Rehoboth Bay, Indian River Bay and Little Assawoman Bay in southeast Sussex County make up what are called Delaware's Inland Bays. A tremendously important recreational and commercial resource for the boating, fishing and tourist industries, they encompass about 32 square miles of water area, which drains a watershed of about 320 square miles.

The Inland Bays are shallow, with an average depth of 3 to 8 feet. Because the bays are so shallow, and because they are poorly flushed by tidal movement, they are especially sensitive to environmental changes. Increases in pollutants, changes in salinity and fluctuations in water temperature, for example, can have dramatic effects on water quality and on the plants, fish, shellfish and microscopic creatures that live in the bays.

The waters are affected by the multitude of activities that take place on land, even miles from the bays --- activities such as farming, lawn fertilizing, septic system use, poultry raising. Even the everyday act of driving is part of the complex problem of water pollution, because the air pollution it causes deposits contaminants on the broad, shallow waters.

Nutrients, mainly nitrogen and phosphorus from fertilizers, poultry manure and septic systems, enter the bays in groundwater and in surface runoff that flows into the bays and its many tributaries.

The results of that pollution have been dramatic. For example:

• Fish kills have dramatically increased in size in the past two years, from an average of about 20,000 fish killed each year from 1996 to 1999 to more than five million killed in 2000 alone. (Totals for 2001 have not yet been tallied, but they will also be high.) Fish kills have also increased in number, from an average of less than three a year from 1996 to 1999, to a total of 12 in 2000. Most fish kills occurred in poorly flushed creeks off the Inland Bays, where the probable cause of death was low dissolved oxygen in the water.

• In 1997, Pfiesteria, a sometimes-toxic microorganism that can cause lesions on fish and may cause sickness in humans, was found in Indian River Bay. Although it appeared in one of its non-lethal forms, the discovery was troubling, as it reminded citizens and officials of the 1987 Pfiesteria outbreak that caused the death of 250,000 fish. The discovery of Pfiesteria (and other harmful algal blooms) in the Inland Bays sent a chill up the spine of tourism officials who worried about the effect that a lethal appearance of the organism would have on the $342 million tourist industry in Sussex County. Recent scientific findings show a clear link between Pfiesteria and excess nutrients in the water.

• Every summer since 1997, prevailing winds have blown huge floating rafts of dead aquatic vegetation (commonly called "seaweed") onto the shores of Dewey Beach. The result of excess nitrogen and phosphorus in the water, the vegetation ends up rotting along the bayfront. The awful smell is an obvious annoyance to property owners and bayfront visitors --- in some cases, rental agents have been forced to relocate renters to other locations because the odor is so bad. In addition, removal of the seaweed is no small challenge. The state Department of Natural Resources and Environmental Control had to purchase two special floating machines, at $38,000 each, to dispose tons of the debris.

• In the summer of 1998, excess nitrogen and phosphorus in the Inland Bays caused massive algae blooms. The effect, called "mahogany tide" or "red tide" depending on the organism, led to a decrease in the level of dissolved oxygen in the water, a loss of desirable submerged aquatic vegetation, and a degradation of finfish and shellfish habitat.

• Also in 1998, thousands of clams died as a result of oxygen deficiencies caused by the accumulation and decomposition of "sea lettuce" in Indian River Bay.

For those thinking ahead, these problems point to bigger issues --- the loss of species, a less diverse ecosystem, the decline of the tourism economy and reduced property values.