Wave exposure, shore level, and season of clearing modulate early algal abundance and succession in an intertidal zone

Abstract

SUMMARYZonation patterns and the structure of intertidal communities are controlled by tidal conditions. Algal diversity, abundance and succession were experimentally tested under different degrees of wave exposure, shore level, and season of clearing at the intertidal zone, Phuket, Thailand. Dead coral patches colonized by algae (20 cm × 20 cm) were cleared at upper, middle, and lower shore levels on sheltered and semi‐exposed shores during both the dry and rainy seasons. Of 17 algal species, including eight Rhodophyta, eight Chlorophyta, and one Phaeophyceae that were recruited on the cleared plots, three species were dominant: Ulva paradoxa, Padina in the Vaughaniella stage, and Polysiphonia sphaerocarpa. Algal diversity on the semi‐exposed shore was higher than on the sheltered shore. In the successional process, U. paradoxa extensively recruited and persisted longer on plots cleared at the middle shore level on the semi‐exposed shores than at the other. It showed a greater abundance in the plots cleared in the rainy season than those cleared in the dry season. Ulva paradoxa persisted for around 5 to 6 months after clearing and was then replaced by the two later species, Padina in the Vaughaniella stage and P. sphaerocarpa. Ulva paradoxa settled more easily and persisted longer at the cleared plots than other algal species because of its opportunistic characteristics and a special physiological adaptation to long periods of emersion. From this study, degree of wave exposure, shore level, and season of clearing likely play important roles in algal recruitment, abundance, and succession patterns.