Erect coralline red alga  
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Corallina vancouveriensis in the rocky intertidal. Seen here in association with the sea anemone Anthopleura elegantissima. This interaction changes the algal morphology to a more filamentous form, and facilitates increased photosynthesis. See text for more details.

C. vancouveriensis at a low tide, subject to desiccation. Note how much water it retains despite this picture being taken at the end of the low tide.


This alga has can be found in two distinct forms: dense beds in unprotected areas and looser beds in protected areas (Riosmena- Rodríguez & Siqueiros-Beltrones 1995). In addition to their calcium carbonate impregnated cell walls, growing in a bed provides an additional way to reduce desiccation stress, making this species one of the few coralline algae able to withstand several hours of exposure outside of water (Johansen 1976). This is in accordance with where it is usually found: outside of tide pools where it must routinely face desiccation stress. Its bushy branches hold more water than other corallines but leave it susceptible to predation by the chiton, Katharina tunicata and to competition with the encrusting corallines (Padilla 1984). Despite these apparent deficiencies this species is quite successful and in empirically derived Markov models this species is what would dominate in the climax community if not for the mussel Mytilus californianus (Wootton 2001). Furthermore, it has intriguing relationships with at least two different animal phyla.

Corallina vancouveriensis can both facilitate and depress growth of the sponge Halichondria panacea. Facilitation occurs when C. vancouveriensis’ predator, Katharina tunicata, is present and controlling the algal density, in which case the sponge grows better in the presence of the alga. This is probably a result of reduced desiccation stress for the sponge. However, if Katharina is not present C. vancouveriensis density will quickly increase and exclude the sponge (Palumbi 1985).

Members of the phylum Cnidaria are also associated with this alga, particularly the clonal sea anemone Anthopleura elegantissima.  By growing in association with these anemones, the alga reduces the water stress it experiences at low tide (these anemones retain a great deal of water in their tissues and in the intervening areas between polyps (Taylor 1985, Personal observation)). With risk of desiccation reduced, C. vancouveriensis can have a more erect and bushy form that greatly increases photosynthetic rate by up to 98% compared to forms not associated with these anemone mats. To reduce desiccation risk, C. vancouveriensis grows compacted thalli that reduce water loss but as a consequence photosynthetic capability is also reduced (Taylor 1985).

Johansen, H. W. 1976. Family Corallinaceae. In. A. Abbott and G.J. Hollenberg (eds), Marine algae of California. Stanford Univ. Press, California, 379-419pp.

Padilla, D. K. 1984. The importance of form: differences in competitive ability, resistance to consumers and environmental stress in an assemblage of coralline algae. Journal of Experimental Marine Biology and Ecology. 79, 105-127.

Palumbi, S. R. 1985. Spatial variation in an alga-sponge commensalisms and the evolution of ecological interactions. The American Naturalist. 126, 267-274.

Riosmena-Rodríguez, R. & Siqueiros-Beltrones, D. A. 1995. Morphology and distribution of Corallina vancouverensis (Corallinales, Rhodophyta) in northwest Mexico. Ciencias Marinas 21, 187-199.

Taylor, P.R. & Hay, M. E. 1984. Functional morphology of intertidal seaweeds: adaptive significance of aggregate vs. solitary forms. Marine Ecology Progress Series. 18, 295-302.

Taylor, P. R. 1985. The influence of sea anemones on the morphology and productivity of two intertidal seaweeds. Journal of Phycology. 21, 335-340.

Wootton, J. T. 2001. Prediction in complex communities: analyses of empirically derived Markov models. Ecology. 82, 580-598.