al creek and adjacent coastal waters can range from less than 5 to over 30 parts per thousand during the year. The plants and animals that inhabit this changing environment are generally well-adapted to it.
The major elements of the salt marsh ecosystem can be seen from the University dock adjacent to the Marine Biology building. Smooth cord grass is the dominant tall green grass found in the lower part of the marsh where the ground stays wet and very muddy as a result of the tides flooding the area twice daily. In late spring through late fall when most of the salt marsh is lush green, darker dead-looking sections of marsh grass can be seen. This dead-looking marsh grass has long, tubular stems and sharp brown- pointed tips and is called the needle rush. These two grasses are replaced toward higher ground by the sea oxeye, which has a succulent leaf with a yellow aster flower in June and the similar, but taller, marsh elder, a shrub that encroaches on part of the wooden walkway leading to the dock. None of these salt tolerant plants, called halophytes, is found beyond the influence of the brackish tidal water.
The tidal creek supports much more marine life during the summer than during the winter. In summer, the warmer temperatures and greater sunlight increases the overall productivity of the salt marsh while in winter the colder temperatures and less sunlight decreases the productivity. While the water in the tidal creek is never crystal clear because the tides constantly stir up the mud, it is significantly clearer in the winter because there are fewer microscopic organisms such as algal cells suspended in it.
At low tide, the surface of the mud banks along the campus' tidal creek is highlighted by the golden hue of millions of algal cells called diatoms. Mud snails aggregate by the thousands on the mud zone. Mullet, Atlantic menhaden, killifishes, blue crabs, mud crabs, white shrimp, and brown shrimp are most responsible for activity at the surface of the water in the creek. Because of the significant tidal flushing, pollution does not accumulate in the creek; blue crabs and shrimp harvested here are safe to eat.
Attached to the dock and its pilings are barnacles, oysters, seaweeds and a variety of encrusting marine life known as hydrazoans, anthozoans, and ascidians. Because they strain microscopic particles from the water, including harmful microorganisms associated with animal waste, oysters from the creek by the campus and many other tidal creeks and rivers near human and animal habitation cannot safely be consumed. Attached and clinging to the stalks of the salt marsh grasses are ribbed mussels and periwinkle snails. In higher marsh sandy zones, fiddler crabs dig burrows, feed, and interact. The one enlarged chela (claw) of the male is useful for defense and communication but it is not effective for food gathering. As a result, males must spend twice as much time feeding as the females, which have two small chelae.
A non-natural, but common element of the salt marsh is marine debris: plastic containers, Styrofoam, cans, and other material of human origin, which ends up along coastal shorelines. These materials come from commercial and recreational boats and ships, marinas and docks where trash containers are absent or overflowing, construction sites and vehicles on roadways near the water, and from deliberate littering. Debris is constantly being redistributed on coastal shores by the action of tides, winds, and waves. Based upon a 1992 study of the rates of accumulation at four sites in Chatham County, over 40,800 kg or 40.8 metric tons of marine debris wash up on coastal shorelines in Chatham County annually (Gilligan et al).
The maritime influence on the campus climate and vegetation is significant. In the spring when it is somewhat hot and humid inland, the campus has cool breezes from the still-cold tidal waters, a form of natural air conditioning. In winter, the relatively warmer tidal waters can prevent vegetation from freezing. For example, cabbage palms, a distinctive tropical element of the low countr