Flower Garden Banks

Off the coasts of Texas and Louisiana is hardly where you’d expect to find coral reefs, yet perched atop North America’s continental shelf, this sanctuary attracts divers to its "gardens" of brightly colored coral and sponges.

At a location 400 nautical miles north of the nearest reef, the corals of this sanctuary push the limits of existence. The contrast between the two Flower Garden Banks (East and West) and Stetson Bank (added to the sanctuary in October 1996) demonstrates what a big difference 30 miles can make.

Stetson is only 30 miles northwest of the Flower Gardens, causing temperatures to be a few degrees cooler in winter. This small difference means that corals do not thrive at Stetson. Instead, you get scattered coral colonies with a dominant sponge community, but no coral reef.

They are a reservoir of Caribbean species north of the tropics that contribute greatly to species diversity in this region. The Flower Garden’s East and West banks are home to a variety of Caribbean reef fish and invertebrates. Key species in this area include star and brain coral, the manta ray, hammerhead shark, and loggerhead turtle.

Unlike many coral reefs and other marine habitats, those of the Flower Gardens and Stetson Bank have not been severely impacted, to date, by human actions. The Flower Gardens still boast 50% coral cover. This offers an excellent opportunity to practice the more cost-effective prevention of habitat degradation versus the usually very expensive clean-up / restoration of a habitat.

Two salt domes form the foundation of Flower Garden Banks NMS. The raw materials for these structures—layers of sediment atop layers of salt-- were formed around the same time that the Gulf itself originated—160 to170 million years ago during the late Jurassic period.

The domes or diapirs were formed by differential pressures in the earth pushing upwards against overlying layers of sediment. In some cases, the pressure was so great that the salt layer comes close to breaking through the sea floor. It is not unusual to encounter these geological structures on the sea floor of the northern Gulf of Mexico. However, unlike the Flower Gardens NMS most of these domes do not support coral reefs.

In June 1974, scientists discovered an underwater salt lake towards the base of East Flower Garden Bank. With a salinity and toxicity that is only tolerable for certain strains of bacteria, this lake supports an unusual chemosynthetic community intriguing to scientists yet difficult to study. Lying at a depth of 220 feet, this lake can only be explored by remotely Operated Vehicle (ROV) or specialized diving.

The sanctuary received its designation in 1992.

Trivia: Flower Garden Banks is home to the US's northernmost coral reefs. Although it is an unlikely location for a habitat so closely associated with the tropics, Flower Garden Banks possesses the four crucial ingredients for coral reefs: clear water, warm temperatures, water movement, and larvae and spore sources.

Return to  The National Marine Sanctuaries