Scum isn’t always bad

It is more than likely that you have already encountered periphyton of some form. You may have encountered it without even really noticing it or knowing what it was. Or you may have thought it was pretty gross.

Periphyton is a bunch of algae, fungi, other microbes, and dead material either growing or aggregating together on or around a surface. “Peri” means around (like in perimeter) and “phyto” means plant. The plant part refers to the algae that are a major component of periphyton. Periphyton can grow on plants (epiphytic), on rocks (epilithic), on top of the sediment surface underwater (benthic), and even on animals (epizooic). Periphyton has been called “pond scum,” “muck,” or even “rock snot.”

Periphyton in the Everglades landscape

In the Everglades, you can find periphyton almost everywhere, especially where the water has low nutrients and isn't too deep. Usually it has a tan or beige color because of the calcium carbonate that enters the water column from the limestone bedrock. In areas with higher nutrients or soft water, the periphyton looks more green. You can find a lot of floating periphyton, which grows in association with bladderwort (Utricularia), a floating submersed aquatic plant. A lot of plants in the Everglades have periphyton growing around their stems, affectionately called “sweaters” by some.

Floating, epiphytic, and benthic periphyton

Periphyton up close and personal

Periphyton might not look or feel pleasant, but it’s a big deal for the Everglades and other aquatic environments. It can suck up excess nutrients in the water and regulate water quality. The photosynthetic algae and cyanobacteria produce oxygen. It is home to yummy algae for aquatic insects and fish. Some algae and insects use the structure provided by periphyton to escape the intense heat and UV radiation of the Florida sun, as well as to keep moist during the winter dry season. An important characteristic of periphyton is that it reacts quickly to changes in the environment, so it is used as an indicator of water quality.

Scanning electron micrograph of Everglades periphyton (450x magnification)

If we look even closer using a microscope, we can see the diverse community of algae, fungi, and bacteria that make up periphyton. A major component of periphyton is a special group of algae called diatoms, which is the subject of my research. More on that next time!