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Big Bend Seagrasses Aquatic Preserve

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"The Big Bend Seagrasses Aquatic Preserve epitomizes the Florida estuarine system: a natural dynamic system that has supported indigenous Floridians for millennia and continues today. These ecological systems provide the best opportunity to study the coastal strand and should continue to be the focus of our best conservation and protection efforts."

-Gary Ellis, Gulf Archaeological Research Institute

  • The Big Bend Seagrasses Aquatic Preserve was established in 1985.
  • Spanning more than 984,000 acres, the Big Bend Seagrasses Aquatic Preserve is the largest aquatic preserve and one of the most pristine places in Florida. 
  • The preserve provides habitat to a wide variety of sea and shore birds including a large nesting colony of frigate birds on Seahorse Key. 
  • It supports a very important commercial shellfish industry including Cedar Key clams, oysters, pink shrimp and blue crab. This area of Florida is also a popular destination during the recreational scallop season. 
  • The Suwannee River region supports essential fish habitat and the most viable population of the threatened gulf sturgeon. Big Bend's vast seagrass beds with mud and sand substrates are important marine habitats to this species.

Resource Management

Staff work with environmental resource permitting agencies to ensure only proper dredge and fill activities occur within the preserve. They also are working with the Florida Department of Agriculture and Consumer Services' Division of Aquaculture to relocate clam leases and establish live-rock leases.

Education and Outreach

The enormous size of the preserve and small staff size limit education and outreach efforts to kiosks, presentations to targeted user groups, including classrooms, and programs at the preserve office in Crystal River Preserve State Park.

Research and Monitoring

Staff are conducting extensive surveys to establish baseline conditions of seagrass habitat, including distribution, abundance, productivity and health. Coupled with their water quality monitoring and efforts by the Suwannee River Water Management District, these surveys help evaluate conditions and address management needs.

Seagrass Monitoring

Seagrass beds are one of the most productive habitats found in the world. The rich biodiversity that makes up seagrass habitats plays a critical ecological and environmental role in Florida's coastal communities. Big Bend Seagrasses Aquatic Preserve is the second-largest contiguous area of seagrass habitat in the eastern Gulf of Mexico. Seagrass monitoring is an integral part of mapping the total acreage of Florida's seagrasses.

Water Quality Monitoring

Water quality monitoring plays a major role in the preserve's understanding of natural and human impacts on coastal waters. Researchers use water quality data to document short- and long-term changes within the water column in an effort to quantify the spatial and temporal variability and trends. These are applied both seasonally and as a function of tidal forcing, of the selected abiotic parameters (e.g., establish baseline data) within Big Bend Seagrasses Aquatic Preserve. Water quality affects humans and other parts of the environment; accordingly, it is essential to develop a proficient water quality monitoring program to recognize and prevent potential negative impacts to Big Bend Seagrasses Aquatic Preserve.

Managed Location Contact: 
Tim Jones
Total Acreage: 
Receives State Funding: 
State Owned: 

Big Bend Seagrasses Aquatic Preserve was established in 1985 and is Florida's largest aquatic preserve, protecting nearly 1 million acres of submerged lands.

The preserve consists mainly of a large, undeveloped expanse of submerged seagrasses and nearshore marshlands located along 150 miles of the northeast coast of the Gulf of Mexico where the Florida peninsula joins the panhandle. The aquatic preserve boundary encompasses all tidal lands, islands, seagrass beds, shallow banks and submerged bottoms from the mean high water line extending nine miles into the Gulf of Mexico. Landward, it includes all natural waterways tidally connected to the preserve to the extent of state jurisdiction or U.S. 98.

Public Access: 

As Florida's largest aquatic preserve, and because of the sparse development along its shores, Big Bend Seagrasses Aquatic Preserve has a wealth of recreational opportunities, including swimming, wildlife viewing, boating, canoeing, kayaking, scalloping and fishing. There are several state parks, national wildlife refuges and two paddling trails.

State Parks and National Wildlife Refuges

Sustainable Use

Big Bend Seagrasses Aquatic Preserve encourages sustainable use of natural resources while minimizing user impacts. With approximately 150 miles of coastline consisting of relatively undeveloped, rural landscapes, the Big Bend region provides many opportunities for the public to enjoy the preserve's natural resources. Popular recreational activities include boating, fishing, kayaking, birding and hiking. Commercial fishing and shellfish harvesting industries rely on the optimal conditions in the Big Bend region. Public support and interagency participation are imperative to protecting natural resources. Public participation in resource management enables an understanding of the important ecological and economic issues of the system.

