Recovery from disturbance of coral and reef fish communities on the Great Barrier Reef, Australia

Abstract

Coral reefs are consistently and increasingly subject to acute disturbance events that often lead to a reduction in live coral cover with concomitant effects on the diversity and abundance of coral reef fishes. Here we examine changes in both hard coral and reef-fish assemblages over 15 yr following major losses of coral from exposed reefs in 2 widely separated sectors of the Great Barrier Reef (GBR), Australia. While the rate and extent of increase in coral cover (from <15 to >60%) was similar in the 2 sectors, differences in the rugosity of the underlying reef framework influenced the structure of fish communities. Soon after disturbance, when coral cover was very low and the limestone reef framework constituted most of the surface relief, the relatively featureless substrate on reefs of the southern sector supported fewer fish species than reefs of the northern sector, which had a more rugose substrate. At first, northern reefs also had a higher proportion of herbivorous fish species, presumably because the more complex reef surface provided shelter and allowed them to exploit the abundant algal turf. With increasing coral cover, coral colonies came to provide most of the surface relief in both sectors, and species richness and the trophic structure of the fish communities converged. Variation in the cover of branching corals explained significant variation in the fish communities in both sectors over time, reflecting the importance of this growth form to small coralassociated fishes. These results show that the recovery of the coral community and the complexity of underlying reef framework interact to determine the functional structure of associated fish communities despite differences in regional settings.