Site History and Resources
Located in the northwestern Gulf of Mexico, Flower Garden Banks National Marine Sanctuary includes three separate areas, known as East Flower Garden, West Flower Garden and Stetson Banks. The banks range in depth from 55 to nearly 500 feet (16 to 150 meters), perched atop underwater hills formed by rising domes of ancient salt, and support several distinct habitats, including the northernmost coral reefs in the continental United States. These and other similar formations throughout the northwestern Gulf of Mexico provide the foundation for essential habitat for a variety of tropical and temperate species.
The combination of location and geology makes the Flower Garden Banks extremely productive and diverse, and presents a unique set of challenges for managing and protecting its natural wonders.
Discovery of the Banks
The Flower Garden Banks have a rich but comparatively short history of exploration and discovery. Although snapper fishermen in the early 1900s nicknamed the area the Texas Flower Gardens because of the brightly colored “rocks” (corals) that were visible through the clear water, the first official documentation of the banks did not occur until the 1930s. For the next 30 years, the banks were occasionally included as part of investigations of larger portions of the Gulf of Mexico. Despite these investigations and rumors of coral reefs from the fishing community, many scientists believed that any coral reefs located here must be dead, primarily because of the depth and water temperatures.
Then, in the 1960s, expeditions conducted by the Houston Museum of Natural Science, the U.S. Navy and volunteer divers settled the debate. Divers visited the reefs and brought back specimens and reports of living, healthy coral reefs that were stunning in their beauty. Exploration of the area soon began in earnest, as the banks became a popular spot for both researchers and recreational divers.
As new technology allowed oil and gas production to move offshore into deeper water in the 1970s, concerns about detrimental impacts to the reefs increased. The Minerals Management Service established "No Activity Zones" around most of the banks in the northern Gulf of Mexico. While these measures controlled impacts from oil- and gas-related activities, they did not cover activities such as diving, anchoring, fishing and shipping. The recreational dive community took action to address anchoring issues and formed the Gulf Reef Environmental Action Team (GREAT). This group raised funds and recruited volunteers to install mooring buoys. These and other divers also offered their services to researchers involved in characterizing and monitoring the banks. Nevertheless, continued anchoring by large ships and impacts from certain types of fishing made it apparent that additional formal protection was needed. It would take the combined efforts of recreational divers, researchers, federal agencies and advocates in congress to get the Flower Garden Banks designated as a national marine sanctuary in 1992.
A strong tradition of discovery and community involvement continues today. The sanctuary science team, in concert with a wide array of partners, continues to explore, study, and monitor the sanctuary ecosystems, as well as those around it that are most likely to influence the sanctuary’s continued health.
East and West Flower Garden Banks
The Flower Garden Banks are unique among ecosystems in the Gulf of Mexico. They contain the northernmost coral reefs in the continental United States. The nearest neighboring tropical coral reefs are 400 miles (643 km) away in the Bay of Campeche, off the Yucatan peninsula of Mexico, while the closest U.S. coral reefs are located 750 miles (1,207 km) southeast, in the Florida Keys.
East Flower Garden Bank is a pear-shaped dome, 5.4 by 3.2 miles (8.7 by 5.1 km) in size, capped by 250 acres (1 square km) of coral reef that rise to within 55 feet (17 meters) of the surface. West Flower Garden Bank is an oblong-shaped dome, 6.8 by 5 miles (11 by 8 km) that includes 100 acres (0.4 square km) of coral reef area starting 59 feet (18 meters) below the surface.
Brain and star corals dominate the coral caps of the Flower Garden Banks, with a few coral heads exceeding 20 feet (6 meters) in diameter. There are at least 21 species of coral on the coral cap, covering over 50% of the bottom to depths of 100 feet (30 meters) (Bright et al. 1984, Continental Shelf Assoc., Inc. 1996, Gittings 1998, Dokken et al. 1999, Dokken et al. 2003,Schmahl 2002, Pattengill-Semmens and Gittings 2003, Schmahl and Hickerson 2004, Aronson et al. 2005, Hickerson and Schmahl 2005), and exceeding 70% coral cover in places to at least 130 feet (40 meters) (Precht et al. 2005). Interestingly, the coral caps do not contain some species commonly found elsewhere in the Caribbean, such as many of the branching corals, sea whips or sea fans. In fact, despite the high cover, only about a third of Caribbean hard coral species are found in the Flower Garden Banks National Marine Sanctuary.
