Nature teaches a lesson Bay dynamics: The Chesapeake estuary may be healthier than we think

September 23, 1995

THE DIVERSE plant and animal life and natural conditions of the Chesapeake Bay have repeatedly proven too complex for humans to directly manipulate. Nature frequently finds a way to frustrate well-intentioned cleanup plans and to teach us a new lesson in the dynamics of the bay.

The latest example is in the report that levels of nitrogen and phosphorus, two key pollutants of the bay, have not declined over the past decade despite major efforts to curb their release into the estuary and the multi-state Bay Agreement to reduce those algae-nurturing chemicals by 40 percent by the turn of the century.

Similarly, levels of dissolved oxygen have not improved since 1984, according to the same Environmental Protection Agency study.

Scientists had expected a decline in water quality as a result of very heavy spring rains in 1993 and 1994, which pushed large amounts of sediment and chemical runoff into the bay and fed harmful algae. But they also predicted that low rain and runoff this spring would provide relief, reducing algae formation. Wrong.

The shallower, narrower Upper Bay was abloom with algae, more oxygen-starved than in the past two years. The impact on aquatic health there was even more serious than in the Lower Bay, which is larger and can better dilute these massive algae-bloom effects. There's also evidence that low-oxygen layers have been trapped on the estuary bottom, endangering survival of eggs and larvae of aquatic species.

Experts found some good news in these past two years of monitoring, however. Overall, there were signs that the bay is a bit healthier than normal, that algae-growth in the entire bay is down about 18 percent over the decade.

Bay scientists also learned that there are good and bad kinds of phosphorus and nitrogen, which could redefine efforts to achieve the arbitrary 40 percent reduction goals for these pollutants. Much of the natural spring runoff of these chemicals appears to be bound in dirt, and less available for feeding harmful algae. That is not as damaging to the bay as the fertilizers, sewage and human-refined chemicals dumped into the estuary.

While there is no cause to relax efforts to reduce human pollution of the bay, these findings are a humbling reminder that the Chesapeake's health in any given year is largely dependent on weather conditions. And that a mere 10 years is less than an eye-blink in the bay's geological life-span.

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