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Barrier islands are long, narrow, offshore deposits of sand or sediments that parallel the coastline. Some barrier islands can extend for 100 miles (160 km) or more. The islands are separated from the main land by a shallow sound, bay or lagoon. Barrier islands are often found in chains along the coastline and are separated from each other by tidal inlets.
Barrier islands serve two main functions. First, they protect the coastlines from severe storm damage. Second, they harbor several habitats that are refuges for wildlife. However, barrier islands are fragile, constantly changing ecosystems, that are important for coastal geology and ecology, are at risk.
Fisherman Island is a typical barrier island consisting of the following zones, from the ocean side toward the sound:
Beach, Dune, Barrier Flat, Salt Marsh, and Maritime Forest.
On the ocean side of Fisherman Island is the beach habitat. The beach is much like a desert in that it lacks fresh water, but a large portion of the beach gets covered almost entirely with salt water twice daily (the entire beach gets covered to the dune base during storms). Animals and plants in this environment (known as the intertidal zone, between tides) must endure long periods of exposure to salt water and drying air. On the beach, the only plant life you'll see is some algae that get washed ashore. Bacteria live in the spaces between the sand grains where water from the surf percolates through. The animals on the beach itself include burrowing animals like mole crabs and clams that filter-feed during high tides, burrowing worms that feed on bacteria in the sand, scavenging crabs (ghost crabs) and various shorebirds (sandpipers, seagulls and pelicans) that eat the crabs, burrowing animals and offshore fish.
Next comes the Dune Habitats. The dunes receive moisture from rain and surf and are occasionally flooded during severe storms. The dunes are still a relatively hostile environment with high salt content, sandy soil and little fresh water. Plants such as sea oats and bitter pancum provide stability to the dunes. Their root systems hold the sand in place and their shoots slow the winds, thereby allowing sand to be deposited. Along the dunes, you will find many crabs, particularly ghost crabs. Again, you will find birds (gulls, terns) that feed on the animals that inhabit the dunes.
The Barrier Flats or Mud Flats come after the dunes. The primary vegetation includes cordgrass and sawgrass. These areas are often flooded daily during high tides.
The mud and sediments are full of anaerobic bacteria (there is little oxygen in the sediments). The bacteria decompose the rich organic material in the sediments and from dead plants and animals. Animals that live in the wet mud filter-feed bacteria and plankton from the tidewaters or feed on bacteria in the mud; these animals include clams, mussels, snails and worms. Various fish come and go with the tides. Fiddler crabs feed on the bacteria in the mud. Ghost crabs and blue crabs feed on the bacteria, small invertebrates and small fish. Various birds (seagulls, egrets, pelicans) feed on the fish, crabs and invertebrates.
FYI - Because decomposition occurs in the absence of oxygen, the mud flats in the barrier-flats habitat tend to smell rotten.
The sound-side of an island is usually dominated by The Salt Marsh. The salt marshes that you find on the sound sides of barrier islands are similar to those found on the coastal mainland. Like the barrier flats, salt marshes are regularly flooded with seawater during high tide and the animals and plants that you find are similar to those in the barrier flats.
Diamondback terrapins are unique land turtles that spend the majority of their life in the water! Salt marshes serve as their safe haven. When you drive over Fisherman Island on the Chesapeake Bay Bridge-Tunnel you’ll notice a long black tube running along the roadway. This barrier deters terrapins from crossing the road. The barrier forces the terrapins to turn around and use the suitable habitat where they are safely living.
If you get the opportunity to wander through the Maritime Forest at Fisherman Island, it is well worth your time. This is the oldest and most stable part of the island, thus it has the most developed vegetation. Cherry, sassafras, sumac and American holly and wax myrtles dominate the maritime forest of Fisherman Island. Migratory and year-round birds use the forest for shelter as well as food. It is a great place to bird watch.
Now that we know what makes up a barrier island, we will briefly look at what causes a barrier island to change.
Barrier islands are constantly changing. They are influenced by the following conditions:
Waves - Waves continually deposit and remove sediments from the ocean side of the island.
Currents – Long shore currents that are caused by waves hitting the island at an angle can move the sand from one end of the island to another.
Tides - The tides move sediments into the salt marshes and eventually fill them in. Thus, the sound sides of barrier islands tend to build up as the ocean sides erode.
Winds - Winds blow sediments from the beaches to help form dunes and into the marshes, which contributes to their build-up.
Sea level changes - Rising sea levels tend to push barrier islands toward the mainland.
Storms - Hurricanes and other storms have the most dramatic effects on barrier islands by creating over wash areas and eroding beaches as well as other portions of barrier islands.
According to the National Wildlife Refuge; The earliest documentation of an island in the vicinity of Fisherman Island is from an 1815 navigational chart of the Chesapeake Bay. Two small islands, named the Bird Islands are shown on the chart just south of Cape Charles. Maps prior to 1815 show only shoals in the area and it is probable that Fisherman Island did not become permanently exposed until around this time.
The first accurate map of Fisherman Island is from a Coast Survey of 1852, which shows Fisherman Island to be about 25 acres. While all of Virginia's other barrier islands are shrinking in size and giving way to the constant battering of the sea, Fisherman Island continues to grow. Upon your visit to GZ you will need to answer the following questions. Be sure to e-mail me the answers before you log the cache online. 1. What do you think is better, one large barrier island or a chain of small ones? Why do you think that? 2. From the overlook, estimate the size of Fisherman Island. 3. Do you think people should be allowed on barrier islands? Why do you think that? 4. Why do you think Fisherman Island is getting larger and the other barrier island, on the east coast, are getting smaller? 5. The sign at GZ tells of a place where you can learn more about Fisherman Island. According to the sign at GZ, what is the exact name of that place and what directions are giving to get you there? Once there, children can earn what? Optional - Send a picture of you at ground zero or something unique that you see. Please do not have the sign in the pictures.