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Browse History: FAQ (2007)

Chesapeake Bay - Frequently Asked Questions:


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 treatment plant upgrades help to keep the bay clean, but it can take multiple years to implement and measure the benefits of these practices.


What were the conditions affecting Bay health in 2007?
The amount of nutrients and sediment deposited into Chesapeake Bay is strongly related to river flow rates and hence weather conditions. Record low rainfall occurred in many regions of the Chesapeake Bay watershed this past summer. The summer drought led to lower–than–average levels of sediment and nutrients flowing into the Bay from June to September. However, annual nitrogen loads were similar to the long-term (1990–2007) average due to slightly higher winter and spring flow conditions. The improved conditions in 2007 compared to 2006 may be due, in part, to the summer drought.

What was the overall health of Chesapeake Bay in 2007?
The overall health score for Chesapeake Bay in 2007 was 42 out of a possible 100. This score shows that overall health could be considered moderately poor. However, the health of the Bay varied from region to region; some regions had relatively good health, such as the Upper Bay and Upper Western Shore, while other regions had poor health, such as the Lower Western Shore (MD) and Patuxent River.

Why was the Upper Western Shore so healthy in 2007?
The Upper Western Shore region had the highest health index score in 2007 with a score of 65. This high score is largely due to a resurgence in aquatic grasses (73% towards the goal), benthic (bottom-dwellers) condition and chlorophyll a. Why many indicators improved in 2007 still needs to be determined, but analysis of historical data shows that this region is very dynamic with health often varying substantially between years.

Why was the Upper Bay so healthy in 2007?
Despite being close to the mouth of the Susquehanna River, the Upper Bay region had the second highest report card scores in 2007. Relatively good conditions in this area may be due to high flushing rates, rapidly pushing sediment and nutrients into more southern regions of the Bay. Ecosystem indicators leading to the high score include low chlorophyll a values, a healthy benthic community, and continuing recovery of aquatic grasses, especially on the Susquehanna flats.

Reporting regions from the Patuxent River north to the Back River scored the worst in 2007. Why?
Low scores in this region of the Bay are likely due to the large population living on watersheds that drain into relatively small rivers. While each region scored poorly in 2007, the indicator scores underpinning the Bay Health Index did differ slightly between regions. For example, the Phytoplankton Index of Biotic Integrity scores ranged from 3% (Patuxent River) to 21% (Lower Western Shore, MD), and the aquatic grasses scores ranged from 2% (Patapsco and Back Rivers) to 23% (Lower Western Shore, MD).

Why did the Choptank River Score improve so much compared to 2006?
Historical analysis of Choptank River indicator scores shows that the health of this region varies greatly between years (see Methods section of Report Card webpage). This annual variation may in part be due to the fact that most nutrient and sediment loads into the region are from diffuse sources (mainly agriculture). Diffuse loads are highly influenced by annual variations in rainfall and therefore, river and stream flow. Indicators that showed the greatest improvement in 2007 were chlorophyll a, water clarity, and Benthic Index of Biotic Integrity.

How healthy were aquatic grasses in 2007?
Overall, there was a slight increase of aquatic grasses area in 2007. Regions recording the largest percentage increase were the Upper Bay, Lower Bay, and Upper Western Shore. While many regions did experience an increase, the Patuxent River, Upper Eastern Shore, and Patapsco and Back Rivers regions experienced a decrease.