West Florida Shelf: A Natural Laboratory for the Study of Ocean Acidification

摘要

In 2007, the United Nations Intergovernmental Panel on Climate Change (IPCC) released its updated synthesis of climate change research, analysis of potential impacts to society, and options for mitigation. Recently, attention on ocean acidification and its consequences has gained momentum in the public sector, particularly since the release of the Kleypas and others (2006) report (for example, write-ups in Nature, August 2006, and The New Yorker, November 2006 issues). The report identifies declining oceanic pH and carbonate-ion concentrations as a consequence of increased atmospheric and surface- ocean carbon dioxide. The possible impact is providing questions that are amenable to both experimental and field study. Seibel and Fabry (2003, as summarized in Kleypas and others, 2006) postulated if reduced calcification decreases a calcifying organisms fitness or survivorship, then such calcareous species may undergo shifts in their latitudinal distributions and vertical depth ranges as the CO2 /carbonate chemistry of seawater changes. To date, very limited quantitative data exist with which to test this hypothesis, particularly in shelf environments. The continental shelves of Florida provide an ideal natural laboratory in which to test latitudinal (and depth) shifts in habitat ranges of calcifying organisms. Both the east and west Florida shelves extend from warm temperate to subtropical latitudes. Along this gradient, carbonate sedimentation changes from predominantly animal-produced shell hashes known as heterozoan carbonates that accumulate at rates of centimeters per 1,000 years, to subtropical reef environments where photozoan carbonate sediments are produced in association with photosynthesis, at rates that can exceed a meter per 1,000 years (hyper-calcification). Changes in either latitudinal or depth distributions of these benthic assemblages on the Florida shelves would provide convincing evidence of ecosystem-level effects of ocean acidification on calcifying organisms. The following report is a compilation of projects performed by students from the University of South Florida College of Marine Science, who participated in Dr. Pamela Hallocks cruise on the R/V Suncoaster during spring 2008.