Beneath the indigo blue waters of the Northern Gulf of Mexico lie the East and West Flower Garden Banks, a pair of topographic features 12 miles apart and approximately 100 miles southeast of Galveston, Texas. These submarine banks rise from depths of 328 feet to crest in a water depth of only 60 feet. The caps of these banks are topped by an assemblage of reef-building corals and associated tropical and sub-tropical organisms. This relatively low diversity coral reef covers nearly 300 acres at the East bank, and 100 acres at the West bank. A wide array of marine life, including numerous species of rays and sharks, sea turtles, and marine mammals, frequent the shallow, warm waters of the Gulf. Over 170 species of fish and approximately 300 species of reef invertebrates inhabit the banks. The colorful coral reefs and diversity of marine life associated with them are unique for their location, far north of where the majority of coral reefs are found. The East and West Flower Garden Banks are the northern most coral reefs on the continental shelf of North America.

The salt domes underlying these banks have furnished the framework for coral reef development, as well as providing a reservoir for oil and gas resources. As exploration and development of these resources have proceeded on the Outer Continental Shelf, the need to know more about the Flower Garden Banks and other offshore submarine banks has become a management concern of the Minerals Management Service (MMS). The MMS is concerned with the long-term impacts of hydrocarbon development activities relevant to environmental quality. This interest has resulted in the development of a monitoring program at the Flower Garden Banks. In consultation with academia and industry, the MMS implemented a program to monitor changes in coral populations and growth, as well as exploring other important factors associated with these reefs.

Since the early 1970’s, the MMS has actively been involved in a program of protective activities at the East and West Flower Garden Banks. This stewardship program began with a comprehensive outline of mapping and delineating potentially sensitive submarine banks. Heading the list of topographic features of concern were the East and West Flower Garden Banks. A program of mapping began in 1974 and extended to a synthesis of information in 1981. This included a multidisciplinary study effort spanning five years of field effort and over a year of integration and synthesis costing approximately $6.5 million. Abstracts of all studies information sponsored by the MMS at the Flower Garden Banks are archived in the MMS Environmental Studies Program Information System (ESPIS). These protective measures have ensured compatibility between an active program of oil and gas development near the banks and the health of this sensitive biological habitat and national treasure.

Initial study objectives consisted of detailed mapping of the banks and photographic surveillance of coral reef communities. This descriptive phase evolved into a comprehensive program of describing the geologic structure of the features and surrounding sediments, characterizing the physical oceanography of the banks, and identifying their biological communities and zonation. Later years focused on understanding and describing processes at the banks. This included looking at movement of water currents and the transport of sediment at the base of the banks. A brine pool was described seeping from the side of the East Flower Garden bank, possessing a unique biological community. Coral community diversity and numbers have been documented in order to scrutinize any possible decline in the health of the coral reef zone. Other study components have looked at coral bleaching which is often associated with warm temperatures, and the ongoing recruitment of coral populations generated from settling plankton. Also of interest are the effects on the environment of human activities, including but not limited to anchoring and long-term impacts from recreational SCUBA diving activities.

This database has provided valuable information needed in numerous National Environmental Policy Act (NEPA) documents, including environmental impact statements (EIS's), lease stipulations, and designation of no-activity zones. At all steps of this process, the MMS has coordinated closely with the numerous stakeholders at the Flower Gardens, including industry representatives, recreational fishermen and divers, other Federal agencies, academic researchers, and private consultants.

In addition a number of industry-sponsored monitoring activities have been conducted at both banks. Until 1990, the investigations have continued sporadically, related to drilling schedules. A majority of these investigations monitored the effects of drilling discharges on the coral reef community. Through time, industry-monitoring of sites near the Flower Garden Banks has indicated no impacts on the banks.

With the designation of the Flower Gardens as a Marine Sanctuary in 1992, the MMS has continued its stewardship. In addition to the ongoing monitoring program, MMS has worked closely with the sanctuary manager on dive programs, facilitating seismic development agreements, oil spill response drills, pipeline sitings, and serving on advisory boards. In 1994, the stewardship of MMS was recognized by the Flower Garden Banks National Marine Sanctuary program for 20+ years of commitment to resource protection, funding of surveys and supporting research at the Flower Gardens. Based on this long record of proactive environmental concern and cooperation, MMS and NOAA look forward to a long and productive relationship affecting the protection and preservation of the valuable natural resources at the Flower Garden Banks.

ONGOING MONITORING EFFORT

At present the MMS in conjunction with NOAA’s National Marine Sanctuary division, conducting a program of long-term monitoring at both the East and West Flower Garden Banks. This monitoring effort was designed to assess the health of the coral reefs, evaluate changes in coral population levels, measure coral and algae cover and growth rates, and investigate other community characteristics. The goal of the program is to address concerns related to both gradual and punctuated degradation of these unique offshore ecosystems. Such data are useful in assessing the impacts of industrial activities, as well as their value to resource management.

SITE SELECTION

Study sites were established on each bank and consist of a 100 m² area. Ropes are tied to corner markers during each trip to guide divers to different areas and stations within the study sites. Loops and knots at various distances along the ropes indicate to divers exactly where they are within the site.

