Stream macroalgae of Hawai`i: an identification guide - Hawaii.gov

Phormidium
Classification: Cyanobacteria (Family
Phormidiaceae)
General habit: masses of entangled filaments
forming mats that are attached to rocks or
vegetation, or growing in sediments in slowerflowing
stream areas, can range in color from light
blue-green to red/purple or black/gray
Species in Hawai‘i: P. ambiguum, P. amoenum, P.
corium, P. favosum, P. formosum, P. foveolarum, P.
inundatum, P. pachydermaticum, P. retzii, P.
splendidum, P. stagnina, P. subfuscum, P.
subincrustatum, P. tinctorium, P. uncinatum,
Phormidium sp.
Island distribution: Kaua‘i, O‘ahu, Maui, Hawai‘i
Distinguishing features: unbranched filaments
entangled and forming a mat, filaments not tapering
along their length, heterocysts absent, cells at the
ends of filaments with a variety of possible
morphologies (Figs E-G)
Compare with: Lyngbya, Oscillatoria
19
A. A mat of Phormidium growing on a damp rock
wall. Scale bar = 5cm. B. A Phormidium mat growing
in bottom sediment of a stream. Scale bar =
5cm. C. A dissecting microscope view of a
Phormidium mat. Scale bar = 2mm. D. Compound
microscope view of intertwined filaments in a
Phormidium mat. Scale bar = 80µm. E, F, G. Individual
filaments illustrating some of the variation
in cell size and terminal cell morphology. Scale
bar = 10µm.