Introduction: Dead Zones in the Chesapeake Bay
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Introduction slide show
Introduction teacher's guide
1. Getting the Lay of the Bay
Use this short slide show to engage students with the Chesapeake Bay. Begin with a map of the Bay and close up images of the rivers from six states and the District of Columbia that feed into the Bay. Share that the Bay is the largest estuary in the United States and that no other American estuary has a higher yield of fish and seafood (including blue crab, oysters, clams, and striped bass).
2. Nutrients Can Be Pollution Too
Next use photos of algal blooms and pictures of dead fish to introduce the problem of pollution, eutrophication, and dead zones in the Bay. Photos of nutrients and suspended sediment entering the Bay from places like farms (fertilizer and manure runoff) and cities (sewage) are used to discuss the factors leading to high nutrient levels in the Bay.
Particular language and concepts to include in the discussion of eutrophication is the relationship between detritus(decaying matter) and microbes(the microscopic organisms that eat the detritus) since these terms will appear when students analyze their food webs. Follow a step by step process of how dead zones are made. The steps to follow are below:
- In normal ecosystem low nutrient levels (limiting factors) keep algae in check
- Adding nutrients causes algal blooms
- Algae die and become detritus (decaying matter)
- Detritus is decomposed by microbes, microbe populations boom
- Microbes use the oxygen in the water
- Low dissolved oxygen in the water kills fish and other organisms
- Dead zones appear in the Bay where nothing can live
After the discussion of the causes of dead zones, the class will be able to summarize what appears to be obvious, that the excess nutrients that people are contributing to the Bay are causing the dead zone problem in the Bay. Next ask the students about the causes of the excess nutrients. The nutrients are being brought to the Bay by rivers and tributaries carrying sewage and fertilizers and manure from farming (factory farms discharge 650 million pounds of chicken manure each year.)
3. Humans And The Bay
In an effort to learn more about the role of people in dead zones ask the students to analyze the feeding relationships of all organisms that comprise the Bay ecosystem. But, in order to understand the feeding relationships amongst organisms in today’s ecosystem, they need to understand what organisms lived there in the past. What did the Chesapeake Bay ecosystem look like 300 years ago, before the arrival of European settlers and large-scale fishing?
More About This Resource...
SubtopicHuman Impacts, Eutrophication