Spatial pattern of intertidal macroalgal assemblages associated with tidal levels

Abstract

The zonation pattern of macroalgal assemblages was investigated from December 1995 to October 1996 on a semi-exposed, rocky intertidal shore at Chungdori (southwestern Korea) based on quantitative and qualitative estimates of species occurrences in 31 permanent quadrats. Variation in cover associated with tidal levels was described for 30 species (that could be discerned with the unaided eyes) including three green, five brown and 22 red algae. Macroalgae inhabiting intertidal zone exhibited distinct zonation patterns. The number of species increased with decreasing intertidal height and was independent of season. The community was dominated by five species (Gloiopeltis furcata, Gelidium divaricatum, Ulva pertusa, Sargassum horneri, Hizikia fusiformis). The intertidal assemblage at the study site can be divided into two groups based on the number of species and the population structure with the division occurring at the critical level of 34 cm above MLW (mean low water). Gloiopeltis furcata, Gelidium divaricatum, Sargassum thunbergii, Monostroma grevillei, and Myelophycus simplex were more abundant in the upper shore zone and rapidly declined in abundance with depth, relative to all other species. Gelidium amansii, Pachymeniopsis elliptica, Hizikia fusiformis, Gigartina intermedia, Laurencia sp., Chondrus ocellatus, Corallina spp. and Gigartina tenella became more dominant in the lower shore zone.