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 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. Sources and control of COemissions from running waters. In Revision.




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, M. Blackburn (Swedish University of Agricultural Sciences), M. Jonsson, R. Sponseller (Umeå University).

Burrows, R.M., E.R. Hotchkiss, M. Jonsson, H. Laudon, B.G. McKie, & R.A. Sponseller. In Press. Nitrogen limitation of heterotrophic biofilms in boreal streams. Freshwater Biology.





Ecosystem production and environmental change

This project is using experimental ponds to identify how increases in temperature and/or organic matter alter pond productivity, food web dynamics, and C cycling. With J. Karlsson, M. Jonsson, P. Byström (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).







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 carbon in freshwater ecosystems


We are interested in large-scale patterns of dissolved organic carbon (DOC) uptake and fate, as well as the importance of a river network perspective in quantifying DOC cycling and ecosystem services. With W.M. Wollheim, M.M. Mineau (University of New Hampshire), J.S. Kominoski (Florida International University), R.T. Barnes (Colorado College), A.J. Ulseth (University of Vienna), 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 Review.


Fish diet analysis with Bayesian mixing models

We will quantify individual-, size class-, and population-level fish diets using stable isotopes, fish stomach contents, and hierarchical Bayesian mixing models. 
With S. Laske (University of Alaska-Fairbanks), F. Rahel, W. Hubert (University of Wyoming).








The role of multiple non-native species in a stream food web

Four exotic fish species (convict cichlid, green swordtail, guppy, tadpole madtom) and one exotic snail species (red-rim melania) have established populations in Kelly Warm Springs, Grand Teton National Park, Wyoming. To understand how exotic species invasions and changes in temperature may impact native species, we are comparing densities and biomass of native invertebrate species before and after the red-rim melania invasion and sampling native and invasive fish and invertebrate populations along a natural temperature gradient. With T. Niekum, S. Laske, R. Hays, R.O. Hall (University of Wyoming).