Pressures on the Sanctuary
Aquaculture and Artificial Reefs
Recently, there have been proposals to utilize offshore oil and gas platforms for aquaculture (fish farming); however, none have yet been undertaken. There is also an active artificial reef program in Texas and Louisiana. Some artificial reefs have already been located in close proximity (within seven miles) of the sanctuary. It is unknown to what extent either of these activities may affect ecosystem function, including processes such as invasive species dispersal, disease frequency in fish and invertebrates, parasite loads, competition, and recruitment. Experiences elsewhere suggest they may be causes for concern. There are currently 15 active oil and gas platforms within the Minerals Management Service four-mile zone encompassing the sanctuary. These platforms provide artificial substrate for organisms including sponges, bryozoans, barnacles, hydroids, corals, and associated fish communities. The oil and gas platforms as well as mooring buoys have provided shallow water habitat for early life history stages of fishes, e.g. sergeant majors (Abudefduf saxatilis), and have allowed for some species to increase their ranges into areas where they did not previously exist (e.g. yellowtail snapper, Ocyurus chrysurus) — a form of range extension referred to as “island hopping” (Pattengill 1998). The artificial reef structure has also been documented to be the probable vector source for the spread of an invasive coral species, the orange cup coral (Tubastraea coccinea) (Fenner 2004). An active gas platform, HIA389A, is located one mile from the reef cap of East Flower Garden Bank, and has extensive colonies of orange cup corals. In 2002 the species was first documented on the natural reef habitat of East Flower Garden Bank. To date, no orange cup coral has been reported from West Flower Garden Bank.
Villareal et al. (2007) reported that the increased substrate availability provided by the oil and gas industry in the Gulf of Mexico has contributed to the increased levels of ciguatoxins regionally, leading to increased incidents of ciguatera poisoning.
Human-induced increases in greenhouse gas emissions are contributing to global-scale warming and are associated with acidification of the world’s oceans (Orr et al. 2005). For corals, warming events have the potential to cause or exacerbate harmful events, such as outbreaks of disease and coral bleaching, and may reduce growth or impair sexual reproduction.
Corals typically respond to elevated seawater temperatures and other stressors by “bleaching,” undergoing physiological changes that result in them expelling their algal symbionts (Figure 12). Historically, the corals within the Flower Garden Banks sanctuary have proven to be resilient following bleaching events. However, in 2005 the worst bleaching event on record occurred, and approximately 45% of the coral colonies at the Flower Garden Banks sanctuary were affected. Mortality was not high overall, but concerns exist over this apparently increasing threat. The coral bleaching during this event diminished below a depth of approximately 95 feet (29 meters), indicating that deeper regions of the reef are less susceptible to factors that cause coral bleaching.
Coral reefs throughout the world have been impacted by a variety of diseases, some of which have decimated coral populations in certain areas. In general, most aspects of these diseases are poorly known. Until recently, very little coral disease has been documented at the Flower Garden Banks sanctuary, probably due to many factors, including distance from shore and excellent water quality. However, within the last several years, a number of incidences of coral disease at the Flower Garden Banks have been documented (Figure 13). Maintaining water quality at the Flower Gardens is critical, as there is evidence from other locations that coral disease severity can increase when reef waters contain elevated nutrient levels. This is probably because the nutrients promote pathogen growth, enhancing their fitness and thus virulence (Bruno 2003).
Significant Regional Habitat
Recent high-resolution multi-beam bathymetric surveys have revealed hard bottom features outside the current sanctuary boundaries that are structurally connected to the geological and biological resources within the sanctuary. An example of the Stetson Bank “ring” has been previously discussed. The Stetson Bank boundaries were created prior to the mapping that revealed the ring around Stetson Bank. The ring is clearly part of the structure of Stetson Bank, and remotely operated vehicle (ROV) surveys have documented the outcroppings and associated biological communities making up the feature. The sanctuary advisory council has recommended adjusting the Stetson Bank boundaries to encompass this ring feature. This will also align regulation and boundaries with the Habitat Area of Particular Concern boundaries encompassing Stetson Bank.
