Mesoamerican Barrier Reef

• Category: Marine and Oceanic Biomes.
• Geographic Location: Central America.
• Summary: The Mesoamerican Barrier Reef is the world’s second-longest barrier reef and a biodiversity hot spot, yet it is highly threatened by anthropogenic activities in the region.

The Mesoamerican Barrier Reef is the Western Hemisphere’s longest barrier reef, and one of the world’s biodiversity hot spots, stretching more than 621 miles (1,000 kilometers) from the northern tip of Mexico’s Yucatan Peninsula southward along the coasts of Belize, Guatemala, and Honduras; it extends more than 50 miles (80 kilometers) out from shore in places. Sited in the western Caribbean Sea, the Mesoamerican Barrier Reef (MAR) is affected by the Caribbean Current and the Loop Current of the Gulf of Mexico. There is a distinct wet season from July to October in the MAR region.

The MAR ecosystem is highly threatened yet biologically rich, encompassing long barrier reefs, near-shore fringing reefs, offshore atolls, and hundreds of patch reefs. Associated shallow and deep lagoons, mangrove forests, and seagrass beds provide habitats, foraging, and nursery grounds for fish and invertebrates. Seagrasses also help stabilize sediments, reduce beach erosion, and promote water clarity.

Biodiversity

The Mesoamerican Barrier Reef is home to more than 500 species of fish. Of particular interest is the recent discovery of major spawning aggregation sites at Gladden Spit, Half Moon Caye, and Caye Bokel for lutjanid, serranid, and carangid fish—important food fish in the Caribbean. Resident fish spawn close to their home reefs, but others, such as cubera and dog snappers, migrate over large distances to spawn in transient aggregations. This comes in response to cues that include location, reef morphology, season, temperature, sunlight period, and lunar and diurnal cycles.

Spawning aggregations are temporally consistent, and generally occur in shallow waters of about 82 feet (25 meters) along the shelf or in deeper waters of about 98–213 feet (30–65 meters) beyond the shelf break, between March and September, with a peak occurring in May each year. Peak abundances can reach 8,000 individuals, but generally there are about 4,000 to 6,000 individuals from March to July in each event.

Sharks and rays form a vital component of the fauna here. Southern stingray (Dasyatis americana), lemon shark (Negaprion brevirostris), and nurse shark (Ginglymostoma cirratum) frequent the lagoons and inter-reef areas for spawning, feeding, hunting, and shelter in both shallow and deep reaches.

In addition to fish, the reef system is home to 350 species of mollusk and 65 species of stony coral. Manatees, sea turtles, the American crocodile, and Morelet’s crocodile are also found in this area. The whale shark, largest fish on the planet, may be found near Isla Contoy. Normally a solitary animal, whale sharks gather in this area to find mates and breed.

Threats and Conservation

Overfishing of fish, lobster, and conch is considered to be a persistent and extensive threat to the MAR, resulting in a reduction of fish sizes, spawning potential, and future catches. Other threats of great concern include unregulated fishing, deforestation in the watersheds, loss of habitat and nursery areas, marine and watershed pollution, coral disease and bleaching, boat groundings, mining and dredging, urban runoff, coastal development, and agriculture.

Global climate change effects such as ocean warming, stronger hurricanes, and ocean acidification are of grave and increasing concern. Extensive coral bleaching occurred in the MAR in 1995, 1998, and 2005, which were particularly warm years. Additional bleaching occurred from 2013 to 2017, and agan in 2023. Over time, severe bleaching and disease can lead to a reduction in species diversity, coral cover, and eventually loss of reef framework. High sedimentation rates and nutrient enrichment of coastal waters from fertilizers increase algal and sponge abundance at the expense of corals, and can be indicative of stressful conditions on the reef. Climate change has made powerful storms such as hurricanes more common. While in the past, coral reefs withstood such storms, the reefs have weakened due to human activity. This is true of the MAR. The coast and reef are now insured to ensure adequate funding required to repair and restore the reefs after hurricanes. After Hurricane Delta hit the area in 2020, conservationists received $800,000 to help the reef.

The region has about 894 square miles (2,315 square kilometers) of coral reefs in total, 23 percent average coral cover, 25 percent macro-algae abundance, and some 1,350 square miles (3,500 square kilometers) of mangrove forest; there are no estimations of seagrass cover. Seagrasses have also been severely damaged by dredging operations, prop scars, and poor water quality. The greatest threats to mangrove and seagrass habitat are direct losses associated with coastal development and freshwater flow.

More than 60 marine protected areas (MPAs) have been established in the MAR region. These MPAs often function better in theory than in reality. Several protected areas are “paper parks,” in that they apparently fail to meet their management objectives.

The Mexican MPAs include Santuario del Manatí (including Chetumal Bay), Arrecifes de Xcalac Reserve, and Banco Chinchorro Biosphere Reserve. Priority monitoring sites for these Mexican sites are Isla Contoy, Cancún, Puerto Morelos, Cozumel, Sian Ka’an, Akumal, and Majahual.

The MPAs in Belize are Glover’s Reef Marine Reserve, South Water Caye Marine Reserve, Sapodilla Cayes Marine Reserve, Port Honduras-Deep River Forest Reserve, Sarstoon-Temash National Park, Gladden Spit, Bacalar Chico Marine Reserve and National Park, and Corazol Bay Wildlife Sanctuary. The priority monitoring sites include Hol Chan, Caye Caulker, Lighthouse Reef, Turneffe Atoll, and Laughing Bird Caye.

There are two protected areas within the MAR region in Guatemala: Punta de Manabique Wildlife Refuge and Sarstún National Park. Río Dulce and Santo Tomás Bay are considered to be priority monitoring sites.

In Honduras, the MPAs are Omoa-Baracoa Marine Reserve, and Turtle Harbor Wildlife Refuge and Marine Reserve. Priority monitoring sites include Cayos Cochinos, Roatán, Guanaja, Río Aguán, Río Plátano Biosphere, Laguna de Caratasca, Puerto Cortés, Tela, and La Ceiba.

Bibliography

Einhorn, Catrin, and Christopher Flavelle. "A Race Against Time to Rescue a Reef from Climate Change." The New York Times, 5 Dec. 2020, www.nytimes.com/2020/12/05/climate/Mexico-reef-climate-change.html. Accessed 20 Nov. 2024.

“Mesoamerican Reef.” World Wildlife Fund, www.worldwildlife.org/places/mesoamerican-reef. Accessed 20 Nov. 2024.

Pikitch, Ellen K., et al. “Habitat Use and Demographic Population Structure of Elasmobranchs at a Caribbean Atoll (Glover’s Reef, Belize).” Marine Ecology Progress Series 302, no. 1 (2005).

Spalding, Mark D., Corinna Ravilious, and Edmund P. Green. World Atlas of Coral Reefs. Berkeley: University of California Press, 2001.