U.S. Department of the Interior
U.S. Geological Survey

USGS Open-File Report 02308
July 2002


ENVIRONMENTAL QUALITY AND PRESERVATION--
Chemical Pollutants and Toxic Effects on Benthic Organisms, Biscayne Bay: A Pilot Study Preceding Florida Everglades Restoration

Introduction

The Florida Everglades, designated a
National Park in 1947, comprise the largest area
of wetlands and mangrove swamps in North
America. In the late 1940s following back-to-back
hurricanes, a massive fl ood-control project
was instigated to construct levees and canals
throughout Central and South Florida. By draining
500,000 acres south of Lake Okeechobee
(Fig. 1) and diverting freshwater fl ow for cattle
farming, urban development, and agricultural,
industrial, and municipal water supplies, the
infrastructure irreversibly damaged the wetlands
and associated ecosystems. The canals
severely altered regional hydrology and salinity
(a measure of dissolved salts) along with
habitats and natural fire resistance (Douglas,
1947). Introduction of agrichemicals and pesticides
affected wildlife. Since the 1950s, the
wetlands have been mined for limestone for
use in cement, concrete, and asphalt. Miners
have excavated thousands of acres, leaving barren
rock pits in place of fertile swamps, and
plan to expand operations to include thousands
more. The original Everglades watershed was
80 km wide, covered an area of 14,480 km2,
and extended for 400 km as a single hydrologic
unit that flowed from the vicinity of Orlando to
Florida Bay. Though only centimeters deep, the
watershed was capable of filtering and removing
most nutrients from the water. Today, reduced
to less than half its size, the watershed filters far
less and removes far fewer nutrients than in the
past. Restoration of the Everglades is a National
priority of branches of both State and Federal
governments.

Figure 1. Index map of Florida. Coral reefs are indicated by orange on inset.

The Problem
Geologically, the porous limestone of
Florida connects the Everglades with Florida and
Biscayne Bays, the Florida Keys, and the largest
offshore tract of coral reefs in the continental
U.S. These areas are also biologically connected
because many marine organisms spend
different stages of their life cycles in the various
ecosystems, most of which are in decline.
Against a backdrop of biogeologic connectivity,
deteriorating coastal environments, rising sea
level and increasing pollution, the problem lies
in not knowing how the Everglades restoration
will affect the stressed co-joined systems. This
report presents results of geochemical, sedimentary,
and microfaunal analyses in a 1-year pilot
study along the western margin of Biscayne
Bay (Phase I) and introduces a 2-year project to
establish environmental status bay-wide (Phase
II) prior to restoration of the Everglades.

Biscayne Bay
Baseline ecosystem status and pollution
data for Biscayne Bay are lacking. An
inshore estuary east of the Everglades (Fig. 1),
Biscayne Bay is the marine component (vs.
terrestrial) of Biscayne National Park (BNP).
Within BNP boundaries are the longest stretch
of mangrove forest remaining on Floridas east
coast, 14 threatened or endangered wildlife
species, and the northernmost coral reefs in the
continental U.S. The bay acts as a buffer zone
for these reefs. Human impacts on the coastal
marine environment of South Florida include
urban development, air, land, and water pollution,
intense recreational and commercial use,
introduction of pathogens and nutrients from
sewage-disposal injection wells and shoreline
landfills, and physical damage to coral reefs and
other bottom communities by derelict fishing
gear, boat anchors and ship groundings. Nutrient
enrichment spurs oxygen depletion in coastal
waters, stressing or killing biota. Coastal landuse
practices (marina, agricultural and industrial
development) cause contamination by chemical
pollutants, pesticides, petroleum products, fertilizers,
and heavy metals. Each impact alters the
coastal ecosystems. Each impact has significant
implications for human issues, including swimmers
health, fishery nurseries and resources,
and management of coastal land development.

