In the Florida Bay a type of flowering plant called sea grass is in abundance. Also in abundance is white, milky water full of calcium carbonate. This is mainly formed by "Melobesia", a small red alga which lives on the sea grass. Also, the organisms produce huge amounts of slime, which is a polysaccharide. There is good reason to think the slime is produced by the algae to control the way their carbonate skeletons are formed. As a side-effect the slime limits the amount of carbonate which goes into solution in the water, so most of it gets deposited on the bottom.