Biodiversity
The Indian River Lagoon’s diverse montage of habitats creates a broad variety of opportunities for life in the estuary. Thousands of species of plants, birds, fish and mammals call the lagoon home.
Photo credit: M. Spradley
The IRL Species Inventory is an effort to document organisms that have been present in the Lagoon at some point in time – but is certainly an incomplete record of the total diversity in the Indian River Lagoon. However, to date, the Inventory contains documentation for 4,460 individual species, including an estimated 2,100 species of plants and more than 2,200 animal species.
The original IRL Species Inventory, first compiled in 1995, listed a total of 2,493 different species of plants, animals and protists. Of these, animals comprised the greatest proportion of species in the inventory (71.4 percent), with 1,779 species grouped into 20 phyla. Plants were grouped into four phyla, consisting of 289 different species. Protista (17 percent) consisted of 425 species in four phyla. No data are available for Kingdom Monera (bacteria).
Sampling of some taxa are more complete and thoroughly documented than others, including fishes, birds, mollusks, chrysophytes, dinoflagellates, rhizopods, ectoprocts, sipunculids, echinoderms, and mammals. Other taxonomic groups, including vascular plants, amphibians and reptiles, and marine macroalgae are relatively complete but could benefit from increased sampling over wider areas of the lagoon. Other taxa are, at the very best, partial lists, for example sponges and chaetognaths.
Ongoing research continues to discover and catalog numerous species of invertebrates, crustaceans, microscopic diatoms, sponges and algae.
The IRL owes its incredible biodiversity to two main factors: its unique geographical position, and its diverse montage of habitat types.
East-central Florida is located in the transition area between the temperate Carolinian climate zone to the north, and the subtropical Caribbean climate zone to the south. Temperate species of plants and animals exist in the Indian River Lagoon at the southernmost extent of their ranges, while subtropical and tropical species exist at their northernmost extents. Generally, the area around Cape Canaveral in northern Brevard County is where vegetation patterns begin to shift from primarily warm-temperate shrubs and trees, to more subtropical and tropical varieties.
Mangroves and salt marshes provide ample breeding, nursery and feeding grounds for a variety of species, and the lagoon’s ocean beaches attract some of the highest numbers of nesting sea turtles in the Western Hemisphere. The IRL also lies within the Atlantic Flyway and is an important stopover for many species of seasonally migratory birds.
Iconic residents of the lagoon include the Atlantic bottlenose dolphin (Tursiops truncatus) and manatee (Trichechus manatus latirostris). An estimated one-third of the U.S. manatee population uses the lagoon, and an estimated 300 dolphins are believed to live permanently in the IRL.
The lagoon’s watershed is also home to 53 species of animals that are classified as either threatened or endangered. Johnson’s seagrass (Halophila johnsonii) is one IRL resident that is found nowhere else in the world; other rare species include the four-petaled pawpaw (Asimina tetramera), smalltooth sawfish (Pristis pectinata), green and leatherback turtles (Chelonia mydas and Dermochelys coriacea) and Kirtland’s warbler (Setophaga kirtlandii).
Biodiversity may be defined as the measure of how healthy an ecosystem is. Healthy ecosystems support high biological diversity, while stressed or highly disturbed ecosystems do not. Biodiversity encompasses not only diversity of species and diverse gene pools, but also diverse habitat and ecosystem types.
Genetic Diversity: Populations with greater genetic diversity are far better equipped to cope with environmental change, and are able to reproduce more successfully than populations with low genetic diversity. Populations with low genetic diversity can become so well adapted to local conditions that any environmental disturbance may be enough to reduce their numbers dramatically, or even destroy them entirely.
Species Richness: Another measure of biodiversity is species diversity. One measure of this is richness, the number of species which occur within a particular taxonomic level (species, genus, family) in a geographic area. In marine ecosystems, species diversity tends to vary widely depending upon latitudinal and longitudinal location. Tropical areas tend to have higher species richness, for example. The lowest species diversity is found in the eastern Atlantic.
Ecosystem Diversity: Ecosystems are the collection of all the plants and animals within a particular area, each differing in species composition, physical structure and function. Ecosystem diversity refers to the number of ecosystems in a geographic area; the Indian River Lagoon is an example of a collection of ecosystems, each of them highly diverse.
The factors which threaten biodiversity in estuaries and in the oceans are generally the same as those which affect biodiversity in terrestrial systems: overexploitation, physical alteration of habitat areas, alien species introductions, and changes in atmospheric composition.
Many threats to the survival of life in the oceans can originate on land. Examples of threats include siltation, nutrient loading, and pollution by toxic chemicals. The continuous growth of human development also threatens coastal and estuarine ecosystems. Habitat degradation which occurs as the result of these problems inevitably leads to loss of species from an ecosystem, and thus, a loss of biodiversity.
