Reproductive biology of Gigartina skottsbergii (Gigartinaceae, Rhodophyta)from Chile

Reproductive phenology and spore viability were studied in a natural bed of Gigartina skottsbergii at the locality of Ancud, Chile. Monthly sampling o f biomass and density disclosed a decrease of both parameters in time, from 40 g m(-2) in June 1996 to 1 g m(-2) December 1997 and from almost 4 thall i m(-2) to 1 thallus m(-2) in the same period, respectively. Mature reprodu ctive structures, cystocarps and tetrasporangial sori, were observed over t he whole study period. Greatest cystocarp densities occurred in October thr ough February (16 to 29 cystocarps cm(-2)) and of tetrasporangial sori betw een July and October (66 to 88 sori cm(-2)). In both types of reproductive structures, sporulation is more frequent in winter and early spring. High m ortality of carpospores and tetraspores was observed in laboratory experime nts performed between June and September.