Browsing by Author "Griffiths, Natalie A."

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    Drivers of nitrogen transfer in stream food webs across continents
    Norman, Beth C.; Whiles, Matt R.; Collins, Sarah M.; Flecker, Alexander S.; Hamilton, Steve K.; Johnson, Sherri L.; Rosi, Emma J.; Ashkenas, Linda R.; Bowden, William B.; Crenshaw, Chelsea L.; Crowl, Todd; Dodds, Walter K.; Hall, Robert O.; El-Sabaawi, Rana; Griffiths, Natalie A.; Marti, Eugenia; McDowell, William H.; Peterson, Scot D.; Rantala, Heidi M.; Riis, Tenna; Simon, Kevin S.; Tank, Jennifer L.; Thomas, Steven A.; von Schiller, Daniel; Webster, Jackson R. (2017-12)
    Studies of trophic-level material and energy transfers are central to ecology. The use of isotopic tracers has now made it possible to measure trophic transfer efficiencies of important nutrients and to better understand how these materials move through food webs. We analyzed data from thirteen N-15-ammonium tracer addition experiments to quantify N transfer from basal resources to animals in headwater streams with varying physical, chemical, and biological features. N transfer efficiencies from primary uptake compartments (PUCs; heterotrophic microorganisms and primary producers) to primary consumers was lower (mean 11.5%, range <1% to 43%) than N transfer efficiencies from primary consumers to predators (mean 80%, range 5% to >100%). Total N transferred (as a rate) was greater in streams with open compared to closed canopies and overall N transfer efficiency generally followed a similar pattern, although was not statistically significant. We used principal component analysis to condense a suite of site characteristics into two environmental components. Total N uptake rates among trophic levels were best predicted by the component that was correlated with latitude, DIN:SRP, GPP:ER, and percent canopy cover. N transfer efficiency did not respond consistently to environmental variables. Our results suggest that canopy cover influences N movement through stream food webs because light availability and primary production facilitate N transfer to higher trophic levels.
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    Global patterns and drivers of ecosystem functioning in rivers and riparian zones
    Tiegs, Scott D.; Costello, David M.; Isken, Mark W.; Woodward, Guy; McIntyre, Peter B.; Gessner, Mark O.; Chauvet, Eric; Griffiths, Natalie A.; Flecker, Alex S.; Acuna, Vicenc; Albarino, Ricardo; Allen, Daniel C.; Alonso, Cecilia; Andino, Patricio; Arango, Clay; Aroviita, Jukka; Barbosa, Marcus V. M.; Barmuta, Leon A.; Baxter, Colden V.; Bell, Thomas D. C.; Bellinger, Brent; Boyero, Luz; Brown, Lee E.; Bruder, Andreas; Bruesewitz, Denise A.; Burdon, Francis J.; Callisto, Marcos; Canhoto, Cristina; Capps, Krista A.; Castillo, Maria M.; Clapcott, Joanne; Colas, Fanny; Colon-Gaud, Checo; Cornut, Julien; Crespo-Perez, Veronica; Cross, Wyatt F.; Culp, Joseph M.; Danger, Michael; Dangles, Olivier; de Eyto, Elvira; Derry, Alison M.; Diaz Villanueva, Veronica; Douglas, Michael M.; Elosegi, Arturo; Encalada, Andrea C.; Entrekin, Sally A.; Espinosa, Rodrigo; Ethaiya, Diana; Ferreira, Veronica; Ferriol, Carmen; Flanagan, Kyla M.; Fleituch, Tadeusz; Shah, Jennifer J. Follstad; Frainer, Andre; Friberg, Nikolai; Frost, Paul C.; Garcia, Erica A.; Lago, Liliana Garcia; Garcia Soto, Pavel Ernesto; Ghate, Sudeep; Giling, Darren P.; Gilmer, Alan; Goncalves, Jose Francisco, Jr.; Gonzales, Rosario Karina; Graca, Manuel A. S.; Grace, Mike; Grossart, Hans-Peter; Guerold, Francois; Gulis, Vlad; Hepp, Luiz U.; Higgins, Scott; Hishi, Takuo; Huddart, Joseph; Hudson, John; Imberger, Samantha; Iniguez-Armijos, Carlos; Iwata, Tomoya; Janetski, David J.; Jennings, Eleanor; Kirkwood, Andrea E.; Koning, Aaron A.; Kosten, Sarian; Kuehn, Kevin A.; Laudon, Hjalmar; Leavitt, Peter R.; Lemes da Silva, Aurea L.; Leroux, Shawn J.; Leroy, Carri J.; Lisi, Peter