A recent observation of note is the discovery of two live Acropora palmatacolonies, one each on the East and West Flower Garden Banks. These discoveries are some of the deepest records of these species (Zimmer et al. 2006).
Less well-known is the deepwater habitat of the Flower Garden Banks that makes up over 98% of the area within the sanctuary boundaries. Habitats below recreational scuba limits include algal-sponge zones, "honeycomb" reefs (highly eroded outcroppings), mud flats, mounds, mud volcanoes and at least one brine seep system. Different assemblages of sea life reside in these deeper habitats, including extensive beds of coralline algae pavements and algal nodules, colorful sea fans, sea whips and black corals, deep reef fish, batfish, sea robins, basket starfish and feather stars.
Stetson Bank is located 70 miles (113 km) south of Galveston, Texas, and 30 miles (48 km) to the northwest of West Flower Garden Bank. Depths at Stetson Bank range from about 55 feet (17 meters) to 170 feet (52 meters). Environmental conditions at Stetson Bank, which include more extreme fluctuations in temperature and turbidity than at the Flower Garden Banks, do not support the growth of reef forming corals like those found at East and West Flower Garden Banks. Divers have described Stetson as having a "moonscape" appearance, with distinct pinnacles that push out of the seafloor for 1,500 feet (457 meters) along the northwest face of the bank. An area referred to as the "flats" stretches out behind the pinnacles region, and is dotted with low relief outcroppings.
The pinnacles of Stetson Bank are dominated by fire coral (Figure 5) and sponges, with cover exceeding 30% (Bernhardt 2000). There are at least nine coral species at Stetson Bank, but with the exception of fire coral and a large area ofMadracis decactis, most colonies are small and sparsely distributed. Algae, sponges and rubble dominate the flats.
A ring of claystone outcroppings forming a halo around the main feature of Stetson Bank (Gardner et al. 1998) was identified through surveys after the designation of the sanctuary boundaries. Sponges, gorgonians and black corals dominate this impressive ring of outcroppings at about 165 - 196 feet (50 - 60 meters) depth. Deep reef fish and invertebrates are prominent inhabitants of the "Stetson Ring." Much of the feature is outside of the current sanctuary boundaries, an issue that has been identified as a priority to rectify through the management plan review.
East and West Flower Garden Banks and Stetson Bank are three among dozens of banks scattered along the continental shelf throughout 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 Mississippi and Atchafalaya watersheds, which drain two-thirds of the continental United States, also play a significant role in the health of this region.
From the south, the Gulf of Mexico is fed by warm water from the Caribbean, which enters the Gulf between Mexico's Yucatan Peninsula and Cuba. Called the Yucatan Current, this water flows northward before turning east then south along Florida’s west coast, forming the Gulf Loop Current and exiting through the Straits of Florida.
The Yucatan Current is variable, sometimes barely entering the Gulf before turning east, and at other times traveling almost to Louisiana's coast before swinging toward Florida. Frequently, meanders of the Gulf Loop Current (which is what the Yucatan Current is called after it enters the Gulf) break away from the main current and form circular eddies that move westward, generally slightly to the south of the Flower Garden, Stetson and other banks to the west. These currents help distribute animal larvae, plant spores and other imports from the south, which accounts in part for the many Caribbean species found in the northern Gulf of Mexico (Lugo-Fernandez et al. 2001, Gold et al. 2004, Sammarco et al. 2004). As it continues, the loop current also carries with it “passengers” from the northern Gulf to destinations along its route to the Atlantic.
Meanwhile, shallow tropical waters of the southern Gulf of Mexico move northward along the Mexican coast into Texas before turning east. These wind-driven currents also cross over the Flower Garden, Stetson and other banks and add to the tropical influence in the region.
