http://epubs.aims.gov.au/11068/43 2021-02-24T03:17:07Z 2021-02-24T03:17:07Z Thongtham, Nalinee Bronstein, Omri Eyal, Gal Hayashi, Tetsuya Yuasa, Hideaki Wada, Naohisa Ogura, Yoshitoshi Gotoh, Yasuhiro Yasuda, Nina Toyoda, Atsushi Tang, Sen-Lin Yoshimura, Dai Forsman, Zac Itoh, Takehiko Sweatman, Hugh Kajitani, Rei Higashimura, Yukihiro http://epubs.aims.gov.au/11068/16738 2021-02-23T22:21:36Z 2020-08-24T00:00:00Z

A ubiquitous subcuticular bacterial symbiont of a coral predator, the crown-of-updates thorns starfish, in the Indo-Pacific Thongtham, Nalinee; Bronstein, Omri; Eyal, Gal; Hayashi, Tetsuya; Yuasa, Hideaki; Wada, Naohisa; Ogura, Yoshitoshi; Gotoh, Yasuhiro; Yasuda, Nina; Toyoda, Atsushi; Tang, Sen-Lin; Yoshimura, Dai; Forsman, Zac; Itoh, Takehiko; Sweatman, Hugh; Kajitani, Rei; Higashimura, Yukihiro Background: Population outbreaks of the crown-of-thorns starfish (Acanthaster planci sensu lato; COTS), a primary predator of reef-building corals in the Indo-Pacific Ocean, are a major threat to coral reefs. While biological and ecological knowledge of COTS has been accumulating since the 1960s, little is known about its associated bacteria. The aim of this study was to provide fundamental information on the dominant COTS-associated bacteria through a multifaceted molecular approach. Methods: A total of 205 COTS individuals from 17 locations throughout the Indo-Pacific Ocean were examined for the presence of COTS-associated bacteria. We conducted 16S rRNA metabarcoding of COTS to determine the bacterial profiles of different parts of the body and generated a full-length 16S rRNA gene sequence from a single dominant bacterium, which we designated COTS27. We performed phylogenetic analysis to determine the taxonomy, screening of COTS27 across the Indo-Pacific, FISH to visualize it within the COTS tissues, and reconstruction of the bacterial genome from the hologenome sequence data. Results: We discovered that a single bacterium exists at high densities in the subcuticular space in COTS forming a biofilm-like structure between the cuticle and the epidermis. COTS27 belongs to a Glade that presumably represents a distinct order (so-called marine spirochetes) in the phylum Spirochaetes and is universally present in COTS throughout the Indo-Pacific Ocean. The reconstructed genome of COT527 includes some genetic traits that are probably linked to adaptation to marine environments and evolution as an extracellular endosymbiont in subcuticular spaces. Conclusions: COTS27 can be found in three allopatric COTS species, ranging from the northern Red Sea to the Pacific, implying that the symbiotic relationship arose before the speciation events (approximately 2 million years ago). The universal association of COT527 with COTS and nearly mono-specific association at least with the Indo-Pacific COTS provides a useful model system for studying symbiont-host interactions in marine invertebrates and may have applications for coral reef conservation.

2020-08-24T00:00:00Z Beltran, Victor H. Leggat, Bill Willis, Bette L. Alvarez Roa, Carlos Quigley, Kate M. http://epubs.aims.gov.au/11068/16737 2021-02-23T22:21:06Z 2021-02-04T00:00:00Z

Experimental evolution of the coral algal endosymbiont, Cladocopium goreaui: lessons learnt across a decade of stress experiments to enhance coral heat tolerance Beltran, Victor H.; Leggat, Bill; Willis, Bette L.; Alvarez Roa, Carlos; Quigley, Kate M. Projected increases in sea surface temperatures will exceed corals' ability to withstand heat stress within this century. Experimental evolution of cultured symbionts (Symbiodiniaceae) at high temperatures followed by reintroduction into corals can enhance coral heat tolerance. Several studies have selected for enhanced tolerance in Cladocopium goreaui (C1) over multiple time scales and then compared the performance of coral juveniles infected with the heat-tolerant C1 selected strain (SS) to the performance of juveniles infected with the C1 wild type (WT). To derive lessons about host benefits when symbionts are experimentally selected, here we compare the performance of SS- and WT-juveniles after 21 cell generations of heat selection versus longer periods (73-131) in recently published experiments. After 21 generations, we found rapid improvement in heat tolerance of SS through an overall shift in the mean tolerance to temperature. This did not translate to improved growth and survivorship of the coral. Specifically, survival did not differ significantly between juveniles of Acropora tenuis hosting WT versus SS at any temperature. Juveniles infected with WT exhibited greater skeletal growth than those infected with SS at 27 and 31 degrees C but not at 32.5 degrees C. SS-juvenile symbiont cell densities increased significantly at 27 degrees C relative to SS-juveniles in the 31 and 32.5 degrees C. Photosynthetic efficiencies in SS-juveniles were higher compared to WT-juveniles at 31 degrees C, equal at 27 degrees C, and lower at 32.5 degrees C. These results suggest that selection over longer generation (>130) times will be needed to confer host benefits and will be dependent on the stability of this association being maintained in nature.

2021-02-04T00:00:00Z Tilbrook, Bronte Smith, Joy N. Van Ooijen, Erik Neill, Craig Fabricius, Katharina E. http://epubs.aims.gov.au/11068/16736 2021-02-23T22:20:40Z 2020-10-27T00:00:00Z

Progressive seawater acidification on the Great Barrier Reef continental shelf Tilbrook, Bronte; Smith, Joy N.; Van Ooijen, Erik; Neill, Craig; Fabricius, Katharina E. Coral reefs are highly sensitive to ocean acidification due to rising atmospheric CO2 concentrations. We present 10 years of data (2009-2019) on the long-term trends and sources of variation in the carbon chemistry from two fixed stations in the Australian Great Barrier Reef. Data from the subtropical mid-shelf GBRWIS comprised 3-h instrument records, and those from the tropical coastal NRSYON were monthly seawater samples. Both stations recorded significant variation in seawater CO2 fugacity (fCO(2)), attributable to seasonal, daytime, temperature and salinity fluctuations. Superimposed over this variation, fCO(2) progressively increased by > 2.0 +/- 0.3 mu atm year(-1) at both stations. Seawater temperature and salinity also increased throughout the decade, whereas seawater pH and the saturation state of aragonite declined. The decadal upward fCO(2) trend remained significant in temperature- and salinity-normalised data. Indeed, annual fCO(2) minima are now higher than estimated fCO(2) maxima in the early 1960s, with mean fCO(2) now similar to 28% higher than 60 years ago. Our data indicate that carbonate dissolution from the seafloor is currently unable to buffer the Great Barrier Reef against ocean acidification. This is of great concern for the thousands of coral reefs and other diverse marine ecosystems located in this vast continental shelf system.

2020-10-27T00:00:00Z MARRA, JOHN SKIRVING, WILLIAM MCCALL, ROBERT STORLAZZI, CURT POMEROY, ANDREW http://epubs.aims.gov.au/11068/16718 2021-02-23T22:21:01Z 2021-01-07T00:00:00Z

Editorial: Flooding on Coral Reef-Lined Coasts: Current State of Knowledge and Future Challenges MARRA, JOHN; SKIRVING, WILLIAM; MCCALL, ROBERT; STORLAZZI, CURT; POMEROY, ANDREW

2021-01-07T00:00:00Z