Current Research

Carbon fluxes in aquatic networks

We are quantifying external and in situ physical and biological controls on aquatic network carbon (C) fluxes. We are also developing models that identify the principal drivers of C fluxes and cycling in river networks. With P del Giorgio (Université du Québec à Montréal), 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 DOI: 10.1038/NGEO2507.

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

Nutrient limitation in boreal streams

We are exploring interactions between nutrient and C availability, metabolism, and microbial assemblages in streams with varying water chemistry and landscape characteristics. With R Burrows, H Laudon, B Mckie (Swedish University of Agricultural Sciences), M Jonsson, R Sponseller (Umeå University).

Ecosystem production and environmental change

These projects are using experimental ponds and whole-lake manipulations to identify how increases in temperature, nutrients and/or organic carbon alter pond productivity, food web dynamics, and carbon cycling. With J Karlsson, M Jonsson, P Byström, M Klaus (Umeå University), et al.

Tracing carbon sources in aquatic food webs

Large subsidies of terrestrial organic matter may support heterotrophic C and nutrient demands in boreal streams and rivers, but the degree to which in-stream photosynthesis contributes to food web dynamics is not well known. We are using stable isotopes to measure the contributions of terrestrial and aquatic C to invertebrate consumers and linking diet sources with ecosystem C fluxes. With E Landström, R Sponseller, J Karlsson (Umeå University).

Landström, E., E.R. Hotchkiss, R.A. Sponseller, & J. Karlsson. Resource use by 
macro-invertebrates in boreal streams. In Preparation.

Ecosystem metabolism

Ecosystem metabolism (photosynthesis and respiration) is a metric that integrates a range of habitats, organisms, and biological processes. I use model estimates of ecosystem metabolism in many of my ongoing research projects to measure rates of food production and consumption, quantify the role of metabolism in carbon and nutrient cycling, and monitor ecosystem responses to environmental change.

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

I am interested in large-scale patterns of dissolved organic matter (DOM) 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. Dissolved organic carbon uptake in streams: A review and assessment of reach-scale measurements. In Preparation.

The consequences of multiple species invasions in a productive spring stream

Four non-native fish species (convict cichlid, green swordtail, guppy, tadpole madtom) and one non-native snail species (red-rim melania) have established populations in Kelly Warm Springs, Grand Teton National Park, Wyoming. We are using historical samples to compare densities and biomass of native invertebrate species before and after the red-rim melania invasion. To quantify how multiple species invasions may influence stream food webs, we also measured fish and invertebrate population densities and biomass as well as fish stomach contents along a natural temperature gradient. With T Niekum, S Laske, R Hays, RO Hall (University of Wyoming).