SFS Annual Meeting

Caleb J. Robbins (Primary Presenter/Author)
University of Alaska Fairbanks, Caleb_Robbins@baylor.edu;

Halvor Halvorson (Co-Presenter/Co-Author)
University of Central Arkansas, hhalvorson@uca.edu;

David Manning (Co-Presenter/Co-Author)
University of Nebraska at Omaha, davidmanning@unomaha.edu;

Elliot Bastias (Co-Presenter/Co-Author)
Unaffiliated, ebastias222@gmail.com;

Cristiane Biasi (Co-Presenter/Co-Author)
Universidade Regional Integrada do Alto Uruguai e das Missões, Campus de Erechim, cristiane.biasi@gmail.com;

Allyn Dodd (Co-Presenter/Co-Author)
Lyon College, allyn.dodd@lyon.edu;

Rebecca Eckert (Co-Presenter/Co-Author)
University of Maryland, reckert@umd.edu;

Alice Gossiaux (Co-Presenter/Co-Author)
LIEC, Université de Lorraine, CNRS, France, alice.gossiaux@univ-lorraine.fr;

Jérémy Jabiol (Co-Presenter/Co-Author)
LIEC, Université de Lorraine, CNRS, France, jeremy.jabiol@univ-lorraine.fr;

Andrew S. Mehring (Co-Presenter/Co-Author)
University of Louisville, andrew.mehring@louisville.edu;

Beth Norman (Co-Presenter/Co-Author)
Lacawac Sanctuary and Biological Field Station, beth.norman@lacawac.org;

Ada Pastor (Co-Presenter/Co-Author)
Aarhus University, adapastor@bio.au.dk;

Abstract: Necromass is a central component of all ecosystems; decomposition recycles elements via microbial and detritivorous pathways. In comparison to terrestrial ecologists, aquatic ecologists have strongly focused on decomposition in terms of mass loss rather than elemental flows, potentially impeding development of aquatic ecosystem theories in its most general terms, and hindering unification of decomposition theory across ecosystem boundaries. However, changes in nutrient content are frequently measured throughout aquatic decomposition. We leveraged this common measurement by synthesizing published measurements of nutrient content (nitrogen (N), phosphorus (P), and carbon:nutrient ratios) in coarse necromass (e.g., leaf litter) to analyze trends and drivers of detrital nutrient content throughout the decomposition process. Results suggest temporal nutrient content trajectories are partially determined by initial nutrient content, with important differences between N and P. We will discuss implications of these patterns and drivers for consumers and ecosystem function, methodological constraints and structure of our dataset, and future directions for freshwater decomposition ecology and its unification with terrestrial theories.

Jordyn Stoll (Primary Presenter/Author)
Kent State University, jstoll7@kent.edu;

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

Abstract: The macronutrients nitrogen and phosphorus are necessary for stream biofilm metabolism and growth, and their availability can limit biofilm processes. When the preferred inorganic forms of these nutrients (i.e., NH4 and PO4) are at low concentrations, biofilms may become dependent on organic pools of macronutrients to grow and maintain metabolic function. To access organic nutrients, specialized acquisition enzymes are required to breakdown organic molecules and release the macronutrients within, and these enzymes (urease for NH4; alkaline phosphatase for PO4) require micronutrient cofactors (nickel and zinc, respectively). To assess the importance of these micronutrient cofactors, we conducted a series of in situ nutrient enrichment experiments using nutrient diffusing substrate to elevate concentrations of macronutrients and micronutrient cofactors. We measured biofilm biomass (chlorophyll-a and ash free dry mass), urease and alkaline phosphatase activity, and biofilm nickel and zinc concentrations. Preliminary results indicate that biofilm growth is limited by nitrogen, therefore organic nitrogen pools are likely an important source of nutrients to biofilms. We expect that biofilms enriched with nickel will have greater urease activity and reach higher biomass than controls, representing nutrient co-limitation by a macro and micronutrient.