Big Bend Seagrasses Aquatic Preserve has two over-arching goals to maintain the natural environment and promote sustainable ecotourism:

Maintain a safe and natural environment for Big Bend’s wildlife, habitats and user groups:

  • To maintain the natural environment for current and future generations, Big Bend Seagrasses Aquatic Preserve works to facilitate research to identify human use conflicts with natural resources and develop methods of prevention. This includes working with regulatory agencies, law enforcement and other resource management entities.
  • Big Bend Seagrasses Aquatic Preserve also works to reduce the amount of debris, contaminants and other resource damages associated with user group activities. This includes educational efforts and promoting awareness about proper boating practices through signage, brochures and presentations, and coordinating cleanup events such as those to remove derelict crab traps.

Promote low-impact, sustainable recreational opportunities:

  • Big Bend Seagrasses Aquatic Preserve seeks to increase awareness of recreational opportunities such as paddle-boarding, kayaking, sailing, canoeing and snorkeling. This is done through identifying appropriate locations for paddling launch sites and working with other agencies and local vendors to educate users of the unique recreational opportunities in Big Bend Seagrasses Aquatic Preserve, such as its historical locations, birding and hiking trails, and kayak and canoeing trails.


Volunteer efforts at St. Martins Marsh Aquatic Preserve focus on keeping the Nature Coast beautiful. Staff are active participants of the Adopt-A-Shore Program - the Citrus County version of the International Coastal Coastal Cleanup - either hosting a site or helping to coordinate another site. The derelict crab trap removal program is another way to help keep the preserve as pristine as possible. Crab traps often become lost or abandoned because of lost buoys, but the derelict traps - often called ghost traps - continue to catch crabs and other wildlife. During a brief off-season, traps are identified at low tide and staff, local crabbers and others remove them.

For information about volunteering at St. Martins Marsh Aquatic Preserve for these or other events, please contact Tim Jones at 352-562-0450.

Archaeological Resources: 

The aquatic preserve contains submerged Archaic and Paleoindian sites. There are Deptford sites and some Swift Creek sites in the north, Weeden Island sites in the south. In addition, there are 19th-century shipwreck sites near the Withlacoochee River, Suwannee River and Cedar Key.

Wildlife Habitat Description: 

The whole of the aquatic preserve, with its seagrass beds and salt marshes, provides nursery and forage areas for finfish and shellfish, including commercially and recreationally important species such as mullet, sea trout, redfish, shrimp, oysters and scallops. It also provides habitat for manatees, ospreys, bald eagles, sea turtles, sturgeon, dolphins and many other species. There are 52 known protected plant and animal species in the aquatic preserve.

At least 19 natural communities are represented within Big Bend Seagrasses Aquatic Preserve. However, most of the aquatic preserve is comprised of seagrass beds, unsurprisingly, and salt marsh. Other benthic - or bottom - communities in the aquatic preserve include mollusk reefs, algal beds and sponge beds. The rivers of the aquatic preserve can be either spring-run streams or blackwater streams. Blackwater streams and rivers originate in swampy areas; the term comes from the water's appearance, which is stained dark brown by organic acids. 

Sinkhole Limestone Outcrop - Sinkholes are generally characterized as cylindrical or conical depressions with steep limestone walls. The vegetative structure of sinkholes may be that of a well-developed forest, where sands cover the rock, and/or the sides of the sinkholes are moderately sloped. These conditions are typically confined to the upper portions and around the rim of the sinkhole. Steeper rock walls usually are more or less covered by mosses, liverworts and ferns with occasional herbs and shrubs. Sinkholes are extremely fragile communities. Their popularity as recreational areas subjects their flora to trampling and their steep walls to severe erosion from foot traffic and, in some cases, from dirt bikes. Sinkhole lakes attract swimmers and divers whose activities may disturb the aquatic community as well.

Shell Mound - A shell mound is unusual among the biological communities in that it is largely a result of the activities of Indians, instead of natural physical factors. Shell mound is generally characterized as an elevated mound of mollusk shells and aboriginal garbage on which a hardwood, closed-canopy forest develops. Shell mound soils are composed of shells and shell fragments with an organic component derived from forest litter. 

Alluvial Forest - An alluvial forest is a hardwood forest found in river floodplains on low levees, ridges and terraces that are slightly elevated above floodplain swamp and are regularly flooded for a portion of the growing season. The physical environment is greatly influenced by ongoing disturbances created by a fluctuating river bed, which is both eroding and depositing substrates.

