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A.
Zimmerman Research
Naples Bay Past and Present: A
Chronology of Disturbance to an Estuary
Funded by: South Florida Water
Management District & The Conservancy of Southwest Florida (Drs.
Ceilley, Schmid, Worley, Brenner, Jaeger)
Introduction: Naples Bay, FL
is typical of many areas along the coast of Florida where dredge and
fill operations have occurred and these actions have destroyed or
degraded the estuarine habitats. In the last 50 years, the Bay has
experienced an explosion of growth and development along most of its
shoreline, thus impacting the fringing mangrove community. Previous
studies have indicated that hydrologic factors have also contributed to
the decline of this system: 1) freshwater and urban runoff that flows
into the Bay has increased, 2) flow and flushing is impeded by dead end
canal systems, and 3) inadequate tidal mixing occurs, particularly
during the summer. These factors have resulted in slight to
moderate eutrophication of the Bay system that is of special concern to
the City of Naples, Rookery Bay National Estuarine Research Reserve,
and the many residents living along the shoreline. In order to
understand the alterations and the response of the system over time, it
is necessary to reconstruct the pre-development ecological and
biogeochemical conditions of the estuary and the timing and extent of
alteration of these conditions. Comparison of past versus present
conditions will help to guide restoration efforts and development plans
around Naples Bay. This study aims to establish an approach for
the reconstruction of recent environmental change in Naples Bay using
biogeochemical information, aiding further research into ultimate
causes of, and therefore solution to, problems such as nutrient
enrichment and hydrologic alteration within the estuary.
 
Methods:
At least three sites will be chosen for sediment
coring. The physical parameters of wet and dry mass and density
will be determined for each sample. In addition to organic
carbon, total nitrogen, and total phosphorous, other chemical analyses
that have been used for environmental reconstructions will be
performed, including biogenic silica, total lipid and lipid biomarker
compounds, stable carbon and nitrogen isotopes, and compound specific
lipid biomarkers. These tools have the ability to identify the
response by various members of the benthic and planktonic community
(bacteria, phytoplankton, macrophytes, etc) to chemical and
hydrological stressors as they occurred. For a reliable time
frame, however, must be grounded in accurate sediment accumulation
rates and horizon dating. 210Pb, 137Cs,
total Pb
concentrations and x-radiographs will be useful for establishing
sediment chronologies. Sediment horizons will also be surveyed
for shell biomarkers to further delineate salinity ranges associated
with the constituents listed above. For example, dramatic
historical shifts in freshwater deliveries to the estuary should be
expressed by changes in shell fragments within a given layer. |