Green rock scum (a.k.a. guano threads) is a terrestrial filamentous green algae species that is found in Europe, North America, South America, Australia and New Zealand (Algaebase 2010). In the North Pacific, it is found along the North American coast from Alaska south to Oregon (Lindeberg and Lindstrom 2010). Plants are yellow-green tangled masses found on soil or rocks at or above the high water mark, where it can withstand long periods out of the water in some sites (Lindeberg and Lindstrom 2010). It is often associated with bird colonies (SeaweedAfrica.org 2010).

View photographs at SeaweedAfrica.org.

View specimen scans at SeaweedAfrica.org.

Read a detailed description of morphology and life history here.