Limestone
Florida Bay has much of a type of flowering plant called sea grass. White, milky water full of calcium carbonate is also common. This is mainly formed by Melobesia, a small red alga which lives on sea grass.p151 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.p139 As a side-effect the slime limits the amount of carbonate which goes into solution.p155