SF Peninsula Fungi - symbiote
This shows about 1 square foot of a bloom of several square feet in the quiet part of the stream beside the Timberview trail at El Corte de Madera Open Space Preserve.  Is it a bacterial mat?  Doesn't look like algae.  I saw several other smaller versions of this elsewhere in the stream.

This shows about 1 square foot of a bloom of several square feet in the quiet part of the stream beside the Timberview trail at El Corte de Madera Open Space Preserve. Is it a bacterial mat? Doesn't look like algae. I saw several other smaller versions of this elsewhere in the stream.