J.; MacKenzie, Richard; Marcarelli, Amy M.; Masese, Frank O.; Mckie, Brendan G.; Oliveira Medeiros, Adriana; Meissner, Kristian; Milisa, Marko; Mishra, Shailendra; Miyake, Yo; Moerke, Ashley; Mombrikotb, Shorok; Mooney, Rob; Moulton, Tim; Muotka, Timo; Negishi, Junjiro N.; Neres-Lima, Vinicius; Nieminen, Mika L.; Nimptsch, Jorge; Ondruch, Jakub; Paavola, Riku; Pardo, Isabel; Patrick, Christopher J.; Peeters, Edwin T. H. M.; Pozo, Jesus; Pringle, Catherine; Prussian, Aaron; Quenta, Estefania; Quesada, Antonio; Reid, Brian; Richardson, John S.; Rigosi, Anna; Rincon, Jose; Risnoveanu, Geta; Robinson, Christopher T.; Rodriguez-Gallego, Lorena; Royer, Todd V.; Rusak, James A.; Santamans, Anna C.; Selmeczy, Geza B.; Simiyu, Gelas; Skuja, Agnija; Smykla, Jerzy; Sridhar, Kandikere R.; Sponseller, Ryan; Stoler, Aaron; Swan, Christopher M.; Szlag, David; Teixeira-de Mello, Franco; Tonkin, Jonathan D.; Uusheimo, Sari; Veach, Allison M.; Vilbaste, Sirje; Vought, Lena B. M.; Wang, Chiao-Ping; Webster, Jackson R.; Wilson, Paul B.; Woelfl, Stefan; Xenopoulos, Marguerite A.; Yates, Adam G.; Yoshimura, Chihiro; Yule, Catherine M.; Zhang, Yixin X.; Zwart, Jacob A. (American Association for the Advancement of Science, 2019-01-09)
    River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth’s biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented “next-generation biomonitoring” by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.
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    Global synthesis of the temperature sensitivity of leaf litter breakdown in streams and rivers
    Shah, Jennifer J. Follstad; Kominoski, John S.; Ardon, Marcelo; Dodds, Walter K.; Gessner, Mark O.; Griffiths, Natalie A.; Hawkins, Charles P.; Johnson, Sherri L.; Lecerf, Antoine; Leroy, Carri J.; Manning, David W. P.; Rosemond, Amy D.; Sinsabaugh, Robert L.; Swan, Christopher M.; Webster, Jackson R.; Zeglin, Lydia H. (2017-08)
    Streams and rivers are important conduits of terrestrially derived carbon (C) to atmospheric and marine reservoirs. Leaf litter breakdown rates are expected to increase as water temperatures rise in response to climate change. The magnitude of increase in breakdown rates is uncertain, given differences in litter quality and microbial and detritivore community responses to temperature, factors that can influence the apparent temperature sensitivity of breakdown and the relative proportion of C lost to the atmosphere vs. stored or transported downstream. Here, we synthesized 1025 records of litter breakdown in streams and rivers to quantify its temperature sensitivity, as measured by the activation energy (E-a, in eV). Temperature sensitivity of litter breakdown varied among twelve plant genera for which E-a could be calculated. Higher values of E-a were correlated with lower-quality litter, but these correlations were influenced by a single, N-fixing genus (Alnus). E-a values converged when genera were classified into three breakdown rate categories, potentially due to continual water availability in streams and rivers modulating the influence of leaf chemistry on breakdown. Across all data representing 85 plant genera, the E-a was 0.34 +/- 0.04 eV, or approximately half the value (0.65 eV) predicted by metabolic theory. Our results indicate that average breakdown rates may increase by 5-21% with a 1-4 C rise in water temperature, rather than a 10-45% increase expected, according to metabolic theory. Differential warming of tropical and temperate biomes could result in a similar proportional increase in breakdown rates, despite variation in E-a values for these regions (0.75 +/- 0.13 eV and 0.27 +/- 0.05 eV, respectively). The relative proportions of gaseous C loss and organic matter transport downstream should not change with rising temperature given that E-a values for breakdown mediated by microbes alone and microbes plus detritivores were similar at the global scale.