Floodplain Marsh - Floodplain marshes are wetlands of herbaceous vegetation and low shrubs that occur in river floodplains, mainly in Central Florida on sandy alluvial soils with considerable peat accumulation. The highest part of the marsh is often a drier, wet prairie-like zone with a large diversity of graminoids (grass-like plants such as grasses, sedges and rushes) and forbs (broad-leaved herbs other than a grass, especially one growing in a field, prairie or meadow). While the progression from high to low marsh generally occurs from the upland edge to the river edge, these vegetation patches also may be scattered throughout the marsh, which provides a diversity of habitats beneficial to wildlife. Floodplain marshes are maintained by regimes of fire and water. Fires apparently burn on a one- to five-year basis under natural conditions and maintain the open herbaceous community by restricting shrub invasion; however, severe fires during drought periods often will burn the mucky peat. Floodplain marshes are flooded with flowing water for about 250 days annually.

Floodplain Swamp - A floodplain swamp is a closed-canopy forest of hydrophytic (growing wholly or partially in water) trees, occurring on frequently or permanently flooded hydric soils adjacent to stream and river channels, and in depressions and oxbows within floodplains. Trees are often buttressed, and the understory and groundcover are sparse. The canopy is sometimes a pure stand of bald cypress, but more commonly bald cypress shares dominance with one or more tupelo species.

Blackwater Stream - Blackwater streams are characterized as perennial or intermittent seasonal watercourses originating deep in sandy lowlands where extensive wetlands with organic soils function as reservoirs, collecting rainfall and discharging it slowly to the stream. The tea-colored waters of blackwater streams are laden with tannins, particulates, and dissolved organic matter and iron derived from drainage through swamps and marshes.

Alluvial Stream - Alluvial streams are characterized as perennial or intermittent seasonal watercourses originating in high uplands that are primarily composed of sandy clays and clayey-silty sands. Alluvial stream waters typically are turbid because of a high content of suspended particulates, including clays, silts and sands, as well as detritus and other organic debris. Water temperatures may fluctuate substantially and generally are correlated with seasonal fluctuations in air temperature. Similarly, other water quality parameters vary substantially and generally fluctuate with seasonal rainfall patterns.The most important characteristics of alluvial streams encountered are the large range of flow rates and sediment loads. Thus, water depth fluctuates substantially and generally is separated into two distinct stages - a normal or low-flow stage and a flood or high-flow stage. During the normal low-flow stage, the water is confined within the stream banks, while during flood stage, the water overflows the banks and inundates the adjacent floodplain communities. Flood stages generally occur once or twice each year during winter or early spring, and occasionally summer.

Spring-Run Stream - These streams are perennial water courses that derive most, if not all, of their water from artesian openings in the underground aquifer. Waters issuing from the aquifer are generally clear, circumneutral to slightly alkaline (pH = 7.0 - 8.2), and perennially cool (66 – 75 °F). These conditions saturate the water with important minerals, allow light to penetrate deeply, and reduce the limiting effects of environmental fluctuations, all of which are conducive for plant growth. Thus, spring-run streams are among the most productive aquatic habitats. 

Aquatic Caves - Aquatic and terrestrial caves are characterized as cavities below the surface of the ground, typically in Florida's karst areas. Karst is a type of landscape where the dissolving of the bedrock has created sinkholes, sinking streams, caves, springs, and other characteristic features.  The limestone aquifers that underlie the entire state could be considered vast aquatic cave communities. Troglobites (also called phreatobites) are organisms specially evolved to survive in deep cave habitats. The occasional observation of various species of troglobites in deep water wells from several regions in the state suggests that this community could be widespread. However, the dependence of troglobites on detrital inputs and other nutrients imported from the surface, generally limits the distribution of well-developed aquatic cave communities to karst areas with surface connections. Cave waters generally are clear, with deep water appearing bluish.

Consolidated Substrate - Marine and estuarine consolidated substrates are mineral-based, natural communities generally characterized as expansive, relatively open areas of subtidal, intertidal and supratidal zones, which lack dense populations of sessile plant and animal species. Consolidated substrates are solidified rock or shell conglomerates and include coquina, limerock or relic reef materials. These communities may be sparsely inhabited by sessile, planktonic, epifaunal and pelagic plants and animals but house few infaunal organisms (i.e., animals living within the substrate). The three kinds of consolidated substrate communities occurring in Florida are of limited distribution. The type present along the Big Bend is limerock substrates that occur as outcrops of bedded sedimentary deposits consisting primarily of calcium carbonate.

