QUANTIFYING CARBON LOSSES FROM TROPICAL WATERSHEDS: THE EFFECTS OF URBANIZATION ON ORGANIC AND INORGANIC CARBON FLUX
Recent evidence has highlighted the importance of streams and rivers in the processing, evasion, and downstream export of carbon. Tropical forests in particular store a disproportionate amount of carbon, but because of high annual runoff rates, mountainous watersheds in the tropics have the potential to deliver large quantities of carbon to downstream coastal ecosystems. Despite the likely importance of tropical streams to regional carbon budgets, relatively few data on carbon transport and efflux exist outside of the Amazon region. In this study we investigated baseflow patterns and controls on dissolved carbon export as well as carbon gas concentrations and efflux from streams draining both forested and urban catchments in northeast Puerto Rico. We found no relationship between pCO2 and baseflow discharge, represented by Strahler stream order, although first-order streams contained the most variability in measured CO2 concentration. Concentrations of dissolved organic and inorganic carbon were significantly higher in the Rio Piedras, a heavily urbanized catchment, but interestingly, annual carbon fluxes converge in these contrasting watersheds. Our results indicate that these tropical coastal streams can be sources of carbon gases to the atmosphere, and that a shift in aquatic carbon sources and/or processing rates associated with urbanization can drastically alter the concentration of both organic and inorganic carbon.
Koenig, L.E., A. Ramirez, and W.H. McDowell (2014): The impacts of urbanization on dissolved organic and inorganic carbon fluxes in a tropical watershed (oral presentation). Joint Aquatic Sciences Meeting 2014 Portland, Oregon. .
This Paper/Book acknowledges NSF CZO grant support.