Benthic Foraminiferal Assemblages from Marshes and Mangroves in the Everglades (South Florida, USA) and Their Application as Proxies for Habitat Shifts Due to Sea Level Rise

This study examined benthic foraminifera from marsh and mangrove environments along the coasts of the Everglades in South Florida for their use as proxies for salinity and applied the results to assess the nature and rates of past habitat changes due to sea level rise over the last ~3400 years. Research on modern foraminiferal assemblages from the Everglades are scarce, and this is the first foraminifera-based paleoenvironmental study for this region. The study of living assemblages examined the extent to which infaunal foraminifera bias modern and fossil assemblages, and which sediment interval should be used as a modern analog for paleoenvironmental studies in this area. As most benthic foraminifera live in the 0–1 cm of sediment, many of these studies are based on the 0–2 cm of sediment. This study revealed a deepening of the living depths in a landward direction, possibly due to the landward increase in the oxygenation of subsurface sediments. However, subsurface production is negligible, and the 0–2 cm is sufficient as a modern analog. The study of the modern foraminiferal distribution found that diversity decreases, dominance increases, and agglutinated taxa increase from the coastline inland. Factors controlling foraminiferal distribution, in order of importance, are salinity, total organic carbon, and total inorganic carbon. Everglades foraminifera are excellent salinity proxies and can be used to determine this area’s history of habitat change. The study on fossil and subfossil assemblages found that environments changed over time from upper mangrove, to lower mangrove, and finally the marine-influenced habitat of the study site today. The shifts in foraminiferal assemblages over time can be related to an increase in salinity with sea level rise and accelerated toward the present by AD 1950. This the first foraminifera-based paleoenvironmental study for this area, and the results can be used to predict shifts in coastal habitats, of importance to South Florida’s growing coastal population