Resilience to Large-Scale Disturbance in Coral and Fish Assemblages on the Great Barrier Reef

Recognition of the complex spatial and temporal variability of abundance and diversity found in many populations has led to a greater focus on the roles of heterogeneity, stochasticity, and disturbance in the structure and persistence of communities. This focus is directly relevant to coral reef communities that are characterized by very high species diversity in a spatially heterogeneous environment, display stochastic variability in community structure at small spatial and temporal scales, and are subject to major disturbances. We monitored coral and fish assemblages over 14 years on fixed sites spread over 80 km of the southern Great Barrier Reef (GBR), Australia, and found evidence of large-scale resilience and predictable recovery of these assemblages. Sometime between November 1987 and October 1989, live coral cover on the shallow northeast flanks of some reefs in the southern GBR decreased from >80% to <10%, probably as a result of storm damage. We compared the fish and benthic communities present in these areas prior to the disturbance (1983–1984) with those present in 1992 and the subsequent changes through to 1998. Hard coral cover increased slowly from 1992 to 1994, then accelerated to be indistinguishable from pre-impact levels by 1998. The response of the coral assemblages was largely due to the predominance of tabulate Acropora species and their characteristics of rapid growth and competitive dominance. Patterns of species richness of the fish families Acanthuridae, Chaetodontidae, Scaridae, and Pomacentridae mirrored that of hard coral, except the Pomacentridae had not recovered to pre-impact levels by 1998. Of the 26 fish species analyzed for changes in abundance, 88% decreased after the disturbance, then subsequently increased, with all but two recovering to pre-impact levels by 1998. Although processes such as settlement and immigration are ultimately responsible for replenishment of local populations, our data suggested that habitat plays a strong role in modifying fish assemblages. Thus, both coral and fish assemblages demonstrated resilience to large-scale natural disturbance and predictability in the structure of the assemblages, with most taxa approaching the asymptote of abundance and species richness that existed prior to the disturbance.