Multiple rivers emptying into the Gulf of Mexico drain the interior of North America (as much as two-thirds of the United States) (Figure 6). These rivers bring with them all of the runoff accumulated from cities, suburbs, agriculatural areas and wild lands along their routes. Before reaching the Gulf, this water source is partially depleted by extractions for municipal, industrial and agricultural consumption, thus reducing freshwater inflows that sustain the estuaries. When healthy, the estuaries filter sediments and pollutants from the water, export organic material for the nearshore food chain, and provide nursery areas for many species, some of which later move offshore to the system of banks along the continental shelf.
Studies of physical oceanography have demonstrated that water flow connects the dozens of banks along the continental shelf of the northwest Gulf of Mexico. More specifically, rates and patterns of current flow in the region make it likely that the larvae and spores of many animals and plants disperse from bank to bank and perhaps to or from features elsewhere in the Gulf of Mexico (Lugo-Fernandez 1998). Observations show that reef corals probably originating at the Flower Garden Banks attach and grow on petroleum platforms in the northwestern Gulf (Bright et al. 1991). Biogeographic investigations showing high similarity in habitats at similar depths in the region further support the likelihood of ecological connections between features (Rezak et al. 1985, Gittings et al. 1992a).
Recent explorations, however, indicate that there may be an even greater physical connection than previously known. Technological advances have allowed higher resolution mapping, which has revealed systems of low-relief geological features (such as rock outcroppings) between some banks. Some have been explored in the last few years, and it appears that they may serve as direct connections between the banks. Transitory species such as jacks have been observed feeding on fish along these deep outrcrops, presumably as they move between the larger features of the region. As we build upon the knowledge established by the discoveries to date, we may discover that these interactions play a crucial role in maintaining the health of the sanctuary's living marine resources.
Added to this are the thousands of oil and gas production platforms in the northwestern Gulf that serve as artificial reefs by providing hard surfaces to which larvae and spores may attach. Platforms also provide substrate for range expansions of tropical species, such as the sergeant major (Abudefduf saxatilis) and tessellated blenny (Hypsoblennius invemar) (Pattengill 1998), as well as invasive species, such as the orange cup coral (Tubastraea coccinea) (Fenner and Banks 2004) and certain barnacles (Gittings 1985). Scientists are still assessing the extent to which this system of platforms affects the overall biological diversity and productivity of the Gulf.
The primary biological habitats within the sanctuary boundaries are as follows (Figure 7):
- Coral Reef: 1.03 square miles (2.68 sq. km), representing 1.84% of the area within the sanctuary. Over 50% coral coverage, representing a remarkably healthy reef system.
- Coral Community (i.e., non-reef-building): 0.019 square miles (0.05 sq. km), representing 0.03% of the area within the sanctuary.
- Coralline Algae Zone:
- Algal nodules: 11 square miles (28.27 sq. km), representing 19.45% of the area within the sanctuary.
- Coralline Algal reef: 1.9 square miles (4.98 sq. km), representing 3.43% of the area within the sanctuary.
- Deep Coral: 4.78 square miles (12.37 sq. km) representing 8.51% of the area within the sanctuary.
- Soft Bottom Community: 37.4 square miles (96.95 sq. km) representing 66.69% of the area within the sanctuary.
Coral Reef Zone
The coral reef zone is the shallowest zone at the Flower Garden Banks, occurring at depths of between approximately 55 and 145 feet (17 to 44 meters). It is dominated by large, closely spaced boulder and brain coral heads, many up to 10 or more feet (greater than 3 meters) in diameter and height. Reef topography is relatively rough, with many vertical and inclined surfaces and crevices. Between groups of coral heads, there are numerous sand patches and channels. This is the part of the sanctuary most familiar to visitors.
This zone is characterized by a high diversity coral assemblage dominated byMontastraea spp., Diploria strigosa, Colpophyllia natans, and Porites astreoides. Coralline algae, and filamentous and leafy algae also occur on reef substrates, but are not dominant members of the benthic assemblage. Madracis mirabilisforms large monotypic stands in deeper portions of the coral reef community. Sponges and Agaricia spp. are common in crevices and cavities of the reef.
