SFS Annual Meeting

5/21/2018  |   11:00 - 11:15   |  420 A

THE EFFECTS OF OVERLAPPING CONSUMER AGGREGATIONS ON THE DECOMPOSITION OF LEAF LITTER. Consumer driven nutrient recycling is a critical process in freshwater ecosystems. Global declines in consumer biodiversity highlight the importance of understanding the unique contributions of consumers to ecosystem processes. Dense aggregations of consumers like fish or mussels excrete nutrients which can have bottom up effects on ecosystem functions by increasing the availability of nutrients and/or altering their stoichiometry. However, interactive effects may occur when consumer groups are stoichiometrically distinct. We used leaf litter decomposition as a model ecosystem process to test whether these overlapping consumer hotspots, via altered nutrient availability, exerted priming effects on decomposition rates. Over six weeks, in 45 stream mesocosms spanning a range of fish and mussel biomasses, we measured water column nutrient levels and the mass loss of a common stream macrophyte (Justicia americana) from 1.25 mm mesh bags. Preliminary results indicate a non-significant decrease in decomposition rate in treatments with single consumer groups and a statistically significant increase in decomposition rate when both fish and mussels were present. These results suggest consumer community overlap may have indirect effects on the decomposition of organic matter.

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


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


Matthew BrabbleRose (Primary Presenter/Author), Oklahoma Biological Survey, North Carolina Wesleyan College, rose.caleb96@gmail.com;


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5/21/2018  |   11:15 - 11:30   |  420 A

ISOSCAPES REVEAL CRITICAL SOURCE AREAS SUSTAINING FLOODPLAIN RIVER FISH ASSEMBLAGES IN NORTHERN AUSTRALIA Many animal populations are controlled by fluxes of energy and nutrients from outside of the habitats they occupy. However, the strength of these subsidies can vary as a consequence of fluctuations in food abundance or the ability of mobile consumers to track food resources. We used sulfur and carbon isotopes to map foraging isoscapes for aquatic consumers across two adjacent floodplain rivers in tropical northern Australia, and modelled the likelihood that a consumer derived its biomass from the location it was sampled or from elsewhere. Small bodied fish species showed a close association with local food resources, in both wet and dry seasons. However, larger mobile species appeared to be dependent on access to specific locations within inundated floodplains for much of their somatic growth. These tended to be deeper areas that retain open water and submerged macrophytes, which support high epiphyte growth. Changes to flow regimes that diminish the depth or duration of inundation of these ‘hotspots’ of high quality food resources, or the presence of barriers that restrict access of mobile consumers to them, are likely to significantly reduce this important floodplain subsidy to river food webs.

Stuart Bunn (Primary Presenter/Author), Australian Rivers Institute, Griffith University, Australia, s.bunn@griffith.edu.au;


Fernanda Adame (Co-Presenter/Co-Author), Australian Rivers Institute, Griffith University, f.adame@griffith.edu.au;


Ben Stewart-Koster (Co-Presenter/Co-Author), Australian Rivers Institute, Griffith University, b.stewart-koster@griffith.edu.au;


Douglas Ward (Co-Presenter/Co-Author), Australian Rivers Institute Griffith University, doug.ward@griffith.edu.au;


David Crook (Co-Presenter/Co-Author), La Trobe University, David.Crook@latrobe.edu.au;


Tim Jardine (Co-Presenter/Co-Author), University of Saskatchewan, tim.jardine@usask.ca;


Francisco Villamarin (Co-Presenter/Co-Author), Universidad Regional Amazónica, francisco.villamarin@ikiam.edu.ec;


Dominic Valdez (Co-Presenter/Co-Author), Australian Rivers Institute, Griffith University, dgvaldez@yahoo.com;


Michael Douglas (Co-Presenter/Co-Author), University of Western Australia & Charles Darwin University, michael.douglas@uwa.edu.au;


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5/21/2018  |   11:30 - 11:45   |  420 A

WINTER BASEFLOW CRITIAL FOR STREAM FOOD WEB PRODUCTIVITY IN APLINE STREAMS Stream basal resource availability, both autochthonous (i.e., within-system; e.g., biofilm) and allochthonous (i.e., external; e.g., coarse benthic organic matter [CBOM]), depends on catchment and stream characteristics (e.g., terrestrial vegetation, hydrological regime) and likely determines food web structure and function. We studied biofilm, CBOM, and macroinvertebrates in three catchments with differing degrees of glacial runoff, and thus hydrological regime, and vegetation cover (alpine prairie to subalpine forest). Biofilm chlorophyll-a (chla) was highest in winter months (Dec-Apr; monthly mean 0.54-1.38 mg/m²) with a secondary peak in September for snowmelt-dominated streams (1.87 mg/m²) while other streams and months had generally low chla (mean <0.32 mg/m²). CBOM was higher in the snowmelt-dominated streams compared to the glacial-fed streams (mean 8.6 vs 4.0 g/m²) without seasonal patterns. Macroinvertebrates consisted mainly of Diptera, Plecoptera and Ephemeroptera with compositions shifting with season and dependent on stream. For example, Baetidae were abundant Mai-July in all streams while high densities of very small Plecoptera coincided with the high chla found in September in snowmelt-dominated streams. Results suggest that hydrological regime drives patterns in food webs with the winter baseflow representing a critical period of high productivity in Alpine streams.

