[ Search | Reply | Next | Previous | Up ]
From: Marilou Hawkins
Date: 11/20/02
Time: 4:11:45 PM
Remote Name: 207.65.228.11
Barrier islands are by their very nature dynamic—the one constant being constant change. The area between the barrier islands called the Outer Banks and the eastern mainland is a set of habitats called an estuarine system. Here lives a remarkable community of life ranging from the magnificent osprey to microscopic zooplankton. It is a richly diverse community whose variety is dependent on the variables of water level, salinity, and temperature. The geographical location puts this area at the northern extremity of southern biota and at the southern extremity of northern biota. In North Carolina, estuaries vary considerably from broad shallow sounds, to narrow bodies of water, with differing water levels, basin types, tidal patterns, salinity, temperature and sediment patterns that make each estuary unique, and are home to equally unique communities of plants and animals. Each habitat creates “niches,” roles that each organism plays in maintaining the balance of the natural system. These patterns of life, who eats and produces what, are described as food chains or food webs. Ninety-five percent of the commercial fish species caught in the state depend on the nutrients and shelter of the estuaries during some part of their lives. Powerful storms, like Dennis, create the most visible and dramatic land reformation changes simply because they redistribute large quantities of soil in a relatively short period of time. The winds and especially the storm surge of hurricanes push barrier island sands toward the mainland in what is termed overwash. The overwash may bury and smother everything on the landward side of the islands including forests, high and low tidal salt marshes, herbaceous grasslands, woody scrub vegetation, and sea grass beds. Inlets—openings between the islands—may be opened or closed, permanently changing the salinity in the brackish water of the sounds. (http://www.wetmap.org/Cape_Hatteras?Suppliment/ch_background) Torrential rains, that frequently accompany hurricanes, can cause flooding, increasing sediment flow from rivers feeding the estuary (that can smother aquatic plants and animals) and rapidly lowering salinity of brackish water on the western side of the sounds. Increased organic pollution brought by the flooding can cause bacterial overgrowth that rapidly depletes the oxygen level of the water and produces large fish kills, which in turn add to the organic matter, creating “dead zones” where nothing but bacteria live until the waters can be remixed and cleansed. Disease and starvation may flow up the food chain as animals dependent on other life forms are deprived of their food source. Mosquitoes, on the other hand, may thrive in newly created, stagnant water bodies, acting as vectors to spread disease to man and animals alike. (http://www.nitrate.com/nov99.htm) Inland forests may be stressed by both the high winds and flooding rains of the hurricane. Many animals are no doubt injured or killed in such storms. (http://lternet.edu/hfr/data/hf002/hf002.html) However, in the long term, hurricanes may bring about greater diversity within the forests by opening the canopy, bringing down old trees that act as nurseries for young seedlings, and providing better conditions for more diverse populations of plants and the animals that live on/with them. (http://www.uga.edu/srel/hugo.htm)