As the river level drops, one sees a vast expanse of a white substance coating the areas where high waters had receded. Some have suggested that this white residue is run-off from limestone road surfacing. Master Naturalist Lars Andersen had a different explanation:
“While spring water is clear, it’s actually loaded with microscopic algae, diatoms and other organisms. In fact, in a healthy spring run, the primary producer (making “food” by photosynthesis) in the system is not the large vascular plants like Vallisneria and Sagittaria, it’s the microscopic algae and diatoms.
During flood, aquatic algae coats all submerged plants, branches, bases of tree trunks, etc. There’s probably also some calcium residue in the mix. When the flood water recedes, this periphyton and deposited algae, diatoms, etc, dry out, creating this chalk-like residue.
Since there is more algae in the water these days than in the past, there is presumably a bit more of this deposited material than there would have been several decades ago. But, having some of this deposited material is natural. In fact it’s a sign of a healthy spring run (plenty of algae and diatoms) and happens after every flood.”
This white coating is evidence of the abundant life, yet it also thrives in areas of low dissolved oxygen and high phosphorus. To learn more about this intriguing algal stew, you might check out this link to several articles. There are also many mentions of periphyton including the Florida Springs Institute Restoration Plan dated 2012, starting on page 31.
OSFR President Joanne Tremblay
joanne.tremblay@oursantaferiver.org
“Giving Our River A Voice”
