Reconstruction of climate-induced environmental changes in the eastern Gulf of Mexico based on foraminifera sediment assemblages

Abstract

Foraminifera assemblages are powerful bioindicators of environmental change and were analyzed in a sediment core collected from the Marquesas Keys, located in the southwestern region of the Florida Keys. The composition and abundance of foraminifera tests within the top 85 cm of the sediment core, dated with ¹⁴C and ²¹⁰Pb, revealed changes in foraminifera assemblages in 1990 CE, 1939 CE, and 1872 CE. Based on the ecological preferences of the dominant species, changes in salinity and submerged aquatic vegetation (SAV) cover may have influenced foraminifera species composition. These changes were likely caused by variation in precipitation patterns in the eastern Gulf of Mexico region associated with shifts in the major ocean-atmosphere teleconnections such as the El Niño Southern Oscillation (ENSO), Atlantic Multidecadal Oscillation (AMO), North Atlantic Oscillation (NAO) along with tropical storms and hurricanes. Prolonged periods of the negative phases of these climate phenomena coincided with shifts in foraminifera assemblages. Despite a generally negative impact of the ocean-atmosphere teleconnections on the South Florida region, a well-developed epiphytic assemblage was recorded in the studied core. The assemblage was recorded in the uppermost part of the core and dated to the period between 1990 and 2010 CE. This implies that a dense SAV community was present within the Marquesas Keys Mooney Harbor since at least the early 1990.