Wednesday, May 25, 2016
13:30 - 15:00

<< Back to Schedule

13:30 - 13:45: / 309-310 ECOLOGICAL SUBSIDIES FROM AN OUTBREAK INSECT CAN AFFECT HEADWATER CONIFEROUS STREAM ECOSYSTEMS

5/25/2016  |   13:30 - 13:45   |  309-310

ECOLOGICAL SUBSIDIES FROM AN OUTBREAK INSECT CAN AFFECT HEADWATER CONIFEROUS STREAM ECOSYSTEMS Western spruce budworms defoliate riparian zone conifers of Pacific Northwest headwater streams. Budworm outbreaks could stimulate heterotrophy in stream ecosystems by enhancing the quantity/quality of organic matter inputs or stimulate autotrophy by increasing light availability and/or nutrient concentrations. We deployed nutrient diffusing substrates in streams unaffected by budworms to assess heterotrophic and autotrophic nutrient limitation, quantify sensitivity to nutrient inputs at varying concentrations, and measure the response to experimental light reduction. Autotrophic production was mostly limited by nitrogen whereas respiration and algal biomass were mostly co-limited by nitrogen and phosphorus. Nutrient amendments at 0.05, 0.1, and 0.5 M produced the same response, suggesting that even low nutrient enrichment from herbivory could stimulate food web activity. Experimental light reduction decreased primary production and stimulated respiration indicating that riparian canopy opening could alter the relative contribution of autotrophy and heterotrophy to food web productivity. Together, these results confirm that coniferous headwater streams in the Pacific Northwest are sensitive to ecological subsidies of an outbreak insect whose activity is expected to increase as a result of climate change.

Clay Arango (Primary Presenter/Author), Central Washington University, arangoc@cwu.edu;


Sally Entrekin ( Co-Presenter/Co-Author), Virginia Tech, sallye@vt.edu;


Jennifer Lipton ( Co-Presenter/Co-Author), Central Washington University, liptonj@cwu.edu;


Presentation:
This presentation has not yet been uploaded.

13:45 - 14:00: / 309-310 ECOLOGICAL LINKAGES BETWEEN STREAMS AND THEIR ADJACENT RIPARIAN ZONES FOLLOWING HEMLOCK WOOLLY ADELGID INVASION

5/25/2016  |   13:45 - 14:00   |  309-310

ECOLOGICAL LINKAGES BETWEEN STREAMS AND THEIR ADJACENT RIPARIAN ZONES FOLLOWING HEMLOCK WOOLLY ADELGID INVASION Reciprocal stream-riparian nutritional subsidies are important to the function of both aquatic and terrestrial ecosystems. In the central Appalachian Mountains, the invasive insect Hemlock Woolly Adelgid (HWA) has severely altered the riparian zones of headwater ravines through its effect on the Eastern hemlock, a foundation tree species in the region. We investigated the associations between stream-riparian subsidy exchanges at 21 headwater streams in Virginia, West Virginia, and Ohio representing a range of HWA invasion histories. Hemlock decline following HWA invasion was negatively associated with the biomass of terrestrial plant material entering streams, and was also related to shifts in the community composition of terrestrial invertebrate inputs. These and other differences in the magnitude and composition of cross-boundary subsidies reflect important food-web shifts. For example, we observed that riparian orb-weaving spider density was related to hemlock decline, likely due to alterations in both near shore habitat structure and emerging insect communities. Thus, initial results indicate that the consequences of a terrestrial invader on stream ecosystems can be significant.

Kristen M. Diesburg (Primary Presenter/Author), The Ohio State University, diesburg.1@osu.edu;


S. Mažeika P. Sullivan ( Co-Presenter/Co-Author), The Ohio State University, sullivan.191@osu.edu;


Presentation:
This presentation has not yet been uploaded.

14:00 - 14:15: / 309-310 SPATIAL HETEROGENEITY IN STREAM TEMPERATURE PROLONGS AQUATIC-TO-TERRESTRIAL SUBSIDY ENHANCING SPIDER GROWTH

5/25/2016  |   14:00 - 14:15   |  309-310

SPATIAL HETEROGENEITY IN STREAM TEMPERATURE PROLONGS AQUATIC-TO-TERRESTRIAL SUBSIDY ENHANCING SPIDER GROWTH The duration of resource subsidies can affect their impacts on recipient consumers. Spatial heterogeneity in stream water temperature was found to desynchronize the emergence timing of mayfly Ephemerella maculata, and prolong their flight period, altering consumer responses. While E.maculata emergence lasted for two weeks in each site, mayflies emerged two weeks earlier from warmer sites than cooler sites. Therefore, the overall emergence of E.maculata from the river lasted for four weeks, and adult female swarms were observed for the same period in an adjacent reproductive habitat. A spider feeding experiment that manipulated the temporal duration of the same total amount of subsidy, simulating the mayfly subsidy from rivers with different degree of spatial heterogeneity, showed synchronous pulsed subsidy from homogeneous river would decrease the growth of juvenile spiders. Loss of habitat heterogeneity can shorten durations of cross landscape subsidies by synchronizing phenology of mobile preys, and degrade predator populations at ecotones.

Hiromi Uno (Primary Presenter/Author), University of California Berkeley, hiromiuno1@berkeley.edu;


Presentation:
This presentation has not yet been uploaded.

