Flux and fate of carbon from cells to ecosystems - coupled fluxes of C, N and P

The research in ecological stoichiometry deals with three basics priciples: The Liebig minimum priciple, the mass balance principle and the principle of homeostatic regulation. These priciples may be applied on all levels from single cells to ecosystems, and the key issue is to determine how carbon (C) uptake, release and sequestration may be governed by key limiting elements like phosphorus (P) and nitrogen (N). Stoichiometric principles is thus instrumental for the understanding of the regulation of C regulation at the cellular or organismal level, carbon flow in food webs, and thus - we believe - global carbon cycling.

Current research here involves the regulation and balance of carbon in organisms from phytoplankton and bacteria to zooplankton and insects at the organismal level, to catchment-lake interactions at the ecosystem scale. Basically this research build on mass-balance principles, but also includes detailed studies on C-metabolism, and the interaction between cycling of C and other key elements like N, P and Si at various levels.

At one end of the scale, the principle can be applied at the ecosystem level. E.g. in collaboration with Norwegian Institute for Water Research and University of Biological Sciences, we have been running a large scale project with the ultimate aim to model nation-wide C-cycling in catchments (funded by NFR), and also here include the role of atmospheric N-deposition and climate on the coupling of the key elements C, N, P and Si. We have modelled how climate, cathment variables and N-deposition in concert affect the concentration and flux of these elements - and the ratios between them - in lakes, and can from this also project future trends (cf. Hessen et al. Limnology and Oceanography 54: 2520-2528) and a series of upcoming papers. We have also together with US and Swedish colleagues made a comparison between ecosystems in Norway, Sweden and USA receiving high and low N-depositon, and demonstrated that high N-depositon likely have shiftet nutrient limitation from N to P in a vast number of lakes (Science, 2009, in press).

At the other end of the scale, we know that access to P and N may regulate the balance between ribosomal and protein synthesis, and thus potentially control growth rate of organisms. We have also recently postulated that P-deficiency and reallocation of P from DNA to RNA may serve as an evolutionary driver towards reduced genome size (Trends in Evolution and Ecology, in press).

Inbetween, we have all the stoichiometrically driven fluxes and species interactions within food webs. Hence Ecological stoichiometry (cf. Sterner and Elser 2002, Ecological Stoichiometry, Princeton University Press) may serve as a unifying tool for adressing key questions related to the flux of energy and matter at all levvels from atoms to ecosystems. A more comprehensive overview and update see Jim Elsers illuminating sites: http://www.elserlab.asu.edu/index.html  and http://stoichiometry.wordpress.com/