In Florida Bay there is a lot of a type of flowering plant called sea grass. There is also a lot of white, milky water full of calcium carbonate. This is mainly formed by "Melobesia", a small red alga which lives on the sea grass. Finally, the organisms produce huge amounts of slime, which is a polysaccharide. There is good reason to think the slime is produced by microorganisms to control the way their carbonate skeletons are formed. As a side-effect the slime limits the amount of carbonate which goes into solution.