Family Description:
Species have an alternation of isomorphic generations, and male and female conceptacles occur on separate plants. Tetrasporangia are zonately divided; sometimes they are replaced by bisporangia (sporangia containing two spores each). Other characters are the same as those described above for the order.

Species description:
An encrusting base that is tightly adherent to rocks gives rise to many erect branches. Both this base and its branches are pink to slightly purple, but like other corallines can bleach white if exposed to excessive sunshine during low tide. This species can usually withstand several hours of exposure, however.

The segments of the Graceful Coral Seaweed are more cylindrical than those of the Common Coral Seaweed, and the axial segments are shorter, being only 1 mm in length. None of the segments is winged. Many branches arise at each joint. Conceptacles are rare, and when present do not differ from those of the Common Coral Seaweed.

Various epiphytes such as bryozoans and encrusting corallines such as Coralline Crust (Mesophyllum lamellatum) can grow on the Graceful Coral Seaweed.

In southern California, researchers discovered that the aggregation of upright branches of Graceful Coral Seaweed into turfs decreased the productivity of each branch, probably because of self-shading or the more limited exposure to nutrients. On the positive side, however, turfs were more resistant to desiccation. Clumps of branches transplanted to tidepools (where desiccation is not a threat) developed non-turf forms, while the reciprocal transplantation of non-turfs to emergent areas resulted in either the development of the turf form or death.

Workers in southern California also discovered an interesting association between the Graceful Coral Seaweed and the Aggregating Anemone (Anthopleura elegantissima). When growing within a bed of the anemone, the coralline alga grew with more open branches that showed high rates of photosynthesis. When the anemones were experimentally removed, new growth of the coralline alga was much more tightly compacted and showed strongly reduced rates of photosynthesis, possibly from self-shading. The researchers determined that when present, the anemones hold water that helps the alga avoid desiccation, but when the anemones are absent, the alga is forced to grow in a form that has less tendency to dry out but is also less efficient at photosynthesis. Therefore, association with the anemone allows the alga to grow in a manner that is more productive.

Like other erect corallines, the Graceful Coral Seaweed is found mainly on our exposed outer coasts, but we have seen it mostly in areas protected from the strongest surf. It is an opportunist and can rapidly colonize new spaces on rocks in the low intertidal zone, but erect branches can also arise fairly quickly from previously established crusts.

It has very low caloric value (1.03 Calories per gram of dry weight).

Graceful Coral Seaweed was originally described from Port Renfrew on the west coast of Vancouver Island, British Columbia, hence "vancouveriensis."

Source:  North Pacific Seaweeds

Synonyms and Alternate Names:
Corallina densa