Unconsolidated Substrate - Marine and estuarine unconsolidated substrates are mineral-based natural communities generally characterized as expansive, relatively open areas of subtidal, intertidal and supratidal zones which lack dense populations of sessile plant and animal species. Unconsolidated substrates are unsolidified material and include coralgal, marl, mud, mud/sand, sand or shell. While these areas may seem relatively barren, the densities of infaunal organisms in subtidal zones can reach the tens of thousands per meter square, making these areas important feeding grounds for many bottom-feeding fish, such as red drum (redfish), southern flounder, spot and sheepshead . The intertidal and supratidal zones are extremely important feeding grounds for many shorebirds and invertebrates. Unconsolidated substrates are important in that they form the foundation for the development of other marine and estuarine natural communities when conditions become appropriate. Unconsolidated substrate communities are associated with, and often grade into, beach dunes, salt marshes, mangrove swamps, seagrass beds, coral reefs, mollusk reefs, worm reefs, octocoral beds, sponge beds and algal beds.

Unconsolidated substrate communities that are composed chiefly of sand (e.g., sand beaches) are the most important recreational areas in Florida, attracting millions of residents and tourists annually. This community is resilient and may recover from recreational disturbances. However, this community is vulnerable to compaction associated with vehicular traffic on beaches and disturbances from dredging activities and low dissolved oxygen levels, all of which can cause infaunal organisms to be destroyed or to migrate out of the area. Generally, these areas are easily recolonized either by the same organisms or a series of organisms that eventually results in the community returning to its original state once the disturbance has ceased.

Mollusk Reefs - Marine and estuarine mollusk reefs are faunal-based, natural communities typically characterized as expansive concentrations of sessile mollusks occurring in intertidal and subtidal zones to a depth of 40 feet. In Florida, the most developed mollusk reefs are generally restricted to estuarine areas and are dominated by the Eastern oyster. Mollusk reefs that are exposed during low tides are frequented by a multitude of shorebirds, wading birds, raccoons and other vertebrates. One of the United States' largest wintering populations of American oystercatchers is situated in the heart of the Cedar Keys. The success of this rookery can be attributed to the oyster reefs located here, which are an excellent and tremendously important food source.

In the Big Bend region, research has shown a 66% net loss of oyster bar area between 1982 and 2011. This rapid loss is very likely due to a departure from historical norms and stems from multiple factors. Extended periods of high salinity are likely stressors of oyster populations, particularly on offshore bars, to the extent that the physical structure of bars are affected by both mortality of older oysters, and the loss of significant recruitment. Once the structure of bars is weakened, bars became less resilient to wave action, particularly during storm events. Evidence suggests that the primary mechanism is reduced survival and recruitment as a result of decreased freshwater inputs, thus causing existing bars to be vulnerable to wave action and sea level rise; once bar substrate becomes unconsolidated, the breakdown of the bar may not be reversible.

Octocoral Beds - Marine and estuarine octocoral beds are soft faunal-based natural communities characterized as large populations of sessile invertebrates of the Class Anthozoa, Subclass Octocorallia, Orders Gorgonacea and Pennatulacea. The dominant animal species are soft corals such as gorgonians, sea fans, sea feathers and sea plumes, sea fingers, sea pansies, sea rods and sea whips.

Sponge Beds - Marine and estuarine sponge beds are soft faunal-based natural communities characterized as dense populations of sessile invertebrates of the phylum Porifera, Class Demospongiae. Sponge beds require hard-bottom (consolidated) substrate (i.e., coquina, limerock, relic reefs) on which to anchor. Hard-bottom substrate occurs sparsely throughout Florida in marine and estuarine areas; however, sponges prefer the warmer waters of the southern portion of the state, significantly limiting the distribution severely.

Algal Beds - Marine and estuarine algal beds are floral-based natural communities characterized as large populations of nondrift macro or micro algae. Vascular plants (e.g., seagrasses) may occur in algal beds associated with soft bottoms. Sessile animals associated with algal beds will vary based on bottom type. For algal beds associated with hard-bottom substrate (lithophytic), faunal populations will be similar to populations associated with octocoral beds and sponge beds. Those associated with soft-bottom substrate (psammophytic) may have similar benthic and pelagic species in addition to infauna species. Recent research has shown that algal beds provide critical habitat for juvenile spiny lobsters, a species of great commercial importance.