DATA COLLECTION REGIME

Stratified Random Photographed Transects

To record areal coverage of coral and leafy algae, stratified random transects are completed at each study site. Fourteen 10 m transects, each containing seventeen non-overlapping photographs are taken on each site during each monitoring expedition. Divers are equipped with a Nikonos III camera, a 28-mm lens and dual strobes mounted on a rectangular aluminum or stainless steel camera frame. The diver ascends to the seafloor and proceeds in a specified direction for a specific number of fin kicks to the point at which the transect begins. Data are gathered for all coral species, algae and other associated organisms, as well as observations of disease or bleaching incidents. From these data, calculations are made on the percent cover, frequency of occurrence and relative dominance of each species, and species diversity and evenness.
 

To note long-term changes in coral cover, stations are repetitively photographed and changes noted between sampling periods. Initially, stainless steel posts are implanted to mark site locations. Photographs are taken from a height of 2.0 m using a 15-mm wide angle lens from directly above the base of the station marker post. Camera attitude is precisely determined by use of a compass and a bubble level. In the lab analysis of individual station photographs is conducted by projecting the images onto a flat surface, generating a calibrated image. The margins of individual coral colonies are traced from the previous year’s images. The current images are superimposed on the previous image templates for temporal comparisons in one of the following categories: growth, loss of tissue, estimates of actual coral cover, and incidents of bleaching and disease.
 

Colonies of Diploria strigosa were established as permanent encrusting growth stations on each bank. Stations were established by placing two permanently installed pins in the reef rock so that the growth margin of the coral would bisect a repeatable close-up photograph of the station. Station pins were installed along the margin of live coral growth adjacent to bare reef rock. A Nikonos camera and strobes were used underwater to produce a calibrated image of each station. Calculations determine the growth and/or retreat rates for each coral station (in cm per year). Net growth rate is defined as the mean rate of change of coral margins observed to advance or retreat using pooled measurements from all stations.
 

At each reef, two videotaped transects of 100-m length are taken during each visit to show the general conditions of the coral community at each study site. From videotapes, observations are made on the general health of the hermatypic coral community and counts of invertebrates and fishes. Estimates of densities are made that could be compared between sites, seasons, and years. Community characterization, including habitat characteristics, coral cover, patterns of abundance, spatial distribution, recruitment or loss of conspicuous reef fish or invertebrates, and relationships between specific taxa and habitats or other biota, is also recorded.
 

The methodology used for measuring accretionary (upward growth of coral) data at the Flower Garden Banks is known as “sclerochronology”. Cores are obtained from live coral colonies using a pneumatic drill attached to a compressor air scuba cylinder. Growth is determined directly by measuring bands found in the coral skeletons. The area between the upper boundary of two sequential high-density growth bands is considered an annual growth increment. These annual bands are produced because the rate of calcium carbonate deposition by the corals varies on an annual cycle in response to environmental and physiological cycles. This method has the advantage of recording growth on the same colony from past decades so that comparisons can be made to current rates.
 

Since 1997, semi-permeable membrane devices (SPMDs) have been deployed at the East and West Flower Garden Banks to trace the presence of hydrocarbons in the water column. Contaminants of interest include Polycyclic aromatic hydrocarbons (PAH), pesticides, and PCBs. The membrane portion of the apparatus is extracted and and dialyzed and analyzed for containments. Beginning in 2001, a new array of data collecting tools will be deployed that will substantially enhance the water quality evaluation process. Ocean Sentinel Platforms (OSPs) will be deployed at both the East and West Banks. OSPs are compact frames of stainless steel and fiberglass that are used to mount in-situ instruments. Each OSP will be equipped with temperature, salinity, turbidity, dissolved oxygen, and phytosynthetically active radiation (PAR) sensors integrated with a high-capacity data logger. There will be one upward-looking Acoustic Doppler Current Profiler (ADCP) installed at either the East or West Bank. During the course of the project, the PI and associates will seek to implement a real-time reporting capability that will transmit data from the OSPs back to land and our over the internet.

Insolation and Temperature Measurements

Insolation (sunlight) is measured at the Flower Gardens by two underwater Li Cor spherical light sensors and Li-1000 data loggers. These sensors are secured to a projecting vertical bar on cages and record hourly averages, 24 hours per day. Data from these loggers is recoverd during the spring and in the fall. Temperature is measured using a Hobo-Temperature recording thermograph that is contained in a watertight cylinder and attached to a bottom structure near the light meters at each study site. The water temperature is recorded at 20 minute intervals every 24 hours.
 