Arial Shogren (Co-Presenter/Co-Author)
University of Alabama, ashogren@ua.edu;

Jonathan P. Benstead (Co-Presenter/Co-Author)
The University of Alabama, jbenstead@ua.edu;

David Manning (Primary Presenter/Author)
University of Nebraska at Omaha, davidmanning@unomaha.edu;

Abstract: Processes regulating the production, transport, and processing of nutrients in particles are poorly characterized, limiting our understanding of the role of fine particulates in riverine carbon (C) and nutrient ([N]itrogen, [P]hosphorus) dynamics at continental scales. We explored how particulate nutrient concentrations varied among 20 wadeable stream sites within 14 NEON domains (2014 to 2020). Across sites, C was tightly coupled to N (R2 = 0.85) compared to P (R2 = 0.28). Particles were relatively P-rich (median molar C:P = 167, median molar N:P = 13), but this depended on watershed size: smaller watersheds had higher C:P than larger watersheds. Among domains, Atlantic neotropical (D04) sites had the lowest C:N, whereas the Northern Plains (D06) had the lowest C:P and N:P, on average. Temporal patterns of particulate C:N and C:P were also domain- and watershed-size-dependent, suggesting distinct particle sources and processing across space and time. For example, particulate C:N and C:P varied seasonally in forested Posey Creek (Virginia, USA), while in the larger Arikaree River (Colorado, USA) particulate C:N and C:P were more consistent across seasons. These patterns point to an intriguing biogeochemical role of particles in streams across the US.

Natalie Griffiths (Primary Presenter/Author)
Oak Ridge National Laboratory, griffithsna@ornl.gov;

Randy Kolka (Co-Presenter/Co-Author)
USDA Forest Service Northern Research Station, rkolka@fs.fed.us;

Colleen Iversen (Co-Presenter/Co-Author)
Oak Ridge National Laboratory, iversencm@ornl.gov;

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

Sarah Shelley (Co-Presenter/Co-Author)
Oak Ridge National Laboratory, shelleysj@ornl.gov;

Abstract: Boreal peatlands are carbon-rich and nutrient-poor ecosystems that are vulnerable to climate change. We investigated how climate change affects detrital nutrient dynamics by measuring decomposition rates and changes in carbon, nitrogen, and phosphorus contents of 6 litter types (spruce needles and fine roots, Labrador tea leaves and fine roots, and two Sphagnum species) over two years in the Spruce and Peatland Responses Under Changing Environments (SPRUCE) experiment. SPRUCE uses ten enclosures to elevate air and peat temperatures (+0 to +9°C) at ambient and elevated CO₂ (eCO₂) (+500 ppm) in a northern Minnesota peatland. We also examined whether the chemistry of senescent litter from vegetation growing in the enclosures was affected by warming and eCO₂. There was little effect of temperature and eCO₂ on aboveground litter decomposition and leaf-tissue chemistries; however, fine-root breakdown increased with warming. There was no clear effect of warming on senescent litter chemistry but eCO₂ resulted in lower nitrogen content in leaves of two shrub species. Overall, there was little initial response of litter breakdown and nutrient contents to warming, but eCO₂ decreased the nutrient content of senescent litter, which may have cascading effects to decomposition.

Gabriele Weigelhofer (Co-Presenter/Co-Author)
Institute of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Vienna, Austria, gabriele.weigelhofer@wcl.ac.at;

Elmira Akbari (Primary Presenter/Author)
Institute of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Vienna, Austria, elmira.akbari@wcl.ac.at;

Abstract: Rehabilitation of riparian forests may help to restore the natural in-stream nutrient uptake capacity via particulate organic carbon (POC) supply. This study investigated the effects of POC on the microbial uptake of phosphorus (P) and nitrogen (N) in laboratory flume experiments. In the flumes, sand was colonized under nutrient-enriched conditions, half with optimum C:N:P ratios and half C limited, under dark and light. Undisturbed samples were taken out and incubated in nutrient-enriched water with fresh and leached leaves. Nutrient uptake rates were determined by changes in water column nutrient concentrations over time. Preliminary results from dark flumes demonstrate that biofilms grown under optimal C:N:P conditions showed higher soluble reactive P uptake than those grown under C-limited conditions, with average rates of 8.1 and 4.1 µg/Lh in treatments with fresh and leached leaves, respectively. In addition, fresh leaves had stronger effects than leached ones. Fresh leaves stimulated nitrate uptake, with average rates of 70.9 and 50.2 µg/Lh under optimal and limited conditions, respectively, whereas leached leaves did not show any effects. The results of this study will improve the mechanistic understanding of the stoichiometric control on the in-stream nutrient retention.

