Rapid transition in the structure of a coral reef community: The effects of coral bleaching and physical disturbance

Abstract

Coral reef communities are in a state of change throughout their geographical range. Factors contributing to this change include bleaching (the loss of algal symbionts), storm damage, disease, and increasing abundance of macroalgae. An additional factor for Caribbean reefs is the aftereffects of the epizootic that reduced the abundance of the herbivorous sea urchin, Diadema antillarum. Although coral reef communities have undergone phase shifts, there are few studies that document the details of such transitions. We report the results of a 40-month study that documents changes in a Caribbean reef community affected by bleaching, hurricane damage, and an increasing abundance of macroalgae. The study site was in a relatively pristine area of the reef surrounding the island of San Salvador in the Bahamas. Ten transects were sampled every 3-9 months from November 1994 to February 1998. During this period, the corals experienced a massive bleaching event resulting in a significant decline in coral abundance. Algae, especially macroalgae, increased in abundance until they effectively dominated the substrate. The direct impact of Hurricane Lili in October 1996 did not alter the developing community structure and may have facilitated increasing algal abundance. The results of this study document the rapid transition of this reef community from one in which corals and algae were codominant to a community dominated by macroalgae. The relatively brief time period required for this transition illustrates the dynamic nature of reef communities.

The Coral Reefs of Eilat — Past, Present and Future: Three Decades of Coral Community Structure Studies

“…Coral mass mortality on reefs may result from a variety of causes such as (below selected references) mechanical destruction during tropical storms (Woodley et al 1981;Rogers 1993), abnormally low or high seawater temperatures (Glynn 1981;Jokiel and Coles 1990), sedimentation (Loya 1976e;Rogers 1990) exposure to air during midday air temperature maxima (Glynn 1976;Loya 1976a), bleaching (Glynn 1993;Brown 1997;Hoegh-Guldberg 1999;Ostrander et al 2000;Loya et al 2001), diseases (Kushmaro et al 1996;Harvell et al 1999), Acanthaster predation (Lourey et al 2000) and anthropogenic activities (Brown and Howard 1985;Nystrom et al 2000). The period of time required for recruitment and recovery of reefs after such disturbances varies from very short (2 years; Shinn 1972) to prolonged (50 years or more; Grigg and Maragos 1974;Pearson 1981) and largely depends on local settings.…”

Endolithic algae: an alternative source of photoassimilates during coral bleaching

“…It threatens coral reefs throughout the world, causing mortality and, in some cases, local extinctions (Wilkinson 1999;Hoegh-Guldberg 1999). However, some coral species have been shown to survive severe bleaching events (Glynn 1993;Brown 1997;Hoegh-Guldberg 1999;Wilkinson 2000;Loya et al 2001), leading to major structural shifts in some coral communities (Glynn 1993;Brown 1997;Ostrander et al 2000;Loya et al 2001). One of the most intriguing questions being asked by coral reef researchers is why some coral species, mostly of massive and encrusting growth forms, survive bleaching events, while others do not.…”

Membrane lipids of symbiotic algae are diagnostic of sensitivity to thermal bleaching in corals

“…C oral bleaching on a global scale is a growing concern because of both the reduction in essential ecological services provided by zooxanthellate corals within reef communities (1,2) and the potentially devastating economic impacts accompanying the phenomenon (3). Small, positive deviations in temperature of Ͻ2°C can trigger massive losses of symbiotic algae, Symbiodinium spp., from their cnidarian host cells (4).…”