West Florida Shelf- A Natural Laboratory for the Study of Ocean Acidificiation - Open-File Report 2010-1134 (Paperback)

Declining oceanic pH and carbonate-ion concentrations are well-known consequences of increased atmospheric and surface-ocean partial pressure of carbon dioxide (pCO2). The possible subject of shifts in seawater carbonate chemistry on biocalcification and survival rates of marine organisms provides questions amenable to both experimental and field study (Kleypas and Langdon, 2006). To date, limited quantitative data exist with which to formalize and test hypotheses regarding such impacts, particularly in continental-shelf settings. The continental shelves of Florida provide an ideal natural laboratory in which to test latitudinal (and temperature and depth) shifts in habitat ranges of calcifying organisms. Both the east and west Florida shelves extend from warm temperate to subtropical latitudes; additionally, the west Florida shelf has very little siliciclastic influx to mask the carbonate production. This study utilizes the natural laboratory of the west and southwest Florida shelf (fig 1.1) to examine the transition from foramol (predominately foraminifera and molluscan) carbonate sediments, characteristic of the west-central Florida shelf, to chlorozoan (algal and coral) sediments characteristic of the southwest Florida shelf. The west Florida shelf is a mixed siliciclastic carbonate ramp that to the south transitions to the carbonate-dominated southwest Florida shelf (Enos, 1977; Brooks and others, 2003). The west Florida shelf is a distally steepened carbonate ramp that is 250 kilometers (km) wide (Read, 1985). It is covered by a veneer of unconsolidated sediment consisting of mainly biogenic carbonate and quartz in the near shore, with subordinate amounts of phosphate. The sediment-distribution pattern is largely a function of proximity to source, with physical processes playing a minor role in distribution. The carbonate sand-and-gravel fraction is produced by organisms within the depositional basin of the west Florida shelf (Brooks and others, 2003). The s