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Aquatic and Marine Ecosystems—Lesson 4: Coastal Ecosystems: Beach, Estuary, Marsh, and Swamp1

Karen Blyler and Joy Jordan 2

For the full version of this document, view the PDF here.

To access other sections and lessons of the Aquatic and Marine Ecosystems: Leader's Activity Guide, view the EDIS topic page here.

Lesson 4


To become familiar with coastal ecosystems including beaches, estuaries, marches, and mangrove swamps.


Here are some learning activities and suggested ways to implement the activities in Lesson 4.

4.1 Florida's diverse coastal ecosystems can be discovered with COASTAL MATCH-UP, in additional to learning about coastal plants.

4.2 What is a beach for besides sunbathing and fun in the ocean? Find out how beaches develop and why they are important with BEACH BONANZA.

4.3 Identify animals that depend on estuaries for survival and understand the functions of estuaries with CREATE AN ESTUARY.

4.4 Why are mangroves so important to humans and animals? MANGROVE MADNESS has the answer!

4.5 WHO EATS WHOM will help to explain the coastal 4.6 food chain and ARE WE IN-SEINE? will help to find animals in the food chain.


After completing the activities in this lesson, help youth reflect on what they have learned by asking the following questions:

  • What is an estuary?

An estuary is a body of water where fresh and saltwater meet and mix.

  • Many animals depend on estuaries for part or all of their life cycle. Name two.

Shrimp and blue crabs.

  • What are three types of mangroves found in Florida?

Red, white, and black mangroves.

  • Why are mangroves called the "protectors" of the estuaries?

Mangroves filter the runoff that flows into the estuaries from upland regions, thus trapping sediments and potential contaminants. Mangroves also buffer the shoreline from the wind and wave action caused by storms, reducing erosion and protecting upland areas.

  • Which state has more miles of sandy beach than any other state?


  • What important function does the beach provide for the land behind it?

The beach protects the land from the ocean and the action of the waves.


Help youth learn to apply what they have learned to their daily lives.

  • Think about where you live. Do you live near a stream, river, lake or coastal region? How can what you do affect the coastal region? What are some of the ways your actions effect the coastal region?

  • What are some action or community projects you, your club, or your class could do to help others become aware of coastal ecosystems?

  • Start a collection of sand from around the state. Compare the sand and learn why it is a certain color, texture, etc. How are beaches different/similar around the state?

Background Basics

Coastal areas exist at the interface of land areas and large bodies of water. Florida has many miles of coastal areas due to the fact that it is a peninsula bordered by the Atlantic Ocean on the east, the Gulf of Mexico on the west, and Florida Bay to the south. In addition to these areas, Florida also has an abundance of bays and estuaries associated with the state's river systems that add many miles to the coastline. These coastal and estuarine ecosystems are extremely productive areas for sea life. These areas are also one of the main features that attract millions of people to Florida.

Of all Florida's natural areas, the coastal ecosystems of beach/dune/barrier islands, salt marshes, estuaries, and mangrove swamps are the most threatened. Nearly 80% of the state's human population lives in coastal areas. The development resulting from this population pressure has consumed large portions of these coastal ecosystems. Human activities around the remaining coastal natural areas can impact water quality, beach development, sedimentation rates, biodiversity, and can further threaten these fragile ecosystems.

In some areas even the salinity of the water can be altered by human activities. (Salinity is a term used to describe the relative amount of salts in water or in soil.) Storm water runoff, sewage discharges, bridges and other structures can alter water flow and either increase or decrease salinity levels. Salinity is important because some organisms can only live within a specific range of salinity. Since saltwater and freshwater from the land are often combined in coastal areas, the varying levels of salinity may determine the types of ecosystems that can exist.

Beach/Dune/Barrier Island Ecosystems

The beach/dune/barrier island ecosystem is probably the most dynamic habitat found in Florida. These areas change constantly with the action of winds, tides, and currents. The most dramatic changes occur during storms as strong winds send waves crashing into dune areas or when hurricanes push storm surges far inland. These natural actions have occurred for millennia shaping and changing the coastal ecosystems.

