Population structure and dynamics of the clonal alga Mazzaella cornucopiae (Rhodophyta, Gigartinaceae) from Barkley Sound, Pacific coast of Canada

The structure and the dynamics of a population of the clonal intertidal alga Mazzaella cornucopiae (Postels et Ruprecht) Hommersand (Rhodophyta, Gigartinaceae) were investigated at Barkley Sound, on the Pacific coast of Canada, between 1993 and 1995. Holdfasts of this abundant alga were mostly perennial, but fronds had higher turnover rates. Total thallus cover, frond density, mean frond length, and stand biomass varied seasonally, being generally highest in spring-summer and lowest in winter. Cystocarpic and tetrasporic (reproductive) fronds were only present during autumn and winter. On an annual basis, fronds were mostly produced by perennating holdfasts, relative to thalli that were recruited from spores. The population was numerically dominated by gametophytic (vegetative) fronds relative to tetrasporophytic (vegetative) fronds, regardless of season and the degree of wave exposure. Mazzaella cornucopiae conforms to a K-strategy in traits mainly studied here: (1) holdfasts are perennial and frequently dominant, (2) reproduction is delayed after recruitment, (3) thalli are iteroparous (repeated reproduction through a life time), (4) recruitment is a minor source of interannual population variation. The similarities and differences with the population dynamics of other members of the Gigartinaceae are discussed.