SPATIAL AND TEMPORAL DISTRIBUTION OF DOMINANT EPIPHYTES ON GRACILARIA FROM A NATURAL SUBTIDAL BED IN CENTRAL-SOUTHERN CHILE

Data are presented on the taxonomy and the temporal and spatial distribution of the most prevalent epiphytic taxa in a natural subtidal bed of Gracilaria in central-southern Chile. Also, the nature of the epiphyte/basiphyte interface is described. Samples were collected from April 1989 to July 1990 from 2.4 to 8.7 m. The following taxa were identified: Ceramium pacificum (Coll.) Kyl., Ceramium sp., Nitophyllum peruvianum (Mont.) Howe, Callophyllis variegata (Bory) Kuetz., Callophyllis pinnata Setch. & Swezy, Rhodophyllis aff. acanthocarpa (Harv.) J. Ag., Plocamium cartilagineum (L.) Dix., Antithamnionella sp. and Ulva lobata (Kuetz.) Setch. & Gardner. Epiphytism was seasonal; biomass maxima were recorded during the spring and summer from a depth of 6.2 m down. Except for Ulva, epiphyte biomass varied significantly (P less-than-or-equal-to 0.01) with seasons, depths and their interactions. The two species of Ceramium posed the most serious problem because of their widespread occurrence, both seasonally and bathymetrically, and their high biomass, particularly in the bathymetric range in which Gracilaria is harvested. Additionally, profuse epiphytism by three taxa of red foliose algae, Nitophyllum, Rhodophyllis and Callophyllis, was recorded at depths between 7.5 to 8.7 m. However, in spite of the fact that in summer their biomass was significantly higher (P less-than-or-equal-to 0.01) than that of Ceramium, they were of lesser concern because they colonize Gracilaria below the harvestable range of the bed. Damage caused by epiphytes might be a consequence of increased algal drag (by red folioses and Ulva) and weakening of the thalli of Gracilaria by penetration of rhizoids (by Ceramium spp.).