Showing papers by "Burke Hales published in 2008"

Evidence for Upwelling of Corrosive "Acidified" Water onto the Continental Shelf

Abstract: The absorption of atmospheric carbon dioxide (CO2) into the ocean lowers the pH of the waters. This so-called ocean acidification could have important consequences for marine ecosystems. To better understand the extent of this ocean acidification in coastal waters, we conducted hydrographic surveys along the continental shelf of western North America from central Canada to northern Mexico. We observed seawater that is undersaturated with respect to aragonite upwelling onto large portions of the continental shelf, reaching depths of approximately 40 to 120 meters along most transect lines and all the way to the surface on one transect off northern California. Although seasonal upwelling of the undersaturated waters onto the shelf is a natural phenomenon in this region, the ocean uptake of anthropogenic CO2 has increased the areal extent of the affected area.

Degradation of phytoplankton-derived organic matter: Implications for carbon and nitrogen biogeochemistry in coastal ecosystems

Abstract: Experiments were conducted using seawater from the Oregon continental shelf to determine: (1) rates of phytoplankton-derived particulate organic matter (POM) and dissolved organic matter (DOM) degradation by natural microbial communities, and (2) whether inorganic nutrients or flagellate grazing limit the bacterial response to, and subsequent degradation of, the DOM. In the initial seawater samples, nutrients were depleted and organic matter concentrations were elevated above concentrations found in upwelled water, indicative of recent bloom conditions. In whole water treatments incubated for 3 d, an average of 24% of the total organic C and 33% of the POC was degraded, with some portion of the POC being converted to DOC. In treatments incubated after POM was removed by filtration, DOC degradation was initially rapid and then proceeded at a slower rate. After 3 d, an average of 41% of the DOC was degraded. Selective degradation of the C-component of both the POM and DOM relative to the N-component was observed. Reductions in flagellate grazing resulted in increases in bacterial abundance and enhanced DOC degradation, while inorganic nutrient amendments had little effect. Overall, these results suggest that a fraction of the phytoplankton-derived POM and DOM can be rapidly degraded, contributing to oxygen consumption on the continental shelf. The long degradation time of a less labile DOC fraction relative to potential offshelf transport mechanisms suggests that Oregon's coastal waters may be a source of DOC to adjacent offshore waters of the North Pacific.

North American Continental Margins : a Synthesis and Planning Workshop : Report of the North American Continental Margins Working Group for the U.S. Carbon Cycle Scientific Steering Group and Interagency Working Group

Abstract: Report of the findings and recommendations of the North American Continental Margins workshop held in Boulder Colorado in September of 2005 to assess the state of carbon cycle science in the margins surrounding North America.

Ocean Acidification's Effects on Marine Ecosystems and Biogeochemistry: Ocean Carbon and Biogeochemistry Scoping Workshop on Ocean Acidification Research; La Jolla, California, 9–11 October 2007

Abstract: Rising atmospheric carbon dioxide (CO2) concentration is causing global warming and ocean acidification. Nearly one third of the total anthropogenic CO2 produced in the past 200 years has been taken up by the oceans. While oceanic uptake of anthropogenic CO2 may lessen the extent of global warming, evidence suggests that effects of anthropogenic CO2 on ocean chemistry have profound consequences for marine organisms, potentially altering ecosystem structure, food webs, and biogeochemical processes. An assemblage of 93 scientists participated in a 3-day workshop to develop research strategies that address present and future ocean acidification impacts. The Ocean Carbon and Biogeochemistry program (http://www.us-ocb.org) sponsored this workshop, with support from the U.S. National Science Foundation, National Oceanic and Atmospheric Administration, NASA, U.S. Geological Survey, and Scripps Institution of Oceanography.