A sharp observer may note that the 74 million pound nitrogen reduction goal is not 40 percent of the 353 pounds entering the Bay in 1985. Nor, for that matter is the 9 million pound phosphorus reduction goal a 40 percent reduction from the 1985 total of 25 million pounds.

So just where is this 40 percent nutrient reduction?

The answer is that the 40 percent agreed upon in 1987 was not based on the total amount of nutrients entering the Bay. Rather, it was based on 40 percent of the controllable amount of nutrients entering the Chesapeake.

Much of the nutrients entering the Bay originate naturally, and are necessary to spur the growth of algae, which helps form the base of the food web. (After all, it is not the creation of algae that causes the Bay's problems, it is that excessive nutrients spur far more algae growth than is needed to feed other Bay creatures).

Other nutrient sources that have been defined as uncontrollable are those coming from Delaware, West Virginia and New York, each of which have sizable amounts of land in the Bay watershed, but are not part of the Bay Program.

Also defined as uncontrollable is deposition from air pollution, which accounts for roughly a quarter of the nitrogen entering the Bay (but is not a major source of phosphorus). Much of the air pollution that contributes to the Bay's problems originates from beyond the watershed, and even beyond the Bay states.

So the bottom line is this: The 40 percent reduction is figured from a controllable nitrogen load to the Bay of about 185 million pounds. The 40 percent phosphorus reduction is figured from a controllable phosphorus load of about 21 million pounds.