Florida Marshes - Your Guide to Florida Freshwaters

MARSHES

NEARLY ONE THIRD OF FLORIDA'S FRESHWATER WETLANDS ARE COMPRISED of marsh ecosystems. In contrast to swamps, marshes are essentially treeless ecosystems that are characterized by shrubs and grasses. A wide variety of marshes exist in Florida and the distribution and character of each marsh ecosystem varies throughout the state. Biologists have found that Florida's marsh environments are delicate habitats possessing significant scientific, ecologic, and economic value.

Although each marsh ecosystem displays a specific recipe of geologic, hydrologic, and biologic characteristics, every marsh in Florida provides flood control, water storage and supply, and unique habitats for native plant and animal species. Several of Florida's marsh areas also provide opportunities for recreation.

Despite their significance and the public's desire to protect them, nearly a quarter of Florida's original marshes have been drained or severely disturbed by development and artificial flooding. Among other things, such disturbances facilitate invasions by non-native plants into our marshes, presenting aquatic plant managers with unique challenges.
Especially in the marshes that surround our lakes and rivers, aquatic plant managers are working to control non-native invasive plants in order to preserve our native plants.

MARSH GEOLOGY
Marsh formation is enhanced by Florida's low, flat, poorly drained karst topography. Coastal limestone and sand ridges funnel surface runoff to inland marshes. An immense amount of surface water is stored in Florida's marshes and they are important areas where surface water permeates the limestone bedrock and recharges the groundwater supply in the aquifer.

Three basic geologic characteristics influence marsh development and promote the accumulation of surface water in Florida:
an impermeable deposit covers the permeable limestone bedrock and prevents surface water from rapidly infiltrating the limestone bedrock;
the water-table lies above a permeable layer of sediment or limestone;
and a hydrologic connection between a marsh region and a lake or river provides a steady source of water to the marsh.

HYDROLOGY
Water is the essential element that dominates marsh habitats. Marshes and other wetland ecosystems undergo cyclical periods of flooding, drought, and deterioration during a five to twenty year cycle. Water levels in marsh environments are continuously fluctuating and individual marshes have unique water level pattens. Marshes are generally wetter in the summer and drier in the winter, although water levels generally are higher in northern Florida because of greater rainfall. Water flow is an important factor in nutrient and detrital distribution. The composition of the plant population is determined by various plant species' tolerance to specific flood patterns and soil chemistry.

SOILS
Three primary soil materials found in marsh environments are peat, marl, and sand.

Peat

Marl

periphyton

Sand

Marsh plants grow quickly after fire

FIRE
Fires shape the marsh landscape and determines the substrate composition. Taking place every one to five years, fires naturally release essential nutrients, prevent accumulation of organic matter, preclude the formation and accumulation of peat and marl, limit invasion of woody plants, and promote a herbaceous plant community.

Summer is the natural fire season, when lightning is prevalent. Natural fires are generally confined to vegetation that emerges from the water surface. Most herbaceous marsh plants regrow quickly after fire.

MARSH TYPES
At least two classification schemes for marshes are recognized and used in Florida: one scheme is based more on geology and soils, and another is based more on vegetation. Here are nine major marsh types based more on geology and soils:

basin marsh large basin; seasonally inundated

bog wet deep peat; sphagnum mosses

depression marsh small rounded depression, seasonally inundated

floodplain marsh floodplain; seasonally inundated

marl prairie flat; marl substrate; seasonally inundated

seepage slope wetland on slope; usually saturated

swale broad, shallow channel; seasonally inundated

tidal marsh intertidal area of emergent plants

wet prairie flat; sand substrate; seasonally inundated

Marshes also may be classed according to vegetation. Predominant marsh plants include green-stemmed, broad-leaved (herbaceous) plants and tall, narrow-leaved (graminoid) reeds, grasses, sedges, rushes, and floating aquatic plants. The vegetative composition of a marsh is influenced by water fluctuations in response to rainfall, evaporation, and river and lake water levels. Some species have adapted to extended flood conditions (and the resulting anaerobic environment) by possessing internal air channels that promote oxygenation.

Most marsh plants reproduce vegetatively (spreading by roots or regrowth of broken fragments) because seedlings seldom survive underwater. When seed development and dispersal does occur, they usually depend on the dry season for germination.

In addition to providing wildlife with food, shelter, and nesting habitats, marsh plants act as nutrient pumps by transporting nutrients from roots in the soil and releasing them to the surface when leaves and stems die. Therefore, a prosperous native plant community is an important component in a healthy marsh ecosystem.

Marsh types based on vegetation include:

Water lily marshes are dominated by floating-leaved plants such as the fragrant water lily (Nymphaea spp.), golden club (Orontium aquaticum), and American lotus (Nelumbo lutea). Water lily marshes seldom dry out completely.