Surveys have also revealed an extensive area of hundreds of patch reefs, forming a horseshoe-shaped feature, located between East and West Flower Garden Banks. Mud volcanoes also were revealed through bathymetric surveys and verified through ROV surveys. These features, many of which contain hard substrates, harbor rich assemblages of black corals, octocorals, and deep reef fish, and offer opportunities for movement between the banks by pelagic animals as intermediate locations for feeding and shelter (Hickerson 2000). Some also have been found to contain habitats for juvenile groupers found as adults on the Flower Garden Banks. These “habitat highways” may prove to be critical to the success of the reefs and banks of the northwestern Gulf of Mexico and should be considered for further protection.
The impacts of fishing and associated fishing activities on the sanctuary have not been precisely documented at the Flower Garden Banks. Conventional hook and line fishing is allowed in the sanctuary. However, illegal fishing by both commercial longliners and recreational spearfishermen has been documented. Lost or tangled bottom fishing gear has been found on numerous occasions, as well as discarded spear heads, and even a lost speargun. Targeted fishing efforts, which are allowed under current regulations, could have a detrimental impact on snapper, grouper, mackerel and jack populations, especially if directed at spawning aggregations. A possible bycatch effect could explain the apparent reduction in hammerhead shark numbers. Fishermen have reported that while they were fishing for snapper and grouper during the winter, all they could catch were hammerheads. It is unknown what the fates of these animals were after release. Observations by long-time divers within the sanctuary suggest that there has been a substantial decline in certain species of fish that are commonly targeted by fishers in recent years, including red snapper (Lutjanus campechanus), large groupers (Mycteroperca sp.) and amberjacks (Seriola dumerili). Technological advances in vessel design and equipment (Global Positioning Systems, advanced fish finders, braided fishing line, etc.) have made it easier to find and catch fish in areas that were previously difficult to access.
Recreational fishing can have a major impact on fish populations (Figure 14). In the Gulf of Mexico, recreational fishers account for up to 64% of the total catch of fish species of concern (Coleman et al. 2004). The red snapper stock is “overfished” and has been undergoing overfishing in the Gulf of Mexico since the late 1980’s . Of the 15 grouper species that are fished regularly in the Gulf of Mexico, the health of only four of these populations has been assessed: red (Epinephelus morio), gag (Mycteroperca microlepis), goliath (Epinephelus itajara) and yellowedge (Epinephelus flavolimbatus). Of these, the gag grouper has been found to be overfished, the goliath grouper has been found to have been previously overfished (but is now recovering due to a total prohibition of take of this species), and the yellowedge grouper population status is “unknown.” Red grouper are under a rebuilding plan as a result of being declared overfished in 1997. In 2002, a stock assessment concluded that red grouper were still undergoing overfishing, though no longer in an overfished condition. Red grouper does not normally occur in the vicinity of the Flower Garden Banks. Population assessments of the other species of grouper in the Gulf of Mexico have not been conducted. Greater amberjack (Seriola dumerili) have been under a rebuilding plan in the Gulf of Mexico since 2003. A new stock assessment in 2006 concluded the stock is not recovering as projected; it is overfished and is still undergoing overfishing. Given the state of overfishing in the Gulf of Mexico, it is reasonable to expect that similar fishing impacts are occurring at the Flower Garden Banks. Marbled grouper (Dermotolepis inermis), a species of particular concern, is seen frequently by divers at the Flower Garden Banks, and has been documented throughout the deeper parts of the sanctuary through ROV surveys. No more than six marbled grouper have been documented in one aggregation. Recent reports suggest that a possible spawning population of marbled grouper was heavily impacted by recreational fishers. Over 70 marbled grouper were extracted over a two-day period in August 2007 from neighboring Geyer Bank. This situation suggests a need to increase protection of this population during spawning periods.
Discarded fishing bycatch (such as dead sharks, moray eels and other non-target species) has increasingly been reported by scuba divers within the sanctuary (Figure 15). Shrimping bycatch has been illegally discarded on Stetson Bank on several occasions. Because shrimp trawls are a prohibited gear within the sanctuary, discharging material associated with shrimping is also not allowed. Impacts of discarded bycatch include smothering of benthic organisms, alteration of the bottom by the addition of shells and other materials, and unnatural attraction of sharks, rays, and other scavengers on the banks. The illegal dumping of bycatch presents a user conflict, as it could increase safety concerns for scuba divers. Unnatural feeding of marine organisms leads to increased aggression of fish, turtles, and moray eels, as the animals may associate a feeding event with deposits of "food" from the surface. This may lead to the unintentional case of mistaken identity as a diver makes an entry into the water. Injuries from barracudas have been anecdotally reported in areas where fish feeding is encouraged (Franklin Viola, pers. comm.).
