable DOC (BDOC) concentrations. We found that DOC and BDOC concentration decreased with increasing fish biomass and high mussel biomass. DOC concentration was not affected by nutrients, but BDOC decreased weakly with increasing ammonium concentrations. Both DOC and BDOC increased strongly with algal production. Our results suggest that consumers exerted an indirect top-down control on the abundance of bioavailable DOC produced from green food webs via controls on algal dynamics and to a lesser degree on nutrient availability.

Thomas Parr (Primary Presenter/Author), U.S. National Park Service, thomas.parr@ou.edu;


Caryn Vaughn (Co-Presenter/Co-Author), University of Oklahoma, cvaughn@ou.edu;


Keith Gido (Co-Presenter/Co-Author), Kansas State University, kgido@ksu.edu;


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5/21/2018  |   10:00 - 10:15   |  420 A

EFFECTS OF DROUGHT AND HURRICANE DISTURBANCES ON MACROBRACHIUM DOMINATED FOOD WEBS: RESPONSES TO HIGHLY VARIABLE FLOWS Climatic changes such as the number, intensity, and frequency of extreme events in the Caribbean can affect benthic species assemblages. Impacts on stream food webs are likely to change along elevational gradients as some species become more dominant than others in response to droughts, floods, and hurricanes. Studies of freshwater shrimps (Macrobrachium carcinus, M. crenulatum, M. faustinum, M. heterochirus) indicate changes in patterns of upstream movement by adults. These shifts in locations are responses to major differences in long-term flow regimes from 1997 to 2017. Weekly sampling of headwater pools in the Luquillo Experimental Forest, Puerto Rico, indicate the abundance and dominance of different species are affected by highly variable flows. The most recent disturbances (drought in 2015 and Hurricanes Irma and Maria) created different environmental conditions that affected upstream movement. The potential for major changes in these patterns of species distributions is expected to increase if partial barriers to movement such as organic and inorganic debris dams occur during high wind and high rainfall events. Major disturbances such as droughts, hurricanes, intense rainfall and associated landslides are predicted to increase over the next several decades.

Alan Covich (Primary Presenter/Author), Odum School of Ecology, University of Georgia, a.covich@gmail.com;


Todd Crowl (Co-Presenter/Co-Author), Florida International University, facrowl@gmail.com;


Omar Perez-Reyes (Co-Presenter/Co-Author), University of Puerto Rico- Rio Piedras, macrobrachium@gmail.com;


Pablo Gutiérrez-Fonseca (Co-Presenter/Co-Author), University of Costa Rica, pabloe.gutierrezfonseca@gmail.com;


Sean Kelly (Co-Presenter/Co-Author), University of Puerto Rico-Rio Piedras, spkelly.84@gmail.com;


John Bithorn (Co-Presenter/Co-Author), University of Puerto Rico, fambithorn@yahoo.com;


Samuel Matta (Co-Presenter/Co-Author), University of Puerto Rico, samuelmattapr@yahoo.com ;


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5/21/2018  |   10:15 - 10:30   |  420 A

OVERLAPPING CONSUMER HOTSPOTS: TOP DOWN AND BOTTOM UP INTERACTIONS IN THE GREEN FOOD WEB Mobile fishes and sedentary mussels generate patches of nutrient regeneration (hotspots) in streams that can overlap at low flows when they are concentrated in the same habitat, but are more diffuse at higher flows as fish disperse. We used flow-through mesocosms to examine how the degree of overlap between these consumer groups influences production in the green food web. To simulate variation in consumer overlap with hydrology, we manipulated mussel biomass (2 species, 3 biomass levels) and fish biomass (1 species, three biomass levels) and measured nutrient dynamics, algal biomass and secondary production for 16 weeks. Mussel effects on N availability changed over time, with positive effects in early weeks, and weaker, negative effects later on. In contrast, fish increased N availability throughout the experiment. Both consumer groups increased P availability, but this effect was dampened when they overlapped. Differential effects on nutrient availability led to differences in stoichiometric ratios, with fish increasing water N:P ratios but mussels having no significant effects. Both consumer groups decreased algal biomass when alone, but these effects were weaker when they overlapped, likely due to an interaction of stoichiometric constraints and grazing.

Caryn C. Vaughn (Primary Presenter/Author), University of Oklahoma, cvaughn@ou.edu;


Thomas Parr (Co-Presenter/Co-Author), University of Oklahoma, Thomas.parr@ou.edu;


Traci DuBose (Co-Presenter/Co-Author), University of Oklahoma, tracipopejoy@ou.edu;


Garrett Hopper (Co-Presenter/Co-Author), Kansas State University, ghopper@ksu.edu;


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