Submersed marshes are characterized by deep water (3-4 feet). Plants are thinly distributed and communities include southern naiad (Najas guadalupensis), pondweeds (Potamogeton sp.), bladderworts (Utricularia sp.), water hyssops (Bacopa caroliniana), primrose willows (Ludwigia sp.), spikerushes (Eleocharis sp.), and swamp lilies (Crinum americanum).

Cattail (Typha sp.) marshes are generally monocultures (only cattails) and they often have relatively deep, nutrient rich water and deep soils. Cattail mashes occur in water as shallow as only a few inches or as deep as four feet.

Flag marshes are named after pickerelweed (Pontederia cordata), fire flag (Thalia geniculata), arrowhead (Sagittaria sp.), and other species with flag-like leaves. Flag marshes may also include maidencane (Panicum hemitomon), spikerushes (Eleocharis sp.), beakrushes (Rhynchospora sp.), bulrushes (Scirpus sp.) and other plants that require regular dry seasons.

Sawgrass (Cladium jamaicense) marshes are widespread in Florida. They are the predominant marsh system in the Everglades, where large areas are comprised of sawgrass. Sawgrass marshes are segregated into two categrories: dense, on higher ground, and sparse, on lower ground in peat or marl.

Wet prairies are the least frequently flooded of all Florida marsh systems. In wet prairies low water levels and frequent drying and burning prevent peat development. Species composition varies according to the flooding periods of each site. Yet, wet prairies are the most diverse marsh systems and include a variety of grasses, sedges, and flowering plants. Wet prairie species are generally flood and drought tolerant. Although some may not survive the dry season, their seeds will germinate when the rainy season commences. As a result, the vegetative composition varies in response to changing water conditions.

In addition to freshwater marshes, Florida hosts a variety of coastal salt marshes:

Salt marshes (also called tidal marshes) include plant species in the grass (Poaceae), sedge (Cyperaceae), and rush (Juncaceae) families. According to the tides, salt marshes undergo changes in salinity, drainage patterns, and temperature. Such demanding environments limit plant diversity. Yet, salt marshes are among the most nutrient rich and productive ecosystems in the state.

Torpedo grass

INVASIVE SPECIES
Within marsh ecosystems, torpedo grass (Panicum repens, at right) and alligator weed (Alternanthera philoxeroides), among other non-native invaders, frequently out-compete native plants and alter the natural ecological balance. The native wildlife that depend on Florida's native plants for food, nesting, and shelter are also affected.

Because of the difficulty in controlling plants where they have taken over entirely, government agencies are trying new techniques to help native plants become re-established. For example, the Florida Wildlife Conservation Commission is experimenting with marsh restoration by scraping. That is, marsh soil, invasive plants, seeds and all, are scraped up and hauled away, and native marsh plants are planted in their place.

MARSH FAUNA
Marshes are rich in aquatic wildlife. Mammals, water fowl, reptiles, and fish may be temporary or permanent residents. Marsh animals are generally nomadic, moving from place to place in response to fluctuating water levels, fire, and climatic conditions. Birds use multiple marsh sites for nesting and hunting prey. During drought, preying birds take advantage of the high concentrations of fish, amphibians, and invertebrates in shrinking pools of water. In return, the decreased fish populations prevent the exhaustion of oxygen in the water, ensuring the survival of at least a few species throughout the dry season. Invertebrates spend the dry season as eggs and hatch when flooding commences. Alligators and muskrats nest and burrow according to the water depth in the marsh. During the dry season, gator holes provide a variety of animals with a crucial source of water.

alligator wood stork raccoon great blue heron

common buckeye moorehen white-tailed deer marsh rabbit

HUMAN IMPACT
Like all wetland ecosystems, Florida's precious marshes are threatend by certain human activities. Each year, marsh ecosystems throughout the state are altered or destroyed by land development, pollution, invasive species, water usage and water control.

Go to this page on our web site for more about human impacts on Florida's wet places.

MARSH CONSERVATION
Currently, massive efforts are underway to restore, protect and conserve the Florida Everglades, the country's largest marsh ecosystem. Marsh conservation includes acquiring channelled and drained marshlands and restoring them by removing channels and dams, and then reflooding. Conservation of the Everglades, and all marshes, takes into consideration the importance of hydrologic cycles and fire regimes. Due to the wide variety of natural conditions among marshes, they must be managed on an individual basis.

To find out what you can do to help conserve Florida's waters, visit this page on our web site.

The Creators

This page authored by Sarah Cervone, with research assistance from Becca Hassell.
Data is from the APIRS database.
This page was designed by Sara Reinhart.
Photography and graphics by Ann Murray, Sara Reinhart and Vic Ramey.

Vic Ramey is the editor.

DEP review by Jeff Schardt and Judy Ludlow.

Main Index

This project is a collaboration of
the Center for Aquatic and Invasive Plants, University of Florida,
and the Bureau of Invasive Plant Management, Florida Department of Environmental Protection


common buckeye	moorehen	white-tailed deer	marsh rabbit