Periodic mass-bleaching and elevated sea temperatures:bleaching of outer reef slope communities in Moorea, French Polynesia

Abstract

Mass-bleaching events (in which corals and other symbiotic invertebrates lose their zooxanthellae) have been occurring every 3 to 4 yr since 1979 The last report of widespread mass-bleaching in the Pacific (which included bleaching around French Polynesia) was in February-April 1991. This paper reports on mass-bleaching along the outer reef slope of Moorea. French Polynesia, in April 1994. Mass-bleaching was extensive at all sites visited, with corals being bleached down to 25 m. Colour loss by corals was due to low area1 densities of zooxanthellae and the percentage of live coral affected ranged between 39.6 (* 7.12, SEM) ( N W sites) and 72.4 (t 7.1 l , SEMI (NE sites). Bleaching also varied as a funct~on of depth and included a wide range of species Acropora spp. showed the most severe bleaching (89.0 to 100% of all colonies completely bleached) and Pontes spp. showed the least amount of bleaching (12 9 to 42.5'K of all colonies partly bleached). Pocillopora spp. showed intermediate bleaching (73.9 to 92.1 % of all colonies either partly or completely bleached). The results of this report indicate that current bleaching is on a scale equal to that of the 1991 bleaching event. Temperatures recorded hourly at 14 m off the outer reef slope from July 1991 to August 1994 (and those from satellite sea surface temperature readings) indicate unusually warm sea temperatures in March 1994, which were approximately l.O°C higher than the highest temperatures recorded in 1992 and 1993, years in which bleaching on a massive scale did not occur. The appearance of warmer temperatures preceded the onset of bleaching by 2 to 3 wk, which strongly confirms the hypothesis that positive thermal anomalies are responsible for recent bleaching events in the Central and Western Pacific.

Endosymbiotic flexibility associates with environmental sensitivity in scleractinian corals

“…In contrast, coral species with high symbiotic specificity (i.e. high fidelity with respect to Symbiodinium) such as massive environmentally resilient poritids are ecological 'winners' [62,63,69,70].…”

“…20-50%) and Porites (approx. 13-43%; [69]). Furthermore, the 'winning' and 'losing' taxa are relatively similar biogeographically [61,62] with the generalists Acropora and Pocillopora showing a higher propensity to bleach, and higher mortality than the specifists such as Porites [63].…”

The adaptation of coral reefs to climate change: Is the Red Queen being outpaced?

“…Evidence of differences in thermal tolerance between genera and shifts in community composition of corals in response to stresses such as rising sea tem-peratures are more abundant (Hoegh-Guldberg and Salvat 1995, Marshall and Baird 2000, McClanahan et al 2000, Loya et al 2001, Obura 2001, McClanahan et al 2002, Riegl 2002, Riegl 2003, McClanahan et al 2007, McGehee 2008, Carpenter et al 2008, McClanahan et al 2009, with broad differences in ther-, with broad differences in thermal tolerance between genera such as Acropora and Pocillopora (relatively sensitive) and Porites and Favia (less sensitive by 1-2°C). Recent studies that have highlighted the flexibility of community composition along latitudinal gradients such as those found down the Great Barrier Reef further emphasize that changes in community composition are a likely outcome of early phases of global climate change Hughes 2001, Hughes et al 2012).…”

Taxonomy of symbiotic dinoflagellates associated with Korean anthozoans

“…These symbiotic dinoflagelktes and their hosts are known to benefit each other, and the symbionts are directly rekted to the bleaching phenomenon of hermatypic corals (Hoegh-Guldberg and Salvat, 1995;Brown, 1997). However, biological studies about the symbiotic dinoflagelktes have never been performed in Korea, in spite of their importance to host survival.…”