ACCESS NUMBER: 30905 

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

National Marine Sanctuary, 1998-1999 

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

National Marine Sanctuary, 1998-1999 

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

SPONSORING OCS REGION: Gulf of Mexico 

APPLABLE PLANNING AREAS: Gulf of Mexico 

FISCAL YEARS: 1998; 1999 

COMPLETION DATE OF REPORT: December 2001 

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 Garden Banks coral reef system is a unique low diversity, 

high cover, coral reef environment located approximately 200-km (110 nmi) southeast of 

Galveston, Texas on the outer continental shelf of the Gulf of Mexico. Designated as a 

National Marine Sanctuary in 1992, the East and West Flower Garden Banks (EWFGB) 

represents the northernmost coral reef on the continental shelf of North America. The 

banks are topographic highs of bedrock displaced upward by the intrusion of two salt 

diapirs. The bedrock is capped with the calcium carbonate deposition of hermatypic 

reef-building corals and calcareous algae. The living coral reef is comprised of 20+ 

species of corals, and supports 250+ species of fishes and 500+ species of 

invertebrates. 

Potential threats to the long-term health of the reef include human impacts from oil and 

gas exploration and production, commercial shipping, destruction of organisms by 

recreational divers and non-point source pollution as well as natural disasters such as 

hurricanes. This effort is the continuation of monitoring efforts begun in 1989 and first 

reported in 1992. 
ACCESS NUMBER: 30905 

OBJECTIVES: 

1. To provide relevant and timely environmental data to those charged with developing 

policies concerning oil and gas exploration and production in the vicinity of sensitive 

ecosystems associated with the Flower Gardens coral reefs, 

2. Document long-term changes in reef-building coral and associated communities at 

the FGB caused by either impacts of petroleum exploration and production or other 

human impacts, 

3. Document long-term natural variation in reef growth and associated communities on 

the FGB and, 

4. Stimulate ancillary research efforts and coordinating monitoring activities with 

agencies and institutions conducting water quality assessments and other studies in 

the vicinity of the EWFGB in order to observe, document, and expediently evaluate 

causes of environmental change. 

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

September - 1 October 1998 and 12-16 September 1999. 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, nondestructive 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. 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. 

Several ancillary studies were conducted at both Flower Garden study sites describing 

algae and micromolluscan populations, primary production of macroalgae, and 

porewater toxicity tests. 

SIGNIFICANT CONCLUSIONS: The dominant coral species at both banks were 

Montastraea annularis and Diploria strigosa. The occurrence of algae increased from 

3% in 1998 to over 20% in 1999. This increase was due to the presence of large 

amounts of red turf algae in the Order Ceramiales and mainly at the expense of bare 

reef rock. The reasons for the initial spike in algal occurrence is not yet known. 

Annual growth rates of Montastraea faveolata were measured using sclerochronology, a 

measurement of accretionary growth bandwidths. One core was removed from banks, 

longitudinally sectioned, and x-rayed to reveal growth bandwidths. Mean accretionary 
ACCESS NUMBER: 30905 

growth from 1998-1999 averaged 7.3 mm/year at the East Bank and 5.0 mm/year at the 

West Bank. 

Sixty permanent encrusting growth stations of Diploria strigosa were photographed at 

each bank and used to calculate growth and/or retreat rates in cm/year. The East Bank 

exhibited a net retreat in 1998 and net advance in 1999. Net retreat was reported for 

both years at the West Bank. 

Repetitive quadrats were used to monitor changes in structure of particular coral 

communities at the EWFGB. Yearly repeated photographs of forty stations at each 

bank were compared to previous years. Percent cover, number of individual coral 

colonies, incidents of coral bleaching and disease, and tissue loss were recorded from 

the photographs. Mean coral cover at the East Bank was greater than 55% in 1998 and 

1999, and 52% both years at the West Bank. Several incidents of bleaching occurred, 

with the highest occurrence recorded at the West Bank in 1999. Only three incidents of 

coral disease were reported. The majority of tissue loss was due to coral retreat/algal 

replacement and sediment deposition on living coral colonies. 

The ancillary studies provided the following results: 

1. Fredericq et al. and Lehman and Albert recorded a combined taxonomic list of 72 

species of algae collected at the FGB. Fredericq et al. noted an abundance of bluegreen algae and speculate it was caused from nutrient loading. 

2. Dunton and Miller reported blue-green algae as the primary source of nitrogen in the 

water column and described the FGB as being “autogenous” in meeting nutrient 

supplies. 

3. Barrera and Tunnell reported an increase of 100 species of the known 

micromolluscan faunal assemblage at the FGB. 

4. Porewater toxicity testing conducted in sediments of the FGB by Nipper and Carr 

revealed no toxicity due to organic or inorganic pollutants. 

The East and West Flower Garden Banks’ coral reef habitats remain healthy and 

productive, particularly in comparison to other reefs of the Mexican Gulf of Mexico, the 

Florida Keys, and the Caribbean Sea. However, some negative shifts in the monitoring 

parameters were recorded (i.e. encrusting growth, algal biomass, and possible disease 

occurrence). It is not known what the impact of these shifts will be or whether they are 

short-term anomalies or the first steps of a long-term trend. Subsequently, continued 

close scrutiny is crucial. The 2000-2001 monitoring data will be critical in assessing the 

true meaning of the 1998 and 1999 results. Of particular interest will be the status of 

the algal bloom and incidence of disease. 

STUDY PRODUCTS: Dokken, Q.R. 2001. Long-term monitoring of the east and west 

flower garden banks national marine sanctuary, 1998-1999. OCS Study MMS-2001- 

101. U.S. Department of the Interior, Minerals Management Service, Gulf of Mexico 

OCS Region, New Orleans, La. 138 pp.