Figure 1. Beach, dune, and barrier island ecosystems change constantly due to winds, tides, and currents
Figure 1.  Beach, dune, and barrier island ecosystems change constantly due to winds, tides, and currents
Credit: Photos taken by 4-H members

Recent human habitation has, in many areas, altered the cycles of sand movement, dune development, and succession. Beach erosion has increased dramatically in some areas to a point where the replenishment of sand is done by dredging offshore areas or trucking sand from inland sandpits. In many instances, various physical structures are installed to prevent the erosion. Sea walls, jetties, groins, and riprap are used to "stop" the natural forces at work.

To understand part of the dynamics of the beach/dune/barrier island complex, one should understand the differences between high wave energy and low wave energy areas. This can be interpreted simply by the size and the frequency of waves. Differences in wave energy will determine the amount of change in the physical environment, and its influence on the plant and animal species that can live in a coastal area.

Very few plants or animals live directly on high energy ocean beaches, but many species depend on them for survival. Arthropods, mollusks, and insects escape the pounding surf by burrowing and/or living below the sand. Gulls, sandpipers, and other shorebirds are common predators that probe the sand for food.

One of Florida's most highly valued food fish, the pompano, also lives in this environment, feeding on sand fleas and mole shrimp that have burrowed into the sand at the shore line. Huge schools of baitfish including menhaden, cigar minnows, and Spanish sardines attract predators such as jack crevalle, Spanish mackerel, bluefish, and other sportfish. Surf fishing off many Florida beaches is a favorite pastime for many coastal residents because of this.

Florida's east coast is considered a high wave energy system. Prevailing wind action on the Atlantic Ocean has many hundreds of miles to build swells. These swells increase as they approach shallow inshore areas and finally break, forming waves of significant height (3–12 ft.) depending on the power of the offshore wind.

The force of high energy waves can move tremendous amounts of sand and bottom material from the beach to offshore sites. When sufficient materials are deposited in these areas barrier islands can develop. Sometimes the opposite occurs and sand is deposited at the beach front, where wind can move it inland to form sand dunes. In either case the beach is the all important buffer zone, absorbing the energy of waves that might otherwise erode dunes and other coastal formations.

The west coast of Florida is much different. The height and frequency of waves along most of this coast are much smaller when compared to the Atlantic side. The smaller surface area of the Gulf of Mexico, combined with varying winds and bottom features, produces less energy for wave formation. Fewer and much smaller beach areas exist in the Big Bend area of the Gulf coast due to the lower wave energy. Those that do exist are often part of a barrier island that also helps protect inshore marshes and land areas.

Salt Marshes

The gentle incline of the Gulf Coast reduces wave force and allows marsh grasses to establish themselves in shallow water areas. Salt marshes are communities of nonwoody, salt-tolerant plants. The largest amount of salt marsh in Florida occurs from Tampa to Pensacola, with the greatest development in the Big Bend area. A smaller area of salt marsh occurs along the Indian River Lagoon and in the vicinity north of Jacksonville, Florida.

Figure 2. Marshes provide a critical wildlife habitat
Figure 2.  Marshes provide a critical wildlife habitat
Credit: Photos taken by 4-H members

Salt marshes are composed of a variety of different species, depending on location, including grasses, sedges, and rushes. This vegetation plays a critical role in shoreline stabilization, trapping sediments, and eventually "building" land in the process. Marshes provide critical wildlife habitat and are breeding/nursery grounds for numerous fish and invertebrates. The plants are producer organisms in food chains and food webs that include insects (e.g., marsh fly, sand gnats, mosquitoes), birds (e.g., king fisher, great blue heron, hooded merganser), shellfish (e.g., fiddler crab, pink shrimp, clams), fish (e.g., croaker, Gulf menhaden, sea trout), and mammals (e.g., raccoon and otter).


Those water areas where saltwater and freshwater meet are known as estuaries. Estuaries such as the Indian River Lagoon, Tampa Bay, and Charlotte Harbor form enormous areas along both coasts of Florida. The west coast of Florida alone has approximately 2.5 million acres of estuarine habitat that include open water, salt marshes, and mangrove swamps.

