Coastal & Marine Geology Program > Center for Coastal Studies > Biscayne Bay Benthic Organisms Project

Chemical Pollutants and Toxic Effects on Benthic Organisms, Biscayne Bay, Florida

Biscayne Bay Forams Home

Photo Gallery:

Common Forams of Biscayne Bay

Issues:

Everglades Restoration

Coral-Reef Health

Project Overview:

Phase I: Pilot Study

Phase II: Bay-Wide Assessment

Methods:

Introduction

Benthic Foram Analysis

Heavy-Metal Analysis

Grain-Size Analysis

References

Project Contact:

Barbara Lidz

Methods - Introduction

To characterize pollution levels in Biscayne Bay and assess community structure as reflected in skeletal sediment components, geochemical, petrological, and foram analyses will be carried out on an economical single-sample set of sediments.

The parameters of grain composition and foram-assemblage composition are measures of community response to environmental change and are consistent with well-documented decline in reef-building corals and with published models that predict response of benthic biota to changes in nutrient supply.

Multivariate analyses were performed on the sedimentological, geochemical and environmental data. The PRIMER statistics package was used to link multivariate data with environmental variables. The data were also assessed using the FORAM Index described by Hallock et al. (2002). The combined data sets were used to identify hotspots of pollution in the bay.

Phase I Sample Collection

Sediment sampling: Landsat satellite image of Biscayne Bay, showing the boundary of Biscayne National Park (red line) and the sediment sampling locations of this study (Phase I: yellow triangles, Phase II: red squares). [larger version 104KB jpeg]

The Phase I pilot study was conducted on 38 sediment samples collected in December 2000 and July 2001 along four short nearshore transects at the western edge of the bay and in limited mid-bay areas (Hoare, 2002).

The transects were off the Dinner Key Marina, Snapper Creek southeast of the marina, and immediately south of a coastal landfill at Black Point (see map at right). Sites were chosen from areas believed to possess elevated concentrations of heavy metals as well as from an area (Snapper Creek) considered to be less polluted.

Salinity, temperature, and dissolved oxygen measurements were not noted at sampling. Such information, dated within 1 to 2 days of sample collection, was consequently obtained from Southeast Environmental Research Center (SERC, 2000, 2001) records maintained at Florida International University.

Because sample sites for the pilot study were localized, results are preliminary. Phase II bay-wide analyses may produce trends that differ from those indicated by the pilot study.

Each sample was washed with deionized water over a 63-mm nylon sieve to separate the fine (<63 mm) from the coarse fraction (>63 µm). Both fractions were dried in an oven at less than 50° C. The fine fraction was sent out for Ion Coupled Plasma (ICP) spectroscopic analysis to obtain data on levels of 30 heavy metals including arsenic, cadmium, chromium, copper, lead, tin, zinc, and mercury. Grain-size analysis was performed on ~3 grams of each coarse fraction by shaking through a series of sieves to classify and quantify the sediment.

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Coastal & Marine Geology Program > Center for Coastal Studies > Biscayne Bay Benthic Organisms Project