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

Data are presented on the taxonomy and the temporal and spatial distri bution of the most prevalent epiphytic taxa in a natural subtidal bed of Gracilaria in central-southern Chile. Also, the nature of the epiph yte/basiphyte interface is described. Samples were collected from Apri l 1989 to July 1990 from 2.4 to 8.7 m. The following taxa were identif ied: Ceramium pacificum (Coll.) Kyl., Ceramium sp., Nitophyllum peruvi anum (Mont.) Howe, Callophyllis variegata (Bory) Kuetz., Callophyllis pinnata Setch. & Swezy, Rhodophyllis aff. acanthocarpa (Harv.) J. Ag., Plocamium cartilagineum (L.) Dix., Antithamnionella sp. and Ulva loba ta (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-o r-equal-to 0.01) with seasons, depths and their interactions. The two species of Ceramium posed the most serious problem because of their wi despread occurrence, both seasonally and bathymetrically, and their hi gh biomass, particularly in the bathymetric range in which Gracilaria is harvested. Additionally, profuse epiphytism by three taxa of red fo liose 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 ca used by epiphytes might be a consequence of increased algal drag (by r ed folioses and Ulva) and weakening of the thalli of Gracilaria by pen etration of rhizoids (by Ceramium spp.).