Of particular concern is the $8 billion
Comprehensive Everglades Restoration Project
(CERP, signed into law in December 2000) to
remove canal and levee infrastructures within
the watershed to restore a natural southward
flow of water. Resource managers urgently
need information on stress responses in organisms
that can be compared with data acquired
through remote sensing, water quality, and biotic
community monitoring. In cooperation with
Biscayne National Park (BNP), the National
Park Service (NPS), and the University of South
Florida (USF), the U.S. Geological Survey
(USGS) has begun a new project to evaluate
pre-restoration conditions throughout Biscayne
Bay using components found in surface sediments.
Project strategies are to assess grain size,
heavy-metal concentrations, sources, pollution
hotspots, distributions of a pollution-sensitive
group of marine microfaunas, and biotic community
structure as reflected by skeletal sand
grains. Long established as paleoenvironmental
and pollutant biomarkers, benthic or bottomdwelling
foraminifera (forams) morphologically
and geochemically record ambient environment
in their shells. The goal is to provide essential
baseline data that can readily be used to monitor
changes in the estuarine ecosystems during and
after implementation of the CERP.
The Phase I pilot study was concentrated
along the western margin of Biscayne Bay. The
pilot study achieved primary objectives:


by developing and implementing improved
methods using geochemical, sedimentary,
and foram analyses to assess and monitor
coastal contamination;

by defining types, distributions, and concentrations
of heavy metals relative to
grain size of host sediments to obtain a better
understanding of heavy-metal sources
and sinks;

by identifying dominant foram assemblages
and key biomarker taxa known as pollutant
indicators to assess environmental status;
and

by quantifying percentages of normal vs.
deformed foram shells to correlate results
with concentrations of heavy metals and
other pollutants.

Phase II will expand these objectives baywide
and will assess present biotic community
structure by identifying and quantifying skeletal
sand grains. Except for coral grains, the most
abundant grains of other organisms belong to the
groups of living organisms that are dominant.
Grain percentages are thus indicators of the type
of environment in which the organisms live. In
contrast, high percentages of coral grains equate
to high rates of coral bioerosion and thus to
poor coral health (e.g., Lidz and Hallock, 2000).
Living coral polyps form a thin cover of tissue
over a skeleton of calcium carbonate. When the
polyps die, increased areas of skeletal coral are
exposed to bioerosion, or breakdown by grazing
and boring organisms. With the exception of
damselfishes, which are aggressive specialized
herbivores that feed on live coral tissue to promote
algal growth within their territories at the
base of coral colonies, few grazers and borers in
general attack healthy corals. Phase II will integrate
Phase I results and will provide bay-wide
database contour maps as decision products to
improve knowledge of biotic community, pollutant
source, transport, distribution, and accumulation
in bay sediments.

The Pilot Study
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 (Fig. 2).
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 baywide
analyses may produce trends that differ
from those indicated by the pilot study.

Grain-Size Analysis
Grain-size analysis revealed that most samples
were poorly sorted, especially those from
the vicinity of Black Point, and that samples at
15 of the 38 sites were composed of >90% sand,
ranging from medium to very fi ne in texture.
The muddiest samples (>50%) were confined to
small areas in the upper bay. Fine sands were
predominant in samples from the Dinner Key
Marina and Snake Creek areas. Correlation of
the grain-size and foram data indicated that
grain size does not affect distribution of benthic
forams.

Figure 2. Map of Biscayne Bay shows 38 nearshore sample sites of the Phase I pilot study (yellow triangles) and additional 120
cross bay sites sampled for Phase II analyses (red squares).

Figure 3. Members of benthic foram assemblages commonly found in Biscayne Bay. When occurring in abundance, each dominant assemblage represents a functional group diagnostic of environment. Except for agglutinated genera, benthic forams secrete their shells from calcium, magnesium, and oxygen dissolved in sea water.  Agglutinated taxa build their shells by cementing tiny particles from their environment together. (A) Oligotrophic symbiont-bearing taxa. (B) Agglutinated taxon. (C) Smaller nutrient-tolerant heterotrophic taxa. (D) Opportunistic taxa. (E) Abnormal (deformed or misshapen) specimens.

Oligotrophic: environment low in dissolved nutrients.
Symbiont-bearing: reef-building stony corals and reef-dwelling benthic forams contain symbiotic algae required for their growth, calcification, and color.
Heterotrophic: environment with abundant dissolved nutrients but not to the point of being eutrophic.
Eutrophic: environment saturated with dissolved nutrients that promote prolific growth of non-symbiotic algae.

