ACCESS NUMBER: 30662

STUDY TITLE: Long-Term Monitoring at the East and West Flower Garden Banks 

REPORT TITLE: Long-Term Monitoring at the East and West Flower Garden Banks 

CONTRACT NUMBER: 14-35-0001-30662 

SPONSORING OCS REGION: Gulf of Mexico 

APPLICABLE PLANNING AREAS: Western and Central Gulf of Mexico 

FISCAL YEARS OF PROJECT FUNDING: 1994; 1995 

COMPLETION DATE OF REPORT: January 1997 

COSTS: FY 1994: $69,497; FY 1995: $67,640 

CUMULATIVE PROJECT COST: $137,137 

PROGRAM MANAGER: David A. Gettleson 

AFFILIATION: Continental Shelf Associates, Inc. 

ADDRESS: 759 Parkway Street, Jupiter, Florida 33477 

PRINCIPAL INVESTIGATOR*: Stephen T. Viada 

KEY WORDS: Northwestern Gulf of Mexico; Flower Garden Banks; corals; community 

structure; population levels; accretionary growth; encrusting growth; bleaching; 

temperature 

BACKGROUND: The East and West Flower Garden Banks are located on the outer 

continental shelf of the Gulf of Mexico, approximately 204 km (110 nmi) southeast of 

Galveston, Texas. They are topographic prominences of bedrock which have been 

uplifted by the upward intrusion of under lying salt deposits or diapirs. The bedrock has 

been capped with a layer of hard bottom, formed from the skeletons of corals and other 

calcareous organisms, and biogenic calcareous sands and gravels. Thriving coral reefs 

comprised of 18 species of hermatypic (reef-building) scleractinian corals occur on the 

banks in a geographic area which is considered area which is considered to be near the 

their northern physiological limits. Environmental threats to the Flower Garden Banks, 

including extensive development of petroleum hydrocarbon resources and other human 

activities on and in the U.S. Department of the Interior, Minerals Management Service 

(MMS) and the NOAA National marine Sanctuary Program to cooperatively sponsor a 

long-term monitoring program on the banks which addresses concerns regarding both 

chronic and acute impacts. The Flower Garden Banks were designated as a National 

Marine Sanctuary in January 1992. 
ACCESS NUMBER: 30662

OBJECTIVES: (1) To provide relevant and timely environmental data to agencies 

which develop policies concerning oil and gas exploration and development in the 

vicinity of biologically sensitive habitats; (2) To document acute and long-term changes 

in reef-building and other associated communities within the high-diversity DiploriaMontastrea-Porites Zone at the Flower Garden Banks which may be attributed to 

impacts of oil and gas exploration and development or other human activities; (3) To 

document natural variation in reef-building and associated communities within this biotic 

zone on the banks; and (4) To duplicate methodologies and, whenever possible, to 

utilize study stations developed during the previous long-term monitoring study in an 

effort to maintain a continuous database of information on the banks. 

DESCRIPTION: The scope of the present monitoring contract specified analyses of 

field data collected during 1992 (which had not been analyzed) and the collection of 

field data and associated analyses during 1994 and 1995. Field efforts in 1994 and 

1995 were conducted within the previously established 100 m by 100 m study site on 

each bank. The following tasks were performed at each study site: 14 stratified random 

photographic transects were photographed and analyzed for the determination of 

population levels of corals and other associated reef biota; 20 permanent growth spike 

stations were measured for the estimation of accretionary growth of the coral 

Montastrea annularis; two coral cores were collected from separate colonies of M. 

annularis and analyzed for the determination of accretionary growth rates by 

measurement of annular corallum density bands (sclerochronology); 60 permanent 

stations were photographed and analyzed for the estimation of encrusting growth of the 

coral Diploria strigosa; 40 permanent 8 m2 quadrat stations were photographed and 

analyzed for counts of coral growth, retreat, disease, and mortality, and estimates of 

percent coral cover and coral bleaching; two diver-held, repetitive video transects were 

recorded and analyzed for the qualitative assessment and documentation of reef health; 

two recording thermographs were retrieved and serviced; one recording light meter was 

deployed and serviced; daily measurement were made of water temperature, salinity, 

dissolved oxygen, and ambient light from near surface and near bottom depths; and six 

sediment samples were collected and archived. 