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

Luz Boyero (Co-Presenter/Co-Author)
University of the Basque Country, luz.boyero@ehu.eus;

Cristina Canhoto (Co-Presenter/Co-Author)
Centre for Functional Ecology, University of Coimbra, Portugal, ccanhoto@ci.uc.pt;

Krista Capps (Co-Presenter/Co-Author)
University of Georgia, kcapps@uga.edu;

Michaël Danger (Co-Presenter/Co-Author)
LIEC, Univ. Lorraine, France, michael.danger@univ-lorraine.fr;

Paul C. Frost (Co-Presenter/Co-Author)
Trent University, Peterborough, Ontario, Canada, paulfrost@trentu.ca;

Mark Gessner (Co-Presenter/Co-Author)
Leibniz-Institute of Freshwater Ecology and Inland Fisheries / Berlin Institute of Technology , gessner@igb-berlin.de;

Natalie Griffiths (Co-Presenter/Co-Author)
Oak Ridge National Laboratory, griffithsna@ornl.gov;

Halvor Halvorson (Co-Presenter/Co-Author)
University of Central Arkansas, hhalvorson@uca.edu;

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

Amy Marcarelli (Co-Presenter/Co-Author)
Michigan Technological University, ammarcar@mtu.edu;

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

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

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

Abstract: Microbial litter decomposers obtain nitrogen (N) and phosphorus (P) from both the litter itself and the surrounding stream water or soil solution. This complicates the quantification of N and P immobilization during decomposition. We used cotton strips as a low nutrient substrate to investigate exogenous controls of nutrient immobilization. We deployed cotton strips in streams and on adjacent riparian soils during peak litterfall at 100 sites representing 11 biomes, and measured residual carbon, N, and P content to calculate nutrient immobilization. Overall, immobilization varied by 3 orders of magnitude and was higher in streams than riparian zones. Immobilization rates were correlated to site-specific conditions such as streamwater nutrient concentration, but were not strongly related to biome or latitude. Although the molar N:P ratio of surface water varied widely, the stoichiometry of immobilized N:P (10) was tightly constrained near the global mean N:P ratio of microbial biomass (7:1). Litter decomposition rate was correlated to nutrient immobilization, with the strongest relationship between decomposition rate and P immobilization. An estimate based on biome-specific data on litterfall suggests that immobilization could account for a substantial amount of whole-stream nutrient uptake during peak litterfall.

Tori A. Hebert (Primary Presenter/Author)
The University of Alabama, tahebert@crimson.ua.edu;

Halvor Halvorson (Co-Presenter/Co-Author)
University of Central Arkansas, hhalvorson@uca.edu;

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

Abstract: Land conversion from forest to agriculture introduces nutrients, like nitrogen (N) and phosphorus (P), which can stimulate microbial autotrophs (algae) and heterotrophs (fungi and bacteria). Recent evidence indicates that algae can stimulate microbial decomposers associated with decaying plant litter, thus eliciting a “priming effect” on organic matter decomposition. We used a full-factorial design manipulating labile C (glucose and acetate) and nutrients (N and P) to test their effects during the red maple litter decomposition within 4 forested and 4 agricultural streams. We deployed nutrient-diffusing substrates (NDS) containing litter and either agar, agar+labile C, agar+NP, or agar+CNP. Land use mediated NDS treatment effects on algal biomass (p<0.001) with the NP treatment having no difference between land uses, but both C and CNP treatments inhibited algae in forested streams. Fungal biomass in forested streams trended higher than agriculture streams (p=0.052), and there were significant NDS effects (p<0.001), with the C treatment having the highest fungal biomass whereas nutrients (NP and CNP) inhibited fungi. We will also report bacterial biomass, litter metabolism, and decomposition rates to better understand the role of the priming effect and nutrient limitation in stream C cycling.