Lost and discarded fishing gear, including longlines, floats and nets, has been observed at East and West Flower Garden and Stetson Banks (Figure 16). Such incidents can cause localized physical injury to coral reefs, and have been documented to entangle and injure resident and transient sea turtles and other organisms. Some debris originating from prior activities, including seismic cables from acoustic surveys, remains embedded in the coral reef around the flanks of East and West Flower Garden Banks.
In 2002, an invasive coral species, Tubastraea coccinea (orange cup coral), was documented at East Flower Garden Bank (Figure 17). Since then, at least two other colonies have been documented. This species is native to the Indo-Pacific and may have entered the South Atlantic and Caribbean by attaching to a ship’s hull, having its larvae discharged in ballast water, or being transported on a reused structure.
This coral species is now common on oil and gas platforms in the Gulf of Mexico. It is suspected that artificial structures, such as oil and gas platforms, played a major role in the spread of this species. They may play a similar role for other species either through transport of the rigs and platforms themselves between locations or with their tendency to act as “stepping stones” of dispersal for species that associate with such structures. It is reasonable to anticipate the introduction of other exotic species in the future (Fenner 2004). Approximately 46 colonies of this invasive species were removed from neighboring Geyer Bank in 2005, and in March 2007, over 100 colonies were noted as thriving at the site. Also in March 2007, at least two colonies of T. coccinea were documented at Sonnier Bank (Ron Hill, NMFS pers. comm.).
Oil and Gas Infrastructure
Existing Structure and Maintenance
The existing platform within the Flower Garden Banks sanctuary, designated as High Island A389A, is a fully operational natural gas production facility. In 2000, additional exploratory wells were drilled from this platform, resulting in the allowable discharge of drilling “muds” (lubricants) and cuttings shunted to within 10 meters of the sea floor. Periodic maintenance of this facility (sandblasting, painting, etc.) is required to control corrosion and ensure structural stability. Within the Minerals Management Service (MMS http://www.mms.gov/) four-mile regulatory zone of both the East and West Flower Garden Banks, there are currently 15 production platforms and approximately 111 miles (179 km) of pipeline (half of which are dedicated oil pipelines). From 2004-06, three of these platforms and approximately 83 miles (134 km) of pipeline were added within the MMS four-mile regulatory zones of the East and West Flower Garden Banks. A gas pipeline has been constructed within the sanctuary near East Flower Garden Bank to connect HIA389A to a subsea station outside of the sanctuary boundaries. This pipeline is used to bring in product from the subsea station to HIA389A for processing and shipment to shore. One platform and approximately 11 miles (17.44 km) of pipeline are located within four miles (6.5 km) of Stetson Bank.
There are small areas outside the MMS “no-activity zones” but inside the sanctuary boundaries. Within these areas, the development of new oil and gas infrastructure could be considered. Development could include new platform installation, exploratory drilling and pipeline routing. A pipeline was constructed in 2004 to connect a gas well outside the sanctuary to the platform located within the sanctuary. The pipeline traverses approximately 1,000 feet (303 meters) of sanctuary habitat consisting of flat, muddy soft bottom.
Discharge of pollutants from sources inside and outside the sanctuary may affect sanctuary resources.
Hydrocarbons and Associated Discharges
Impact from an oil spill or other hydrocarbon release is an ongoing concern. Major oil spills in the Gulf of Mexico are very rare, but if one did occur, it could have significant effects on the water, living resource, and habitat quality of the sanctuary. Threats to the sanctuary can result from discharges from leaking pipelines and damage to platforms (particularly resulting from natural events, such as hurricanes) or dragging of anchors. During the 2005 hurricane events, it was evident that regional response assets were severely overtaxed because of land-based and nearshore impacts. In such cases, offshore oil spills are treated as lower-priority issues, and potentially pose an elevated threat to offshore natural resources. Ongoing operational effluents from oil and gas facilities include drilling lubricants, produced water (water separated from the oil or gas after it is pumped from the reservoir), and operational discharges (sewage, graywater, deck wash).
