PATTERNS OF SEASONAL DEMOGRAPHIC-CHANGE IN THE ALTERNATE ISOMORPHIC STAGES OF MAZZAELLA SPLENDENS (GIGARTINALES, RHODOPHYTA)

Seasonal alternation of life-history phase dominance in a Vancouver population of Mazzaella splendens (Setchel ct Gardner) Hommersand (Gigartinaceae, Rhodophyta) is the result of temporally synchronous differential rates of increase and decrease in density. Gametophytes increase in density more rapidly than tetrasporophytes in spring, attaining higher summer densities, and decrease more rapidly in autumn, resulting in a winter predominance of tetrasporophytes. This demonstrates real ecological differences between the alternate isomorphic phases of this alga, with gametophytes apparently adopting a strategy of greater exploitation of favourable conditions to offset greater loss in unfavourable times, while tetrasporophytes maintain a somewhat more stable density throughout the year.