SFS Annual Meeting

5/21/2019  |   14:00 - 14:15   |  251 DE

SIMPLE TWIST OF RATES -- COMMUNITY MODELS FOR SEASONAL ECOSYSTEMS Most organisms exist in seasonal environments where energy and nutrients change with temperature, rainfall, and other factors. While seasonal environments certainly influence organisms by shaping phenology and other life history components, biotic interactions among species may in turn influence the availability of nutrients and energy within ecosystems. “Coupled matrix models” are a new modeling tool for exploring the complex interactions that arise in ecosystems experiencing strong seasonal effects and disturbances. Species (or guilds of species) are represented as stage-structured populations linked together via aggregate density-dependence on a central ecosystem resource, such as space or nutrient availability. Sensitivity and network analysis then allow the identification of strong and weak biotic interactions, as well as the projection of future community dynamics under novel, non-stationary environments such as those imposed by climate change. Applications using riparian vegetation and fish communities identified pairwise species interactions that impose controls on the distribution and abundance of plant and fish biomass, but also identified climate scenarios where these interactions are likely to weaken or disappear entirely. Understanding feedbacks between population dynamics and ecosystem responses will help us navigate complex phenological changes due to climate change.

Dave Lytle (Primary Presenter/Author), Oregon State University, lytleda@oregonstate.edu;


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5/21/2019  |   14:15 - 14:30   |  251 DE

THE CHANGING PULSE OF RIVERS: DAM-INDUCED ALTERATION OF FLOW PERIODICITY AND SYNCHRONY Phenological dynamics are controlled by seasonal patterns in riverine hydrology. Well known examples include how flow regimes cue the onset of fish migration and spawning, elicit seed release by riparian plants, and trigger insect emergence. So, should we be concerned about dams that do everything from dampening flow seasonality (storage operations) to inducing rapid, periodic fluctuations in flow (hydropower operations)? Here, we used the wavelet transform to quantify how dams have affected scales of flow variability for hundreds of rivers across the United States. According to mean daily discharge, we found that natural yearly and/or seasonal flow periodicity was largely dampened during post-dam periods due to reservoir storage. Cross-wavelet analysis according to 15-min discharge data revealed large-scale spatial synchrony in flow regimes that emerged as a consequence of seasonality at ‘natural’ time-scales and dam management at ‘artificial’ time-scales. Both the loss of flow seasonality and the emergence of novel signals at human-relevant-scales (e.g. 1-day, 1-week) represent important alterations to the natural flow regime. This work advances the notion that dams alter high-level properties of flow regimes, thus having important implications for organismal phenology both today and in the future.

Julian Olden (Primary Presenter/Author), University of Washington, olden@uw.edu;


Albert Ruhi (Co-Presenter/Co-Author), Department of Environmental Science, Policy, and Management, University of California, Berkeley, albert.ruhi@berkeley.edu;


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5/21/2019  |   14:30 - 14:45   |  251 DE

THE TIMES THEY ARE A CHANGING - CAN WE CONSERVE OR DESIGN METABOLIC REGIMES TO PROTECT RIVER SPECIES AND ECOSYSTEMS? River ecosystems vary widely in the magnitude and timing of primary productivity and allochthonous carbon supply. These differences in energetic inputs to river ecosystems are ultimately determined by river climate (light, flow, and thermal regimes) and constrained by physical disturbance and nutrient supply. For many rivers, climate and land use change are leading to significant alterations in river climate, increasingly frequent or severe physical disturbances and increased nutrient loading. These impacts propagate into shifts in metabolic regimes. Reduced energy supply is likely to reduced secondary production, while shifts in the timing of energy input peaks may disadvantage those consumers whose life history is timed to take advantage of predictable patterns of energy supply. Efforts to protect or recover freshwater biodiversity will likely be more successful if they can restore critical aspects of the metabolic regime.

Emily Bernhardt (Primary Presenter/Author), Duke University, emily.bernhardt@duke.edu;


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5/21/2019  |   14:45 - 15:00   |  251 DE

TIMING IS EVERYTHING: EXPLORING INTERANNUAL VARIABILITY IN STREAM METABOLISM The life histories and resource usage of aquatic consumers are related to the timing, quantity, and quality of carbon inputs. Ecosystem metabolism can be used as an integrative descriptor of the energetics of systems by examining the separate components of primary production and ecosystem respiration. Metabolism exhibits phenological patterns, and the timing and predictability of these patterns is important for understanding temporal dynamics of communities. Changing phenological responses have been observed across terrestrial, lentic, and marine systems but considerably less is known about the patterns or variation of ecosystem metabolism in lotic systems. Here, we use near-continuous estimates of metabolism from a multitude of sites to examine interannual variability in the timing, magnitude, and shape of stream metabolism. We compare these patterns to corresponding changes in stream or adjacent terrestrial systems to explore potential controls on the regularity of metabolic patterns. Beginning to link the phenology of ecosystem metabolism to drivers can improve our understanding of the temporal dynamics of stream ecosystems and offer new approaches for linking stream ecosystem energetics to community structure.

Philip Savoy (Primary Presenter/Author), Duke University, philip.savoy@gmail.com;


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


Jim Heffernan (Co-Presenter/Co-Author), Duke University, james.heffernan@duke.edu;


Audrey Thellman (Co-Presenter/Co-Author), Univeristy of North Carolina at Chapel Hill, athellma@unc.edu;


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5/21/2019  |   15:00 - 15:15   |  251 DE

USING DIEL VARIATION IN DISSOLVED METABOLITES TO EXPLORE THE INFLUENCE OF NUTRIENT LOADING ON STREAM METABOLIC REGIMES Point measurements of stream nutrient concentrations sampled exclusively during daylight hours provide a limited perspective on daily cycles of aquatic metabolic regimes and may mask areas of chronic loading due to sampling bias of periods with higher primary production. Our objective is to determine how chronic anthropogenic N loading influences diel variation in nutrient demand within the stream ecosystem metabolic regime by evaluating diel variation in concentrations of dissolved metabolites and continuous whole-stream metabolism estimates over an algal growing season. In our mountain headwater study area, stream ecosystems are likely to be nutrient-limited under natural conditions, but resort development in recent decades allows us to compare two similar stream reaches with contrasting N loading due to wastewater management practices. Diel patterns in nitrate concentrations demonstrate larger amplitudes in a reach with higher N loading. In general, chronic nutrient loads appear to influence nutrient demand via alteration of the stream metabolic regime. Continued examination of diel and seasonal cycles in metabolic behavior and inorganic nutrient concentrations in this setting will provide more detailed insight into the mechanisms by which stream metabolic regimes are influenced by anthropogenic nutrient loading.

Meryl Storb (Primary Presenter/Author), USGS WY-MT Water Science Center, mstorb@usgs.gov;


Robert Payn (Co-Presenter/Co-Author), Montana State University, Montana Institute on Ecosystems, rpayn@montana.edu;


Juliana D'Andrilli (Co-Presenter/Co-Author), Montana State University, juliana@montana.edu;


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