Coral Community Zone
The coral community zone is comprised of areas that, while not considered to be “true” coral reefs, do contain hermatypic (reef-building) coral species at low densities, or are characterized by other coral reef associated organisms, such as the hydrozoan Millepora spp. (fire coral), sponges and macroalgae. Coral communities are found in depth ranges similar to those that contain coral reefs (59 to 165 feet/18 to 50 meters), where other environmental factors have not allowed full development of coral reefs. The “coral community” includes the “Millepora-sponge” zone described by Rezak et al. (1985), and also includes some other coral associated assemblages. Stetson Bank is dominated by this community type between 59 and 139 feet (18 to 42 meters).
The coral community at the Flower Garden Banks (formerly known as the low-diversity coral reef) is characterized by the blushing star coral, Stephanocoeniaintersepta, the large star coral, Montastraea cavernosa, and the large grooved brain coral, Colpophyllia natans, and occurs between depths of 132 and 182 feet (40 to 55 meters). The lettuce corals Agaricia spp. and brain coral Diploriastrigosa are also an important part of the community. Crustose coralline algae are the dominant encrusting form on dead coral rock, along with leafy algae and numerous sponges. The dominance of hard corals declines with depth, and few coral colonies occur between 148 to165 feet (45 to 50 meters) at East and West Flower Garden Banks. Coral communities at Stetson Bank are dominated by theMillepora-sponge assemblage, along with areas of Madracis decactis and individual colonies of Diploria strigosa and several other coral species.
Coralline Algae Zone
Found in depths between 148 and 297 feet (45 to 90 meters), the coralline algae zone is made up of algal nodule fields, pavements and coralline algal reefs. Coralline algae occurs within the photic zone above approximately 280 feet (85 meters), as coralline algae is a photosynthetic organism (i.e., requires light to survive). This zone is biologically rich in sponges, algae, gorgonians, and black coral and harbors healthy populations of deep reef fish including rough tongue bass (Pronotogrammus martinicensis), scamp (Mycteroperca phenax), and marbled grouper (Dermotolepis inermis).
The coralline algae zone at the Flower Garden Banks (including the area formerly known as the “algal sponge zone”) is dominated by crustose coralline algae that form large beds of algal nodules (also called “rhodoliths”), or massive reef structures composed of large plates and ridges. A variety of sponge species are abundant in this zone, along with numerous antipatharians (black corals) and octocorals (sea whips). Few reef building corals occur at these depths, and are primarily limited to small isolated colonies.
Deep Coral Zone
Found in depths between typically below 295 feet (90 meters), the deep coral zone is dominated by eroded reef outcroppings, azooxanthellate (non-reef building) solitary hard corals, antipatharian and gorgonian corals, deep reef fish, sponges, bryozoans, and crinoids (feather stars).
The deep coral community at the Flower Garden Banks (formerly known as the “drowned reef” zone) occurs below water depths that support active photosynthesis. Rock surfaces are often highly eroded, and lack coralline algal growth. The deep coral zone is sometimes characterized by turbid water conditions, and reef outcrops may often be covered with a thin layer of silt (particularly at Stetson Bank).
Soft Bottom Community Zone
Large expanses of mud, sand, and silt substrates, which typify the soft bottom community zone, are found in the deepest parts of the banks and surrounding the banks. Features of the soft bottom community include pits, burrows, Cirrhipathes (Stichopathes) fields, stalked anemones, and other echinoderms. Squat lobster (Munida sp.) are often observed in this zone.
Deeper areas of the sanctuary are characterized by a soft, level bottom composed of both terrigenous sediments originating from coastal rivers and carbonate sediments resulting from calcareous planktonic remains and erosion of rocky outcrops and coral reef communities. Soft bottom communities are often characterized by sand waves, burrows and mounds. Transitional zones between soft bottom communities and hard bottom features are characterized by exposed rubble, isolated patch reefs or exposed hard bottom. Areas with buried or exposed carbonate rubble are often colonized by antipatharians, octocorals, or solitary hard corals. Soft bottom communities serve as important feeding areas for reef and reef-associated fishes (Rexing 2006).
