Two divergent haplogroups of a sacsin-like gene in Acropora corals

Reef-building corals are declining due to environmental changes. Sacsin is a member of the heat shock proteins and has been reported as a candidate protein associated with the stress response in Acropora corals. Recently, high nucleotide diversity and the persistence of two divergent haplogroups of sacsin-like genes in Acropora millepora have been reported. While it was not clear when the two haplogroups have split and whether the haplogroups have persisted in only A. millepora or the other lineages in the genus Acropora. In this study, we analyzed a genomic region containing a sacsin-like gene from Acropora and Montipora species. Higher nucleotide diversity in the sacsin-like gene compared with that of surrounding regions was also observed in A. digitifera. This nucleotide diversity is derived from two divergent haplogroups of a sacsin-like gene, which are present in at least three Acropora species. The origin of these two haplogroups can be traced back before the divergence of Acropora and Montipora (119 Ma). Although the link between exceptionally high genetic variation in sacsin-like genes and functional differences in sacsin-like proteins is not clear, the divergent haplogroups may respond differently to envionmental stressors and serve in the adaptive phsiological ecology of these keystone species.

Broad scale proteomic analysis of heat-destabilised symbiosis in the hard coral Acropora millepora

Coral reefs across the globe are threatened by warming oceans. The last few years have seen the worst mass coral bleaching events recorded, with more than one quarter of all reefs irreversibly impacted. Considering the widespread devastation, we need to increase our efforts to understanding the physiological and metabolic shifts underlying the breakdown of this important symbiotic ecosystem. Here, we investigated the proteome (PRIDE accession # PXD011668) of both host and symbionts of the reef-building coral Acropora millepora exposed to ambient (~ 28 °C) and elevated temperature (~ 32 °C for 2 days, following a five-day incremental increase) and explored associated biomolecular changes in the symbiont, with the aim of gaining new insights into the mechanisms underpinning the collapse of the coral symbiosis. We identified 1,230 unique proteins (774 host and 456 symbiont) in the control and thermally stressed corals, of which 107 significantly increased and 125 decreased in abundance under elevated temperature relative to the control. Proteins involved in oxidative stress and proteolysis constituted 29% of the host proteins that increased in abundance, with evidence of impairment to endoplasmic reticulum and cytoskeletal regulation proteins. In the symbiont, we detected a decrease in proteins responsible for photosynthesis and energy production (33% of proteins decreased in abundance), yet minimal signs of oxidative stress or proteolysis. Lipid stores increased > twofold despite reduction in photosynthesis, suggesting reduced translocation of carbon to the host. There were significant changes in proteins related to symbiotic state, including proteins linked to nitrogen metabolism in the host and the V-ATPase (-0.6 fold change) known to control symbiosome acidity. These results highlight key differences in host and symbiont proteomic adjustments under elevated temperature and identify two key proteins directly involved in bilateral nutrient exchange as potential indicators of symbiosis breakdown.

Optimasi Penggunaan Waktu Pembersihan untuk Suksesi Transplantasi Karang Acropora Millepora di Perairan Malang Rapat, Bintan

