SFS Annual Meeting

5/22/2018  |   11:00 - 11:15   |  321

ECOLOGICAL AND EVOLUTIONARY RESPONSES OF ZOOPLANKTON TO EXTREME EUTROPHICATION Extreme eutrophication of waterbodies has challenged our theoretical understanding of how ecosystems function. We studied zooplankton over a gradient of eutrophication in Iowa lakes to examine how and why stoichiometric theory fails to predict dynamics in these systems. Using data from 130 lakes across Iowa from 2009-2015, we found that zooplankton communities were functionally different between N- and P-limited lakes. Consistent with stoichiometric nutrient recycling theory, N-rich taxa dominated in N-limited lake-years. Surprisingly, however, P-rich Daphnia did not vary in biomass between N- and P-limited lake-years. We thus examined intraspecific variation in Daphnia among a subset of these lakes to test whether intraspecific responses reduce the functional impacts of zooplankton in hypereutrophic systems. Daphnia growth is thought to peak under a narrow range of total phosphorus (TP) concentrations (i.e., the knife-edge hypothesis), but the predictions of this hypothesis were not supported in Iowa lakes. Instead, we found that genetic differences in growth and fecundity reaction norms between Daphnia clones from mesotrophic and hypereutrophic lakes support the lack of a stoichiometric knife-edge. We suggest that both ecological and evolutionary responses are important components of how ecosystems respond to eutrophication.

Eric Moody (Primary Presenter/Author), Middlebury College, erickmoody@gmail.com;


Grace Wilkinson (Co-Presenter/Co-Author), University of Wisconsin-Madison, wilkinso@iastate.edu;


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5/22/2018  |   11:15 - 11:30   |  321

VARIATION IN PHOSPHORUS USE AMONG RECOMBINANT DAPHNIA GENOTYPES Resurrecting diapausing (resting) eggs of the aquatic keystone herbivore, Daphnia, preserved in lake sediments for centuries has revealed striking shifts in nutrient use physiology that are correlated with nutrient enrichment (i.e., cultural eutrophication). As such, this system allows us to address key issues in ecological genomics with a unique temporal approach that is not possible with more common space-for-time substitutions (i.e., comparing populations to infer evolutionary trajectories). Previous work illuminated transcriptome-wide variation underlying such major changes in phosphorus kinetics between ancient and modern genotypes. Here, we use quantitative trait loci (QTL) mapping to identify genomic regions underlying P-use. An F2 mapping population has been constructed by crossing a ~5-yr-old (dam) clone with a ~50-yr-old (sire) clone that differ in P-use. F2 genotypes exhibit substantial physiological variation in P-use. These genotypes have been sequenced to identify loci underlying differences in P-use. By identifying sections of the genome that enable Daphnia to be P sinks in lakes we should be able to generate predictions about the evolution of Daphnia populations in response to eutrophication, and concomitant changes in the key ecological functions they perform.

Ryan Sherman (Primary Presenter/Author), Oklahoma State University, ryan.sherman@okstate.edu;


Brian Couger (Co-Presenter/Co-Author), Oklahoma State University, mcouger@okstate.edu;


Ashok Ragavendran (Co-Presenter/Co-Author), Brown University, ashok_ragavendran@brown.edu ;


Lawrence Weider (Co-Presenter/Co-Author), University of Oklahoma, ljweider@ou.edu;


Puni Jeyasingh (Co-Presenter/Co-Author), Oklahoma State University, puni.jeyasingh@okstate.edu;


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5/22/2018  |   11:30 - 11:45   |  321

STOICHIOMETRIC NICHES IN A SPECIES-RICH COMMUNITY The elemental composition of living organisms is known to shape their ecology and influence the structure and functioning of ecological systems. Here we examined the biogeochemical niches of multiple unionid mussel species that co-occur in species-rich and dense communities. We sampled mussel abundance and the tissue nutrient content (C, N, P) of six mussel species across six sites in the Sipsey River, Alabama. We described each species’ multidimensional stoichiometric niche by calculating the: 1) stoichiometric niche volume; 2) stoichiometric niche overlap and nestedness; 3) stoichiometric niche shape. Further, we examined the relationship between tissue and excretion stoichiometric ratios (N:P). Overall, our results suggest that there are phylogenetic signatures in biogeochemical niches and there is some partitioning of elemental needs within this species-rich community. Most notably, Lampsilini species tended to occupy a larger biogeochemical niche volume, but clustered in a different space than species from other phylogenetic tribes. This variation leads to species-specific differences in nutrient excretion stoichiometry, but not differences in egesta stoichiometry. In the future, we plan to examine other functional traits in these organisms to fully understand niche partitioning and the ecological functions provided by species-rich communities.

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


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


Monica M. Winebarger (Co-Presenter/Co-Author), University of Alabama, mmwinebarger@crimson.ua.edu;


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5/22/2018  |   11:45 - 12:00   |  321

ENGINEERED NANOPARTICLES INCREASE EXCRETION RATES OF NITROGEN AND PHOSPHORUS BY FRESHWATER SNAILS IN WETLAND MESOCOSMS Wetlands are exposed to engineered nanoparticles through discharge from wastewater and agricultural runoff. We conducted an experiment to examine the combined effects of chronic dosing of nanoparticles and nutrients on wetland food webs. Three levels of nanoparticles (control, gold, copper) were crossed by two levels of nutrients (ambient vs. chronic nutrient dosing) in 18 outdoor wetland mesocosms. We measured the rate of excretion of nitrogen (N) and phosphorus (P) in freshwater snails after six months exposure to chronic nanoparticle and nutrient dosing. Ten Physella acuta snails were collected from each mesocosm. Individual snails were placed into tubes containing filtered, control mesocosm water. Snails were incubated for 95 ± 0.5 minutes (mean ± SE). Mass-specific, time-corrected N and P excretion rates were calculated as the change in concentration per unit time divided by snail dry mass. Excretion of N and P was significantly higher in all nutrient-dosed mesocosms than ambient nutrient controls. However, under ambient nutrient levels, gold and copper nanoparticle treatments each significantly increased snail N and P excretion. These results imply that nanoparticles may interfere with snail digestion and nutrient assimilation, particularly under low nutrient conditions.

Brittany Perrotta (Primary Presenter/Author), Baylor University, bperrotta16@gmail.com;


Marie Simonin (Co-Presenter/Co-Author), Duke University, simonin.marie@gmail.com;


Cole Matson (Co-Presenter/Co-Author), Baylor University, Cole_Matson@baylor.edu;


Emily Bernhardt (Co-Presenter/Co-Author), Duke University, ebernhar@duke.edu;


Ryan S. King (Co-Presenter/Co-Author), Baylor University, Ryan_S_King@baylor.edu;


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