Salinity in parts per thousand (ppt)
Salinity is the saltiness of seawater — the amount of salts dissolved in water, measured in parts per thousand. The open ocean averages 35 ppt (that is 3.5% saltiness) and the Casco Bay estuary typically ranges from 5 to 33 ppt. Salinity levels are influenced by tides and the volume of fresh water flowing into the Bay.