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Flower Garden Banks

Flower Garden Banks National Marine Sanctuary (NMS) contains the northernmost coral reefs in the continental United States. The coral reef cap begins at about 55 feet (~17 m) in Flower Garden Banks National Marine Sanctuary and continues to a depth of about 160 feet (~50 m). But, that's not the bottom of the sanctuary. A variety of other habitats are found below the reef cap where depths range from 160 to 476 feet (~145 m).

Situated 70 to 115 miles off the coasts of Texas and Louisiana, the Flower Garden Banks sanctuary includes underwater communities that rise from the depths of the Gulf of Mexico atop underwater mountains called salt domes. The Flower Garden Banks (often simply the "Flower Gardens") is a US National Marine Sanctuary in the northwestern Gulf of Mexico, located roughly 105 miles (170 km) south of Sabine Pass, Texas. They are relatively isolated from other Caribbean and Gulf of Mexico coral reefs. The nearest reefs are 400 miles away in the Gulf of Mexico off the coast of Tampico, and over 745 miles from the coral reefs of the Florida Keys.

At the beginning of the 20th century, snapper and grouper fishermen nicknamed this area the "Texas Flower Gardens" because of the colorful marine life they saw on the reefs below them. By the time the sanctuary was designated, the term 'banks' had been added to the name as a reference to the salt dome formations upon which the reefs are perched.

East Flower Garden, West Flower Garden and Stetson Banks are only three among dozens of banks scattered along the continental shelf of the northwestern Gulf of Mexico. All of these banks are part of a regional ecosystem, heavily influenced by current patterns within the Gulf. Inflows from the large watershed that drains two-thirds of the continental United States also play a significant role in the health of this region.

East and West Flower Garden Banks are actually salt domes rising above the sea floor. Stetson Bank, located about 30 miles northwest of West Flower Garden Bank, is also a salt dome formation. As the Gulf of Mexico deepened and rivers began to flow from the land to the sea, mud, sand, and silt were steadily deposited over the salt layers. Eventually, pressures from these denser overlying sediments became great enough that the salt layers began to push upward. In some places the salt layers broke through completely, while in others they simply forced the seafloor to bulge upward in distinct domes.

Salt domes occur across the continental shelf of the northwestern Gulf of Mexico (see map below). Many of these are also named banks such as McGrail, Bright, Alderdice, Sonnier, etc. Some salt domes occur on land in coastal Louisiana and Texas. High Island, TX and Avery Island, LA are two examples. The oil that is part of the Strategic Petroleum Reserve is stored in such salt domes [hollowed out to make room for the oil]. In a number of salt domes (such as at Avery Island, Louisiana, home of McIlhenny's Tabasco Sauce), the salt is close enough to the surface to be mined.

The formation of offshore salt domes in the warm waters of the Gulf provided a colonization site for coral, which arrived and began reef-building roughly ten to fifteen thousand years ago. Two reefs, East Flower Garden Bank and West Flower Garden Bank, were part of the National Marine Sanctuary when it was created in 1992. In 1996, the smaller nearby Stetson Bank was added to the sanctuary.

The coral reef communities of East and West Flower Garden Banks probably began developing on top of the salt domes 10,000 to 15,000 years ago. These communities have thrived to the extent that dense coral reefs hide all traces of the deformed bedrock underneath. The nearest tropical reefs to the Flower Gardens are 400 miles away off the coast of Tampico, Mexico. Scientists believe that corals at the Flower Gardens probably originated from Mexican reefs when currents in the western Gulf of Mexico carried the young corals northward. A few of these larvae were lucky enough to settle on the hard substrate (sea floor) of the Flower Gardens salt domes. This location in the northwestern Gulf of Mexico provided all the comforts of home for hard corals: a hard surface for attachment, clear sunlit water, warm water temperatures (between 68 and 84 degrees Fahrenheit), and a steady food supply.

The difference in location between the Flower Garden Banks and Stetson Bank (about 30 miles NW) produces an amazing difference in the habitat. Because of Stetson's more northerly position, winter water temperatures are four degrees Fahrenheit cooler, on average, than the Flower Garden Banks. That small temperature difference is enough to prevent corals from growing fast enough to pile up into a coral reef at Stetson, as they have at the Flower Garden Banks.

Typical for coral reefs, the Flower Garden Banks contain a large number of aquatic species. Almost three hundred species of fish, twenty-one species of coral, several species of crustaceans, four dominant species of sponges, and a wide variety of sharks, skates, and ray. The loggerhead sea turtle is resident. Several resident whale sharks turn in frequent appearances; manta ray are also commonly sighted.

From their discovery in the early 1900s, to their designation as a National Marine Sanctuary in 1992, the Flower Garden Banks have come a long way. With proper management of human activities, the Flower Garden and Stetson Banks can be expected to continue providing enjoyment and wonder for humans and providing crucial habitat for marine life for years to come.

Although fishers are believed to have discovered and named the Flower Garden Banks, the first recorded discovery did not occur until 1936. The Flower Garden and Stetson Banks were included in a hydrographic survey of the Gulf of Mexico, conducted by the U.S. Coast & Geodetic Survey (now the National Ocean Service, of which the National Marine SanctuarySystem is a part). The survey provided valuable information about the geology and topography of the banks. Reviewers of this and other surveys conducted in the 1950s concluded that the banks probably originated from plugs of salt pushing the overlaying sediments up to form underwater mountains.

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