Hal Halvorson (Primary Presenter/Author)
University of Central Arkansas, halvorso@gmail.com;

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

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

Tyler Grandjean (Co-Presenter/Co-Author)
University of Central Arkansas, tgrandjean1@cub.uca.edu;

Patrick Jarman (Co-Presenter/Co-Author)
Purvis High School, patrickjarman@gmail.com;

Abstract: Algae can directly influence leaf litter decomposition by provisioning labile carbon (C) exudates to microbial heterotrophs such as fungi and bacteria. While the intensity of this algal priming effect is highly variable, dissolved nutrients may control priming by constraining degradative enzyme activity. We conducted a flume experiment to test algal priming effects on enzymatic activity and decomposition of Liriodendron tulipifera leaf litter. Litter was incubated under light or dark conditions and low vs. high N:P (amendment molar N:P=1 or 256, respectively) for five weeks. On average, light inhibited decomposition rates, and higher N:P concentrations increased decomposition regardless of light (P<0.001). Activity of the C-acquiring enzyme phenol oxidase was also greater under high dissolved N:P (P<0.05), whereas beta-glucosidase activity was consistently inhibited by light (P<0.001). The C-acquiring enzyme beta-xylosidase showed a light x N:P interaction (P<0.05) in which light inhibited activity more strongly under low N:P as compared to high N:P. Phosphatase activity also showed strong light x N:P interactions (P<0.001). These results provide a mechanistic link between dissolved N and P availability and degradative enzyme activity, which will improve predictions of controls on algal priming during leaf litter decomposition.

Roman Alther (Co-Presenter/Co-Author)
Eawag, Swiss Federal Institute of Aquatic Science and Technology, roman.alther@eawag.ch;

Andrin Krähenbühl (Co-Presenter/Co-Author)
Eawag, Swiss Federal Institute of Aquatic Science and Technology, andrin.kraehenbuehl@eawag.ch;

Florian Altermatt (Co-Presenter/Co-Author)
Eawag, Swiss Federal Institute of Aquatic Science and Technology, florian.altermatt@eawag.ch;

Eva Cereghetti (Primary Presenter/Author)
Eawag, Swiss Federal Institute of Aquatic Science and Technology, eva.cereghetti@eawag.ch;

Abstract: The strong seasonality of leaf fall in temperate climates causes many decomposition studies to take place in autumn, when allochthonous leaf input peaks. Yet, leaves are found in streams throughout the year and microorganisms alongside macroinvertebrates process available material outside of these key months. By limiting the timescale of our observations, we ignore the role of the phenology of animal communities, the seasonality of abiotic variables, and the decay-related change in leaf quality. Here, we considered these elements by combining two year-long experiments with the knowledge of population dynamics of amphipods. One laboratory experiment measured microbial decomposition and change in nutrient ratio of decomposing leaves. One field experiment measures decomposition rates of leaf bags, amphipod abundance and plant material inputs at two headwaters at six weeks intervals. Thanks to the extent of the individual experiments and the use of different methods, we could assess the change through time of a) decomposition rates, b) contribution of shredders, and c) decomposing leaves’ quality. With our holistic approach and long-term empirical studies, we show how the decomposition process consists of individual aspects with unique seasonal dynamics, yet all ultimately linked to each other.

