The Florida Straits, just miles off the Florida coastline, claim the single richest concentration of marine life in the Atlantic Ocean, according to the most complete survey of its kind ever conducted.
Scientists were surprised to find that the Florida Straits also have the Atlantic’s greatest concentration of endemic species, or species found nowhere else in the world. Many are considered "micro-endemics," or species with ranges restricted to very small geographical features, such as an isolated island platform or a coastal lagoon. Those precariously small areas make life there far more delicate than previously thought.
Blind skates, dwarf sharks, searobins and the Atlantic saw shark are among the many species that make their home in the waters shared by Florida, Bahamas and Cuba, but are found nowhere else.
"Most people believe that marine species have large ranges and can just swim their way out of trouble," said Michael L. Smith, Caribbean biodiversity fellow with the Center for Applied Biodiversity Science (CABS) at Conservation International (CI). "But we now know that there are hundreds of species in the Florida Straits, and in the broader Caribbean region, with ranges so small that even localized human activities can cause their extinction."
Marine species in the Florida Straits and the Caribbean are threatened by widespread development that reaches even the most remote islands and keys. Other threats include destructive fishing methods, the dredging of estuaries and harbors and laying natural gas pipelines on the sea floor.
"Anyone who remembers the building of an airstrip that eliminated a dozen of Bermuda’s marine species in the 1940s knows that humans can easily wipe out large numbers of creatures in a single careless act," said Kent Carpenter, professor at Old Dominion University. "We have found species in all parts of the Caribbean region with very tiny ranges. They can be put at risk by the kinds of local development that are occurring every day on every coast in the region."
Eighty-four scientists carried out the study, which was initiated by the United Nations Food and Agriculture Organization (FAO) and published in a three-volume series entitled, The Living Marine Resources of the Western Central Atlantic. Scientists from CABS at CI and Old Dominion University analyzed a vast collection of mapping data, resulting in the largest database of species ranges ever recorded for the region.
The scientists mapped close to 1,200 species of marine fishes and other animals in the tropical western Atlantic Ocean, resulting in the best basis to date for identifying the areas of highest priority for protection of Atlantic species.
The fish species that cause the Florida Straits to rank highest in the Atlantic are concentrated on the continental slope, rather than on the continental shelf or in the Caribbean’s well-known coral reefs.
The second leading area in the Atlantic for marine species richness and endemism lies in southern Caribbean waters along the coasts of Colombia, Venezuela, Netherlands Antilles, and Trinidad and Tobago.
More than 20 percent of the fish species covered by the study are endemic to the Caribbean and nearby seas. Such a high level of endemism stands in contrast to the widespread view that marine species tend to have broad distributions and that they might therefore be buffered against extinction.
Another unexpected finding is that the unique species live in deep water. Because the species in the deepwater areas of endemism reproduce at very low rates, scientists are concerned that their populations are at great risk of collapse. Many of the micro-endemic species are being taken as dead discard from deepwater trawling, and others are directly targeted for fishing.
The study was part of FAO’s program to publish scientific guides about marine biodiversity in several ocean areas. Species were mapped individually by leading marine scientists and were analyzed at CABS at CI in order to find concentrations of endemic species and other patterns of distribution.