ACCESS NUMBER: 30905 

STUDY TITLE: Long-term Monitoring of the East and West Flower Garden Banks 

National Marine Sanctuary, 2000-2001 

REPORT TITLE: Long-term Monitoring of the East and West Flower Garden Banks 

National Marine Sanctuary, 1998-2001 

CONTRACT NUMBER: 1435-01-98-CT-30905 

SPONSORING OCS REGION: Gulf of Mexico 

APPLABLE PLANNING AREAS: Gulf of Mexico 

FISCAL YEARS: 2000; 2001 

COMPLETION DATE OF REPORT: June 2003 

COSTS: FY 2000; FY 2001 CUMULATIVE PROJECT COST: 

PROJECT MANAGER: Quenton R. Dokken 

AFFILIATION: Center for Coastal Studies, Texas A&M University-Corpus Christi 

ADDRESS: 6300 Ocean Dr., NRC Suite 3200 Corpus Christi, TX 78412 

PRINCIPAL INVESTIGATORS: Q.R. Dokken, I. MacDonald, J.W. Tunnell, Jr., and 

Terry Wade 

KEY WORDS: Coral reef, monitoring, marine sanctuary, biology, habitat, scleractinian, 

hermatypic corals, sclerochronology 

BACKGROUND: The Flower Gardens Banks National Marine Sanctuary (FGBNMS; 

designated 1992) includes deepwater coral habitats associated with two topographic 

high points located on the outer continental shelf in the northwestern Gulf of Mexico. 

The East Flower Garden Bank (EFGB) is located about 193 km southeast of Galveston, 

Texas (27o 54.5’ N, 93o 36.0’ W) and the West Flower Garden Bank (WFGB), about 20 

km west of EFGB, is located about 172 km southeast of Galveston (27o 52.4’ N, 93o 

48.8’ W; Figure 1.1.1.1). The Flower Garden Banks (FGB) are found in the most active 

offshore oil/gas exploration and production area in the world. Approximately 4,000 

production platforms are located in the northern Gulf of Mexico and are concentrated in 

the northwestern quadrant where the FGB are located. Two kilometers east of the 

EFGB, a production platform has been producing natural gas continually since its 

installation in 1982. Currently, there are no data suggesting that oil and gas production 

in the vicinity has been detrimental to the coral communities of the FGB (Dokken et al. 

1999, 2001). The purpose of the long-term monitoring efforts on the coral reefs of the 

FGB that began in 1989 (Gittings et al. 1992) is to provide relevant and timely 
ACCESS NUMBER: 30905 

environmental data to those charged with managing oil/gas exploration and production 

in the vicinity of the FGB coral reefs. 

OBJECTIVES: 

1. To document long-term changes in community composition of reef-building coral 

and associated communities; 

2. To document long-term natural variation in reef growth; 

3. To stimulate ancillary research efforts and coordinate monitoring activities by 

other agencies and institutions; and 

4. To evaluate and synthesize monitoring data and other research in order to 

assess the impact of change and provide recommendations to managers. 

DESCRIPTION: Research cruises were conducted aboard the M/V Fling during 27 

September - 1 October 1998, 12-16 September 1999, 17-22 September 2000, and 16-

21 September 2001. Data collection was conducted within previously established 100 x 

100 m study sites on both the East and West Flower Garden Banks (Flower Garden 

study sites). Repetitive and random, non-destructive photographic techniques provided 

data pertaining to the condition of coral reef organisms. Percent cover of scleractinian 

corals and major reef biota was determined from digitized images from random and 

repetitive photography of the coral reef community. Repetitive photography and 

sclerochronology were utilized to determine lateral growth rates of selected coral 

species. Growth rates and cover of live corals was compared between this study and 

previous studies conducted within the same study sites. 

Additionally, water quality, insolation, and temperature parameters were monitored at 

both sites. Two semi-permanent platforms were installed with new water quality 

monitoring instruments, YSI 6600 Data Sondes, at the EFGB and WFGB. The sensor 

suite installed in the sondes comprises pressure (depth), temperature, salinity 

(conductivity), light in the range of photosynthetically active radiation or PAR, dissolved 

oxygen, pH, and turbidity. Semi-Permeable Membrane Devices (SPMD) were used to 

monitor the presence of hydrocarbons and other analytes in the water column. 

Photosynthetically Active Radiation (PAR) and temperature were also monitored in an 

attempt to relate community changes with major fluctuations of irradiance and 

temperature. 

