A hurricane is a low-pressure system that generally forms in tropical regions as a consequence of several factors, such as pre-existing weather disturbances, warm sea-surface temperatures, moisture and relatively light, high altitude winds.  In addition, a hurricane is usually accompanied by thunderstorms.  To be classified as a hurricane, rather than a tropical storm, the wind speed at the earth’s surface must be 74 mph or greater and last for a minute or longer.  Each year an average of ten tropical storms develop over the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico and about 6 of these low-pressure systems will develop into hurricanes.  The major effects of these hurricanes happen when they come ashore.  Statistics show that in the twentieth century Atlantic Hurricanes were responsible for approximately 160,000 deaths along the coastal regions of North and Central America.  Most of these fatalities were due to inland flooding and heavy rainfall rather than storm surges at the coast.  In addition to loss of human life, hurricanes have many other environmental impacts.  High winds damage structures, blow over trees and may spawn tornadoes on land.  Storm surges push large amounts of water ashore causing damage to piers and harbors.  Huge volumes of rain may lead to landslides on steep slopes; these landslides can then cause structural damage to roads and buildings.  By far the most damaging effect of the hurricane is inland flooding.  Inland flooding can lead to pollution surges from animal feedlots, manure and waste lagoons on farms, agricultural pollutants such as fertilizer and pesticides and waste from industry and automobiles.
         When these polluted floodwaters reach the coast they can have a major impact on estuaries that are the home for young fish and shellfish.  Estuaries are ideal habitats for these animals because of their shallow, warm waters that contain lots of plant life and are rich in nutrients.  In addition, these sounds have low salinity levels and narrow inlets from barrier island so large predators are deterred.  The most serious pollution threat from these floodwaters is increased sedimentation, which results in the large particles blanketing the bottom of the estuary, covering the shellfish and shading plants, such as sea grass.  When sediments cover oysters and other shellfish it makes it difficult for them to filter water.  In addition to the sediment, dead plants and animals also flow into the estuaries with the floodwaters.  These organism sink to the bottom and begin to decompose, a process that lowers oxygen levels in the water.  When fast waters rush in they do not mix with the sound waters causing a layer of oxygen rich water to overlie the oxygen poor waters.  Unfortunately, the fish tend to remain in the oxygen poor deeper waters since they are higher in salinity and these poor water conditions cause skin disease on the fish making them easy prey for seagulls and other predators.  In the case of Hurricane Floyd, more organic matter was flushed into the sound in a few weeks than in a typical year.  In the spring, rising temperatures cause the decomposition to accelerate and oxygen poor water spreads, which could continue to affect growth and reproduction within the estuary.

References:

Herring, David, NASA Earth Observatory.  Hurricane Floyd’s Lasting Legacy, Assessing the Storm’s Impact on the Carolina Coast.  March 1, 2000.  http://www.earthobservatory.nasa.gov/Study/FloydIntro/

-- Hurricane Floyd: Fearing the Worst. March 20, 2000.  http://www.earthobservatory.nasa.gov/Study/FloydFear/fear.html

NPR radio. October 25, 1999.  http://www.npr.org/ramfiles/atc/19991025.atc.04.ram

Landsea, Christopher W, AOML/Hurricane Research Division.  FAQ: Hurricanes Typhoons, and Tropical cyclones, Part D: Tropical Cyclone Winds.  August 9, 2001.  http://www.aoml.noaa.gov/hrd/tcfaq/tcfaqD.html