Geographic and habitat partitioning of genetically distinct zooxanthellae (Symbiodinium) in Acropora corals on the Great Barrier Reef

Abstract

Intra- and intercolony diversity and distribution of zooxanthellae in acroporid corals is largely uncharted. In this study, two molecular methods were applied to determine the distribution of zooxanthellae in the branching corals Acropora tenuis and A. valida at several reef locations in the central section of the Great Barrier Reef. Sun-exposed and shaded parts of all colonies were examined. Single-stranded conformational polymorphism analysis showed that individual colonies of A. tenuis at two locations harbour two strains of Symbiodinium belonging to clade C (C1 and C2), whereas conspecific colonies at two other reefs harboured a single zooxanthella strain. A. valida was found to simultaneously harbour strains belonging to two distinct phylogenetic clades (C and D) at all locations sampled. A novel method with improved sensitivity (quantitative polymerase chain reaction using Taqman fluorogenic probes) was used to map the relative abundance distribution of the two zooxanthella clades. At two of the five sampling locations both coral species were collected. At these two locations, composition of the zooxanthella communities showed the same pattern in both coral species, i.e. correlation with ambient light in Pioneer Bay and an absence thereof in Nelly Bay. The results show that the distribution of genetically distinct zooxanthellae is correlated with light regime and possibly temperature in some (but not all) colonies of A. tenuis and A. valida and at some reef locations, which we interpret as acclimation to local environmental conditions.

Fluctuating algal symbiont communities in Acropora palifera (Scleractinia: Acroporidae) from Taiwan

“…Nevertheless, this scenario should be corroborated by studying more coral species co-occurring in the same environment before a firm conclusion can be stated. Recent studies have taken the further step of suggesting that Phylotype D is a heat-tolerant Symbiodi- *PCR amplifications were unsuccessful due to the poor quality of the DNA extraction nium (Glynn et al 2001, Baker 2003a,b, 2004, Ulstrup & van Oppen 2003, Fabricius et al 2004, Little et al 2004, Rowan 2004. Glynn et al (2001) showed that Far-Eastern Pacific corals hosting Phylotype D symbionts had suffered less from the 1998 coral bleaching event than those coral associated with other symbiont phylotypes.…”

The role of zooxanthellae in the thermal tolerance of corals: a ‘nugget of hope’ for coral reefs in an era of climate change

“…Since, type D zooxanthellae did exist in some of the Keppel corals and was not evident in the Davies population, even after a long period of transplantation and despite bleaching, the change is likely to have been a shuffling of existing zooxanthella types. Low background levels of zooxanthella type D (as low as ca 0.001%) have been detected using quantitative PCR methods in C-dominated Acropora valida corals on the GBR (Ulstrup & van Oppen 2003), suggesting that this strategy is potentially available to other coral populations and species. However, the fact that Davies transplants did not change symbiont type suggests that symbiont switching may only take place under certain conditions.…”

Real-time PCR reveals a high incidence of Symbiodinium clade D at low levels in four scleractinian corals across the Great Barrier Reef: implications for symbiont shuffling

“…Clade C-and clade D-specific ITS1 primer pairs were obtained from Ulstrup and van Oppen (2003) (Table 2). A 25 ll real-time PCR reaction contained: 1· IQ SYBR Green supermix (BioRAD), 180 nM clade Symbiodiniumuniversal forward primer, 180 nM clade C-or D-specific reverse primer and 2.5 ll coral DNA template (MilliQ H 2 O in case of no-template controls).…”