The discharge of untreated sewage from vessels is not allowed within the sanctuary. However, the discharge from a U.S. Coast Guard-approved marine sanitation device is currently allowed. Marine sanitation devices are only required to remove suspended solids and treat for potential human pathogens. Nutrients and other pollutants are not removed by these systems. Other vessel discharges include “graywater” from showers and galleys, deck runoff and incidental release of petrochemicals from engine use.
The quality of coastal waters of the northern Gulf of Mexico is in decline due to pollutants associated with the discharge of major river systems (such as the Mississippi and Atchafalaya), general coastal runoff throughout the region, and habitat alteration (e.g., salt water intrusions in marshes). Predominant current patterns direct much of this water away from the sanctuary, but minor changes in circulation patterns could bring contaminated water to the sanctuary.
The 2005 hurricane events proved conclusively that the Flower Garden Banks sanctuary is not immune to impacts from terrestrial sources. Hurricane Rita flushed the coastline of the Texas and Louisiana, resulting in a persistent plume of contaminated water, which reached out and beyond the Flower Garden Banks sanctuary and was evident for several months. It is unknown what the contaminants were in the vast plume, or what the long term effects on the reef environment will be (Figure 18).
Liquefied Natural Gas
The development of offshore liquefied natural gas (LNG) receiving terminals should be monitored in the region. LNG ports could potentially affect water quality as well as biologically important planktonic stages of fish and invertebrates critical to the continued health of the reefs and banks in the region. An “open loop” system (i.e., a system that uses seawater to warm the natural gas from its liquefied form and discharges the water directly to the surrounding waters), is located in the West Cameron Area, 35 miles (57 km) from the reef cap of East Flower Garden Bank. The Gulf Gateway Energy Bridge deepwater port is owned by Excelerate Energy Limited Partnership and has been operational since March 20, 2005.
Shipping and Transport
The sanctuary is located adjacent to a major shipping lane leading to the Port of Houston, one of the busiest ports in the nation. Historically, significant impact to coral resulted from anchoring of large ocean going vessels at the sanctuary. This impact has been minimized by the establishment of a “no-anchor” area by the International Maritime Organization (IMO) and through sanctuary regulations. However, an anchoring incident could still occur. The practice of exchanging petrochemicals between ships within nearby lightering zones could result in unintended spills. Furthermore, the release of ballast water by ships preparing to take on cargo may unintentionally introduce exotic species into the sanctuary or surrounding sensitive habitats. In the past, significant injury to sanctuary resources has also resulted from improperly attended cables between tugs and towed barges.
Visitation by scuba divers and fishermen is relatively low at present, but is expected to increase. Estimates of diver use are between 2,500 and 3,000 divers per year, resulting in a total of at least 10,000 dives annually in the sanctuary. Most of these divers arrive in one of two dive charter vessels, carrying either a maximum of 20 or 34 customers. Private vessels and researchers also visit the banks regularly. Currently, the maximum size of individual vessels allowed to use mooring buoys is 100 feet, but the number or type of vessels is not addressed.
The sanctuary is becoming internationally known as a prime dive destination, and with increased recognition will likely come higher levels of visitation. It is recognized that non-consumptive recreational diving activity may result in habitat injury, due to inappropriate physical contact with the coral reef (standing, touching, holding or accidental kicking), alteration of animal behavior (avoidance or attraction of fish species, chasing or touching marine animals), unintentional fish feeding during night dives, or other factors. Very few quantitative studies of the impact of scuba divers on coral reefs have been conducted. One study suggests that relatively low levels of scuba diving activity (less than 6,000 divers per year) have minimal impact on coral reefs (Hawkins et al. 1999). Coral reefs in other parts of the world have experienced degradation associated with intense visitor use, especially by snorkelers in very shallow (less than 3 meters deep) reef zones (Allison 2005). It has also been proposed that divers may act as vectors for some types of coral disease by the use of dive gear that has been contaminated while diving in areas with high incidence of coral disease and not properly disinfected (Marano-Briggs 2006).
