The Smithsonian Marine Ecosystems Exhibit features six aquarium displays depicting important ecosystems of the Indian River Lagoon and surrounding coastal waters. The highlight of the exhibit is a 3,300-gallon model of a Caribbean coral reef.

Coral Reef Model Ecosystem 
Coral reefs occur in clear, warm (70 – 85 °F) subtropical and tropical oceans worldwide. They play host to more animals and plants than any other marine community and are one of the most biologically diverse ecosystems on earth.

Florida is the only state to have substantial coral reef formations; extending from Stuart on the east coast to the Dry Tortugas west of Key West in the Gulf of Mexico. The massive limestone skeletons produced by corals provide protection from storms which helps to reduce coastal erosion and flooding. Coral reefs provide habitat for many ecologically and commercially important fishes, crustaceans, and other invertebrates. They are also sensitive to changes in global temperature, which makes them a valuable tool for studying changes in the earth's climate over geological time.

The high diversity of plants and animals on coral reefs is a valuable natural resource and future source of new medicines and industrial chemicals. Many compounds have been discovered that have potential pharmaceutical value, including some used to treat AIDS and cancer. The exhibit's 3,300-gallon coral reef ecosystem was modeled after a barrier coral reef formation. Barrier reefs are comprised of a forereef (which is exposed to the open ocean), the reef crest (which can be exposed at low tide and serves to absorb wave energy), and the backreef (or lagoon.) The reef off Looe Key in the Florida Keys is an example of a barrier coral reef.

Over 10,000 pounds of carbonate rock was used to construct the exhibit's reef. The majority of the reef rock was collected between 10 and 20 years ago off Mayaguana, in the Bahamas. All of the specimens used in the exhibit were collected in the Bahamas and Florida. There are hundreds of species of algae and invertebrates, including thirty-three species of hard and soft corals, and fifteen species of fishes living, growing, and interacting in this complex habitat. top

Seagrass Model Ecosystem
Seagrasses are flowering plants that have evolved to live submerged in muddy and/or sandy soft bottom habitats along protected coastlines and estuaries of North and South America, Europe, Asia and Australia. While some seagrasses can be found as deep as twenty meters (about sixty feet), in the IRL they are only found from the low tide zone down to about three feet. Of the approximately fifty species known worldwide, seven occur in the Indian River Lagoon (IRL). One of the species, Johnson's seagrass, Halophila johnsonii, is found exclusively in coastal lagoons of eastern Florida.

Seagrasses along with their attached epiphytes (plants that grow on other plants) are considered to be one of the most productive communities in the entire ocean. In addition to supporting a large complex food web which includes many commercially and recreationally important species, seagrasses are responsible for increasing the oxygen levels and the clarity of the surrounding water. The roots stabilize the soft bottom while their leaves and blades reduce currents and wave action which causes finer suspended particles to settle out. 

Seagrass ecosystems serve as nurseries for the juveniles of many coastal species of fishes and invertebrates. They move into these complex habitats to take advantage of their ample food and refuge when young and depending on the species, either move towards the ocean and/or deeper areas of the IRL as they grow.

The 500-gallon Seagrass Model Ecosystem includes nearly a foot of natural substrate and three species of seagrass, including manatee grass, Syringodium filiforme, turtle grass, Thalassia testudinum, and shoal grass, Halodule wrightii. Our seagrass model ecosystem supports a wide variety of the organisms typical of the IRL, including seahorses, pipefish, grass shrimp, snails, sea slugs, hermit crabs, gobies, and herring. Other inhabitants like pinfish, mangrove snappers, sheepshead, spot, and seatrout, which are only temporary residents of seagrass beds, are only included in the exhibit when appropriate. top

Mangrove Model Ecosystem
Mangrove ecosystems are found worldwide, replacing saltmarshes along tropical and subtropical protected shorelines. The transition from temperate salt marshes to mangroves occurs within the Indian River Lagoon. There are three species of mangroves in Florida: the red mangrove, Rhizophora mangle,  grows closest to the water's edge; the black mangrove, Avicennia germinans, occurs shoreward of the red; and the white mangrove, Laguncularia racemosa, is usually found the furthest inland of the three species.