Jane Marks (Primary Presenter/Author)
Northern Arizona University, jane.marks@nau.edu;

Adam Wymore (Co-Presenter/Co-Author)
University of New Hampshire, adam.wymore@unh.edu;

Zacchaeus Compson (Co-Presenter/Co-Author)
University of North Texas, zacchaeus.compson@unt.edu;

Michaela Hayer (Co-Presenter/Co-Author)
Northern Arizona University, michaela.hayer@nau.edu;

Courtney Roush (Co-Presenter/Co-Author)
Northern Arizona University, cmr627@nau.edu;

Meghan Schrik (Co-Presenter/Co-Author)
Northern Arizona University, ms3398@nau.edu;

Bruce Hungate (Co-Presenter/Co-Author)
Northern Arizona University, bruce.hungate@nau.edu;

Egbert Schwartz (Co-Presenter/Co-Author)
Northern Arizona University, egbert.schwartz@nau.edu;

Benjamin Koch (Co-Presenter/Co-Author)
Northern Arizona University, ben.koch@nau.edu;

Abstract: Integrating omics with isotopes allows us to answer new questions and revisit old questions. Here we demonstrate how these new tools have reshaped our understanding of decomposing leaves. Sequencing has revealed greater species richness of fungi on leaves than indicated by spore production. Species presence however, does not predict their importance, as many bacterial and fungal species can be dormant. Using quantitative stable isotope probing (qSIP) to identify growing microbes we found that most growing fungal species on leaves enter the water with the leaf, whereas most growing bacteria colonize from the water column. The majority of bacteria on litter are growing, whereas the majority of fungi are dormant. Using leaves labeled with 13C and 15N we demonstrate that more C and N is transferred to invertebrates from slowly decomposing leaves whereas faster decomposing litter support more microbial biomass. Results challenge the view that faster is better, suggesting that microbes compete with invertebrates on labile leaf litter but facilitate invertebrates on recalcitrant litter. We present a new emerging paradigm for understanding linkages between aquatic and terrestrial ecosystems and the fates of dead leaves in streams.

Carri LeRoy (Primary Presenter/Author)
Evergreen State College, leroyc@evergreen.edu;

Shannon Claeson (Co-Presenter/Co-Author)
USFS PNW Research Station, shannon.claeson@usda.gov;

Iris Garthwaite (Co-Presenter/Co-Author)
Northern Arizona University, ig334@nau.edu;

Debra Finn (Co-Presenter/Co-Author)
Missouri State University, dfinn@missouristate.edu;

Angie Froedin-Morgensen (Co-Presenter/Co-Author)
The Evergreen State College, amorgensen@gmail.com;

Brandy Kamakawiwo'ole (Co-Presenter/Co-Author)
The Evergreen State College, kambra20@evergreen.edu;

Victoria Cowan (Co-Presenter/Co-Author)
The Evergreen State College, cowvic21@evergreen.edu;

Lauren Thompson (Co-Presenter/Co-Author)
The Evergreen State College, tholau29@evergreen.edu;

Madeline Thompson (Co-Presenter/Co-Author)
The Evergreen State College, thomad29@evergreen.edu;

Maya Nabipoor (Co-Presenter/Co-Author)
The Evergreen State College, mayanabipoor@gmail.com;

Lily Messinger (Co-Presenter/Co-Author)
The Evergreen State College, lilymessinger@gmail.com;

Jordan Moffett (Co-Presenter/Co-Author)
The Evergreen State College, jamandamoffett@gmail.com;

Logan Lancaster (Co-Presenter/Co-Author)
The Evergreen State College, lanlog02@evergreen.edu;

Lauren Walker (Co-Presenter/Co-Author)
Lewis and Clark College, walker.laurenjean@gmail.com;

Nichole Criss (Co-Presenter/Co-Author)
The Evergreen State College, nicholemcriss@gmail.com;

Joy M. Ramstack Hobbs (Co-Presenter/Co-Author)
The Evergreen State College, hobbsj@evergreen.edu;

Mailea Miller-Pierce (Co-Presenter/Co-Author)
Washington State University, m.miller-pierce@wsu.edu;

John Bishop (Co-Presenter/Co-Author)
Washington State University, bishopj@wsu.edu;

