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SFS Annual Meeting

Wednesday, May 22, 2019
09:00 - 10:30

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09:00 - 09:15: / 253 AB A GLOBAL STUDY OF NUTRIENT CONTROLS ON ORGANIC MATTER PROCESSING

5/22/2019  |   09:00 - 09:15   |  253 AB

A GLOBAL STUDY OF NUTRIENT CONTROLS ON ORGANIC MATTER PROCESSING Organic matter entering streams as senesced plant litter is often of poor nutritional quality, and microbes must assimilate nutrients from the environment to build biomass and use this carbon resource. Large-scale studies of the role of external nutrients on litter decomposition are often confounded by variation in litter chemistry. We deployed cotton strips, a nutrient-poor substrate (C:N = 240, C:P = 4100) consisting almost entirely of cellulose, in more than 500 streams and riparian zones to estimate decomposition rates and related those process rates to nutrient accumulation. Cotton placed in riparian zones rarely assimilated nutrients, and C:N and C:P ratios increased during decomposition. Nutrient content of cotton was a poor predictor of decomposition rates, likely due to the overriding influence of moisture limitation on terrestrial decomposition. However, cotton placed in streams accumulated substantial N and P, which lowered C:N and C:P. Microbially colonized cotton C:N strongly predicted decomposition rates (r2 = 0.78), with the fastest decomposing cotton have C:N <60. These results supports the idea that riparian carbon processing is not nutrient-limited, but in-stream organic matter processing is strongly controlled by available nutrients (especially N).

David Costello (Primary Presenter/Author), Kent State University, dcostel3@kent.edu;


Devan Mathie (Co-Presenter/Co-Author), Kent State University, dmathie20@gmail.com;


Scott Tiegs (Co-Presenter/Co-Author), Dept. of Biological Sciences, Oakland University, tiegs@oakland.edu;


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09:15 - 09:30: / 253 AB WIDESPREAD INTRASPECIFIC VARIATION IN RESPONSE TO PHOSPHORUS LIMITATION IN A NEW ZEALAND SNAIL

5/22/2019  |   09:15 - 09:30   |  253 AB

WIDESPREAD INTRASPECIFIC VARIATION IN RESPONSE TO PHOSPHORUS LIMITATION IN A NEW ZEALAND SNAIL Similar to the variation predicted among species in response to phosphorus (P) limitation, variation within-species should also be widespread because of population differentiation and variation in ploidy level. Differences among populations in response to P limitation is predicted because of local adaptation to varying P availability. Variation among ploidy levels in response to P limitation is predicted because, relative to diploids, polyploids require more dietary P to replicate additional sets of chromosomes. We report population, ploidy, and genetic-level variation in response to phosphorus limitation in a New Zealand freshwater snail (Potamopyrgus antipodarum) that occurs as diploid, triploid, or tetraploid and features significant genetic structure among populations. We show that lakes inhabited by P. antipodarum vary widely in P availability. We also present evidence that variation in P availability among lakes might drive some of the variation in sensitivity to P limitation that we observe in these snails.

Maurine Neiman (Co-Presenter/Co-Author), University of Iowa, maurine-neiman@uiowa.edu;


Amy Krist (Primary Presenter/Author), University of Wyoming, krist@uwyo.edu;


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09:30 - 09:45: / 253 AB EFFECTS OF A DIVERSE SET OF PARASITES ON NUTRIENT RECYCLING BY THEIR HOSTS

5/22/2019  |   09:30 - 09:45   |  253 AB

EFFECTS OF A DIVERSE SET OF PARASITES ON NUTRIENT RECYCLING BY THEIR HOSTS Consumer driven nutrient recycling provides an important flux of inorganic nutrients to primary producers. Parasites are consumers themselves, and can alter nutrient recycling by their consumer hosts. Previous work on the effects of parasites on host nutrient recycling suggest that parasitized hosts excrete nitrogen at greater rates, and that their excretion stoichiometry has a higher N:P than uninfected hosts. We tested the hypothesis that these are general traits of parasitized consumers by measuring the effects of parasites on their host’s excretion rates in four pairs of aquatic host-parasite interactions (baetid-mermithid, heptageniid-mermithid, heptageniid-dipteran, & perlodid-hydrachnidian). Parasite effects on host excretion rates were highly variable and specific to individual host-pathogen pairs. Only the perlodid stonefly showed a parasite-induced change in excretion stoichiometry. The two mayflies parasitized by the mermithid showed parasite-induced changes in N and P excretion rates, but in opposite directions. The dipteran parasite showed no effect on host excretion rates. Stoichiometric mismatch between host and parasite did not predict parasite effects on host excretion. We hypothesize that changes in host metabolism in response to parasitism likely complicate the relationship between host and parasite stoichiometry and consumer driven nutrient recycling.

