NO3, Fe, and diazotroph biomass - observations (left) and model (right) over top 50 m - from Fig 1, Dutkiewicz et al, 2014

Life on the Edge – How shifting marine province boundaries could provide a new metric for global change

In their new competition theory paper, appearing in the 2014 issue of Biogeosciences, Dutkiewicz et al examine the sensitivity of the biogeography of nitrogen fixers to a warming climate and increased aeolian iron deposition in the context of a global earth system model.

The new paper employs concepts from the resource-ratio theory to provide a simplifying and transparent interpretation of modeling results. Resource-ratio theory, a model of species interactions based on their use of shared resources, was proposed in 1972 by Robert MacArthur and later expanded in an article (1980) and a book (1982) by David Tilman. This “resource-ratio theory” has been used to make a number of testable predictions about competition and community patterns in many areas of the ecological sciences.

In their paper, the team, having demonstrated that a set of clearly defined, easily diagnosed provinces are consistent with the theory, use the framework to show that the regions most vulnerable to province shifts and changes in diazotroph biogeography are the equatorial and South Pacific, and central Atlantic. Warmer and dustier climates favor diazotrophs due to an increase in the ratio of supply rate of iron to fixed nitrogen.

The authors suggest that the emergent provinces could provide a standard diagnostic for global change models, allowing for rapid and transparent interpretation and comparison of model predictions and the underlying mechanisms. Their analysis suggests that monitoring of real world province boundaries, indicated by transitions in surface nutrient concentrations, would provide a clear and easily interpreted indicator of ongoing global change.


Dutkiewicz, S., Ward, B. A., Scott, J. R., and Follows, M. J. (2014) Understanding predicted shifts in diazotroph biogeography using resource competition theory, Biogeosciences, 11, 5445-5461, doi: 10.5194/bg-11-5445-2014.