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 treament plant upgrades help to keep the bay clean, but it can take multiple years to implement and measure the benefits of these practices.
What was the overall health of the Chesapeake Bay in 2009?
The overall health score for Chesapeake Bay in 2008 was 46 out of a possible 100 points, the best it has been since 2002. This score shows that overall health was moderate. The highest ranked region, for the third year in a row, was the Upper Western Shore (B-) and the lowest ranked region was the Patapsco and Back Rivers (F). Eight reporting regions had improved grades in 2009, four remained unchanged, and only two had slightly worse grades.
What were the conditions affecting Bay health in 2009?
The amount of nutrients and sediment deposited into Chesapeake Bay is strongly related to river flow rates and hence, weather conditions. The total nutrient and sediment loads to Chesapeake Bay did decrease in 2009 overall. These loads directly affect the health of the Bay. In 2009, tributaries immediately adjacent to the Bay received unusually high levels of precipitation while the majority of the Susquehanna River watershed (in Pennsylvania and New York) received less precipitation than normal. This most likely led to decreased 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 Overview, 2009 Summer Review, and USGS’s Chesapeake Bay website.
Why was the Upper Western Shore so healthy in 2009?
The Upper Western Shore region had the highest health index score for the third year in a row, with a score of 61%. This moderately good score is largely due to continued healthy levels of aquatic grasses (82%) and moderately good benthic condition (75%). Dissolved oxygen continues to pass the threshold 100% of the time, as it has done for the past 6 years.
Tributaries from the Patuxent River north to the Back River were the least healthy in 2009. 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 2009, the indicator scores underpinning the Bay Health Index differed slightly between regions. For example, the Phytoplankton Index of Biotic Integrity scores ranged from 10% (Patapsco and Back Rivers) to 26% (Lower Western Shore, MD), and the aquatic grasses scores ranged from 5% (Patapsco and Back Rivers) to 22% (Lower Western Shore, MD).
Why did water clarity improve in 2009?
Water clarity may have improved in 2009 because the lower nutrient and sediments loads coming off the land. Streamflow in 2009 was a little below average, but more importantly, the normal peak of flow in the spring shifted to late April, May, and June. This affects how the phytoplankton and macroalgae respond and grow. With the delay of the spring freshet, the growth of these plants was also delayed. Additionally, the total nitrogen and sediment loads to Chesapeake Bay were lower than in 2008, and have been low for several years, compared to the wet year of 2003. This decreased load, and delayed timing of the streamflow, may have led to better water clarity during the summer monitoring period.