Coral Transplantation: Regeneration and Growth of Acropora Fragments in a Nursery

Abstract Coral reef degradation has been widely reported for the past 20 years. Because the recovery rate is usually low, various methods of restoration have been explored in different regions of the world. Among the effective and commonly used methods to restore coral communities is the transplantation of coral colonies or fragments. In this investigation fragments of Acropora pulchra were used in a semiprotected nursery in southern Taiwan between 1996 and 1998 to test, in situ, the possible effects of different factors on the generation of new branches and the initial skeletal extension rates of transplants. The variables under study here were the origin and length of the fragments, their new orientation, presence of tissue injury, and position in the fragment. All these factors were found to make a difference in either one or both aspects of coral growth (i.e., branching frequency and skeletal extension rate). These two factors clearly determine the success rate of a small fragment developing into a large colony that has a much higher probability to survive and grow on its own. It is now obvious that the efficiency of coral generation through fragment culture can be enhanced if the variables examined here are taken into consideration. Once coral colonies are formed, they can be fragmented again to generate more corals or can be transplanted to a suitable site.     

Millennial-scale dynamics of staghorn coral in Discovery Bay, Jamaica

Populations of the staghorn coral, Acropora cervicornis, collapsed throughout the Caribbean region from the late 1970s through the 1990s. We tested the hypothesis that this recent, multidecadal interruption in coral growth was a novel event in the late Holocene. Eight cores, extracted from a lagoonal reef in Discovery Bay, Jamaica dated to 440–1260 CalBP and consisted almost entirely of A. cervicornis rubble. The A. cervicornis in the cores showed significantly less internal bioerosion than A. cervicornis from modern death assemblages in Discovery Bay, indicating generally shorter post‐mortem exposure at the sediment–water interface in the past. A. cervicornis grew continuously and was buried rapidly during the millennium preceding the 1980s, with the exception of a possible hiatus in growth and burial at some point 300–600 years ago. In the 1980s, a combination of perturbations, which included overfishing and (possibly) other forms of human interference, caused an unprecedented disruption in the growth and burial of staghorn coral populations in Discovery Bay.     

Bimodal signatures of germline methylation are linked with gene expression plasticity in the coral Acropora millepora

Background

In invertebrates, genes belonging to dynamically regulated functional categories appear to be less methylated than “housekeeping” genes, suggesting that DNA methylation may modulate gene expression plasticity. To date, however, experimental evidence to support this hypothesis across different natural habitats has been lacking.

Results

Gene expression profiles were generated from 30 pairs of genetically identical fragments of coral Acropora millepora reciprocally transplanted between distinct natural habitats for 3 months. Gene expression was analyzed in the context of normalized CpG content, a well-established signature of historical germline DNA methylation. Genes with weak methylation signatures were more likely to demonstrate differential expression based on both transplant environment and population of origin than genes with strong methylation signatures. Moreover, the magnitude of expression differences due to environment and population were greater for genes with weak methylation signatures.

Conclusions

Our results support a connection between differential germline methylation and gene expression flexibility across environments and populations. Studies of phylogenetically basal invertebrates such as corals will further elucidate the fundamental functional aspects of gene body methylation in Metazoa.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-1109) contains supplementary material, which is available to authorized users.     

Characterization of fatty acid composition in healthy and bleached corals from Okinawa, Japan

Under bleaching conditions, corals lose their symbiotic zooxanthellae, and thus, the ability to synthesize fatty acids (FAs) from photosynthetically derived carbon. This study investigated the lipid content and FA composition in healthy and bleached corals from the Odo reef flat in Okinawa, southern Japan, following a bleaching event. It was hypothesized that the FA composition and abundance would change as algae are lost or die, and possibly microbial abundance would increase in corals as a consequence of bleaching. The lipid content and FA composition of three healthy coral species (Pavona frondifera, Acropora pulchra, and Goniastrea aspera) and of partially bleached and completely bleached colonies of P. frondifera were examined. The FA composition did not differ among healthy corals, but differed significantly among healthy, partially bleached, and completely bleached specimens of P. frondifera. Completely bleached corals contained significantly lower lipid and total FA content, as well as lower relative amounts of polyunsaturated FAs and higher relative amounts of saturated FAs, than healthy and partially bleached corals. Furthermore, there was a significantly higher relative concentration of monounsaturated FAs and odd-numbered branched FAs in completely bleached corals, indicating an increase in bacterial colonization in the bleached corals.     

Archetypal ‘elkhorn’ coral discovered in the Pacific Ocean

The discovery of a population of elkhorn corals in the Central Pacific Ocean has important taxonomic implications, as this distinctive colony morphology was previously known only from the endemic and critically endangered Atlantic species Acropora palmata. Phylogenetic analyses confirmed that the Pacific elkhorn coral is genetically distant from A. palmata, and most likely represents a species previously synonymized with Acropora abrotanoides. The Pacific elkhorn coral is rare, and is of particular scientific interest because it represents one morphological extreme in the dominant genus of reef-building corals. The discovery of the Pacific elkhorn coral raises a number of important general issues in relation to biodiversity conservation, as this coral would not qualify for threatened species listing under current IUCN categories and criteria despite being demonstrably rare.     

Photosynthetic activity of a temperate coral Acropora pruinosa (Scleractinia, Anthozoa) with symbiotic algae in Japan

Physiological properties of the temperate hermatypic coral Acropora pruinosa Brook with symbiotic algae (zooxanthellae) on the southern coast of the Izu Peninsula, Shizuoka Prefecture, central Japan, were compared between summer and winter. Photosynthesis and respiration rates of the coral with symbiotic zooxanthellae were measured in summer and winter under controlled temperatures and irradiances with a differential gasvolumeter (Productmeter). Net photosynthetic rate under all irradiances was higher in winter than in summer at the lower range of temperature (12–20°C), while lower than in summer at the higher range of temperature (20–30°C). The optimum temperature for net photosynthesis was apt to fall with the decrease of irradiance both in summer and winter, whereas it was higher in summer than in winter under each irradiance. At 25/ 50/100 μmol photons nr² s^?1, it was nearly the sea‐water temperature in each season. Dark respiration rate was higher in winter than in summer, especially in the range from 20–30°C. In both seasons the optimum temperature for gross photosynthesis was 28°C under 400 μmol photons nr² s^?1 and lowered with decreasing irradiance up to 22°C under 25 μmol photons nr² s^?1 in summer, while 20°C under the same irradiance in winter. The optimum temperature for production/respiration (P/R) ratio was higher in summer than in winter under each irradiance. Results indicated that metabolism of coral and zooxanthellae is adapted to ambient temperature condition under nearly natural irradiance in each season.