A DIVERSE ECOSYSTEM

Overview

On virtually any barrier island, wind and sand combine to create sand dunes. Dunes play a vital role in protecting coastlines and property. They act as buffers against severe storms, protecting the lands beyond the dune from salt water intrusion, high wind and storm surges. Dunes also act as sand reservoirs, which are important for replenishing coastlines after tropical storms, hurricanes, intense wave action, or other erosional events.

Human Impacts

In spite of the stabilizing ability of dune plants, dunes are highly susceptible to human impacts. Vehicles traversing beaches, as well as heavy foot traffic, damage vegetation by shifting sand and roots, thus destabilizing the dune community. Coastal development can also impact the natural process of dune replenishment by adversely influencing natural erosion patterns.

Learn more by visiting the Smithsonian Marine Station website.

Overview

Stable backdune areas give rise to scrub communities built upon sandy or well drained soils, with the predominant vegetation being herbaceous shrubs, evergreen oaks, or pines. While coastal scrub communities are impacted more by the strong winds and flooding brought on during storm events, most types of scrub are maintained primarily by fires. Frequent fires are more beneficial to oak scrub and scrubby flatwoods communities; while less frequent fires are more beneficial to sand pine scrub and other pine-dominated scrub types. A number of animals are found in scrub habitats, including some of Florida’s most threatened and endangered species. Many other animals also utilize scrub areas for feeding and for shelter.

Human Impacts

Coastal scrub communities, commonly referred to as coastal strand, are vanishing ecosystems due to developmental pressures in the coastal zone. Most of the coastal habitats from Cape Canaveral in Brevard County, to Miami in Dade County have been highly fragmented due to development. In Brevard County alone, it has been estimated that the natural scrub community was diminished by 69% during the period between 1943 – 1991.

Learn more by visiting the Smithsonian Marine Station website.

Overview

Maritime hammocks, also known as maritime forests, tropical hammocks or coastal hammocks, are characterized as narrow bands of forest that develop almost exclusively on stabilized backdunes of barrier islands, inland of primary dunes and scrub. Florida, which has the longest coastline in the contiguous United States, has approximately 468,000 acres of barrier islands, with maritime forests occupying the highest, most stable areas of these islands.

Human Impacts

Because maritime forests occur on the most stable areas of barrier islands, they are attractive sites for development. In maritime forests, the canopy is typically closed, making these areas shady and cool compared to adjacent scrub, dune and beach areas. When developed, the process of land clearing involves disturbing or destroying most, if not all, the natural vegetative cover to make space for homes, parking areas, drainage fields, septic systems and roads. Following construction, native vegetation is often replaced by lawns and ornamental shrubs, many of which are exotic.

Learn more by visiting the Smithsonian Marine Station website.

Overview

Mangrove forests are among the world’s most highly productive ecosystems. The term mangrove is loosely used to describe a wide variety of often unrelated tropical and subtropical trees and shrubs that share common characteristics. Mangroves perform a vital ecological role providing habitat for hundreds of different species including fish, reptiles, mammals and birds that all utilize mangroves as habitat during some period of life. Additionally, many species, though not permanent mangrove inhabitants, make use of mangrove areas for foraging, roosting, breeding, and other activities. In addition to providing vital nursery and feeding habitat to fishes, mangroves also assist in shoreline protection and stabilization.

Learn more by visiting the Smithsonian Marine Station website.

Overview

Florida’s mangroves and salt marshes have historically been problem areas in one important respect:  they are preferred breeding habitat for saltmarsh mosquitoes, an important nuisance species affecting both human and animal health. Mosquito control impoundments are areas of saltmarsh or mangrove forest that have been diked to allow control of water levels. Within the dikes, perimeter ditches are flooded artificially in order to control mosquito breeding and reproduction without the use of pesticides. Saltmarsh mosquitoes only lay eggs in moist, but not wet soils. Keeping water levels high in impoundments during mosquito breeding season interrupts their lifecycles and keeps their numbers down to manageable levels.  The use of impoundments for mosquito control replaced extensively spraying pesticides like DDT that was common in earlier decades.

Negative Effects

Although impoundment is an effective method for controlling mosquito populations, there can be severe environmental impacts on impounded wetlands isolated from adjacent estuaries. Particularly important are issues of water quality degradation, isolation of important fishery species from critical nursery habitats, interruption of nutrient flow between wetlands and estuarine waters, creation of unnaturally high water levels, and hypersaline conditions that may develop in closed impoundments when evaporation of water occurs. Advances in mosquito control have resulted in many impoundments being rotationally managed. Impoundments of this type are connected to the lagoon during the fall and winter months, and have natural flow regimes. During the late spring and summer months, they are flooded to control mosquitoes.

