The ecology of the giant limpet Patella laticostata on intertidal limestone platforms at Rottnest Island, Western Australia

Abstract

Populations of the giant limpet Patella laticostata were studied on the wave-beaten seaward edge of intertidal limestone platforms at Rottnest Island. Individuals had feeding territories which consisted of small pits in the shallow subtidal/low intertidal region (pitted zone) and larger, more evenly-spaced terraces somewhat higher on the shore (terraced zone). Populations were concentrated in areas of high wave impact, where average densities were 1-4 limpets 0.25m⁻². The size of Patella laticostata was positively correlated with the area of its feeding territory, and limpets in the pitted zone generally were smaller than those in the terraced zone. The growth rate of Patella laticostata was lower in the pitted zone than in the terraced zone, possibly due to spatial constraints on feeding in pits. An isolated population of Patella laticostata in the low intertidal zone of an undercut rock face had an intermediate growth rate. The gonad index of Patella laticostata did not differ between sexes and there was an even sex ratio. Mark-recovery studies indicated that there was little net displacement of individuals over a year, and that survival rate was potentially high (up to 92%) in adult populations. The shell of Patella laticostata often was overgrown with turf-forming algae, except in those individuals with an epizoic acmaeid limpet (Patelloida nigrosulcata). Patella laticostata dominates the low intertidal community at the edge of wave-exposed platforms and its grazing appears to maintain a coralline-algal dominated "barren zone" in these areas.