Coastal & Marine Geology Program > St. Petersburg Coastal and Marine Science Center > 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

Benthic Foram Analysis

Cockey et al. (1996) and Ishman (1997, 2000) have shown the value of assessing foram assemblages in studies of both surficial sediments and sediment cores from the Florida reef tract and Florida Bay environments.

Photo Gallery:
Common Forams of Biscayne Bay

Laevepeneroplis

Assemblages of specific benthic forams characterize 'functional groups' on the basis of taxa present. In turn, the functional groups characterize the environment in which the taxa live: symbiont-bearing larger forams, nutrient-tolerant smaller taxa, pollution-tolerant opportunists, and agglutinated taxa (see Foram Photo Gallery assemblages A-D).

Presence of abundant oligotrophic symbiont-bearing taxa indicates good water quality. The water is warm, clear, and low in nutrient content with normal marine salinities. Such conditions are suitable for growth of corals and coral reefs.

Smaller nutrient-tolerant heterotrophic taxa indicate presence of organic-rich food sources. These conditions are neither suitable for coral growth nor heavily polluted.

Opportunistic taxa tolerate a wide range of stressful conditions, notably environments low in oxygen, variable in salinity, and high in anthropogenic pollution.

Agglutinated taxa generally inhabit areas where water is undersaturated with respect to calcium carbonate, such as in estuarine or brackish environments.

The abundance of abnormally developed vs. normal specimens indicates the degree of stress in the environment. Studies elsewhere have shown that deformed specimens can develop in presence of heavy metals and that deformed shells contain higher levels of heavy metals (lead, zinc, copper, chromium, and cadmium) than normal shells.

The pilot study yielded 53 identifiable foram genera typical of estuarine environments. Opportunistic taxa, abundant at all sites, indicate the bay ecosystem is experiencing stress whether from salinity, nutrients, heavy metals, or other pollutants.

Photo Gallery:
Common Forams of Biscayne Bay

deformed Triloculina

Deformed specimens, which belonged primarily to a single group of heterotrophic taxa, were found at 27 sites and ranged from subtle to very grotesque in appearance (see Foram Photo Gallery assemblage E).

Surprisingly, distributions of high heavy metal concentrations and high percentages of abnormal foram specimens showed little correlation. Highest metal concentrations were found in the upper part of the bay near the city of Miami, but highest deformity percentages occurred off the Black Point landfill, indicating possible leaching of contaminants into the bay.

General trends indicate an offshore increase in diagnostic symbiont-bearing forams and an offshore decrease in opportunists and abnormal specimens. These trends signify that the quality of water in the central bay is better (closer to normal marine conditions) than near shore. The opportunistic forams consistently showed strong correlation with most of the heavy metals and with aluminum and iron.

Statistical analysis of the foram assemblages confirmed that bay characteristics are estuarine but also indicated that conditions are stressed. Comparison of present low percentages of symbiont-bearing taxa in the bay, a group physiologically similar to symbiont-bearing reef-building corals, with previous higher percentages measured by others (Ishman et al., 1997) is a particularly significant indication that general water quality in the bay has declined over the 3-year period.

continue to Heavy-Metal Analysis

Coastal & Marine Geology Program > St. Petersburg Coastal and Marine Science Center > Biscayne Bay Benthic Organisms Project