Estuaries are intricately interwoven with surrounding ecosystems through geological, biological, chemical, and ecological processes. The inflow of freshwater from springs and rivers, nutrients from upland areas, organic matter from salt marshes, tidal influences, and sediment loads from the land and offshore sources can all contribute to the health or demise of the fragile estuarine ecosystem.

Two important factors related to the biological characteristics of estuary ecosystems are the diversity of habitats and the high productivity of the associated food webs. The variety of habitats including sandy bottom, sea grass beds, oyster bars, and mud flats provide living areas for over two thirds of Florida's commercially important fish and shellfish. The high nutrient levels in estuarine waters provide a rich "soup" that nourish plants and animals making estuaries one of the most productive ecosystems on earth.

Many fish, including redfish and mullet, spawn in offshore locations where the eggs develop into larvae that are carried into estuaries by tides and currents. Huge numbers of microscopic algae, diatoms and other types of phytoplankton are estuarine producers that juvenile fish depend on for food. Larger plants such as turtle grass, manatee grass, and shoal grass provide food and cover for other consumers (e.g., crabs, scallops, shrimp, and small fish). Second order and third order consumers (e.g., great blue heron, cormorant, seatrout, redfish, and coastal shark species) also roam these fertile areas in search of smaller prey.

Although estuaries are not sites of human development in the same ways as the beach/dune/barrier islands, they still receive a great deal of human use. This use takes on many forms including: recreational boat traffic, shrimping, docking and loading areas, a place for municipal discharge and sites for mariculture. These uses have impact beyond the estuaries waters' both ecologically and in relationship to human values. Humans are influenced economically, aesthetically and culturally by this resource. With proper management and effective planning Florida's estuaries can remain a viable and important part of our future.

Mangrove Swamps

The mangrove swamp ecosystem exists in the southern part of the state from Cape Canaveral on the east coast to Tampa Bay on the west side. This limitation in distribution is a result of sensitivity to freezing temperatures. Although, mangroves have been reported sporadically north to the Mississippi Delta, but only in relatively frost free areas do the true mangrove forests develop. Mangroves can attain heights of 80 feet, but hurricanes often destroy mangroves before they have an opportunity to reach these heights. In the process though, mangroves buffer the storm and provide protection to inland areas. These bands of coastal mangroves also function as critical nursery areas for many species of fish and shellfish. The prop roots of the red mangrove give protection to shrimp, blue crab, and snook. Mangroves also provide areas for oysters to grow. Mangrove leaves drop to the water and as they decay, provide food for many species. The mangroves also help trap sediments from upland areas, filter estuarine waters of nutrients and can remove some pollutants from the water column.


The total area that Florida's coastal ecosystems cover is quite small when compared to the entire land mass of Florida. By some estimates, approximately 3% of Florida's land area consists of barrier islands, mangrove swamps and salt marshes. This should give you an idea of the limited area coastal ecosystems occupy, and the fragile nature of these areas. It's also easy to see that with 80% of the human population on or near these important coastal ecosystems the potential impact upon them is tremendous. By using the following activities in Lesson 4 individuals can gain a better understanding of these important ecosystems. From this understanding, an awareness hopefully will develop that leads individuals to act in appropriate ways to help protect and preserve this most important piece of Florida, our coastal ecosystems.

Learn More

To read more and to access the activities for Lesson 4, view the PDF here.

To access other sections and lessons of the Aquatic and Marine Ecosystems: Leader's Activity Guide, view the EDIS topic page here.


1. This document is 4H350, one of a series of the 4-H Youth Development Program, UF/IFAS Extension. Original publication date May 1998. Revised November 2014. Reviewed October 2017. Visit the EDIS website at
2. Karen Blyer, state 4-H science coordinator; and Joy Jordan, 4-H curriculum specialist (retired); UF/IFAS Extension, Gainesville, FL 32611. Original version written by Jerry Cullen, Elise Cassie, Tammy Cushing, Wendy Flanagan, and Mike Harrington; UF/IFAS Extension, Gainesville, FL 32611.

Publication #4H350

Date: 1/25/2018

  • Critical Issue: Youth


  • Sarah Hensley