Learn more by visiting the Smithsonian Marine Station website.

Overview

Salt marshes form in sheltered coastal areas where sediments accumulate and allow the growth of a variety of plants that comprise the foundation of the ecosystem. Salt marshes are biologically diverse communities adapted for harsh environmental conditions that include desiccation, flooding, and extreme temperature and salinity fluctuations. Marshes act as nurseries to a wide variety of organisms, some of which are notably threatened, or important fisheries species.

Rapid growth of marsh vegetation and utilization of incoming nutrients make salt marshes highly productive systems, on par with tropical rainforests in terms of their productivity. In addition to providing habitat and food sources for many organisms, salt marshes benefit humans and surrounding ecosystems by sheltering coasts from erosion and flooding. They also act as filters for stormwater runoff, trapping sediments and utilizing nutrients in stormwater that flows across them.

Learn more by visiting the Smithsonian Marine Station website.

Overview

Tidal flats are highly productive components of ecosystems and are responsible for recycling organic matter and nutrients from both land and ocean sources.  They provide enormous water carrying capacity, helping to protect areas of the IRL from storm surge as well as stormwater runoff. Tidal flats also help to reduce erosion, dissipate wave energy, and reduce the impacts of storms by forming a buffer zone between deeper channels of the lagoon and the shoreline. In combination with mangroves and saltmarshes, these intertidal habitats are of great importance to large numbers of invertebrates and fish because they support a complex estuarine food web and provide resting and feeding areas to large numbers of indigenous and migratory birds.

Threats to Tidal Flats

Water and sediment quality characteristics are important factors in maintaining healthy lagoon habitats. Tidal flats face a number of human and natural threats including sea level rise, loss of habitat, salinity fluctuations, pollution, erosion and invasive species. Ever-increasing growth of the human population and development along Florida’s coastline, coupled with alterations caused by mosquito impoundments, have led to changes and degradation in Florida’s wetland and coastal areas. It is estimated that since the 1950’s, 75% of the mangrove forests and salt marshes bordering the Indian River Lagoon have been destroyed, altered or functionally isolated. In more recent years, the importance of coastal wetlands has been recognized and much work has been devoted to reconnecting wetlands to the lagoon in order to restore natural water flow and function.

Learn more by visiting the Smithsonian Marine Station website.

Overview

Oyster reefs, often referred to as oyster bars, are common submerged habitats in the southern United States. Within the Indian River Lagoon, oyster reefs may be found in the vicinity of spoil islands and impounded areas. In addition to being commercially valuable, oyster reefs serve a number of important ecological roles in coastal systems: providing important habitat for a large number of species; improving water quality by filtering particulates out of the water; stabilizing bottom areas to prevent erosion, and influencing water circulation patterns within estuaries.

Threats to Oyster Reefs

Over-harvesting, as well as persistent diseases such as MSX and Dermo have taken a devastating toll on many oyster populations along the east and Gulf coasts. In recent years, oyster reef restoration has been a concern for resource managers all along the East Coast of the United States, but especially in areas like the lagoon where oyster harvesting has historically been commercially important. While fisheries throughout the lagoon have declined in recent years, there has been renewed interest in re-establishing oyster reefs, primarily due to the water quality benefits they convey when present in the ecosystem.

Learn more by visiting the Smithsonian Marine Station website.

Overview

Seagrasses are a type of submerged aquatic vegetation (SAV) that evolved from terrestrial plants and have become specialized to live in the marine environment. Physiologically, they are not very different from the grasses that grow on land and produce flowers and seeds. Within seagrass communities, a single acre of seagrass can produce over 10 tons of leaves per year. This vast biomass provides food, habitat, and nursery areas for a myriad of adult and juvenile vertebrates and invertebrates. Because seagrasses support such high biodiversity, and because of their sensitivity to changes in water quality, they have become recognized as important indicator species that reflect the overall health of coastal ecosystems. When seagrasses do well, other animals and plants also do well; when seagrasses decline, other species follow.

Threats to Seagrass Communities

Seagrasses are subject to a number of biotic and abiotic stresses such as storms, excessive grazing by herbivores, disease, and anthropogenic threats due to point and non-point sources of pollution, decreasing water clarity, excessive nutrients in runoff, sedimentation and prop scarring. What effect these stresses have on seagrasses is dependent on both the nature and severity of the particular environmental challenge.

Learn more by visiting the Smithsonian Marine Station website.