U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2004–3116

October 2004

Florida in a Tank—

The Role of Experiments in Ecosystem Restoration

Printed on recycled paper

Introduction 

South Florida is undertaking a massive restoration effort 

under the Comprehensive Everglades Restoration Plan (CERP), 

which was approved by Congress as part of the Water Resources 

Development Act of 2000. The primary goal of the CERP is to 

restore more natural freshwater flow through the South Florida 

ecosystem. In the last century, changes in delivery of freshwater 

to the estuaries of South Florida, including Biscayne Bay and 

Florida Bay, have altered their natural patterns of salinity. Many 

detrimental environmental effects, such as seagrass die-offs and 

loss of biodiversity, have been blamed on changing salinity. The 

goal of the U.S. Geological Survey (USGS) Ecosystem History 

Projects has been to identify natural cycles of change prior to 

human alteration of the environment and to distinguish natural 

change from anthropogenic change. 

Understanding natural cycles of change and the way a 

system originally functioned is essential to establishing success criteria for restoration. Knowledge about how human 

activities and natural fluctuations affect ecosystem change can 

be obtained by observing potential cause-and-effect relationships in the field, forming hypotheses, and then testing these 

hypotheses under controlled conditions. If laboratory conditions 

faithfully replicate field conditions, then laboratory experiments can generate new hypotheses that can be tested by field 

observations. 

The USGS has replicated several South Florida ecosystems 

in the USGS Leetown Science Center in West Virginia (figs. 1 

and 2). Through laboratory studies, we hope to do the following:

• Develop new techniques for deriving water-chemistry 

information from organisms that secrete calcium carbonate

• Apply these techniques to document seasonal salinity 

changes during a century or more

• Understand the effects of salinity and other ecosystem 

fluctuations on submerged aquatic vegetation (including 

seagrass and macroalgae) and associated animal life

• Develop success criteria for CERP

Figure 1. Map of the eastern United States showing the location of 

a study area in Whipray Basin, Fla., and of the USGS laboratory at 

the Leetown Science Center, Kearneysville, W. Va., where the Florida 

ecosystem has been replicated. Photographs show the similarity of 

turtle grass (the seagrass Thalassia testudinum) in both places. Base 

satellite image map from the National Oceanographic and Atmospheric 

Administration, 2003. USGS satellite image of South Florida from 1993. 

Photographs of turtle grass by J.B. Murray, USGS.

U.S. Geological Survey Leetown Science Center, 

Kearneysville, W. Va.

Study site in Whipray 

Basin, Fla.
USGS Laboratory Systems

Culture and test systems in tanks (mesocosms) at the USGS 

Leetown Science Center (LSC) were designed to replicate marine 

and estuarine seagrass ecosystems typical of South Florida 

(fig. 2). The systems at the LSC are monitored by using multiparameter water-chemistry sensors and data loggers (see box 

below). To provide comparison data from the real world (fig. 3), 

these parameters are measured at various sites in Florida Bay 

by water-monitoring stations installed by Everglades National 

Park and the USGS. Data are stored at the loggers and are downloaded to computers during periodic field visits.

The success of the LSC laboratory systems is indicated by 

the diversity of species that they support (figs. 4 (this page) 

and 5 (page 4)). Currently, the LSC systems maintain over 200 

species of plants and animals, including macroalgae, submerged 

aquatic angiosperms (true seagrasses), many types of calcareous algae, mollusks (snails and clams), echinoderms (seastars, 

urchins, brittle stars), numerous cnidarians (corals, anemones), 

crustaceans, and an array of worms of various phyla. Examples 

of experiments conducted in the LSC mesocosms are provided 

in the boxes on page 3.

Figure 2. Schematic diagram of the tank systems in the USGS Leetown 

Science Center greenhouse. Control systems A and B reproduce the 

diversity found in Florida Bay. Systems 1–8 are the environments for 

experiments.

Figure 3. Comparison of water temperatures of tanks in control system 

A in the USGS Leetown Science Center (fig. 2) with water temperatures 

from two data loggers (A and B) in Whipray Basin, Fla. The example 

data from January to May 2004 demonstrate that laboratory temperatures are very similar to those in the study area, although they do not 

match the low temperatures caused by storms.

Figure 4. Images illustrating the diversity of organisms in tanks in 

control system A in the USGS Leetown Science Center (fig. 2). A, Two 

species of anemones and several types of macroalgae. B, Several species of coral and macroalgae. Photographs by W.B. Schill (A) and J.B. 

Murray (B), both of the USGS.

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Experiments on Organisms that Secrete Calcium 

Carbonate

Many organisms secrete calcium carbonate (CaCO3) as they 

grow and thereby incorporate information about the water in 

which they live. The proportions of elements in seawater (for 

example, calcium, magnesium, barium, and strontium) are 

influenced by salinity and temperature and are reflected in the 

composition of calcium carbonate layers secreted by organisms 

as they grow (see figure below). We can determine historical 

patterns of seasonal temperature, salinity, and water-chemistry 

variability by analyzing the elemental composition of calcareous shells, including those of mollusks, ostracodes, and foraminifera, extracted from sedimentary layers in shallow cores. 

