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Chesapeake Bay - Frequently Asked Questions:

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General

What is the Chesapeake Bay annual ecosystem health report card?
The report card is a scientifically robust and geographically detailed annual assessment of Chesapeake Bay ecosystem health. The report card combines multiple indicators (regarding water quality and habitat) of ecosystem health into a single score for 15 regions the Bay.

When is the report card released?
The report card is expected to be released annually in early to mid April.

How does the report card score ecosystem health?
Currently, this report card rates Chesapeake Bay health as defined by progress of six indicators toward established scientifically derived ecological thresholds or goals. A low report card score therefore means that the area of interest rarely meets the ecological threshold levels. A high score means that the area often meets the threshold levels.

How many indicators does the report card include?
There are three water quality indicators (chlorophyll a, dissolved oxygen, and water clarity) and three biotic indicators (aquatic grasses, Benthic Index of Biotic Integrity, and Phytoplankton Index of Biotic Integrity). Other indicators, especially those related to fish and shellfish, will be added to the report card in the future as suitable data becomes available.

How were the report card indicators chosen?
Indicators for the Chesapeake Bay report card were chosen so that they would relate to the management objectives established in the Chesapeake 2000 Agreement, represent key ecological processes, and fulfill practical requirements such as data availability and geographic coverage.

Does the report card address human health issues?
No - Indicators used in the report card have been chosen to measure the health of the Bay's ecosystem and not how healthy the Bay is for human use, such as swimming and fish consumption.

What do the grades mean?
A: All water quality and biological health indicators meet desired levels. Quality of water in these locations tends to be very good, most often leading to very good habitat conditions for fish and shellfish.

B: Most water quality and biological health indicators meet desired levels. Quality of water in these locations tends to be good, often leading to good habitat conditions for fish and shellfish.

C: There is a mix of good and poor levels of water quality and biological health indicators. Quality of water in these locations tends to be fair, leading to fair habitat conditions for fish and shellfish.

D: Some or few water quality and biological health indicators meet desired levels. Quality of water in these locations tends to be poor, often leading to poor habitat conditions for fish and shellfish.

F: Very few or no water quality and biological health indicators meet desired levels. Quality of water in these locations tends to be very poor, most often leading to very poor habitat conditions for fish and shellfish.

What are the factors that affect the grades on a long-term basis?
There are several factors that affect the grades on a multi-year scale. The amount of rainfall in the area can influence how much nutrients and sediment enter the Bay. For example, in 2002 the bay scored a 55% because there were several years of low rainfall. But after the wet conditions of 2003, the health of the Bay deteriorated to a 36%, and has not recovered quickly. Another factor affecting the bay's health on a multi-year basis is the amount of restoration and best management practices that are occurring throughout the bay watershed. For example, stormwater retention ponds and wastewater treament plant upgrades help to keep the bay clean, but it can take multiple years to implement and measure the benefits of these practices.

2010

What was the overall health of the Chesapeake Bay in 2010?

The overall health score for Chesapeake Bay in 2010 was moderately poor, scoring 42 out of a possible 100 points. This is the first time in four years that the score has declined, but it only decreased from 2009 by 4%. The highest ranked region in 2010 was the Upper Bay (57%, a C+) and the lowest ranked region was the Lower Western Shore (MD) (13%, an F). Two reporting regions had improved grades in 2010, three remained unchanged, and nine declined in score.

What were the conditions affecting Bay health in 2010?

The amount of nutrients and sediment deposited into Chesapeake Bay is strongly related to river flow rates and hence, weather conditions. These loads directly affect the health of the Bay. In 2010, high streamflow occurred during two winter storm events. This most likely led to increased nutrient and sediment input from the Susquehanna River and higher than normal inputs from tributaries in Maryland and Virginia. For further information on nutrients, sediments, and streamflow, please see the USGS’s Chesapeake Bay website.

Tributaries from the Patuxent River north to the Back River were the least healthy again in 2010. Why are those regions consistently the lowest ranked in the Bay every year?

Low scores in these regions are likely due to the large human population living in watersheds that drain into relatively small rivers. Highly urbanized watersheds tend to have lower BHI scores than watersheds that are less developed.

While these regions did all score poorly in 2010, the indicator scores underpinning the Bay Health Index differed slightly between regions. For example, chlorophyll a scores ranged from 0% (Patapsco and Back Rivers) to 2% (Lower Western Shore, MD), but dissolved oxygen scores ranged from 52% (Patapsco and Back Rivers) to 56% (Lower Western Shore, MD).

Why did many regions decline in 2010?

Researchers believe that two closely timed, large-scale weather events in winter 2010 played a role in the decreases seen in many regions this year. Ecosystem health is affected by many factors, including human activities and natural variations in rainfall, which is the major driver of stormwater runoff from urban, suburban and agricultural sources. The higher rainfall and associated stormwater runoff from the two closely timed, large-scale winter weather events likely contributed to slight declines in water quality and biological health indicators Bay-wide.