14:15 - 14:30: / 309-310 SEASONAL VARIABILITY OF AQUATIC-TERRESTRIAL FOOD-WEB LINKAGES IN A SUBTROPICAL ESTUARINE SYSTEM

5/25/2016  |   14:15 - 14:30   |  309-310

SEASONAL VARIABILITY OF AQUATIC-TERRESTRIAL FOOD-WEB LINKAGES IN A SUBTROPICAL ESTUARINE SYSTEM Although reciprocal ecological linkages between freshwater systems and their adjacent riparian zones have received significant attention, cross-boundary subsidies in estuarine systems remain less studied. We conducted surveys of riparian orb-weaving spiders (Tetragnathidae, Araeanidae, Nephilidae) – known to respond to emerging aquatic insect availability in freshwater systems – at eight sites representing a gradient of salinity along a cypress-marsh-mangrove ecotone in southwest Florida. Across all study sites, salinity ranged from 13.8 to 33.4 ppt during the summer-wet season and 0.23 to 25.9 ppt during the winter-dry season. Spider assemblages, dominated by Tetragnathidae, generally exhibited higher densities during the dry season. However, spider density was highest in the mesohaline mangrove creek sites during the wet (37.1 ± 11.4 orbs) and dry (192.5 ± 79.2) seasons compared to cypress swamps (20.3 ± 10.5, dry) and euhaline mangrove river sites (6.9 ± 3.6, wet; 19.4 ± 12.2, dry). We anticipate that current analysis of emerging aquatic insects and other food-web variables (e.g., insectivorous fish) will shed light on potential mechanisms driving the observed patterns in spiders.

Martha J. Zapata (Primary Presenter/Author), The Ohio State University, zapata.22@osu.edu;


S. Mažeika P. Sullivan ( Co-Presenter/Co-Author), The Ohio State University, sullivan.191@osu.edu;


Presentation:
This presentation has not yet been uploaded.

14:30 - 14:45: / 309-310 TERRESTRIAL-AQUATIC CONNECTIONS: A RIPARIAN INVASIVE SHRUB ALTERS ECOSYSTEM SUBSIDIES AND AQUATIC FUNCTIONAL DIVERSITY

5/25/2016  |   14:30 - 14:45   |  309-310

TERRESTRIAL-AQUATIC CONNECTIONS: A RIPARIAN INVASIVE SHRUB ALTERS ECOSYSTEM SUBSIDIES AND AQUATIC FUNCTIONAL DIVERSITY We investigated the impacts of the invasive riparian shrub Lonicera maackii (Amur honeysuckle) on organic matter subsidies and macroinvertebrate community structure in a headwater stream. Invasive honeysuckle was removed along a 160m stream reach in August 2010. Autumnal, in-stream leaf litter was assessed over 75d, while macroinvertebrate community taxonomic and functional trait dynamics were measured over three years. Honeysuckle removal significantly reduced canopy cover, increased light availability, and differentially influenced the timing and abundance of leaf litter genera within the stream (P < 0.01). The honeysuckle riparian forest was associated with decreased aquatic macroinvertebrate density and species richness and resulted in a different macroinvertebrate community that was taxonomically and functionally unique compared to the honeysuckle removal reach (P < 0.05). The removal reach also supported a greater macroinvertebrate functional trait richness during winter and spring seasons in comparison to the honeysuckle reach (P < 0.05). These findings suggest riparian invasive shrubs can substantially impacts terrestrial subsidies entering headwater streams, influencing the timing and abundance of leaf litter habitat and food resources that support aquatic macroinvertebrate communities.

Rae McNeish (POC,Primary Presenter), California State University Bakersfield, rae.mcneish@gmail.com;


M. Eric Benbow ( Co-Presenter/Co-Author), Michigan State University, benbow@msu.edu;


Ryan W. McEwan ( Co-Presenter/Co-Author), University of Dayton, rmcewan1@udayton.edu;


Presentation:
This presentation has not yet been uploaded.

14:45 - 15:00: / 309-310 COMPLEX INTERACTIONS AMONG PHENOLOGY, COMPOSITION, RETENTION AND TEMPERATURES AFFECTING INCORPORATION OF CROSS-ECOSYSTEM RESOURCE SUBSIDIES TO STREAMS

5/25/2016  |   14:45 - 15:00   |  309-310

COMPLEX INTERACTIONS AMONG PHENOLOGY, COMPOSITION, RETENTION AND TEMPERATURES AFFECTING INCORPORATION OF CROSS-ECOSYSTEM RESOURCE SUBSIDIES TO STREAMS Input rates of cross-ecosystem resource subsidies are important, but other processes and structures interact with inputs to determine the consequences for the recipient system. In recent studies, my group and I have demonstrated the interactions of inputs with other processes, such as the phenology of inputs, quality (size and type), and retention of subsidy resources. Temperature and nutrient regimes also influence the rates of incorporation of subsidies to recipient consumers. The nature and magnitude of recipient population responses across a range of subsidies may depend on whether consumers can show numerical responses or functional responses or aggregative (within generation). It is essential to note that most studies have been binary, i.e. either addition or removal of one level of a resource subsidy, however, the shape of the response curve may be asymptotic across a range of subsidy inputs, or even hump-shaped as other resources become co-limiting or subsidies at high input rates become stressors. We need to develop more quantitative hypotheses about how the dynamics of the recipient or donor system affect the response to subsidy inputs.

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


Presentation:
This presentation has not yet been uploaded.