Long-term effects of the 1998 coral bleaching event on reef fish assemblages

Abstract

Coral bleaching events constitute compound disturbances often resulting in coral death as well as successive degradation of the reef framework. The 1997/1998 El Niño Southern Oscillation (ENSO) was the most severe on record and affected coral reefs worldwide. The present study examined the response of fish assemblages in plots of transplanted coral before and after the 1998 bleaching. Multidimensional scaling ordinations (MDS) demonstrate significant changes in assemblage composition related to habitat alteration. Within-site variability increased with disturbance, the increase being most apparent following substrate erosion. The differences in long-term responses as opposed to short-term responses were striking. Six mo after coral death, total abundance as well as taxonomic richness had increased at one of the sites, but not the other, whereas 6 yr later, both measures had decreased significantly at both sites. Functional groups, with documented affiliations with coral, were significantly influenced by the habitat alteration. Herbivore abundance increased as an immediate response to bleaching, but was subsequently decimated in eroded habitat. The loss of structural complexity had major detrimental effects on the entire fish community. In conclusion, we present evidence of severe and long-lasting secondary impacts of a catastrophic bleaching event, with no apparent recovery. The discrepancies between short-term and long-term responses underline the importance of long-term monitoring of fish assemblages following habitat alteration.

Ecosystem structure and processes at Kaloko Honokohau, focusing on the role of herbivores, including the green sea turtle Chelonia mydas, in reef resilience

“…Some evidence suggests that even robust herbivorous reef fish populations may be capable of maintaining only 50 to 65% of the substratum in a cropped state (Williams et al 2001). Although herbivorous fish may be capable of increasing their grazing rates and/or population sizes in response to higher algal production, evidence for this in the published literature is limited (McClanahan et al 1999, Williams et al 2001, Garpe et al 2006. Moreover, herbivorous reef fish, with the exception of Naso spp.…”

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

“…Wave action removed most of the living coral colonies in both sectors, but a salient difference between reefs in the 2 locations was the rugosity of the underlying calcareous reef substrate (substrate complexity), which was flat on southern reefs but more complex and rugose in the northern sector. We suspect that the particularly low topographic complexity in the CB sector provided inadequate shelter for many species, leading to lower abundance and diversity (Almany 2004, Dominici-Arosemena & Wolff 2005, Garpe et al 2006. Without cover and refuges, the risk of predation would have increased, and competition for available shelter would have intensified.…”

“…The recent literature concerning the state of coral reefs is mostly based on short or intermittent time scales, limited by the time scale for academic funding (HoeghGuldberg 1999, Goreau et al 2000, Bellwood et al 2004, Garpe et al 2006. Coral reefs are dynamic systems that are frequently affected by various forms of disturbance (Connell 1978, Hughes & Jackson 1985, Hughes 1989, Done 1992, Bythell et al 2000, Kleypas & Eakin 2007, but corals grow slowly relative to the duration of research grants: even fast-growing corals such as tabulate Acropora spp.…”

“…There have been many studies of short-term responses of fish communities to disturbance and a few longer term studies showing that reef-fish diversity and abundance decline with declining coral cover , Garpe et al 2006). However, very few studies have been sustained for long enough to record changes in reef fish assemblages as the coral recovered, and results to date are variable.…”

Responses of reef fish communities to coral declines on the Great Barrier Reef

“…tropical storms). However, subsequent erosion of coral skeletons without coral recruitment will gradually reduce topographic complexity and may have lagged detrimental effects on entire fish communities (Garpe et al 2006). The structural complexity of the underlying substrate will also moderate effects of coral losses on reef fishes; highly rugose substrates may support diverse fish communities even if corals are removed, while flat substrates may not (Halford et al 2004, Emslie et al in press).…”