SIGNIFICANT CONCLUSIONS: Estimates of total coral cover, cover and relative 

dominance of individual coral species, and species diversity within the East and West 

Flower Garden Banks study sites are comparable with previous studies conducted 

within the same study sites. Specific differences in the estimates between studies are 

not considered to represent trends or deterioration of habitat quality. Estimates of the 

growth rates of M. Annularis and D. strigosa made at both study sites indicate favorable 

conditions for both accretionary and encrusting growth during the 1994-1995 field 

surveys. Accretionary and encrusting growth estimates made from re-established as 

necessary to maximize accuracy of growth rate estimates. Coral bleaching was 

observed on 8 m2

 photographic quadrats collected during 1992, 1994, and 1995. The 

extent of bleaching observed on the two study sites was most pronounced during 1995. 

STUDY RESULTS: Means total coral cover on the East and West Flower Garden 

Banks study sites was 48.2% and 44.1%, respectively. Total coral cover was higher in 
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both 1995 and 1994 than in 1992, and higher on the East Flower Garden Bank study 

site than the West Flower Garden Bank study site. M. annularis was the dominant reef 

component on the East and West Flower Garden Banks study sites, followed by D. 

strigosa. Cover of M. annularis and Siderastrea siderea was significantly higher in 1995 

transects than in both 1994 and 1992. Cover of M. cavernosa was higher in 1994 

transects than in 1992. A significant bank by year interaction was observed in Porites 

astreoides. Accretionary growth rates of M. annularis were estimated from stations 

established during the 1994 field effort. Mean growth rates from 1994-1995 were 

similar to those estimated during the 1989-1991 monitoring study. Accretionary growth 

rates determined from sectioned coral core samples fell within the range of 

measurements derived from permanent growth station data during the 1994-1995 

surveys. A new set of permanent stations for the measurement of encrusting growth of 

D. strigosa was established during the 1994 field effort. Estimates of encrusting growth 

rates of M. annularis were measured from 1992 station photographs only. Estimates of 

net encrusting growth rates of D. strigosa during the 1991-1992 period were 

substantially less than those estimated for the 1994-1995 period. Because of problems 

with the 1992 data and the resultant low sample size, it is possible that the differences 

may be an artifact of sampling error. As a result, statistical comparisons between 1991-

1992 and 1994-1995 data were not conducted. Net encrusting growth rates of D. 

strigosa and the Est and West Flower Garden Banks study sties were positive during 

the 1991-1992 period and 1994-1995 period were very close. Coral growth was clearly 

identifiable in 8 m2

 quadrat station images collected during 1992, 1994, and 1995, and 

included examples of both unimpeded encrusting growth and interspecific competition 

between several species. Number of observations of coral growth far exceeded 

observations of coral bleaching, disease, and retreat during this period. Occurrences of 

coral bleaching were much higher in quadrat images collected during the 1995 field 

effort than those from 1992 and 1994. Bottom temperatures measured on recording 

thermometers on the two study sites were in excess of 30°C during 1995. This period 

coincided with widespread coral bleaching on both study sites. Total daily irradiance 

and percent light transmission were recorded at both study sites in 1995. Temporal 

trends between the sites were quite similar, with slightly lower irradiance values 

collected at the deeper West Flower Garden Bank study site. 

STUDY PRODUCT: Continental Shelf Associates, Inc. 1996. Long-term Monitoring at 

the East and West Flower Garden Banks. Final synthesis report for the U.S. 

Department of the Interior, Minerals Management Service, Gulf of Mexico OCS Region, 

New Orleans, LA. Contract No. 14-35-0001-30662. 112 pp. 

*P.I.'s affiliation may be different than that listed for Program Manager.