In order to interpret these data, we must understand the 

biology of the living organism. What is its growth rate? What 

is its life span? How do environmental variables such as salinity and temperature alter the growth rate? Is growth constant? 

Laboratory experiments using the LSC systems test the effects 

of various environmental scenarios on the survival, growth, and 

reproduction of the shell-forming animals mentioned above as 

well as algae that produce calcareous skeletons. Examples of 

ongoing experiments include the following:

• Investigating the effects of increasing salinity and temperature; the experiment reproduces conditions caused by 

evaporation of warm bay waters

• Investigating the effects of a rapid influx of freshwater; the 

experiment reproduces conditions associated with a storm 

or the release of impounded waters

Experiments on Seagrass 

The die-off of seagrass beds is a worldwide problem and 

a critical issue in any estuarine ecosystem because seagrasses 

are essential components of those systems. Seagrass meadows 

provide feeding grounds, nurseries, and habitats for many forms 

of marine life, including such economically valuable species as 

shrimp, lobster, and commercially harvested fish. They also are 

important foraging sites for many species of migratory birds. In 

addition, seagrass beds anchor sediments and impede sediment 

resuspension and coastal erosion during storms and thus play 

a role in protecting other marine ecosystems, including coral 

reefs. The immense surface areas of the seagrass plants and the 

sediments underlying them (see figure below) harbor microbes 

that perform many important functions, including nitrogen 

cycling, sulfur and metal reduction, and metabolism of organic 

pollutants. 

Seagrass beds are considered critical habitats within the 

South Florida ecosystem, and many hypotheses have been 

proposed to explain die-offs such as those that occurred in 

Florida Bay in 1987–88, when about 18 percent of the beds 

were affected. Unfortunately, seagrass biologists have lacked 

experimental systems to test these hypotheses under controlled 

conditions. As a result, the causes of these die-offs and the 

factors that control the health and distribution of seagrasses 

remain poorly understood. An understanding of these factors is 

essential if resource managers are to prevent further losses and 

restore damaged systems. We are using the culture and test systems at LSC and advanced molecular methods to study seagrass 

and to do the following:

• Identify disease agents associated with seagrass die-offs

• Define the role of environmental stressors (such as salinity 

fluctuations) in seagrass die-offs

• Investigate the role of seagrasses in estuarine biogeochemical processes

Clams (Chione cancellata) being placed in a study area in Whipray 

basin, Fla. (A), are the same species being grown in the USGS Leetown Science Center (B). The water chemistry at both sites is being 

monitored, and its effects on the elemental composition of the calcium 

carbonate shells that the clams are secreting will be determined; this 

information will calibrate the standards used in interpreting paleoecology from buried shells recovered in cores. Photographs by J.B. Murray, 

USGS.

Seagrass in control system A in the Leetown Science Center (A) 

and USGS scientists collecting samples of the sediment underlying 

seagrass beds in Whipray Basin, Fla. (B). Both the seagrass and the 

sediment harbor microbes that perform many important functions. 

Photographs by J.B. Murray (A) and W.B. Schill (B), both of the USGS.

A

B

A

B
Figure 5. Images of the diverse plants and animals in the USGS 

Leetown Science Center mesocosms. The second photograph from 

the top is by W.B. Schill, USGS; all other photographs in this figure 

are by J.B. Murray, USGS.

Importance of Experimental Studies in Restoration

Adaptation and selection of plants and other organisms occur 

over biologically significant periods of time in response to 

natural changes to the ecosystem. Anthropogenic changes to the 

South Florida ecosystem during the 20th century altered the natural patterns of change. As restoration proceeds, the natural rates 

of change must be considered. If restoration induces rapid rates 

of change to the ecosystem that exceed natural rates of change, 

then plants and other organisms may not be able to adapt.

Results of the experimental studies conducted in the mesocosms and results of the advanced molecular analysis, linked 

to the ecosystem history studies, provide insights into the rate 

of restoration that is tolerable by the system. These results will 

enable resource managers responsible for implementing the 

CERP to develop a model to predict future response to restoration changes. The resource managers can then set realistic targets 

and performance measures for restoration. Knowledge gained 

from this study should be applicable to other estuarine ecosystems throughout Florida and the Gulf of Mexico and, with modifications, to similar threatened ecosystems around the world.

What’s Next?

Current plans to utilize the USGS Leetown Science Center 

mesocosms include the following studies:

• Investigations of reef-decline issues, such as coral diseases, heavy-metal contamination, pesticide contamination, and coral genetics

• Identification of the effects of invasive species within the 

marine and estuarine ecosystems of South Florida

• Extension of chemical analysis techniques to study the 

carbonate structures of marine macroalgae 

By James B. Murray, William Bane Schill, 

and G. Lynn Wingard 

For more information on the mesocosms

and ongoing studies, please contact: 

James Murray, jbmurray@usgs.gov 

For more information on microbial and molecular studies, 

please contact: 

Bane Schill, bane_schill@usgs.gov

For more information on ecosystem history research in 

South Florida, please contact: 

Lynn Wingard, lwingard@usgs.gov

http://sofia.usgs.gov/flaecohist