Science as Inquiry
Science in Personal and Social Perspectives
The Chesapeake Bay is one of the largest and most productive estuaries in the world. More than 14 million people live within its watershed, which encompasses 64,000 square miles of land in portions of six states (Delaware, Maryland, New York, Pennsylvania, Virginia, and West Virginia), as well as the District of Columbia. Freshwater, supplied by over 150 rivers and streams and saltwater from the Atlantic Ocean combine to create the unique conditions which support over 2,700 species of plants and animals. The Bay is 195 miles long, 30 miles wide at its widest point, and 4 miles wide at its narrowest point. Its average depth is 21 feet. But to truly appreciate the Bay, one must go beyond the facts and figures and get to know its personality. Contemplate the "comings and goings" of the Bay's inhabitants. In a typical year, this body of water changes as gracefully as the seasons.
The Chesapeake Bay is obviously a vital resource which we need to preserve and protect. How do we know how it's doing? How do you take the pulse of such a large and complex ecosystem? In order to assess its health, what would you monitor and why? Scientists collect data on sediments, water quality, distribution of seagrasses, and populations of oysters, fish, and crabs, among other things. These are called environmental indicators, and in addition to helping us monitor the health of the Bay, indicators allow us to set goals by which we can measure our progress toward improving the Bay’s health.
It may still seem mind-boggling, however, to comprehend all the factors contributing to the health of the Bay. To simplify our thinking, the Chesapeake Bay Foundation has come up with the following logical equation: our assessment of the Bay's health boils down to "what we put in" (nutrients, toxins, sediments, etc.), "what we take out" (harvest), and "the Bay's ability to filter" (forested buffers, wetlands, underwater grasses, oysters).
What We Put In
Nutrients, such as nitrogen and phosphorus, are a major focus of monitoring efforts. What are the sources of these nutrients, and how do they enter the Bay? What are the implications of elevated nutrient levels in the Bay? The Maryland Department of Natural Resources conducts continuous monitoring of physical and chemical parameters at several sites on the upper Chesapeake Bay. Use the graphs and the narratives as tools to study some water quality parameters in the Bay. Investigate the relationships between nutrient levels and phytoplankton, dissolved oxygen (DO) and water temperature. What level of DO is considered to be good for life in the Bay? Which holds more oxygen: cold water or warm water? Why is it true that we sometimes see a higher percent saturation of DO during the day when the water is warmer and a lower percent saturation of DO during the night when the water is cooler? What two factors influence water temperature? Why do nutrient levels decrease as the summer goes on? Chlorophyll a is a measure of what?
You can also check current conditions (DO, water temperature, salinity, Secchi depth) at 8 key stations in the mainstem Bay and see how they compare with the monitoring data collected since 1985.
What We Take Out
Many people rely on the Bay's fisheries for their livelihoods and their recreational enjoyment. Select a fish species from the NOAA Chesapeake Bay Office Species Information page (list of fish species is on the left). Read about your species' life history and view its commercial landing data (click on the Data & Maps tab). Based on your research, is your species overfished or depleted? Based on its life history, could there be reasons for your species' decline other than overfishing (e.g. habitat loss, decline in water quality due to pollution, sedimentation, increased nutrients)? What effects has the decline of your species had on the ecosystem as a whole?
The Bay's Ability To Filter
The Bay's underwater grasses improve water quality by absorbing nutrients from the water column. Investigate bay grass, or submerged aquatic vegetation (SAV), coverage and status in the Bay. What are the reasons for its decline over the past century? In addition to improving water quality, what other important functions does SAV serve in the Bay ecosystem?
Oysters are filter feeders, consuming phytoplankton and improving water quality by filtering the water. Chesapeake Bay, whose name means "Great Shellfish Bay," was historically marked by high abundances of oysters that were able to filter the bay water in a period of three days. It takes the current oyster population one year to filter the bay water. What are the reasons for the decline in the oyster population?
The grades are in for 2000, and on its most recent test, the Chesapeake Bay scored 28 out of 100 (according to the new State of the Bay Report released by the Chesapeake Bay Foundation). The Chesapeake Bay’s health has actually shown modest signs of improvement since its historic low in 1983, but it is still a long way from being saved and restored.
More Bay Info
There are many more sites on the Web with information about the
Chesapeake Bay. If you would like to investigate the topic further, check out the resources on our Chesapeake Bay page.
Current Data Tip of the Month
Data Tip of the Month Archives
On-Line Data Resources
ChesSIE-Chesapeake Science on the Internet for Educators
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