Browning of freshwater ecosystems: culprits and consequences of global change

Background/Question/Methods

Growing evidence suggests that terrestrial-derived dissolved organic carbon (DOC) export to aquatic ecosystems is on the rise.  Increasing temperatures, land use change, altered hydrology, and atmospheric deposition have all been identified as culprits for this global-scale “browning” of freshwater ecosystems.  How will increasing DOC inputs from land influence the structure and function of freshwater ecosystems in the coming decades?

Results/Conclusions

In this talk, I review and synthesize existing knowledge about how changing DOC inputs affect freshwater ecosystems.  In particular, I focus on the following topics: 1) Allochthony: the mechanisms and degree to which terrestrial organic matter supports production of aquatic food webs, 2) Stability: the importance of terrestrial DOC as a donor-controlled resource that determines how ecosystems respond to perturbations, and 3) Alternate carbon pathways: the direct and indirect mechanisms by which terrestrial DOC influences carbon flow, including microbially mediated CO2 recycling and methanotrophy.  Importantly, this review will highlight a suite of techniques and approaches, including simulation modeling, experiments, and molecular tools that are being used to better understand how changes in the strength of land-water linkages will influence aquatic food webs and function under existing and future global change scenarios.