| Nutrients, such as
nitrogen and phosphorus, are essential for healthy marine and
freshwater environments. However, an overabundance of nutrients
can literally be too much of a good thing. Excessive nutrients can
trigger excessive algal growth resulting in reduced sunlight, loss
of submerged aquatic vegetation loss of bottom-dwelling animal
habitat, and a decrease in oxygen dissolved in the water column.
On the Gulf of Mexico’s Texas-Louisiana Shelf, an area of
hypoxia covering 6-7,000 square miles forms during the summer
months and has doubled in size over the past 10 years. The cause
of this condition is believed to be a complicated interaction of
excessive nutrients transported to the Gulf by the Mississippi
River, physical changes to the river, such as channelization and
loss of natural wetlands and vegetation along the banks, and the
interaction of saltwater of the Gulf. The nature of the hypoxia
problem is further complicated by the fact that some of the
Mississippi River’s nutrient load is vital to maintaining the
productive of the Gulf fisheries, but too much can eventually
adversely affect commercial and recreational fishing.
Approximately 40% of the U.S. fisheries landings, including a
substantial part of the nation’s’s most valuable fishery
(shrimp), come from this productive area. Commercial landings of
all species in both 1995 and 1996 for Louisiana, Mississippi and
Texas were 1.4 billion lb., with 82% taken from Louisiana waters
for both years.
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