The Caribbean Sea is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico and Central America to the west and southwest, to the north by the Greater Antilles starting with Cuba, to the east by the Lesser Antilles, and to the south by the northern coast of South America. The Gulf of Mexico lies to the northwest.
The entire area of the Caribbean Sea, the numerous islands of the West Indies, and adjacent coasts are collectively known as the Caribbean. The Caribbean Sea is one of the largest seas and has an area of about 2,754,000 km2 (1,063,000 sq mi). The sea's deepest point is the Cayman Trough, between the Cayman Islands and Jamaica, at 7,686 m (25,217 ft) below sea level. The Caribbean coastline has many gulfs and bays: the Gulf of Gonâve, Gulf of Venezuela, Gulf of Darién, Golfo de los Mosquitos, Gulf of Paria and Gulf of Honduras.
The Caribbean Sea has the world's second largest barrier reef, the Mesoamerican Barrier Reef. It runs 1,000 km (620 mi) along the coasts of Mexico, Belize, Guatemala, and Honduras.
The Caribbean is home to about 9% of the world's coral reefs, covering about 50,000 km2 (19,000 sq mi), most of which are located off the Caribbean Islands and the Central American coast. Among them stands out the Belize Barrier Reef, with an area of 963 km2 (372 sq mi), which was declared a World Heritage Site in 1996. It forms part of the Great Mayan Reef (also known as the MBRS) and, being over 1,000 km (600 mi) in length, is the world's second longest. It runs along the Caribbean coasts of Mexico, Belize, Guatemala and Honduras.
Since 2005 unusually warm Caribbean waters have been increasingly threatening Caribbean coral reefs. Coral reefs support some of the most diverse marine habitats in the world, but they are fragile ecosystems. When tropical waters become unusually warm for extended periods of time, microscopic plants called zooxanthellae, which are symbiotic partners living within the coral polyp tissues, die off. These plants provide food for the corals and give them their color. The result of the death and dispersal of these tiny plants is called coral bleaching, and can lead to the devastation of large areas of reef. Over 42% of corals are completely bleached, and 95% are experiencing some type of whitening. Historically the Caribbean is thought to contain 14% of the world's coral reefs.
The habitats supported by the reefs are critical to such tourist activities as fishing and diving, and provide an annual economic value to Caribbean nations of US$3.1–4.6 billion. Continued destruction of the reefs could severely damage the region's economy. A Protocol of the Convention for the Protection and Development of the Marine Environment of the Wider Caribbean Region came in effect in 1986 to protect the various endangered marine life of the Caribbean through forbidding human activities that would advance the continued destruction of such marine life in various areas. Currently this protocol has been ratified by 15 countries. Also, several charitable organisations have been formed to preserve the Caribbean marine life, such as Caribbean Conservation Corporation which seeks to study and protect sea turtles while educating others about them.
In connection with the foregoing, the Institute of Marine Sciences and Limnology of the National Autonomous University of Mexico, conducted a regional study, funded by the Department of Technical Cooperation of the International Atomic Energy Agency, in which specialists from 11 Latin American countries (Colombia, Costa Rica, Cuba, Guatemala, Haiti, Honduras, Mexico, Nicaragua, Panama, Dominican Republic, Venezuela) plus Jamaica participated. The findings indicate that heavy metals such as mercury, arsenic, and lead, have been identified in the coastal zone of the Caribbean Sea. Analysis of toxic metals and hydrocarbons is based on the investigation of coastal sediments that have accumulated less than 50 meters deep during the last hundred and fifty years. The project results were presented in Vienna in the forum "Water Matters", and the 2011 General Conference of said multilateral organization.
The region has a high level of biodiversity and many species are endemic to the Caribbean.
Marine biota in the region have representatives of both the Indian and Pacific oceans which were caught in the Caribbean before the emergence of the Isthmus of Panama four million years ago. In the Caribbean Sea there are around 1,000 documented species of fish, including sharks (bull shark, tiger shark, silky shark and Caribbean reef shark), flying fish, giant oceanic manta ray, angel fish, spotfin butterflyfish, parrotfish, Atlantic Goliath grouper, tarpon and moray eels. Throughout the Caribbean there is industrial catching of lobster and sardines (off the coast of Yucatán Peninsula).
There are 90 species of mammals in the Caribbean including sperm whales, humpback whales and dolphins. The island of Jamaica is home to seals and manatees. The Caribbean monk seal which lived in the Caribbean is considered extinct. Solenodons and hutias are mammals found only in the Caribbean; only one extant species is not endangered.
There are 500 species of reptiles (94% of which are endemic). Islands are inhabited by some endemic species such as rock iguanas and American crocodile. The blue iguana, endemic to the island of Grand Cayman, is endangered. The green iguana is invasive to Grand Cayman. The Mona ground iguana which inhabits the island of Mona, Puerto Rico, is endangered. The rhinoceros iguana from the island of Hispaniola which is shared between Haiti and the Dominican Republic is also endangered. The region has several types of sea turtle (loggerhead, green turtle, hawksbill, leatherback turtle, Atlantic ridley and olive ridley). Some species are threatened with extinction. Their populations have been greatly reduced since the 17th century – the number of green turtles has declined from 91 million to 300,000 and hawksbill turtles from 11 million to less than 30,000 by 2006.
All 170 species of amphibians that live in the region are endemic. The habitats of almost all members of the toad family, poison dart frogs, tree frogs and leptodactylidae (a type of frog) are limited to only one island. The Golden coqui is in serious threat of extinction.
In the Caribbean, 600 species of birds have been recorded, of which 163 are endemic such as todies, Fernandina's flicker and palmchat. The American yellow warbler is found in many areas, as is the green heron. Of the endemic species 48 are threatened with extinction including the Puerto Rican amazon, and the Zapata wren. According to Birdlife International in 2006 in Cuba 29 species of bird are in danger of extinction and two species officially extinct. The black-fronted piping guan is endangered. The Antilles along with Central America lie in the flight path of migrating birds from North America so the size of populations is subject to seasonal fluctuations.Parrots and bananaquits are found in forests. Over the open sea can be seen frigatebirds and tropicbirds.