What is the key concept for this section? What are the two biggest threats to marine systems? List five human activities that pose major threats to marine systems and eight human activities that...

What is the key concept for this section? What are the two biggest threats to marine systems? List five human activities that pose major threats to marine systems and eight human activities that threaten coral reefs. Explain why the Chesapeake Bay is an estuary in trouble. Summarize the story of what is being done to address its problems.