Oyster reefs are major components of estuarine systems and active reefs indicate that the system is suitable for many other estuarine-dependent species. Since Perkinsus marinus (Dermo) is salinity sensitive, Oyster Sentinel provides scientists, resource managers, water regulators, environmentalists and the general public with easy access to current data that can be used as an indicator of the adequacy of freshwater inflows into monitored bays.