Abstract: Complex interactions in riparian ecosystems among plants, nutrients, and herbivores can influence organic matter dynamics in streams. The relatively young streams on the North flank of Mount St. Helens (Lawetlat’la, WA, USA) are colonized by dioecious Sitka willow (Salix sitchensis). Female willows dominate the landscape with a 2:1 sex ratio, colonize significantly closer to stream edges, produce larger inflorescences, and contribute litter in the form of leaves, wood, and catkins. In addition, a stem-boring weevil (Cryptorhynchus lapathi; Coleoptera: Curculionidae) attacks females at a higher rate and causes branch die-back and aseasonal litter fall during the summer. Male willow litter is higher in %N and has a lower C:N ratio, significantly increasing leaf litter decomposition rates for males. In experimental terrestrial plots, weevil removal and nitrogen addition differentially influenced male and female litter quality, leading to altered in-stream leaf mass loss and macroinvertebrate colonization. Plant genetics have been shown to influence ecosystem processes, and in this set of studies, we find that a genetic difference like plant sex can interact with nutrient availability, herbivore resistance, landscape heterogeneity, and aquatic community members to influence organic matter processing.

Isaiah Leach (Co-Presenter/Co-Author)
Georgia Southern University, il00333@georgiasouthern.edu;

Montana Carter (Co-Presenter/Co-Author)
Georgia Southern University, mc09271@georgiasouthern.edu;

Eli Miller (Co-Presenter/Co-Author)
Georgia Southern University, em04535@georgiasouthern.edu;

Loni Keller (Co-Presenter/Co-Author)
Georgia Southern University, lk02287@georgiasouthern.edu;

Angela Shaffer (Co-Presenter/Co-Author)
Georgia Southern University, as17251@georgiasouthern.edu;

Checo Colon-Gaud (Co-Presenter/Co-Author)
Georgia Southern University, jccolongaud@georgiasouthern.edu;

Victoria Baglin (Primary Presenter/Author,Co-Presenter/Co-Author)
Georgia Southern University, vb04987@georgiasouthern.edu;

Abstract: We used leaf packs to assess the effects of climate change on decomposition rates and macroinvertebrate communities. We deployed replicate packs into 9 experimental ponds at the Bo Ginn National Fish Hatchery in Jenkins County, GA. Ponds were used to simulate predicted climate change scenarios (e.g., extended drought periods). Leaf packs were deployed in temporarily flooded and permanently flooded wetlands then collected in ~30, 60, 90-day intervals. We predicted that: (1) permanent wetlands would provide stable and favorable conditions for macroinvertebrate communities, thus support greater diversity; (2) differences in macroinvertebrate community diversity, as well as varying abiotic conditions would result in faster decomposition rates in permanent wetlands; (3) temporary wetlands would be less diverse than permanent wetlands, as they would be exposed to harsher conditions (e.g., higher temperatures, lower DO, and reduced habitat). Leaf decomposition rates were faster in permanent wetlands (k = -0.0085), than in dry environments (k = -0.0054) or temporary wetlands (k = -0.0062). Macroinvertebrate communities differed in abundance, biomass, and overall structure with temporary wetlands initially lagging permanent wetlands. Our study shows the responses of consumer communities and associated ecosystem services to predicted climate change scenarios.

Mikey Fager (Primary Presenter/Author)
University of Georgia, mikeyfager@gmail.com;

Abstract: Secondary production in forest streams depends on the quality and quantity of detritus. Colonization of detritus by microbes tends to increase its palatability to consumers, coincident with decreases in its ratio of carbon (C) to nutrients (e.g., ratio of C to nitrogen [N]). This is important for consumer nutrition because stream detritivores are elevated in N compared to the detritus they consume. As warming is expected to increase rates of microbial growth and C loss, we hypothesized that warming would lead to higher nutrient content in detrital material. In this study, we warmed a stream by ~2ºC and analyzed the C and N content of its detritus relative to pre-treatment and a reference stream (before-after, control-impact). Warming led to significantly lower detrital C:N in the warmed stream compared to the reference for buried and suspended fine particles (p = 0.006 and p = 0.002, respectively), while leaf litter C:N showed no trend with warming. Responses of coarse and fine particles may be driven by differences in microbial communities associated with these particle types (i.e. fungi vs. bacteria) and have important growth implications for different functional feeding groups of macroinvertebrates.