Heavy-Metal Analysis
Potential sources of heavy-metal pollution
include leachates from copper bottom paint on
boats in marinas and a coastal landfill at Black
Point, and from one or more of the 25 (3,000-
ft-deep) disposal wells located at Black Point.
Other potential sources include the highly polluted
Miami River, the Turkey Point Nuclear
Power Plant and sacrificial anodes on boats
docked at marinas. Sacrificial anodes protect
other metals on boats from breakdown by electrolysis.
Geochemical analyses indicated that concentrations
of silver, copper, lead, and zinc were
highest near marinas in the upper part of the bay.
Water circulation at these sites is more restricted
than at other sites in the pilot study, implying
longer residence times for the contaminants. A
statistical cluster analysis showed that copper,
lead, and zinc clustered strongly with aluminum
and iron, which are often associated with clays.
Clays in the marine environment suggest a terrigenous
source. Of the metals detected in the
geochemical analysis, copper, lead, zinc, and
mercury were the only ones significantly higher
than in normal marine water. Trends indicate
a decrease in heavy-metal concentrations from
north to south along the shoreline, away from
the older part of urbanized Miami, and a general
decrease from nearshore to the center of
the bay. Strontium and calcium typically occur
together in a biogenic environment (i.e., where
sediments are derived from organisms) and were
accordingly found in the samples.

Benthic Foram Analysis
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 (Fig. 3A-D).
Presence of abundant oligotrophic symbiontbearing
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. 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
(Fig. 3E). 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 signifi cant indication
that general water quality in the bay has
declined over the 3-year period.

Summary
In a cooperative study with the NPS and
BNP, the USGS and USF are assessing environmental
quality in Biscayne Bay to provide pre-
Everglades restoration baseline data and decision
products that will facilitate restoration and/
or preservation of ecosystems within the bay.
The study is based on components of surface
sediments. The data will be used to construct
contour maps of grain size, heavy-metal distribution
and concentration, foram assemblages
diagnostic of pristine to heavily polluted waters,
and dominant types of skeletal sand grains.
These products will establish present conditions
in the bay and can be applied to monitor future
changes in biota (i.e., environment, water quality,
and pollution) as well as to document past
changes by comparison with historical records
determined from analogous studies of sediment
cores.
In general, overall results of the Phase I
pilot study along the western bay margin indicate
that the highest concentrations of heavy
metals are found off densely urbanized areas,
that most abnormalities in foram shells are
found off the Black Point landfill, and that
nearshore ecosystems within the bay are under
stress. The stress is probably due both to natural
(rising sea level) and anthropogenic (increasing
pollution) causes. The Phase II bay-wide geochemical,
sedimentary, and microfaunal analyses
will delineate more precise trends in pollution
and will include the origin of biogenic sand
grains that will identify the biotic structure of
benthic communities.

References Cited
Hoare, A.M., 2002, Analysis of Biscayne Bay Sediments: Do Benthic Foraminifera Reflect Trace Metal
Contamination? Unpublished M.S. Thesis, College of Marine Science, University of South Florida,
St. Petersburg, FL, 107 p.
Douglas, M.S., 1947, The Everglades: River of Grass
(revised ed., 1988): Pineapple Press, Sarasota, FL., 448 (revised ed., 1988): Pineapple Press, Sarasota, FL., 448 p.
Ishman, S.E., Graham, S., and DAmbrosio, J., 1997, Modern benthic foraminiferal distributions in Biscayne
Bay: Analogs for historical reconstructions: U.S. Geological Survey Open-File Report 97-34, 23 p.
Lidz, B.H., and Hallock, P., 2000, Sedimentary petrology of a declining reef ecosystem, Florida reef tract
(U.S.A.): Journal of Coastal Research, v. 16, no. 3, p. 675-697.
SERC, 2000 and 2001, Southeast Environmental Research Center, <http://serc.fiu.edu/wqmnetwork/
SFWMD-CD/DataDL.htm> South Florida Water Quality Monitoring Network, Florida International
University, Miami, FL.

For more information, please contact:
Barbara H. Lidz
U. S. Geological Survey
600 4th Street South
St. Petersburg, FL 33701
Phone: 727-803-8747 x3031
Fax: 727-803-2030
Internet: blidz@usgs.gov

This report is preliminary and has not been reviewed for
conformity with U.S. Geological Survey editorial standards
or with the North American Stratigraphic Code. Reference
therein to any specifi c commercial product, process, or service
by trade name, trademark, manufacturer, or otherwise does
not necessarily constitute or imply its endorsement, recommendation,
or favoring by the United States Government or
any agency thereof.