The metabolic regimes of flowing waters

Abstract

The processes and biomass that characterize any ecosystem are fundamentally constrained by the total amount of energy that is either fixed within or delivered across its boundaries. Ultimately, ecosystems may be understood and classified by their rates of total and net productivity and by the seasonal patterns of photosynthesis and respiration. Such understanding is well developed for terrestrial and lentic ecosystems but our understanding of ecosystem phenology has lagged well behind for rivers. The proliferation of reliable and inexpensive sensors for monitoring dissolved oxygen and carbon dioxide is underpinning a revolution in our understanding of the ecosystem energetics of rivers. Here, we synthesize our current understanding of the drivers and constraints on river metabolism, and set out a research agenda aimed at characterizing, classifying and modeling the current and future metabolic regimes of flowing waters.The fuel that powers almost all of Earth's ecosystems is created by organisms capable of the alchemy of photosynthesis, in which solar energy, water, and carbon dioxide are converted into reduced carbon compounds that are then used to sustain life. We measure this conversion of solar energy into organic energy as the gross primary productivity (GPP) of ecosystems. The collective dissipation of this organic energy through organismal metabolism (of both autotrophs and heterotrophs) is measured as ecosystem respiration (ER). Together, GPP and ER are the fundamental metabolic rates of ecosystems that constrain the energy supply and energy dissipation through food chains, and the balance of these two fluxes, measured as net ecosystem production (NEP), determines whether carbon accumulates or is depleted within an ecosystem. Terrestrial ecosystems often have predictable annual cycles, with both GPP and NEP typically peaking during warmer and wetter months of the year. In many well-studied lakes productivity peaks when warming temperatures, lengthening days, and high nutrient concentrations occur in concert. The life cycles of many consumers are likely synchronized to these seasonal oscillations such that periods of peak energetic demand by consumers coincide with or follow the peak productivity of their preferred plant or prey (e.g., Lampert et al. 1986;Berger et al. 2010). As a result, ecosystem respiration tends to

Dynamic stream network intermittence explains emergent dissolved organic carbon chemostasis in headwaters

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Spatiotemporal Variability in Water Sources Controls Chemical and Physical Properties of a Semi‐arid Urban River System

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Metabolic Variance: A Metric to Detect Shifts in Stream Ecosystem Function as a Result of Stream Restoration

“…; Bernhardt et al. ) at a higher level of resolution, these types of models are not always feasible to implement in a time frame and budget available for most restoration projects. The methods described below were selected with these limitations in mind.…”

“…) rather than ecosystem function (e.g., productivity, nutrient cycling) (Allan and Castillo ; Darby and Sear ; Bernhardt et al. ; Frainer et al. ).…”

“…; Bernhardt et al. ), suggesting the role of metabolic measurements in stream systems that connect to instream hydraulic manipulations or changes.…”