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Keywords: Caribbean, eutrophication, LTER (long-term ecological research), coastal settings, human ... - page 4 / 14





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Caribbean seascape, including Dominica, Martinique, and the Barbados on the eastern boundary; Cuba and Hispaniola (Haiti and the Dominican Republic) to the north; and Jamaica and the Cayman Islands to the north- west. Although south Florida is not geolog- ically part of the Caribbean Sea, it is considered part of the region because of the strong oceanic connection downstream though east-west water circulation. The wider Caribbean region thus includes coastal re- gions in the Caribbean Sea proper and up- stream areas in south Florida and theYucatán Peninsula (including the Usumacinta– Terminos lagoon complex). The Caribbean Sea includes four major basins, with approximately half of the water deeper than 3600 meters (m) (Richards and Bohnsack 1990). Many areas exceed 4000 m in depth, with the deepest region—in the Cayman Trench, located between Cuba and Jamaica—ranging from 7535 to 7686 m. Because of the active semi-independent movement of the Caribbean plate, there are earthquakes and volcanic activity throughout the region (Dillon et al. 1987). Seasonal vari- ation in temperature is small, ranging from 25 degrees Celsius (˚C) in the winter to 28˚C in the summer. Ocean circulation in the region is strongly influenced by the trade winds that form westward patterns, causing upwelling along the South American conti- nent. Water flows into the Caribbean Sea mostly through the Grenada, St. Vincent, and St. Lucia pas- sages in the southeast. The water continues westward as the Caribbean Current, the main surface circulation in the Caribbean Sea. The flow turns westward as it crosses the Cayman Basin, and it enters the Gulf of Mexico as a narrow boundary current through the Yucatán Straits, where it forms both the loop current in the Gulf of Mexico and the Gulf Stream south of Florida (Fratantoni 2001). The average flow of these currents is 24 million m3 per second, with near- surface velocities approaching 80 to 150 centimeters per second in the Yucatán Current (Coats 1992). This water circulation results in high connectivity among the different basins. Vast regions of the Caribbean are influenced by river discharge. Mean discharge to the region that includes the coastal areas of Venezuela, Trinidad and Tobago, and Grenada (figure 2) is more than 2100 km3 per year (Fekete et al. 2002), but a significant volume of Amazon water is also delivered to the Caribbean via the North Brazilian Current (Hellweger and Gordon 2002). The two largest rivers of the region, the Orinoco (1103 km3 per year; figure 2) and the Magdalena (228 km3 per year; figure 3) (Restrepo and Kjerfve 2000), account for well over 60% of the fresh water discharged directly into Figure 2. Spatially mapped correlation coefficients between the monthly clima- tology of Orinoco River (Venezuela) discharge and the ocean color (reciprocal of monthly averaged water-leaving radiance at 412 nanometers, from SeaWiFS [Sea-viewing Wide Field-of-view Sensor] data) between November 1997 and October 2002. The region of high positive correlation shows that the hydro- logical regime of the Orinoco is in phase with the ocean color field, suggesting a vast region of fluvial influence of the Orinoco’s highly colored waters. The adjacent region of negative correlation west of the plume is an area where upwelling-induced phytoplankton blooms tend to be out of phase with the Orinoco discharge. best studied over decadal time periods and large spatial areas (Kaiser 2001, Hobbie et al. 2003). The sites described in this article are national reserves, parks, or research areas from the Caribbean region that are described as vulnerable or heavily influenced by human activities. Ecological research at some of these sites has been performed on a regular basis since the 1970s. However, the long-term records of selected eco- logical processes for these sites are inadequate to quantitatively define the magnitude and direction of ecosystem change, which limits the development of appropriate coastal man- agement plans. The ocean ecosystem of the wider Caribbean region The Caribbean Sea is considered the smallest ocean basin and classified as the second largest sea in the world (2,512,950 square kilometers [km2]) (figure 1; Dillon et al. 1987). Located in the Western Hemisphere between North and South Amer- ica, the Caribbean Sea is bordered on the north and east by the West Indies archipelago, on the south by South America, and on the west by the Central American isthmus and the Yucatán Peninsula. All Central American countries except El Salvador have extensive coastal areas along the Caribbean Sea. Several oceanic islands are a major feature of the

846 BioScience • September 2004 / Vol. 54 No. 9

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