Field studies in Chondracanthus chamissoi (C. AGARDH) KÜTZING: seasonal and spatial variations in life-cycle phases

Abstract

Chondracanthus chamissoi (C. Ag.) Kützing is a commercial resource in certain areas oí the Chilean coast and is becoming increasingly important due to its food valué in Asían countries. This species grows only in natural beds that require to be rationally exploited in order to avoid their depletion. Since the first step necessary to develop this exploitation is a knowledge of the dynamics of the populations, the study oí seasonal and spatial variations in abundance and reproduction oí a natural bed in the locality of Puerto Aldea has been carried out. Samples taken bimonthly at four different depths during an entire year resulted in the detection of a sharp seasonality of biomass of sterile as well as reproductive plants with its máximum in summer months due mainly to the increase in growth of plants rather than in density. Reproductive plants only contributed 30% of the total biomass. Reproductive sporophytes were more abundant throughout the year. Reproductive gametophytes and sporophytes behaved differently over depth, with cystocarpic plants being more abundant at shallower depths and tetrasporophytes showing no differences along the bathymetric profile. Nevertheless, phase ratios calculated considering sterile and reproductive plants resulted in a higher proportion of haploid (gametophytes) plants. Differences appear to be due to phase-spedfic behavior at early stages of development or to difieren tial rates of attachment to the sustrate by drifting frond pieces.