Long-term monitoring has proved critical in providing a continued database needed in management decisions. In addition, this program has expanded the descriptive information of the banks and the surrounding environment. The above methodologies have been employed in a monitoring program funded by MMS and NOAA which has been performed since 1991. Various organizations have been involved in the monitoring program and are listed as follows:

1991 1995 1996-2001

- Texas A&M University - Continental Shelf Associates, Inc. - Texas A&M University-Corpus Christi

It has been generally noted that the health of both the East and West Flower Garden Banks is excellent. This is especially encouraging since they are the northernmost coral reefs located on the North American continental shelf . These coral colonies are obviously at their northern physiological limits for tropical reef-building corals, and thus community diversity is reduced --only 21 of the 65 western Atlantic reef-building coral species occur there. With the exception of a punctuated algal presence detected during the 1998 and 1999 monitoring surveys, virtually no significant changes have been detected in coral reef populations, cover, or diversity at the Flower Garden Banks since quantitative surveys of the reefs began. There is no conclusive evidence that highlights one reason over another for the increased algal cover. Researchers anticipate the results of the 2000 and 2001 surveys to see if there are any identifiable trends that will reveal a scientifically sound reason for substantial retreat of coral cover due to the presence of algae. Thus, there is no evidence of deterioration of habitat quality. As in the past, researchers predict that the data will suggest where advance and retreat conditions are found, these conditions are dictated by natural factors, such as competition for space, rather than man-induced stress. The situation appears to be such that vectors such as disease are acting only on limited scales.

Since monitoring began, a number of processes at work on the coral reef have been observed and documented. One event of great interest has been the recurring synchronous spawning of many of the sessile organisms at the banks. This recurring event resembling an underwater snowstorm occurs eight days following the August and September full moon. Future monitoring efforts and research should be conducted to observe further the persistence of mass spawning on an annual basis.

Coral bleaching has often been observed during summer cruises during the monitoring program. This bleaching, characterized by the expulsion of symbiotic algae, is associated with sea water temperatures exceeding 30°C. In 1991 thermographs installed on both banks indicated temperatures greater than 30°C at the East Flower Garden Bank. Following this period, significantly more bleaching was observed there than at the West Flower Garden Bank where temperatures were slightly lower. Nevertheless, bleaching was never observed to affect more than 2.4% of the coral cover. Although the bleaching has a spectacular appearance, mortality is seldom associated with the event. The distant location of the Flower Garden Banks (~100 miles from shore) has left them largely undisturbed by human activities. One of the potential impacts has been from recreational divers, especially the anchoring of vessels associated with this activity. The installation of mooring buoys in 1990 should limit this problem. MMS divers participated in implanting ship mooring buoy sites.

A review of the potential effects of industrial activities indicated that tanker spills and spills resulting from platform accidents pose the most realistic threats to the corals at the Flower Gardens reefs. Discharges of produced waters and drilling fluids are not considered to pose substantial threats because of existing regulations applicable in the vicinity of the banks and dilution by intervening water masses. Required shunting to within 10 m of the bottom, and negligible upward transport by currents minimize the potential for discharged contaminants to reach the reef communities located atop the banks.
 

Plans are being made by the MMS in coordination with the NOAA Flower Garden Banks Marine Sanctuary Program to continue the long-term monitoring at both banks. The proposed monitoring is a four-year continuation of the previous MMS monitoring studies developing one of the most long-term databases related to the environmental health of the banks in existence. It will continue the use of previous methodologies on an annual basis and will include greater emphasis on water quality measurements and continuous light incidence measurements as described above.
 

Information from the Flower Garden studies has proven useful in numerous MMS management decisions related to oil and gas leasing and development. This usefulness has included formulation of lease stipulations and post-lease sale decisions on development.

The MMS Environmental Studies Program has laid the foundation for the environmental information base on these coral reefs. The aesthetic value of this marine resource was given national status on January 12, 1992, when the Flower Gardens were designated as the country's tenth national marine sanctuary by the National Oceanic and Atmospheric Administration and is now known as (Flower Garden Banks National Marine Sanctuary). Additionally, Stetson Bank was included as part of the National Marine Sanctuary in 1996. Currently Stetson Bank is not included in the MMS’ long-term monitoring strategy going on at the East and West Bank, but has been the subject of investigation since October 1993 through various non-profit organizations and now a permanent research area for NOAA’s Sanctuary office.

Boundaries of the East and West banks of the sanctuary include all areas of the reef crest at less than 100-m depth, and those areas greater than 100-m depth with the "no activity" zone around each bank established by the MMS. This includes approximately 19 square nautical miles at the East Flower Gardens and 23 square nautical miles at the West Flower Gardens.

The MMS, in cooperation with the NOAA Marine Sanctuary Program, has continued long-term monitoring studies. These studies will continue to provide continuity in data and generation of information needed in resource management decisions. This monitoring program has confirmed and continues to validate and sustain the present understanding that lease stipulations in place provide effective mitigation of potential impacts from oil and gas operations to the offshore environment.
 

Report Availability

Copies of the technical report for this study are available online or through the:

Minerals Management Service
Public Information Office
1201 Elmwood Park Boulevard
New Orleans, Louisiana 70123-2394

(504) 736-2519 or 1-800-200-GULF

The Environmental Studies Program Information System (ESPIS) is a free, computerized database established by MMS to make information gathered by the Environmental Studies Program more widely accessible. This System allows full text search and retrieval of this scientific information. Copies of many of the Environmental Studies Program reports and pertinent Technical Summaries are available by searching ESPIS.