Tujuan penelitian ini adalah mengetahui pertumbuhan, tingkat kelangsungan hidup dan mengetahui pengaruh frekuensi waktu pembersihan terhadap keberhasilan transplantasi karang keras (Acropora millepora) di Perairan Malang Rapat, Bintan. Penelitian ini dilakukan dengan metode transplantasi menggunakan modul terbuat dari semen berbentuk balok. Transplantasi karang dilakukan dengan empat perlakuan, perlakuan A (fragmen dibersihkan setiap 1 minggu), perlakuan B (fragmen dibersihkan setiap 2 minggu), perlakuan C (fragmen dibersihkan setiap 3 minggu) dan perlakuan D (tidak ada pembersihan fragmen) dengan 5 kali pengulangan setiap perlakuan. Pengamatan dilakukan setiap minggu selama 12 minggu penelitian. Hasil penelitian menunjukkan pertumbuhan mutlak pada perlakuan A sebesar 14,94 ± 4,98 mm, perlakuan B sebesar 18,16 ± 5,93 mm, perlakuan C sebesar 12,30 ± 3,78 mm dan perlakuan D sebesar 12,22 ± 4,34 mm. Laju pertumbuhan fragmen karang pada perlakuan A sebesar 1,24 ± 0,41 mm/minggu, perlakuan B sebesar 1,51 ± 0,49 mm/minggu, perlakuan C sebesar 1,02 ± 0,31 mm/minggu, dan laju perlakuan D sebesar 1,01 ± 0,36 mm/minggu. Tingkat kelangsungan hidup fragmen karang Acropora millepora pada perlakuan A dan B sebesar 100% (tidak mengalami kematian), sedangkan perlakuan C dan D sebesar 83,08% (mengalami kematian). Hasil uji statistik menunjukkan terdapat perbedaan yang nyata antara pertumbuhan karang Acropora millepora berdasarkan perbedaan waktu pembersihan. Perlakuan B (pembersihan fragmen setiap 2 minggu sekali) merupakan perlakuan dengan pertumbuhan optimum.

Differences in genetic diversity and divergence between brooding and broadcast spawning corals across two spatial scales in the Coral Triangle region

The Coral Triangle region contains the world’s highest marine biodiversity, however, these reefs are also the most threatened by global and local threats. A main limitation that prevents the implementation of adequate conservation measures is that connectivity and genetic structure of populations is poorly known. The aim of this study was to investigate the genetic diversity, population structure and connectivity patterns of tropical corals in Indonesia on two different spatial scales, as well as by comparing two different reproduction strategies. Genotyping was based on microsatellite markers for 316 individual Seriatopora hystrix colonies and 142 Acropora millepora colonies sampled in Pulau Seribu and Spermonde Archipelago in 2012 and 2013. Differences in allelic diversity and a strong signature of divergence associated with historical land barriers at the Sunda Shelf were found for the brooding coral Seriatopora hystrix. However, differences in diversity and divergence were not pronounced in the broadcast spawning coral Acropora millepora. Within Spermonde Archipelago, two groups were identified: (1) sites of the sheltered inner-shelf and mid-shelf, which were found to be highly interconnected and (2) mid-shelf and outer-shelf sites characterised by higher differentiation. These patterns of contemporary dispersal barriers and genetic diversity can be explained by the differences in life history of the corals, as well as by oceanographic conditions facilitating larval dispersal. The contemporary dispersal barriers found within the Spermonde Archipelago emphasise the need for incorporating connectivity data in future conservation efforts.

Life-Long Coral Skeletal Acclimatization at CO2 Vents in Papua New Guinea Reveals Species- and Environment-Specific Effects

The responses of corals and other marine calcifying organisms to ocean acidification (OA) are variable and span from no effect to severe responses. Here we investigated the effect of long-term exposure to OA on skeletal parameters of four tropical zooxanthellate corals living at two CO2 vents in Papua New Guinea, namely in Dobu and Upa Upasina. The skeletal porosity of Galaxea fascicularis, Acropora millepora, and Pocillopora damicornis was higher (from 17% to 38%, depending on the species) at the seep site compared to the control only at Upa Upasina. Massive Porites showed no differences at any of the locations. Pocillopora damicornis also showed a ~ 7% decrease of micro-density and an increase of the volume fraction of the larger pores, a decrease of the intraskeletal organic matrix content with an increase of the intraskeletal water content, and no variation in the organic matrix related strain and crystallite size. The fact that the skeletal parameters varied only at one of the two seep sites suggests that other local environmental conditions interact with OA to modify the coral skeletal parameters. This might also contribute to explain the great deal of responses to OA reported for corals and other marine calcifying organisms.

Thermal stability and structure of glyceraldehyde-3-phosphate dehydrogenase from the coral Acropora millepora

The thermal stability of a critical coral metabolic enzyme increases significantly in the presence of its cofactor. X-ray crystallography identifies the protein backbone changes associated with cofactor occupancy.