@Sea - Diving to Extremes - Habitat Information

	HYDRATES AND SEEPS: THE BASIS FOR AN AMAZING FOOD WEB Approximately 100 miles south of Louisiana and Texas, the broad continental shelf of the Gulf of Mexico becomes very steep. Instead of falling smoothly to the 3600 meter depths found at the center of the basin, the slope heaves and twists across most of its northern edge. These mounds, ridges, and valleys were formed over geologic time from the upheavals of a vast salt deposit buried over 100 million years ago. Oil and methane (natural gas) seeps dot the continental slope and slope break in the Gulf of Mexico. During the Jurassic Period (208-146 million years ago), the area now known as the Gulf of Mexico was dry. Massive amounts of salt were deposited on the dried sea bed. When the waters returned, sediment accumulated, covering the salt deposits and subjecting them to great pressure. The overlying sediments eventually became rock. Under these rock layers, salt rose to the surface and formed huge pillars called diapirs. The diapirs created cracks in the rock layers, allowing methane-rich natural gas to escape. The enormous pressure from salt upheavals formed craters at the surface of the sea floor. Here, salt mixed with water forming pools of brine that are four to five times as salty as seawater. These brine pools are home to large communities of mussels (Bathymodiolus childressi). These mussels contain symbiotic bacteria on their gills that feed on methane gas, synthesizing carbohydrates using energy released in a series of chemical reactions in a process called chemosynthesis. In turn, the mussels consume the bacteria, along with other particulates filtered from the water column. Thus, the asociated living community thrives in this lightless deepwater ecosystem where photosynthesis is not possible. The combination of cold water, high pressure due to the water depth, and cracks seeping gas, form the unusual geological features known as gas hydrates. In these formations, gas is trapped in a lattice of water crystals forming methane ice. In locations where gases escape from the cracks under the Gulf of Mexico, bacterial mats form. These bacterial colonies give off an enormous amount of carbon dioxide. In fact, gas hydrates are the single largest sources or organic carbon on Earth! The worldwide amounts of carbon bound in gas hydrates is conservatively estimated to total twice the amount of carbon to be found in all known fossil fuels on Earth. Certain types of bacteria living on these formations transform sulfate and hydrocarbons into hydrogen sulfide. Tubeworms (Lamellibrachiasp.) flourish at gas hydrates like Bush Hill. The worms are able to extract oxygen and hydrogen sulfide (normally lethal to marine life) with their plume-like gills or via root-like structures at their bases. Tubeworms have a type of hemoglobin that carries the hydrogen sulfide to symbiotic bacteria. The tubeworms, in turn, obtain nutrition from these bacteria. Hydrates are also home to iceworms (Hesiocaeca methanicola).This is a newly discovered species of polychaete worm found living on the exposed surfaces of methane gas hydrate mounds. These pink worms are about 1-2 inches in length, and apparently carve out holes in the surface of the gas hydrate. It is not yet known to what extent the worm colonies use the hydrate mounds for protection or nutrition, but they are at present the only animals known to inhabit this unique habitat. The worms, discovered during a JSL dive in 1997, represent the first time animals have been found living in the methane mounds. The research projects on the continental slope of the Gulf of Mexico taking place during Diving to Extremes are very important. Discoveries made during this mission will help scientists increase their understanding of the biogeochemical processes and interactions that support lush chemosynthetic communities in complex Gulf geological settings. CHECK OUT OUR RELATED LINKS SECTION FOR MORE!