Janine Rüegg (Primary Presenter/Author), University of Lausanne, janine.ruegg@unil.ch;


Tom Battin (Co-Presenter/Co-Author), Ecole Polytechnique Fédérale de Lausanne, tom.battin@epfl.ch;


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5/21/2018  |   11:45 - 12:00   |  420 A

SEASONAL TOP DOWN EFFECTS OF FISH ON BENTHIC MACROINVERTEBRATES AND PERIPHYON IN A COLDWATER MICHIGAN STREAM We conducted a manipulative field experiment to test the seasonal strength of fish predation on benthic macroinvertebrates and periphyton at the patch scale. We hypothesized that excluding predators will increase prey density and the predation effect will be weaker in winter due to decreased metabolic rates of predators. We placed paired exclosure and open-control cages in a 250-m stream reach (n=12 pairs) during late-summer 2015 and winter 2016 for 32 and 31 days, respectively. Periphyton density (chlorophyll-a) from three cobbles in each cage was significantly lower in exclosures than open controls for the late-summer trial. Periphyton density in the winter trial was not significantly different between exclosures and open controls. The most common families in the late-summer trial were Gammaridae, Hydropsychidae, Brachycentridae, Baetidae, and Elmidae (78% of invertebrates); a predation effect was observed in Brachycentridae and Elmidae. The most common families in the winter trial were Gammaridae, Hydropsychidae, Nemouridae, Baetidae, and Ephemerellidae (79% of invertebrates); a predation effect was observed in Hydropsychidae and Nemouridae. Thus, there was evidence of weak top-down control by fishes in the study stream during both seasons.

Carl R. Ruetz III (Co-Presenter/Co-Author), Annis Water Resources Institute, Grand Valley State University, ruetzc@gvsu.edu;


Steven L. Kohler (Co-Presenter/Co-Author), Western Michigan University, steve.kohler@wmich.edu;


Travis J. Ellens (Primary Presenter/Author), Grand Valley State University, ellentra@gvsu.edu;


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5/21/2018  |   12:00 - 12:15   |  420 A

ESTIMATING QUALITATIVE FOOD WEB STRUCTURE FROM BIOMONITORING AND LITERATURE-BASED DIET DATA TO DETECT CHANGES IN ECOSYSTEM FUNCTION Ecosystem function is an increasingly important component in bioassessment but many types of function are too intensive to be incorporated into routine biomonitoring schemes. Using food webs to assess interspecific interactions or community stability requires large samples for extensive gut analysis or processing using molecular techniques. Estimating food webs using a combination of direct sampling and literature data may work as a feasible alternative. This approach was attempted using seasonal invertebrate biomonitoring data collected from six sites on the Ogeechee River with jab nets. For each sample a 200 (±20%) invertebrate subsample was taken and identified to lowest feasible taxonomic level, generally genus. Samples demonstrated considerable variability in community structure by site and season, with lower species richness and evenness in the spring. Taxon specific feeding interactions were identified from the literature and used to construct qualitative sample food webs. Food webs were then assessed for differences in structural properties such as number of links, linkage density, prey-predator ratios, mean food chain length and connectance. Changes in these properties may affect the resilience of communities to human impacts and may therefore be important for biomonitoring and management.

Julien Buchbinder (Primary Presenter/Author), Georgia Southern University, jb19126@georgiasouthern.edu;


Checo Colón-Gaud (Co-Presenter/Co-Author), Georgia Southern University, jccolongaud@georgiasouthern.edu;


Stephen Vives (Co-Presenter/Co-Author), Georgia Southern University, svives@georgiasouthern.edu;


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5/21/2018  |   12:15 - 12:30   |  420 A

EFFECTS OF FISHES ON AQUATIC INSECTS IN LINKED AQUATIC-TERRESTRIAL FOOD WEBS Aquatic insects are important sources of energy for freshwater fishes and important sources of energy in linked aquatic-terrestrial food webs. The consumption of aquatic insects by fishes reduces the energy available to aquatic and terrestrial food webs. Our research predicted that fishes alter local food webs and affect ecosystem productivity. Emergence traps and fish exclusion cages were used to collect emergers from treatments with and without fish to determine the reduction of emergance by fishes to terrestrial ecosystems. Fish and benthic communities were sampled and recorded, fish diets were sampled, and terrestrial insectivorous spider abundances were recorded. Data suggests that fish sampled were primarily water column feeding fish and that the stage of aquatic insects consumed varied across species. Fish exclusion cages yielded higher emergent insect biomass above the former beaver dam, and that the terrestrial spider densities were higher above cages without fish. Our results will help to determine the direct and indirect effects of fishes on ecosystems, allow for the testing of new theory in ecology about the role of size-structured prey, and frame the potential role of fish species loss or introduction in linked aquatic-terrestrial food webs.

Jeff Wesner (Co-Presenter/Co-Author), University of South Dakota, Jeff.Wesner@usd.edu;


Tyler Seidel (Primary Presenter/Author), University of Minnesota, t.seidel983@gmail.com;


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