Ryan Utz (Co-Presenter/Co-Author)
Chatham University, rutz@chatham.edu;

Roy Weitzell (Co-Presenter/Co-Author)
Chatham University, rweitzell@chatham.edu;

Liane Moos (Primary Presenter/Author)
Chatham University, liane.moos@chatham.edu;

Abstract: Autumn leaf senescence is a major contributor of allochthonous deposits of organic material to stream energy systems. Replacing native with invasive species in riparian zones may impact nutrient availability and content of leaf deposits, as many invasive species favor fast growth over constructing more robust leaf structures. We compared larval growth of a common shredder, Tipula, fed on ten species of commonly-occurring native and invasive riparian plants of the eastern U.S. A recirculating tank system was used to house 100 larva as individual replicates; thus, all leaves were exposed to the same microbiome. Growth was collected biweekly and tanks with dead larva were replaced. Results varied greatly by species, with patterns suggesting that terrestrial flora invasions are associated with accelerated leaf decomposition. Findings suggest these invasions may result in enhanced leaf processing rates that are species-specific. Future analyses will explore if senesced leaf traits, such as toughness or chemical composition, explain the pattern in all tested leaf species. Three of the top five growth rates were observed with invasive species. The two invasive species that resulted in the fastest growth, Celastrus orbiculatus and Fallopia japonica, also exhibited the highest survivorship.

James Wood (Primary Presenter/Author)
West Liberty University, James.Wood@westliberty.edu;

Marisa Tordella (Co-Presenter/Co-Author)
Weset Liberty University, mntordella@westliberty.edu ;

Emily Huff (Co-Presenter/Co-Author)
West Liberty University, ethuff@westliberty.edu;

Abstract: Nutrients can increase the breakdown rate of organic material in streams, however the power of nutrients to stimulate breakdown becomes less clear when streams become impaired by chemical stressors and vary in watershed size. We examined the effects of water chemistry on the breakdown rate of wood veneers at 30 sites across a range of watershed sizes, nutrients levels, and water chemistries to test the hypothesis that the effects of nutrients on breakdown are observable across diverse insitu conditions. Our study sites ranged from 1st order headwaters streams to an 8th order river, and from biologically intact to severely impaired. Dissolved inorganic nitrogen (DIN) ranged from ~100-2500 µgL-1 and SRP from ~8-35 µgL-1. We found no consistent positive effects of nutrients; rather we found a negative influence of DIN and iron on breakdown rate. Water temperature was the only parameter significantly positively correlated with increased breakdown rate across our range of study sites. Our highest DIN and lowest breakdown rates were observed at sites impacted by acid mine drainage. Our results indicate the local condition can overshadow the stimulatory effects of nutrients on the breakdown rate of organic materials.

John Olson (Co-Presenter/Co-Author)
Dept of Applied Environmental Science, California State University Monterey Bay, CA, USA, joolson@csumb.edu;

Gretchen Wichman (Primary Presenter/Author)
School of Natural Sciences, California State University Monterey Bay, CA, USA, gwichman@csumb.edu;

Abstract: Carbon processing in streams is important for the foundation of aquatic food webs. However, the influence of salinity on leaf breakdown rates is poorly understood. Tidally-influenced streams could be used for measuring carbon processing in environments with fluctuating salinity. Periodic surges of saltwater could disrupt both saltwater and freshwater species that specialize in decomposition. We expect a slower rate of leaf litter decay because it could be difficult for bacteria and fungi to adapt to quickly changing conductivity. We deployed 8 conductivity data loggers and 16 leaf packs in 4 coastal streams. We positioned a set of loggers and leaf packs near the beach river mouth plus another set upstream. The intent is to measure leaf breakdown rates in tidally-influenced and non tidally-influenced reaches of the four streams. I will present initial results like the rate of leaf litter decay and the salinity gradient across urban and agricultural watersheds. Coastal streams could be a good platform for assessing carbon processing in saline environments.

