Current Research

Metabolic signatures of Swedish streams and rivers

"Taking the pulse of Swedish rivers: Using metabolism to monitor ecosystem responses to environmental change" was recently funded by the Swedish Research Council Formas. This project will (1) determine how rates of ecosystem metabolism in Swedish rivers are shaped by regional climatic and anthropogenic gradients from hemi-boreal to the arctic, (2) quantify the extent to which streams in the Swedish landscape degrade terrestrial organic carbon and contribute to greenhouse gas evasion, and (3) advance the use of metabolism as a tool for environmental monitoring programs. PIs: R Sponseller, J Karlsson (Umeå University), ER Hotchkiss (Virginia Tech), H Laudon (Swedish University of Agricultural Sciences).

Dynamics of carbon and nutrient transport and fate

High-frequency time series of water chemistry, climate, hydrology, and ecosystem process (carbon metabolism, nutrient cycling, food web dynamics) data can be used to identify changing patterns and controls of carbon and nutrient variability, transport, and fates within and among ecosystems. Considering linked nutrient, carbon, and water cycles will help us better understand how the efficiency of ecosystem- and catchment-scale carbon and nutrient transformations may respond to environmental change. Collaborators from a Stream Resiliency Research Coordination Network Working Group: J Jones, C Ruffing (University of Alaska Fairbanks), L Koenig (University of New Hampshire), A Helton (University of Connecticut), J Sabo (Arizona State University), T Royer (Indiana University Bloomington), et al.

Biogeochemistry of boreal river networks

We are measuring the sources, transformations, and fluxes of dissolved organic matter and greenhouse gases in a large boreal river network, from soils to the sea. The Romaine River is in the process of being dammed for hydropower, so we will also have the opportunity to identify distinct contributions of river/reservoir sections at varying stages of pre- and post-dam to network- and landscape-scale biogeochemistry. With P del Giorgio, M Gérardin (Université du Québec à Montréal), et al.

Hotchkiss, E.R. & P.A. del Giorgio. Integrating gas exchange rates along a large boreal river. In Preparation.

Hotchkiss, E.R. & P.A. del Giorgio. Controls on CO2 and CH4 replenishment and loss in a boreal river discontinuum. In Preparation.

Metabolic controls on carbon emissions and export in running waters

We are quantifying the role of aquatic ecosystem metabolism in modifying stream network carbon fluxes in the boreal Krycklan Catchment. We are also using data and model simulations to identify the principal sources of carbon dioxide emissions from temperate, boreal, and arctic streams and rivers. With J Karlsson, R Sponseller, J Klaminder, M Rosvall (Umeå University), H Laudon (Swedish University of Agricultural Sciences), et al.

Hotchkiss, E.R., R.O. Hall, R.A. Sponseller, D. Butman, J. Klaminder, H. Laudon, M. Rosvall, & J. Karlsson. 2015. Sources of and processes controlling CO2 emissions change with the size of streams and rivers. Nature Geoscience 8: 696-699.

Hotchkiss, E.R., R.M. Burrows, J. Klaminder, H. Laudon, R.A. Sponseller, & J. Karlsson. Integrating stream metabolism with river network carbon fluxes. In Preparation.

Ecosystem production and environmental change

Ongoing collaborations are using experimental ponds and whole-lake manipulations to identify how increases in temperature, nutrients, organic carbon, and/or fish harvest alter productivity, food web dynamics, and carbon cycling. A new collaboration recently funded by the Swedish Research Council Formas will quantify the effects of changing ice-cover regimes on emissions and metabolism of carbon in northern aquatic ecosystems. With J Karlsson, P Byström, J Ask, M Klaus, M Jonsson, M Hamdan (Umeå University), et al.

Klaus, M., S. MacIntyre, E.R. Hotchkiss, A.-K. Bergström, & J. Karlsson. Depth-integrated metabolism in clear and brown boreal lakes: the importance of accounting for vertical oxygen fluxes. In Preparation.

Byström, P.,  P. Hedström, E.R. Hotchkiss, P. Rodríguez, F. Vasconcelos, & J. Karlsson. Warming decreases fish population densities and biomass. In Preparation.

Sources, uptake, and fate of organic matter in freshwater ecosystems

We are interested in large-scale patterns of dissolved organic matter uptake and fate, how these may shift with environmental change, and the consequences for aquatic food webs. Collaborators from different working groups and workshops: WM Wollheim, MM Mineau (University of New Hampshire), JS Kominoski (Florida International University), RT Barnes (Colorado College), AJ Ulseth (University of Vienna), IF Creed (Western University), AK Bergström (Umeå University), et al.

Mineau, M.M., W.M. Wollheim, I.D. Buffam, S.E.G. Findlay, R.O. Hall, E.R. Hotchkiss, L.E. Koenig, W.H. McDowell, & T.B. Parr. 2016. Dissolved organic carbon uptake in streams: A review and assessment of reach-scale measurements. Journal of Geophysical Research - Biogeosciences 121: 2019-2029.

Creed, I.F., A.K. Bergström, et al. Global change-driven effects on dissolved organic matter and implications for aquatic food webs. In Preparation.