Mazzaella splendens (Setchell & N.L.Gardner) Fredericq

Common name: Rainbow Leaf

Type locality: “north end of Carmel Beach”, Carmel, California, USA (Setchell & Gardner 1937).

Taxonomy: Rhodophyta: Florideophyceae: Gigartinales: Gigartinaceae: Mazzaella splendens


Mazzaella splendens is quickly noticeable among the various species present in the intertidal zone, due to its distinct trait of iridescence when caught by the light.  This reflectivity helps the thallus stand out from other algae in the intertidal zone, as the reflection displays colors atypical of the pigmentation of most intertidal algae.  The most distinct morphological trait aside from the variety of colors that can be produced under the right conditions is a large reddish blade attached to a small stipe, typically featuring dichotomous branching and ruffled edges that draw comparison to species of the green algae genus Ulva (though the thicknesses of the blades differ significantly between the two).

Figure 1: Mazzaella splendens specimen collected at Cattle Point, San Juan Island, WA.

Figure 1: Mazzaella splendens specimen collected at Cattle Point, San Juan Island, WA.


Specimens of M. splendens have been most commonly found along the west coast of North America and Canada, and seemingly not many other places (if any at all), according to the Algaebase entry.  The herbarium kept at the University of Washington-owned laboratories in Friday Harbor seems to confirm this, with virtually all specimens of the species having been found in the surrounding area.  Notable locations where they have been taken from include Dallas Beach, Reuben Tarte State Park, Brown Island, Mitchell Bay, and various parts of Vancouver Island.


Mazzaella splendens specimen taken from Eagle Cove, San Juan Island, WA.

Figure 2: Mazzaella splendens specimen taken from Eagle Cove, San Juan Island, WA.


Two specimens have been pressed and dried for archival in the herbarium located in the Friday Harbor Laboratories, with the PHYKOS IDs 00033  and 00139, and alternate labels JLS 168 and JLS 128 .

Research Notes:

Species of Mazzaella follow a triphasic life history unique to red algal groups.  While the cycle still involves the alternation between sporophyte and gametophyte generations, there is an additional generation not present in other algal clades known as the carposporophyte generation (Ross, Donaldson, & Saunders, 2003).  During the carposporophyte phase, red algal plants become epiphytic on other plants in the haploid phase of the life history, in a state called syngamy.  After this state of near-symbiosis ends, the carposporophyte splits from its host and enters into the macroscopic diploid plant life stage (Searles, 1980).
The cells of red algae are quite diverse in morphology, ranging from unicellular forms with one chloroplast, mitochondrion, and nucleus, to species that exist primarily in multicellular forms with large cells that contain several of these organelles each.  The most readily identifiable aspect of the Mazzaella that separates it from green or brown species is the presence of certain accessory pigments within chloroplasts called phycobilipigments, and their processing centers called phycobilisomes.  These pigments make possible the absorption of colors that cannot be absorbed by Chlorophyll a, such as orange, yellow, and green (Gantt, 1980).  There are four different types of this pigment, some of which are shared with cyanobacteria.  The presence of some of these pigment types allow for the distinct coloration notable in some red algal species, such as Mastocarpus and Mazzaella, while other groups, such as Halosaccion spp., do not exhibit this.  This may be due to a higher concentration of blue light-absorbing pigment in some species compared to others.
Mazzaella splendens is a species of primarily blade-like morphology, with a thallus ranging from twenty to forty centimeters in length (Hughey and Hommersand, 2010), often in a cordate or noncordate to broadly lanceolate shape.  The thallus is several cell layers thick, which is immediately noticeable when one grasps it between their fingers and compares it to species that are two cell layers thick, such as Ulva spp.  The color has been described as ranging from dark purple to blackish (Abbott & Hollenberg,1976), but the specimens that have been observed in the field during my stay at Friday Harbor have been primarily a sort of darker red in color*.  Another quickly noticeable trait of the thallus is a blue iridescence that is only visible when the specimen is wet.  The thallus is attached to its holdfast by a small stipe several times less broad than the blade, and features a tapering apex or a terminal cleft.

*Of course, the difference in conditions between California (which was the setting of the book cited) and northern Washington may account for this difference in tinge, but the remainder of the morphological characteristics should not differ widely between specimens found in the two locations.


Literature Cited:

Abbott, Isabella A. and Hollenberg, George J. 1976.  Marine Algae of California.  Stanford University Press, Stanford, California.

Gantt, Elizabeth.  1980.  Structure and Function of Phycobilisomes: Light Harvesting Pigment Complexes in Red and Blue-Green Algae.  International Review of Cytology 66: 45-77.

Hughey, J.R. & Hommmersand, M.H. (2010). A molecular study of Mazzaella (Gigartineaceae, Rhodophyta) and morphological investigation of the splendens clade from Pacific North America. Phycologia 49: 113-135.

Ross, P. J., Donaldson, S. L., Saunders, G. W. (2003). A molecular investigation of Mazzaella (Gigartinales, Rhodophyta) morphologically intermediate between Mazzaella linearis and M. splendens. Botanica Marina 46 (2): 202 – 213.

Setchell, W.A. & Gardner, N.L. (1937). Iridophycus with special reference to the South American species. University of California Publications in Botany 19: 195-244.

Additional Resources:



Molecular data:


Luke Schaefer is an undergraduate from the University of Washington.