The level of recreational and commercial fishing is not precisely known at the Flower Garden Banks. Reports by long-time users of the sanctuary and observations by sanctuary staff and others suggest that the level of fishing activity has been increasing in recent years. Stetson Bank is heavily used during mackerel season, and fishers target wahoo aggregations, which are currently without catch limits, at the East and West Flower Garden Banks. Local fishers report that it is necessary to travel farther offshore in recent years to find certain species (red snapper, grouper, etc.) compared to in the past (J. Stout, pers. comm.). Large commercial charter fishing vessels (“headboats”) have been observed regularly at Stetson Bank, and smaller fishing charters offer trips to the Flower Garden Banks. As noted above, technological advances in vessel design and equipment have made it easier to find and catch fish.
As interest and use in the sanctuary increases, there will potentially be conflicts among users arising from competing objectives. As an example, recreational fishers and dive charters may compete for use of the same reef areas. Typically, recreational fishers target the same types of large fish that divers travel to the sanctuary to see. In addition, fishing in an area where diving is occurring can pose a potential safety risk. This type of user conflict is occurring at the current user level, especially at Stetson Bank, and can be expected to intensify as the number of users increases.
Fishing and shrimping vessels have been discarding bycatch in sanctuary waters while tied to mooring buoys, and private vessels visiting the sanctuary have been observed depositing food scraps into the water.
As the number of users increases, it is anticipated that competition for mooring buoys will increase. Use of the mooring buoys is currently guided by a “first-come, first-served” policy, which could lead to conflicts without additional installations. It could also lead to maintenance or safety concerns as vessels begin to tie in tandem to existing buoys, causing excessive strain on the mooring system.
The experience of swimming and diving with large charismatic animals is one of many attractions of the sanctuary. However, physical contact with animals, such as whale sharks (Figure 19), manta rays, and sea turtles, may alter the animal’s behavior and have other undocumented impacts that should be investigated. Physical contact with sea turtles, which are on the endangered and threatened species lists, is already prohibited, but other large marine animals are not as strictly protected. In the past, changes in behavior of some animals subject to physical contact have been observed. In one case, a diver riding a manta ray (a strongly discouraged activity) inadvertently forced it to collide with the reef, putting both the diver and the manta ray at risk.
Over the past three decades, the sanctuary has been subjected to increasing sources of underwater sounds, the effects of which are poorly understood. These sources include boat engines and generators, as well as commercial, experimental and exploration activities, the most prominent being acoustic air gun surveys, pile driving, and work boat transits associated with the oil and gas industry. As far as we know, no sounds occur at levels considered detrimental to sanctuary resources, but concerns have been expressed about the cumulative impacts of these sounds. These impacts could include altering feeding or mating behaviors or causing animals to avoid areas they would otherwise occupy (Pearson et al. 1992, Engas et al. 1996).
There is some evidence that unnatural nighttime levels of artificial light from dive vessels and other sources have altered the behavior of some marine animals on the reef. For example, barracudas and other predators aggregate around illuminated vessels at night to feed on smaller fish attracted to the lights. Intense light from underwater photography and video by divers has been observed to alter the behavior of sea turtles and other species. In addition, sea turtles and fish can be awakened during nightly resting periods and clearly disturbed by dive lights, flood lights and strobes. Dive lights often allow predators, such as dog snappers (Lutjanus jocu) and black jacks (Carangoides ruber), to prey on smaller reef fish as they trail scuba divers at night.
The Flower Garden Banks have been in the path of numerous tropical storms and hurricanes (Figure 20). In 2005, two powerful hurricanes illustrated that the reefs of the sanctuary are not immune to the force of these storms. The eye of Hurricane Rita passed within 30 miles (48 km) of East Flower Garden Bank, resulting in coral heads as large as 13 feet (4 meters) in diameter being overturned and transported. Enormous barrel sponges were sheared off, and sand patches were scoured. Some fields of delicate pencil coral (Madracis mirabilis) at East Flower Garden Bank were severely impacted. Sections of Stetson Bank pinnacles were sheared off, and valleys were scoured clean. Impacts were documented by researchers as deep as 250 feet (76 meters) in the brine seep at East Flower Garden bank (K. Parsons-Hubbard, pers. comm.). Impacts from the 2005 hurricane event continued to be visible in July 2007.