EFFECTS OF SHORE HEIGHT AND VISITOR PRESSURE ON THE DIVERSITY AND DISTRIBUTION OF FOUR INTERTIDAL TAXA AT LABRADOR BEACH, SINGAPORE

Abstract

To date, the majority of research on the rocky intertidal has focused on temperate rocky shore communities whereas study sites in the tropics have been relatively distant from the equator. We examined four key groups of marine organisms, i.e. macroalgae, anthozoans, decapods and gastropods, in relation to shore height and visitor pressure, at Labrador beach, Singapore (just 1°16.0'N). To reveal any vertical zonation the shore was divided into four 10m-wide zones, parallel to shore, approximately spanning high to low spring tide marks. To determine the effects of visitor pressure, the shore was also divided horizontally into three 60m long sectors; representing a gradient in distance from the public entrance to the beach. Sampling data from quadrats positioned randomly within these zones and sectors were converted into Shannon-Wiener and Margalef diversity index scores. The number of visitors to each horizontal sector was monitored, and the substrate composition in the sampled areas was assessed using point intercept transects. A total of 28 genera of macroalgae, 14 genera of anthozoans, 20 genera of decapods and 25 genera of gastropods were identified. Diversity scores for macroalgae, anthozoans and decapods were highly significantly different among the different shore heights, with the highest diversity found in the lower shore zones. Anthozoan diversity in the sector closest to the entrance of the beach, where the highest numbers of visitors were recorded, was significantly lower than the sectors further away. It requires further work, however, to identify the extent to which visitor pressure may affect marine organism diversity and distribution in the intertidal zone at Labrador Park.