5/19/2015  |   10:30 - 10:45   |  101A

OF OLIVES AND CARP: INTERACTIVE EFFECTS OF TWO INVADERS ON LINKED STREAM-RIPARIAN FOOD WEBS Multiple invasive species may interact, influencing one another and generating synergistic effects on food webs and ecosystem processes. We investigated the interaction between two nonnative species widespread in the western USA: common carp and Russian olive (RO), an invasive riparian tree associated with di-nitrogen fixation. Deep Creek, Idaho was an International Biological Program site in the early 1970’s; at that time carp were rare. Subsequently, RO was introduced and now forms a dense stand, increasing allochthonous inputs and benthic organic matter. Since 1971, carp biomass has increased ~8X (an increase our bioenergetic analysis suggests could not have been sustained by pre-RO resources) and ~67% of gut contents presently consist of olives. A small-scale, short-term experimental removal of these subsidized carp caused ~3X increase in chlorophyll-a concentration, suggesting they may limit algae and macrophyte biomass. However, carp that have consumed nitrogen-rich olives excrete ~4X more N compared to those that have not, which may amplify recycling and export from streams invaded by both species. This scenario is characteristic of an ‘invasional meltdown,’ with attendant changes in food webs and ecosystem processes.

Kaleb Heinrich (Primary Presenter/Author), University of Alabama, kheinrich@ua.edu;


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

5/19/2015  |   10:45 - 11:00   |  101A

REMOVAL OF THE INVASIVE SHRUB, LONICERA MAACKII, FROM RIPARIAN FORESTS INFLUENCES HEADWATER STREAM BIOTA AND ECOSYSTEM FUNCTION We investigated the impacts of the invasive riparian shrub Lonicera maackii (Amur honeysuckle) on nutrient dynamics, organic matter subsidies, and the macroinvertebrate community in a headwater stream. Honeysuckle was removed along a 160m stream reach in August 2010. Autumnal, in-stream leaf litter was assessed over 75d, while macroinvertebrate density and algal biomass was measured for three years and a nutrient limitation study was conducted seasonally. Honeysuckle removal significantly reduced canopy cover, light availability, and nitrogen (all P < 0.01) and differentially influenced the timing and abundance of leaf litter genera within the stream. For example, Platanus spp. contributed the most organic matter within the removal reach (35-40%) but was mainly absent in the control reach. Macroinvertebrate density significantly increased one year after invasive removal, and was primarily driven by Simuliium sp. Honeysuckle removal also resulted in in-stream nitrogen limitation (P < 0.05). These findings suggest removal of a dominant invasive shrub substantially impacts terrestrial organic matter and nutrient subsidies into headwater streams, influencing the timing and abundance of leaf litter habitat and food resources for aquatic macroinvertebrates.

Rae McNeish (Primary Presenter/Author), California State University Bakersfield, rae.mcneish@gmail.com;
Dr. McNeish is an early career freshwater ecologist located at California State University, Bakersfield. Her research focuses on terrestrial-aquatic connections and how anthropogenic activities, pollutants, and terrestrial management practices impact freshwater ecosystems. Current research projects are exploring the ecological and biological connections associated with anthropogenic litter and microplastics in the environment while working towards establishing standardized microplastic methodologies.

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;

5/19/2015  |   11:00 - 11:15   |  101A

STREAM ECOSYSTEM RESPONSES TO THE TERRESTRIAL INSECT INVADER, HEMLOCK WOOLLY ADELGID Eastern hemlock dominates ravine and riparian headwater streams throughout central Appalachia and exerts critical influences on stream ecosystems. The invasive insect pest Hemlock Woolly Adelgid (HWA) can cause complete mortality of hemlocks, with unresolved consequences to stream-riparian food webs. At 21 headwater streams of Virginia, West Virginia, and Ohio, we investigated the influence of HWA invasion on water chemistry, benthic and emergent aquatic insects, and riparian spiders of the families Tetragnathidae and Araneidae. A suite of negative relationships between water-chemistry parameters (TDS, total P, PO4, NH4) and hemlock decline appear to underlie shifts in benthic insect abundance, diversity, and the percent of individuals belonging to the EPT orders. Although tetragnathid spider density was positively related to hemlock decline, we found no relationships between emergent insects and hemlock decline. Additional analysis of aquatic insect community composition may further inform these results. While preliminary, our results suggest that hemlock decline due to HWA is associated with in-stream biological and chemical properties, and is likely tied to aquatic-terrestrial energetic fluxes. We expect to enhance these findings using naturally abundant stable isotopes.