Brad Taylor (Co-Presenter/Co-Author), North Carolina State University Dept. of Applied Ecology; Rocky Mountain Biological Laboratory, bwtaylo3@ncsu.edu ;


Kara Cromwell (Co-Presenter/Co-Author), University of Wisconsin-Madison, kara.cromwell@gmail.com;


Andrew Sanders (Primary Presenter/Author), North Carolina State University Dept. of Applied Ecology; Rocky Mountain Biological Laboratory, ajsande5@ncsu.edu;


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09:45 - 10:00: / 253 AB NITROGEN FIXATION EFFICIENCY DECREASES WITH BOTH INCREASING N:P STOICHIOMETRIC IMBALANCE AND POPULATION ACCLIMATION TO NITROGEN SUFFICIENT CONDITIONS

5/22/2019  |   09:45 - 10:00   |  253 AB

NITROGEN FIXATION EFFICIENCY DECREASES WITH BOTH INCREASING N:P STOICHIOMETRIC IMBALANCE AND POPULATION ACCLIMATION TO NITROGEN SUFFICIENT CONDITIONS Diazotrophic cyanobacteria differentiate heterocytes to synthesize the enzyme nitrogenase under nitrogen (N) deficient conditions in order to convert atmospheric N2 into bioavailable N for vegetative cell growth. However, the efficiency by which N is acquired via fixation may be affected by the degree to which a population is acclimatized to N deficient conditions and the magnitude of stoichiometric imbalance of resources. In this study, N:P ratios in growth media were altered, and Anabaena flos-aquae which were previously gown under either N-limited or N-sufficient conditions were grown over a period of one month to simulate summer bloom conditions. Experimental blooms were sampled weekly for particulate carbon, N, phosphorus (P), dissolved nutrients, and chlorophyll-a. A. flos-aquae biomass increased proportionally to reactive N in the medium. Thus, N fixation efficiency was increased as the N deficiency relative to P decreased. Also, N fixation efficiency increased with the acclimation to N-limited conditions. This study demonstrates that cyanobacterial blooms relying on fixed N for growth yield far less biomass than blooms occurring under N sufficiency, and are less efficient at producing the cell quota of N when not previously acclimated to N deficient conditions.

Thad Scott (Co-Presenter/Co-Author), Baylor University, Thad_Scott@baylor.edu ;


Felicia Osburn (Primary Presenter/Author), Baylor University, felicia_osburn1@baylor.edu;


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10:00 - 10:15: / 253 AB STOICHIOMETRY OF ALGAL-MEDIATED PRIMING EFFECTS DURING LEAF LITTER DECOMPOSITION: A META-ANALYSIS

5/22/2019  |   10:00 - 10:15   |  253 AB

STOICHIOMETRY OF ALGAL-MEDIATED PRIMING EFFECTS DURING LEAF LITTER DECOMPOSITION: A META-ANALYSIS Periphytic algae exude labile carbon (C) that can strongly alter heterotrophic decomposition of organic matter via priming effects. Though highly variable, the intensity of algal priming may depend on dissolved nitrogen (N) and phosphorus (P) availability, in turn affecting the stoichiometry of nutrient immobilization/mineralization during decomposition. We conducted a meta-analysis of experiments addressing stoichiometric constraints on algal priming intensity and algal effects on standing litter-periphyton C:N:P content and nutrient mineralization during leaf litter decomposition. Across 9 datasets, algal priming intensity varied widely, from algae inducing a 410% decrease to a 104% increase of decomposition rates. Priming intensity was weakly related to inorganic N and P concentrations, but was strongly positively correlated with dissolved N:P (r=0.772, P<0.05). Amid this variation, net algal effects on litter-periphyton C:N, C:P, and N- and P-specific mineralization were weak and highly variable. Despite these inconsistent effects, algae tended to reduce litter-periphyton C:N and increase N mineralization rates with increasing priming intensity associated with higher dissolved N:P (P<0.05). Our findings suggest algal priming effects switch from negative to positive with increasing dissolved N:P, subsequently altering the role of heterotrophic microbes in nutrient mineralization during organic matter decomposition.

Halvor Halvorson (Primary Presenter/Author), University of Southern Mississippi, Halvor.Halvorson@usm.edu;


Kevin Kuehn (Co-Presenter/Co-Author), The University of Southern Mississippi, kevin.kuehn@usm.edu;


Steve Francoeur (Co-Presenter/Co-Author), Biology Department, Eastern Michigan University, steve.francoeur@emich.edu;


Robert Findlay (Co-Presenter/Co-Author), University of Alabama, rfindlay@ua.edu;


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10:15 - 10:30: / 253 AB PATTERNS IN N, P, AND SI STOICHIOMETRY FROM AGRICULTURAL RIVERS IN EAST-CENTRAL ILLINOIS

5/22/2019  |   10:15 - 10:30   |  253 AB

PATTERNS IN N, P, AND SI STOICHIOMETRY FROM AGRICULTURAL RIVERS IN EAST-CENTRAL ILLINOIS Understanding controls on the timing and magnitude of nitrogen (N), phosphorus (P), and silica (Si) concentrations and loads will allow us to better characterize the mechanisms affecting N:P:Si export from agricultural watersheds. The availability of these essential nutrients affects the composition of algal communities, and can influence shifts between diatoms and harmful, cyanobacterial dominance. Using samples collected weekly for 17 years (2000-2017) from two rivers in east-central Illinois, we calculated N:Si and P:Si molar ratios for each sample, as well as interpolated daily loads using the R package, Loadflex. These values exhibited a relationship with discharge, indicating strong hydrologic control on the stoichiometry of nutrient export. N:Si ratios were consistently above the Redfield ratio for diatoms (16N:20Si) during periods of higher flow through the winter and spring, but fluctuated above and below the ratio during low flow periods in the summer. P:Si fluctuated above and below the Redfield ratio (1P:20Si) throughout the year, and specific high flow events corresponded with peaks in P:Si. These results revealed important stoichiometric patterns and have implications for predicting water quality and cyanobacteria occurrence in the agricultural Midwest and other human-dominated landscapes.

Todd V. Royer (Co-Presenter/Co-Author), Indiana University Bloomington, troyer@indiana.edu;


Lienne Sethna (Primary Presenter/Author), Indiana University, lsethna@iu.edu;


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