SIGNIFICANT CONCLUSIONS: Through the 1998 - 2001 sample period the FGB 

appeared to be healthy and productive. Relative to other coral reef systems of the Gulf 

of Mexico and Caribbean Sea, the FGB have low diversity of stony corals and high coral 

cover, generally ~ 50%. Located approximately 180 km from the nearest landmass, the 

FGB are relatively isolated from terrestrial based impacts when compared to reef 

systems such as those of the Florida Keys and southern Gulf of Mexico. Although 

afforded a measure of protection from shore side development and watershed drainage 

impacts, within the FGB there is potential for habitat damage from industrial and 

recreational activities occurring in the near vicinity such as marine shipping, oil/gas 

production, and sport diving. Prior to designation as a National Marine Sanctuary in 

1992, substantial anchor damage was observed. Since designation, no damage from 
ACCESS NUMBER: 30905 

these activities has been documented. No significant impact from oil/gas activity has 

been documented before or after Sanctuary designation; and recreational activities 

have not been demonstrated to have a negative impact. 

Variability of accretionary growth and encrusting growth was the rule. Annual 

accretionary growth of Montastraea faveolata at the EFGB averaged 7.5 mm/year 

(range = 5.05 – 11.19). At the WFGB annual encrusting growth ranged from 3.88 to 

8.01 mm/year and averaged 5.73 mm/year. No significant upward or downward trends 

in growth rates were evident, and no correlations of growth to environmental parameters 

could be ascertained. Rates of coral growth at the Flower Garden Banks were in the 

mid to upper range of growth rates of corals at various Caribbean Sea reefs. Encrusting 

growth, measured on colonies of Diploria strigosa, was also variable over time, but 

appeared balanced (i.e. gain versus loss of tissue). No significant long-term trends in 

encrusting growth were evident. 

Habitat characters such as degree of bleaching and percent cover of algae and bare 

reef rock varied annually from 1998 to 2001. However, as with the growth data, no 

trends were evident and no change appeared to be long term. Disease was a minor 

component of the FGB ecosystem dynamics with no apparent significant impact. 

Random photographic transects were completed outside the boundaries of the 

designated 100 m2

 study area to test whether or not the study area remained 

representative of the reef habitat. No inconsistencies between the reef character 

outside the designated study area and the study area were evident. The study area 

continued to be representative of the reef habitat at each bank. 

Based on the results of the random transect data, cover of Montastrea annularis 

complex at the EFGB appeared to be increasing perhaps at the expense of reef rock, 

M. cavernosa and Diploria strigosa, but the data is inconclusive. Algal cover increased 

in 1999, but then declined. Reef rock was also negatively correlated with algal cover. It 

appeared that M. annularis complex and algae are colonized more of the non-living 

surfaces of the bank. The significant positive correlation between algae and total coral 

suggested that algae were not expanding at the expense of coral cover. 

Unlike EFGB, the WFGB did not exhibit a dramatic increase in cover of M. annularis 

complex. The correlations between M. annularis complex, D. strigosa, M. cavernosa

and total coral cover were indicative of the fact that these three species are the 

predominant corals on the bank. The same negative correlation between reef rock and 

algae recorded at the EFGB was also seen here. It appeared that like the EFGB, algae 

primarily colonized non-living surfaces (i.e. reef rock). Unlike the EFGB, M. annularis

complex did not appear to be expanding into areas of non-living substrate. In addition, 

there were no significant correlations between M. annularis complex and D. strigosa or 

M. cavernosa or algae and total cover as seen at the WFGB. It appeared that the coral 

community at the WFGB remained stable throughout the monitoring period despite the 

increase in algal cover. 
ACCESS NUMBER: 30905 

Light intensity in the water column indicated that the water clarity of the Flower Garden 

National Marine Sanctuary was between that of the clearest coastal waters and clearest 

oceanic waters. Periodic changes in water clarity reflected changes in cloud cover and 

concentrations of suspended particles and plankton. It was speculated that flushing 

events occurred with changing current patterns changing the transmissivity of the water 

column. 

The temperature regime for 2000 and 2001 was unremarkable with temperatures 

staying within normal parameters. With the peak temperature less than 30o

C, bleaching 

was not a major event with the exception of the Millepora alcicornis colonies, which 

seem to be particularly susceptible. 

Considering recommendations of prior reports, the Minerals Management Service and 

Flower Garden Banks National Marine Sanctuary made substantial progress in 

implementing many of the recommendations. The in situ water quality monitoring 

instrumentation was upgraded; and the 2002 and 2003 monitoring program, as 

specified within the published RFP will include: 

1) Expanded algal studies, nutrient flows, and nutrient concentrations will be 

conducted. 

2) More rigorous measurements of potential contaminants will be conducted in the 

laboratory. 

3) Continued analysis of population densities of the herbivore, Diadema antillarum.

4) Deep water stations below the coral cap will be established and monitored. 

5) Fish census will be conducted. 

These actions will not only expand our knowledge and understanding of the Flower 

Garden Banks ecosystem, but will also improve the foundation from which management 

decisions are made.