Mangroves perform several important functions. Their roots stabilize the shoreline by decreasing water flow, which also allows sediments to accumulate. While mangrove roots provide a complex habitat for an array of organisms including algae, sponges, and barnacles, as well as fish and crabs, its fallen leaves support a large foodweb. And, like seagrass beds, mangrove communities serve as nurseries for many ecologically and economically important fishes and invertebrates.

The 1,500-gallon Mangrove Model Ecosystem simulates a mangrove community at the water's edge, which is typically dominated by red mangrove trees. Due to the importance of tides on this community, this is the only model ecosystem with a simulated tidal cycle.

The decaying plant material which must be added on occasion, helps to support a resident population of mosquitofish, blennies, killifishes, mojarras, fiddler crabs, coffee snails, and oysters. When they're available, a juvenile snapper, flounder, barracuda, or needlefish might be included, however, they can quickly outgrow the display by eating the resident fishes! top

Hardbottom Model Ecosystem
Within the inlets and along the dredged portions of the Intracoastal Waterway of the Indian River Lagoon there are limestone ledges which are geologically similar to the nearshore oceanic reefs. These limestone ledges, combined with with artificial structures like pilings and concrete rubble, help to support the unsurpassed biodiversity of the Indian River Lagoon.

The Hardbottom Model Ecosystem is housed in a 500-gallon aquarium which includes a silica sand substrate and several coquina limestone rocks. The rocks provide habitat for a variety of algae and invertebrates, including boring urchins, sea cucumbers, anemones, sponges, tunicates, snapping shrimp, and hermit crabs. However, most of the attention in this exhibit is focused on some of the lagoon's larger and more aggressive species, like snook, sheepshead, snappers, spiny lobsters, blue crabs, and stone crabs. top

Nearshore Model Ecosystem
The nearshore reefs along the east coast of Florida between the Sebastian and St. Lucie Inlets consist of flat pavements of coquina limestone. This type of sedimentary rock is formed when sand shells become compressed and cemented together over time. Since the last Ice Age ended around 18,000 years ago, sea level has increased incrementally, which has exposed a series of rocky reefs running parallel to the shore off the east central coast of Florida. The closest reefs are found in 10 to 25 feet of water and can be seen within one-hundred yards from shore in some places. There is another series of reefs in 50 to 70 feet of water and again in 80 to 90 feet of water. In the deeper reefs, the ledges can be as high as ten feet.

These reefs support a variety of algae, invertebrates, and over 100 species of fish, including a number of commercially and recreationally important species. Many of the fishes found on nearshore reefs start out in the shallow nursery habitats of the Indian River Lagoon.

The exhibit's 500-gallon Nearshore Ecosystem is based on the reefs nearest to the shore in about fifteen feet of water. The Coquina limestone rocks were placed on the local silica sand. In addition to a variety of algae, common inhabitants include, sea urchins, snails, anemones, sea cucumbers, sand dollars, gobies, blennies, lookdowns, and damselfish. top 

Oculina Reef Model Ecosystem
In the deep offshore waters of east central Florida lies a unique coral reef system comprised of a single species of coral called the ivory tree coral, Oculina varicosa. These reefs are found at depths from 250 to 300 feet, and stretch over ninety nautical miles along the edge of the continental shelf from Fort Pierce to Cape Canaveral, Florida and nowhere else. This delicately branching coral grows at the slow rate of about a 1/2" per year, forming bushy, spherical colonies which can grow up to five feet in diameter.

Oculina corals are pure white because they lack the characteristic color from tiny microscopic algae called zooxanthellae that live symbiotically within most shallow water corals. Because they live too deep to depend on symbiotic algae, Oculina corals must catch their food, which consists of zooplankton and suspended organic matter.

Deep water Oculina reef systems play host to an extremely diverse assemblage of fishes and invertebrates, many of which are of commercial value. It serves as a breeding ground for gag and scamp grouper and as a nursery for juvenile snowy grouper. As a result, the federal government has designated these reefs as an Area of Particular Concern. The depth of Oculina reefs make it extremely difficult to aquire specimens for the exhibit's 500-gallon display. The coral rubble, Oculina corals, and other invertebrates like brittle stars, sea stars, anemones, urchins, and crabs living in the exhibit were collected during two research cruises by Harbor Branch Oceanographic Institution's submersible. And while many of the fishes found in this habitat also live in shallower waters, most are very aggressive predators (including some on corals) which can not be maintained in our model ecosystem. top