One of the biggest threats to marine organisms is the phenomenon known as OCEAN ACIDIFICATION where because of increased CO2 in our waters, due to the burning of fossil fuels, has caused the ocean to become more acidic. This increase in acidity inhibits the ability for many corals and mollusks, including oysters and clams, in building their shells. This could result in coral reefs eroding and shellfish fisheries collapsing. AND As ocean levels rise the relative sea level rise is different for different locations; that is why the National Park Service is installing a TORTUGAS TIDE GAUGE to monitor sea level rise to better protect the cultural and natural resources in the Dry Tortugas. Sponsored by Everglades National Park, Florida Keys National Marine Sanctuary and USEPA; directed by Erik Hutchins.