Size matters: bleaching dynamics of the coral Oculina patagonica

Abstract

A 2-yr continuous photographic monitoring of a tagged population of the encrusting coral Oculina patagonica in the Mediterranean was conducted to study intra-colonial bleaching dynamics and the relationship between bleaching, mortality, and colony size. Surveys of non-tagged colonies showed that during the peak bleaching season (August, sea surface temperature = 31°C), non-bleached colonies were frequently found to be small colonies averaging 4.6 ± 2.3 cm in diameter. Within tagged colonies, percent bleached surface area was correlated to water temperature. In colonies that underwent bleaching, the perimeter of the colony was affected first, and, as water temperatures increased, bleaching progressed toward the colony center. During the summer months, partial mortality occurred in the perimeter region of bleached colonies in 22% of the tagged colonies and 25% of the tagged colonies died; 40% of the colonies that died belonged to the largest size group. This partial mortality caused an average decline of 46 ± 27% in the average colony size, resulting in a shift to a smaller size group within the monitored population. Since in this species, colonies as small as 2 cm in diameter are reproductive, bleaching may have a less significant effect on the reproductive fitness of the small size groups in the population. The high mortality of large colonies, high survivorship of the small colonies, and the decline in colony size, due to partial mortality, suggest that, in the case of bleaching in populations of O. patagonica, small colony size is advantageous.

Breakdown of the coral-algae symbiosis: towards formalising a linkage between warm-water bleaching thresholds and the growth rate of the intracellular zooxanthellae

“…Individual colony bleaching patterns, which typically proceed from the tips or edges towards the base or centre (see e.g. Shenkar et al, 2005), also conform to the known colonyscale topology of MI, wherein the tips and edges consistently contain zooxanthellae with higher MI (Fang and Chen, 1989;Jones and Yellowlees, 1997). Indeed, Wooldridge (2009a) uses the ATP-dependent CO 2 -limitation model (Fig.…”

Repeated bleaching events may result in high tolerance and notable gametogenesis in stony corals: Oculina patagonica as a model

“…80% of the colonies undergo bleaching (Kushmaro et al 1998, Israely et al 2001, Fine & Loya 2003. When the water temperature drops, most of the colonies regain their symbiotic algae and recover (Shenkar et al 2005). O. patagonica is a gonochoric coral, in which female and male gonads appear in May and July (respectively) and reach maturity by late August.…”

Impact of the 2005 coral bleaching event on Porites porites and Colpophyllia natans at Tektite Reef, US Virgin Islands

“…Baird and Marshall (2002) reported no association between colony size class and bleaching mortality for scleractinian coral of reproductive size at two locations on the Great Barrier Reef. In contrast, Shenkar et al (2005) reported that large Oculina patagonica coral colonies had higher mortality from bleaching than small colonies, which were less likely to bleach for a site in the Mediterranean Sea. Hoeksema (1991) reported a similar result for Fungiidae corals in the Java Sea.…”

“…Coral bleaching diVerentially aVects coral species (Marshall and Baird 2000), coral morphology types (Wnger corals having higher mortality than mounding corals) (Loya et al 2001), and colony size-frequency distributions by removing larger sized colonies (Hoeksema 1991;Loya et al 2001;Shenkar et al 2005). Recently, Ritchie (2006) showed the loss of antibodies in Acropora palmata mucus during 2005 summer bleaching in the Florida Keys.…”