What are coral reefs? What is ocean acidification? Objective Students will be able to: 1. Define the vocabulary terms coral reefs and ocean acidification. 2. Identify the role of pH in ocean acidification. 3. Describe coral reef vulnerabilities to human actions that can threaten its survival. Background American Samoa has unusual coral reefs in some ways. First, many of the reefs are dominated by a marine plant that does not even look like it is alive: coralline algae. This is a plant that usually grows as a smooth pink coating (it looks like pink paint) that slowly spreads a thin layer across Duration: 60 Minutes.