HR: 1330h
AN: B33D-05    [Abstracts]
TI: Assessment of Ecosystem Change Using Benthic Foraminiferal Data From Three Nearshore Cores, Biscayne Bay, Florida
AU: * Williams, C P
EM: williams@geo.siu.edu
AF: Southern Illinois University Carbondale, Geology Department MC 4324, Carbondale, IL 62901 United States
AU: Ishman, S E
EM: sishman@geo.siu.edu
AF: Southern Illinois University Carbondale, Geology Department MC 4324, Carbondale, IL 62901 United States
AB: The benthic foraminifer record from mid-bay cores indicates a relative increase in salinity over the past 150 years has impacted the marine ecosystems of Biscayne Bay. However, the magnitude and rates at which this has occurred remains unresolved. Benthic foraminifer data from three nearshore cores in Biscayne Bay document the transition from terrestrial to marine environments. The variability and magnitude of changes between brackish and marine conditions determined from these data are important for differentiating natural (sea-level) from anthropogenic (water management) influences on the nearshore ecosystem. Three cores were collected from nearshore localities in Biscayne Bay: Chicken Key, Black Point North and Middle Key. The cores were sampled continuously every 2cm. Each sample was processed and a database compiled of foraminiferal assemblage data. Non-metric multidimensional scaling (MDS) based upon these data is used to describe changes to the coastal ecosystems. The MDS plots represent the relative differences between foraminiferal assemblages at each depth in the core and may indicate long-term ecosystem change. Middle Key and Chicken Key are essentially barren of foraminifera below 30cm, which suggests that the sediments in the lower section of each core were not deposited in a marine environment. The transition at each location begins with a brackish assemblage dominated by Ammonia and Elphidium. Each site becomes increasingly marine up to the modern samples at the top of the cores. Black Point North includes foraminifera throughout its 86.5cm depth. The site has been dominantly brackish with increases in Miliolinella, Quinqueloculina and Triloculina indicative of strong shifts toward marine conditions near the base and at the top of the core.
DE: 3030 Micropaleontology
DE: 4235 Estuarine processes
DE: 4804 Benthic processes/benthos
DE: 4815 Ecosystems, structure and dynamics
DE: 9604 Cenozoic
SC: Biogeosciences [B]
MN: 2005 Joint Assembly