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


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

5/19/2015  |   11:15 - 11:30   |  101A

IS BIGGER ALWAYS BETTER? TADPOLES GROW LARGER AND FASTER, BUT WITH LOWER SURVIVAL WHEN RAISED WITH AN INVASIVE PLANT The quantification of the effects of plant invasion on wildlife has shown strong negative, neutral and even positive influences on biota from particular regions, however, an examination of the impact of plant invasion across several regions is lacking. To address whether plant invasion impacts amphibians and what mechanisms may be contributing to potential impacts, we used aquatic mesocosms to raise anuran larvae (Wood Frog, Lithobates sylvaticus) from two regions of the United States with leaf litter from invasive Purple Loosestrife (Lythrum salicaria), native hardwood trees, and a mixture of both. We examined survival, number of days to metamorphosis, and size at metamorphosis and quantified the influence of plant material quality on anuran fitness. Further, we quantified whether the effects of L. salicaria translated to variation in anuran biomass or standing stock of limiting nutrients. Our results show L. salicaria negatively influenced survival of L. sylvaticus, but decreased time to metamorphosis and increased size of metamorphic individuals in two different regions. Post-metamorphic amphibian size was predicted by quality of L. salicaria plant material compared to native hardwood plant material.

Armand Cann (Primary Presenter/Author), Loyola University Chicago, acann@luc.edu;


Kyle Barrett (Co-Presenter/Co-Author), Clemson University, rbarre2@clemson.edu;


John Crawford (Co-Presenter/Co-Author), U.S. Geological Survey, jtcrawford@usgs.gov;

5/19/2015  |   11:30 - 11:45   |  101A

DOES SPECIES MATTER? COMPARING THE EFFECTS OF INTRODUCED AND NATIVE TADPOLES ON AQUATIC ECOSYSTEM FUNCTION Amercian bullfrogs, Rana catesbeiana, are a concern in much of their introduced range because they compete with and eat native species. However, less is known about how bullfrog tadpoles affect aquatic ecosystem function. In the southwest, bullfrogs are introduced and Woodhouse’s toads, Anaxyrus woodhousii, are native. We compared nutrient excretion and egestion, and grazing effects of both tadpole species in the San Pedro River, in Arizona. Then, we conducted a mesocosm experiment to determine how these factors influenced algae biomass, primary production, and dissolved and particulate nutrients. Woodhouse’s tadpoles had higher carbon (C), nitrogen (N), and phosphorus (P) egestion rates, but bullfrog tadpoles excreted and egested at a higher N:P ratio. Woodhouse’s tadpoles decreased algae biomass through grazing. However, bullfrog grazing and nutrient excretion had a positive affect on primary production. Neither species influenced dissolved nutrients, but both decreased particulate C:P and N:P ratios. This research indicates that introduced bullfrog tadpoles may have different ecosystem effects than native toad tadpoles. Since desert streams are often N-limited, bullfrog introduction could potentially alter this limitation and increase primary production.

Robin Greene (Primary Presenter/Author), Arizona State University, rgreeners@gmail.com;

5/19/2015  |   11:45 - 12:00   |  101A

IMPACTS OF NEW ZEALAND MUDSNAILS (POTAMOPYGRUS ANTIPODARUM) ON ECOSYSTEM METABOLISM IN A COLD WATER STREAM IN WISCONSIN, USA. Aquatic invasive species have colonized freshwater ecosystems across North America impacting structure and function of native systems. New Zealand mud snails (Potamopyrgus antipodarum) were recently discovered in Black Earth Creek, Wisconsin. We used publically available data on dissolved oxygen, temperature, discharge and solar radiation to estimate daily rates of gross primary production (GPP) and ecosystem respiration (ER) at three locations over a continuous four year period. As the first year of data was likely before the P. antipodarum invasion and one of the three sites is upstream of the known invasion, we used a before-after control-impact design to evaluate the impacts of P. antipodarum on GPP and ER. After correcting rates of GPP and ER with daily rates from the control site we found no significant change in GPP and a significant increase in ER of approximately 17 and 9 percent per year at each of the impact sites. Although we cannot causally link P. antipodarum to changes in stream metabolism our results indicate that ER increased, relative to a control site, in Black Earth Creek after invasion.

Michael Shupryt (Primary Presenter/Author), WI Department of Natural Resources, Michael.Shupryt@wisconsin.gov;


Maureen Ferry (Co-Presenter/Co-Author), WI Department of Natural Resources, maureen.ferry@wisconsin.gov;