The benthic habitat of Flower Garden Banks National Marine Sanctuary provides critical protection, food, and shelter for the associated fish community. At least 280 species of fish have been documented within the sanctuary, including colorful reef inhabitants such as parrotfish, wrasse, angelfish, boxfish, smooth trunkfish and squirrelfish (Bright and Pequegnat 1974, Pattengill 1998). Large schools of barracuda (Sphyraena barracuda) and pelagic jacks (Caranx spp.) greet divers as they enter the waters of the sanctuary in the summer. Winter brings enormous schools of mackerel (Scomberomorus sp.). The conspicuous deeper water fish in the sanctuary include rough tongue bass, threadnose bass, vermillion snapper, red snapper, scamp, and marbled grouper. Commercially targeted species include the snapper, grouper, jacks, and mackerel.
In June 1997, the "Mardi Gras wrasse" (Halichoeres burekae) was first observed by divers from the Reef Environmental Education Foundation (REEF) at East Flower Garden Bank, and subsequently in schools at Stetson Bank (Weaver and Rocha 2007) (Figure 8). This wrasse turned out to be not only new to the Flower Garden Banks sanctuary, but also new to science. The wrasse has also been reported from the reefs of Vera Cruz, Mexico, in the southern Gulf of Mexico.
Smooth trunkfish (Lactophrys triqueter) are common throughout the Caribbean, but the golden morph of the species is very rare (Pattengill-Semmens 1999) (Figure 9). It was first described at the Flower Garden Banks, and has since been rumored to occur in just one other place in the Caribbean.
Loggerhead and hawksbill sea turtles reside at all three banks of the sanctuary throughout the year. Loggerheads (Caretta caretta) are most often seen at night or in the late afternoon resting underneath ledges or coral heads (Figure 10). In the early morning they often leave the reef to feed in deeper areas of the sanctuary (Hickerson 2000). They can also be seen on the surface catching a breath. Sea turtles surface about once an hour for a couple of minutes, and then submerge to sleep or forage.
The most frequently observed loggerheads are juveniles approaching maturity, perhaps suggesting that the sanctuary reefs serve as a temporary residence for these animals while they prepare to move on to adult feeding areas. Adult female loggerheads have also been sighted on several occasions. Recent satellite and radio tracking studies have shown that while resident at the banks, loggerhead sea turtles have home ranges that are quite specific, but not entirely within sanctuary boundaries (Hickerson 2000).
Because hawksbill sea turtles (Eretmochelys imbricata) are primarily sponge-eaters, Stetson Bank offers an abundant food source and is likely an excellent habitat for these turtles. A young hawksbill sea turtle has been a resident of Stetson Bank since 1999. A small number of transient hawksbills have also been reported at both the Flower Garden Banks and Stetson Bank (Hickerson 2000).
Sharks & Rays
Approximately 20 species of sharks and rays have been documented at the Flower Garden and Stetson Banks, some seasonal, others year-round (Childs 2001). During the winter months, schooling scalloped hammerhead sharks (Sphyrna lewini) and spotted eagle rays (Aetobatus narinari) are visitors to all three banks. The reason for the seasonality of their visits is unclear, but the occurrence is quite predictable. Other winter visitors include occasional sandbar (Carcharhinus plumbeus) and tiger sharks (Galeocerdo cuvier), as well as spinner sharks (Carcharhinus brevipinna), which are often seen leaping out of the water. Summer months usually bring whale sharks (Rhincodon typus) to the area. These filter-feeding creatures can reach over 30 ft (9 m) in length. Nurse sharks are sometimes seen resting under ledges or in crevices in the coral, while large schools of silky sharks (Carcharhinus falciformis) are known to aggregate around oil and gas platforms in the vicinity of the sanctuary during the winter months. Silky sharks have recently been observed in large schools, exhibiting mating behavior at Stetson Bank.Manta (Manta birostris) and the very similar-looking mobula rays (Mobula spp.) are regular visitors to the sanctuary (Figure 11). At least 58 different individuals have been documented and identified by distinctive markings on their undersides. Recent acoustic tracking of the manta rays have revealed that the mantas are moving between at least the three banks of the sanctuary — an animal that was tagged on Stetson Bank appeared on the East Bank, and then the West Bank, 30 to 40 miles (48 to 64 km) away from Stetson Bank (R. Graham, pers. comm.). While it is known that these species move between banks, it is unknown to what extent these and other migratory animals utilize other banks in the region
Maritime Archaeological Resources
To date, imagery and documentation of Flower Garden Banks National Marine Sanctuary reveals no evidence of submerged archaeological artifacts.