Patterns of abundance and distribution of species in intertidal rock pools

Abstract

Rock pools are unique and complex habitats in intertidal areas. Quantitative studies of assemblages in pools are few. Abundances and distributions of species in pools on a rock platform near Sydney (Australia) were sampled for two years. Pools of four different depths (5, 15, 30 and 40 cm deep) and up to four strata within each pool (0–5, 5–15, 15–30 and 30–40 cm, from the top of the pool) were sampled, replicated at four sites. The abundances and distributions of most species of plants and animals in pools did not differ between strata nor at different depths in the pools. Abundances of only three species, the encrusting alga, Hildenbrandia prototypus Nardo, the trochid snail, Austrocochlea constricta (Lamarck) and the limpet, Cellana tramoserica (Sowerby) varied significantly between strata and depths. In contrast to other studies on rock pools, most species showed no significant temporal variations in mean abundances in the sites sampled. Significantly large, spatial and temporal, random fluctuations did, however, occur in abundances in individual pools. The consistency of abundances at larger spatial scales indicated that disturbance in these habitats may not be an important structuring process. The large variation between pools does, however, suggest that the history of each pool may have a more significant role in the character of its assemblage. Some implications of small-scale variability are discussed.