The sea grasses that grow in the lagoon do best with salinities between 20 and 30 ppt. Low salinities in the summer stress seagrass at a time when they should be having their best growth. The impact of the freshwater is also compounded by sediment clouding the water making it hard for light to penetrate to reach the sea grass. When seagrass beds decline it also impacts the fish and shellfish that depend on the seagrass to spawn and hide from predators. Many fish species can tolerate low salinity but often their eggs cannot be fertilized at low levels because as the water becomes fresher it becomes less dense and the eggs cannot float on the surface to be fertilized. Sustained salinity below 15 ppt will kill clams and other shellfish outright. You wouldn’t want to be a clam in Indian River County right now.