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Study Site

San Salvador Island (24o05'N, 74o30'W), located in the southeastern edge of the Bahamian Archipelago, possesses numerous small hypersaline lakes. San Salvador is a small island (~ 180 km2), isolated from other Bahamian Islands (the nearest island is > 50 km away), and supports a small human population (< 2,500). The earliest recorded observation of the hypersaline lakes (45 to >160 ‰) is contained in the diary of Christopher Columbus, who is thought to have first set foot in the New World on San Salvador. Dense microbial mats blanket the shallow sediments in many of these lakes and are the dominant biotic feature. The lakes are virtually unimpacted by terrigenous, atmospheric, or anthropogenic nutrient inputs. By far, the largest perturbations the lakes experience are the freshwater and sediment inputs attributable to hurricanes and other major storms.

Annual rainfall on San Salvador averages only ~ 101 cm and evaporation exceeds precipitation in most years. With the onset of the dry season in November, large areas of the mats become and remain desiccated for much of the year. At the edges of the lakes, some communities may remain desiccated for several years, depending on yearly rainfall. Additionally, as lake levels recede and water within the mats evaporates, exposed mats are subjected to intense solar radiation (>2300 µE m-2 s-1), high temperatures (> 35oC), and even greater salinity levels. In many respects, these systems represent 'life at the edge', while, at the same time, typifying much of the earth's more desiccated environments.