Distribution information for algal beds is lacking. The location of major beds must be determined before this natural community can be managed adequately. The primary threat to algal beds are dredging and filling activities that physically remove or bury the beds. Other damage occurs from increased turbidity in the water column that reduces available light; pollution, particularly from oil spills; and damage from boats.

Seagrass Beds - Seagrass beds are plant-based natural communities typically characterized as expansive stands of vascular plants. This community occurs in subtidal (rarely intertidal) zones, in clear, coastal waters where wave energy is moderate. Seagrasses are not true grasses. The three most common species of seagrasses in Florida are turtle grass, manatee grass and shoal grass. Nearly pure stands of any one of these species can occur, but mixed stands are also common. Attached to the seagrass leaf blades are numerous species of epiphytic algae and invertebrates. Together, seagrasses and their epiphytes serve as important food sources for manatees, marine turtles and many fish. The dense seagrasses also serve as shelter or nursery grounds for many marine invertebrates and fish. Marine and estuarine seagrass beds occur most frequently on unconsolidated substrates of marl, muck or sand, although they also may occur on other unconsolidated substrates. The dense blanket of leaf blades reduces the wave-energy on the bottom and promotes settling of suspended particulates. The dense roots and rhizomes of the seagrasses stabilize settled particles. Thus, marine and estuarine seagrass beds are generally areas of soil accumulation. 

Seagrass beds are extremely vulnerable to human impacts. Many have been destroyed through dredging and filling activities or have been damaged by sewage outfalls and industrial wastes. In these instances, the seagrasses are either physically destroyed or succumb as a result of decreased solar radiation resulting from increased water turbidity. Seagrass beds are also highly vulnerable to oil spills. Low concentrations of oil are known to greatly reduce the ability of seagrasses to photosynthesize. Extreme high temperatures also have adverse impacts on seagrass beds. The areas surrounding power plant outfalls, where water temperatures may exceed 95 degrees F, have been found to be lethal to seagrasses. Seagrass beds are susceptible to long-term scarring cuts from boat propellers, anchors and trawls. Such gouges may require many years to become revegetated. When protected from disturbances, seagrasses have the ability to regenerate and recolonize areas. Additionally, some successful replanting efforts of seagrass beds have been conducted. However, the best management is to preserve and protect seagrass beds in their natural state.

Salt Marsh - A salt marsh is a largely herbaceous community that occurs in the portion of the coastal zone affected by tides and seawater and protected from large waves, either by the broad, gently sloping topography of the shore, by a barrier island, or by location along a bay or estuary. The width of the intertidal zone depends on the slope of the shore and the tidal range. Salt marsh may have distinct zones of vegetation, each dominated by a single species of grass or rush. Tidal fluctuation is the most important ecological factor in salt marsh communities, cycling nutrients and allowing marine and estuarine fauna access to the marsh. This exchange helps to make salt marsh one of the most biologically productive natural communities in the world. Salt marshes are also extremely important because of their storm buffering capacity and their pollutant filtering actions. The dense roots and stems hold the unstabilized soils together, reducing the impact of storm wave surge. The plants, animals and soils filter, absorb and neutralize many pollutants before they can reach adjacent marine and estuarine communities. These factors make salt marshes extremely valuable as a natural community.

Mangrove Swamp - A mangrove swamp is a dense forest occurring along relatively flat, low wave energy, marine and estuarine shorelines. The dominant plants of mangrove swamp are red mangrove (Rhizophora mangle), black mangrove (Avicennia germinans), white mangrove (Laguncularia racemosa) and buttonwood (Conocarpus erectus). Red mangrove often dominates the lowest (or deep-water) zone, followed by black mangrove in the intermediate zone, and white mangrove and buttonwood in the highest, least tidally influenced zone. The density and height of mangroves and the diversity of associated herbaceous species can vary considerably within a mangrove swamp. Mangroves are vulnerable to cold, with red mangroves the least resistant to freezes.

Composite Substrate - Composite substrates consist of a combination of natural communities such as "beds" of algae and seagrasses or areas with small patches of consolidated and unconsolidated bottom with or without sessile floral and faunal populations. Composite substrates may be dominated by any combination of marine and estuarine sessile flora or fauna, or mineral substrate type. Typical combinations of plants, animals and substrates representing composite substrates include soft and stony corals with sponges on a hard bottom such as a limerock outcrop; algae and seagrasses scattered over a sand bottom; and patch reefs throughout a coralgal bottom. Any of the remaining marine and estuarine natural communities can grade into composite substrate communities.

Habitat-Wildlife Type: 
Aquatic Preserves
Last Modified:
April 1, 2021 - 12:19pm

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