If underwater grasses and bottom-dwelling organisms had a chance to grade the Bay last year, they likely would have flunked it.

They didn’t have that opportunity. But a team of scientists did it for them.

Their first-ever Chesapeake Bay Report Card assigns scores for six indicators that reflect water or habitat quality, then uses them to come up with an overall Habitat Health Index used to assign a grade. Besides the Baywide score, the report card also grades the health of 15 regions within the Chesapeake.

“We’re providing a detailed snapshot of last year,” said Bill Dennison, a researcher with the University of Maryland Center for Environmental Science who led the report card project. “We are drilling down to the tributary-specific level to talk about how the Bay is doing at the tributary level.”

Dennison said that allows the public, as well as state and federal water quality managers and scientists, to examine factors that influence water and habitat quality from place to place.

Indeed, while the overall Bay scored 37 on the 100 point scale (earning a D+), there was a wide range of conditions throughout the Chesapeake. The Upper Bay scored a Chesapeake-best 55 (for a C+) while the Patapsco/Back Bay scored a rock-bottom 13 (for an F).

Dennison said that over time he hopes the annual index spurs debate—or even competition—between areas. “I want some civic pride taking place,” he said.

That might happen.

“I don’t think that many of us like the idea of getting ‘D’ at any point in time,” said Frank Dawson, of the Maryland Department of Natural Resources. “For me personally, it reminds me that we need to continue our resolve.”

The Congressional Government Accountability Office, in a report issued two years ago, called on the Bay Program to develop a Bay health assessment that integrated multiple measures of ecosystem’s condition into a simple score readily understood by the public.

Many Bay Program participants have been reluctant to adopt such an approach, saying the Bay ecosystem is too complex to be summed up in a single score.

Dennison acknowledged that the Bay is complex, stretching 200 miles from top to bottom, covering 4,400 square miles of water, 11,000 miles of shorelines, and multiple habitats from oyster bars to muddy bottom to seagrasses.

But, he said, “we have come up with a way that encapsulates the best possible science to address the question of how the Bay is doing.”

The Habitat Health Index was developed by a team of scientists from the University of Maryland and several state and federal agencies. It is derived from two other indices, each of which integrates three elements:

  • The Water Quality Index is determined using information about chlorophyll a (a measure of algae), dissolved oxygen and water clarity.
  • The Biotic Index is determined using information about Bay grass abundance, benthic communities and phytoplankton communities.

Each indicator is measured on a 100-point scale, with 100 representing healthy ecosystems based on published scientific literature and technical reports. They are then averaged to get the water quality and biotic indices.

The Habitat Health Index for each localized region is derived by averaging the Biotic Index and Water Quality Index. The Baywide score is determined by averaging the Habitat Health Index for all 15 regions.

By looking at multiple factors, the index approach avoids distortions that might be caused by looking at a single indicator. For instance, many areas reported better-than-normal dissolved oxygen conditions last year, but that benefit was offset by the effects of heavy rains in the late spring and early summer that flooded the Bay with nutrients and sediment, clouding the water and leading to a huge loss of Bay grasses in many areas.

“Last year was the worst water clarity that we’ve ever measured since monitoring began,” Dennison said.

The data is drawn from multiple monitoring programs, many of which have been in place for decades. “The Chesapeake is one of the few places in the world where you could pull this off,” Dennison said.

In the future, other indicators may be added, including such things as fish and shellfish, as well as land use within watersheds. And while the index is limited to the Bay and tidal portions of its tributaries for now, Dennison said it may move farther into the watershed in the future.

The full report is available online at: www.eco-check.org/reportcard/chesapeake/.