Late Cenozoic Paleoceanography and Paleoclimate
Benthic Foraminiferal Ecology and Marine Ecosystem Restoration
Holocene paleoclimatic records from the Antarctic Peninsula region of
Antarctica.
The
Antarctic Peninsula continental shelf, coastal bays, and fjords
provide regions in which glaciomarine sediments have accumulated for
at least the last 10,000 years. These sediments represent a complex
interplay of facies controlled by biogenic, terrestrial, and glacial
conditions closely linked to the oceanography of the Antarctic
Peninsula region. Sediment cores provide us with high-resolution
paleoclimatic and paleoceanographic records. Using relationships
between modern benthic foraminiferal distributions, oceanographic,
and sedimentologic conditions it is possible to interpret
fluctuations in benthic foraminiferal distributions in sediment cores
to changes in environmental conditions.
My research in the Antarctic Peninsula region of Antarctica continues with funding from the National Science Foundation (NSF), Office of Polar Programs to better define the relationship between benthic foraminiferal distributions, benthic water mass characteristics, glaciological, and sedimentological processes, and to apply this information to down-core sediments. I am presently working with a group of researchers from Colgate, Hamilton College, Stanford, Mont Claire State University, University of New Hampshire and Queens University to decipher the paleoclimatic record from sediment cores collected from the Larsen-A and Larsen-B regions of the eastern margin of the Antarctic Peninsula.
A Holocene climate record from the Chesapeake
Bay
The
Chesapeake Bay is a major estuarine system that is 320 km long, 20 to
40 km wide, and covers an area of 6500 km2 on the east coast of the
United States. The Bay fills a dendritic river valley system that was
flooded during the postglacial sea-level rise beginning about 10, 000
years ago and includes as its tributaries the Susquehanna, Potomac,
James, Rappahannock, Patuxent, Choptank, and Nanticoke Rivers. The
watershed of the Chesapeake Bay drains 166, 000 km2 that includes New
York, Pennsylvania, Delaware, Maryland, the District of Columbia, and
Virginia. The Chesapeake Bay experiences large seasonal and
inter-annual variability in salinity, temperature, and dissolved
oxygen. The variability in these conditions is strongly controlled by
precipitation since there is a significant correlation between
precipitation and riverine discharge. In addition, discharge plays an
important role in the nutrient and suspended sediment load
concentrations delivered to the Bay, and its physical estuarine
processes.
My work in the Cheaspeake Bay uses benthic foraminifera as paleoceanographic indicators of salinity, nutrient flux, and dissolved oxygen conditions within the Bay throughout the Holocene. Collections of modern sediment samples seasonally and during extreme climatic conditions are, and will be used to determine the environmental controls on benthic foraminiferal spatial distributions within the Bay. These data will be used to interpret temporal foraminiferal distributions in cores collected in the Spring of 1999 from the R/V Marion Dufresne. This work is in collaboration with researchers from the U.S. Geological Survey, Maryland Geological Survey, University of Rhode Island, and Virginia Institute of Marine Science.
Late Cenozoic benthic foraminiferal trends and
their paleoceanographic and tectonic implications.
The Antarctic Ice Sheet has played a significant role
in the evolution of global oceanographic circulation. Study of marine
deep sea, continental shelf, and
continental margin sediment cores provide us with records of
significant oceanographic changes during the late Cenozoic that
include changes in sea-level and deep water mass production.
My work in the area of late Cenozoic oceanography and tectonics is related to bottom water mass production, sea-level, Antarctic ice volume, and coastal tectonics in the southern hemisphere. The late Miocene and Pliocene marine sediments from the Antarctic continental margin, Chile, and New Zealand provide significant localities to study late Cenozoic sea-level fluctuation, as well uplift history. This work is evolving through collaboration with colleagues at the University of Otago, NZ, Universidad Catolica del Norte, Cologne University, Universidad de Chile, and University of Aberdeen. Funded by NSF International Programs.
South Florida ecosystem
restoration.
The South Florida ecosystem is complex and dynamic. The evolution of
the ecosystem has been influenced by the influx of fresh water
related to natural hydroperiods in the Everglades wetland, to
hurricane events, and to sea-level rise, as well as to anthropogenic
changes, such as alteration of the natural hydroperiod and changes in
flow between Florida Bay and the Atlantic. Reduced fish and shellfish
populations, altered seagrass densities and die-offs, and increased
phytoplankton blooms show that the ecosystem has undergone
significant change, the causes of which remain poorly understood.
Detailed studies of aquatic animals and vegetation conditions have
been investigated in detail; however changes in the benthic community
have not been as rigorously addressed.
My work in south Florida establishes the relationships between modern faunal distributions and environmental conditions. This information then is applied to interpret historical (the last 150 years) environmental changes in Florida and Biscayne Bays and relate those changes to natural and anthropogenic events in the southern Florida region. Results from these analyses show distinct salinity changes occurring at the turn of the century and about 1940. Associated with the salinity shifts in the Bays are increases in the abundance and/or density of seagrass. This information is being used by land- and water-use managers in their restoration efforts on the Everglades and Florida Bay. This work is in collaboration with colleagues from the U.S. Geological Survey, Duke University, Metropolitan-Dade Department of Resources Management, and South Florida Water Management District.
Comments and questions: sishman@geo.siu.edu
Department of Geology e-mail: geology@geo.siu.edu
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