Robert Danczak (Co-Presenter/Co-Author)
Pacific Northwest National Laboratory, robert.danczak@pnnl.gov;

James Stegen (Co-Presenter/Co-Author)
Pacific Northwest National Laboratory, james.stegen@pnnl.gov;

Lupita Renteria (Co-Presenter/Co-Author)
PNNL, lupita.renteria@pnnl.gov;

Amy Goldman (Co-Presenter/Co-Author)
PNNL, amy.goldman@pnnl.gov;

Emily Graham (Co-Presenter/Co-Author)
Pacific Northwest National Laboratory, emily.graham@pnnl.gov;

Vanessa Garayburu-Caruso (Primary Presenter/Author)
Pacific Northwest National Laboratory and Washington State Univeristy, v.garayburucaruso@wsu.edu;

Abstract: River corridor metabolomes reflect organic matter processing that drives aquatic biogeochemical cycles. Recent work highlights the power of ultrahigh-resolution mass spectrometry for understanding metabolome composition and river corridor metabolism. However, there have been no studies on the global chemogeography of surface water and sediment metabolomes using ultrahigh-resolution techniques. Here, we describe a community science effort from the Worldwide Hydrobiogeochemistry Observation Network for Dynamic River Systems (WHONDRS) consortium to characterize global metabolomes in surface water and sediment spanning multiple stream orders and biomes. We describe the distribution of key aspects of metabolomes including elemental groups, chemical classes, and inferred biochemical transformations. We show that metabolomes differ across surface water and sediment and that surface water metabolomes are more rich and variable. We use inferred biochemical transformations to identify core metabolic processes shared among surface water and sediment. Finally, we observe significant spatial variation in sediment metabolites between rivers in the eastern and western portions of the contiguous US. Our work provides a basis for understanding global patterns in river corridor biogeochemical cycles and also demonstrates that community science endeavors can enable global research projects that are unfeasible with traditional research models.

Max Kelly (Primary Presenter/Author,Co-Presenter/Co-Author)
University of Georgia, Max.kelly@uga.edu;

LuLu Lacy (Co-Presenter/Co-Author)
Florida International University, lululacy@gmail.com;

Rafael Perez (Co-Presenter/Co-Author)
University of Puerto Rico, rafael.perez13@upr.edu;

Jesús E. Gómez (Co-Presenter/Co-Author)
University of Puerto Rico, jesuslobo06@gmail.com;

Pablo E. Gutiérrez-Fonseca (Co-Presenter/Co-Author)
University of Costa Rica, pabloe.gutierrezfonseca@gmail.com;

Alonso Ramírez (Co-Presenter/Co-Author)
North Carolina State University, alonso.ramirez@ncsu.edu;

Catherine Pringle (Co-Presenter/Co-Author)
Odum School of Ecology, University of Georgia, cpringle@uga.edu;

Abstract: This study provides before impact data for an ongoing BACI (Before/After/Control/Impact) study of stream flow reduction effects on stream ecosystem processes. We examined leaf litter decomposition rates in two study streams draining El Yunque National Forest (EYNF) in Puerto Rico. We measured decomposition rates over 50 days (in both the presence and absence of dominant shrimp macroconsumers) in five pools along a 100m reach in each stream. Electric exclosure devices were used to prevent shrimp access to Dacryodes excelsa leaf packs, while control leaf packs (unelectrified) remained accessible to shrimp. Stream A had significantly greater rates of leaf breakdown in shrimp access (k -0.0242 ± 0.004) versus exclosures (K -0.0161 ± 0.0017). In contrast, Stream B did not display significantly different decomposition rates in shrimp access (k -0.0125 ± 0.0016) versus exclosures (k -0.0148 ± 0.0042). We attribute greater leaf decomposition rates in access versus exclusion treatments in stream A to greater macroconsumer shredding activity as reflected by 3x greater shrimp abundance in Stream A (28.34 ± 5.8) versus Stream B (9.69 ± 1.96). This baseline data will provide context for our future stream flow reduction experiment in stream B.