Introduction The Gulf of Mexico is a marginal sea, 1.5 million km2 in surface area with no major islands, open to the south but surrounded by continental land masses (North and Central America) to the west, north, and east. Barrier islands parallel much of the coast of the eastern Gulf of Mexico. North of Tarpon Springs, Florida (the mouth of the Anclote River, 25°10ʹ N), salt marshes and coastal swamps replace mangroves along the coastline. Specic to the area under consideration here (Figure 6.1), the continental shelf off the west coast of Florida is 800 km long and 25-250 km wide; the depth gradient on the shelf is 0.2-4 m km−1, but at the upper slope it steepens to 6-9 m km−1. Shelf and slope sediments off northwestern Florida are siliceous, but are mostly carbonate off the west coast of the peninsula (Brooks and Holmes 2011, Hine and Locker 2011).