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National Committee on Marine Sciences (NCMS)

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    Increased coral larval supply enhances recruitment for coral and fish habitat restoration
    Harrison, Peter L.; dela Cruz, Dexter W.; Cameron, Kerry A.; Cabaitan, Patrick C. (Frontiers Media SA, 2021-12-01)
    Loss of foundation reef-corals is eroding the viability of reef communities and ecosystem function in many regions globally. Coral populations are naturally resilient but when breeding corals decline, larval supply becomes limiting and natural recruitment is insufficient for maintaining or restoring depleted populations. Passive management approaches are important but in some regions they are proving inadequate for protecting reefs, therefore active additional intervention and effective coral restoration techniques are needed. Coral spawning events produce trillions of embryos that can be used for mass larval rearing and settlement on degraded but recoverable reef areas. We supplied 4.6 million Acropora tenuis larvae contained in fine mesh enclosures in situ on three degraded reef plots in the northwestern Philippines during a five day settlement period to initiate restoration. Initial mean larval settlement was very high (210.2 ± 86.4 spat per tile) on natural coral skeleton settlement tiles in the larval-enhanced plots, whereas no larvae settled on tiles in control plots. High mortality occurred during early post-settlement life stages as expected, however, juvenile coral survivorship stabilised once colonies had grown into visible-sized recruits on the reef by 10 months. Most recruits survived and grew rapidly, resulting in significantly increased rates of coral recruitment and density in larval-enhanced plots. After two years growth, mean colony size reached 11.1 ± 0.61 cm mean diameter, and colonies larger than 13 cm mean diameter were gravid and spawned, the fastest growth to reproductive size recorded for broadcast spawning corals. After three years, mean colony size reached 17 ± 1.7 cm mean diameter, with a mean density of 5.7 ± 1.25 colonies per m–2, and most colonies were sexually reproductive. Coral cover increased significantly in larval plots compared with control plots, primarily from A. tenuis recruitment and growth. Total production cost for each of the 220 colonies within the restored breeding population after three years was United States $17.80 per colony. A small but significant increase in fish abundance occurred in larval plots in 2018, with higher abundance of pomacentrids and corallivore chaetodontids coinciding with growth of A. tenuis colonies. In addition, innovative techniques for capturing coral spawn slicks and larval culture in pools in situ were successfully developed that can be scaled-up for mass production of larvae on reefs in future. These results confirm that enhancing larval supply significantly increases settlement and coral recruitment on reefs, enabling rapid re-establishment of breeding coral populations and enhancing fish abundance, even on degraded reef areas.
    We thank the Australian Centre for International Agricultural Research (ACIAR) for funding this research: grant ACIAR/FIS/2014/063 to PH, PC and J. Bennett. Thanks to ACIAR staff Chris Barlow, Ann Fleming, and Mai Alagcan for their ongoing support. Sincere thanks to the Galsim Family for use of Tanduyong Island as a field research base during the coral restoration fieldwork. We also thank staff and students at the Bolinao Marine Laboratory, Marine Science Institute, University of the Philippines, Diliman for their assistance with reef work: Elizabeth Gomez, Charlon Ligson, Rickdane Gomez and Fernando Castrence (including fish surveys), Marcos Ponce, Joey Cabasan, Sheldon Boco, Gabriel de Guzman, Albert Ponce, and Allan Abuan. We also thank Grant Cameron for field support and helping design, build and refine the prototype floating spawn catcher frames in 2016 and 2017.
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    Spatial planning insights for Philippine coral reef conservation using larval connectivity networks
    Pata, Patrick R.; Yñiguez, Aletta T. (Frontiers Media SA, 2021-10-06)
    The marine habitats of the Philippines are recognized to be some of the most biodiverse systems globally yet only 1.7% of its seas are designated as marine protected areas (MPAs) with varying levels of implementation. Many of these MPAs were established based on local-scale conservation and fisheries objectives without considering larger-scale ecological connections. The connectivity of reefs through larval dispersal is important in the regional-scale resilience against anthropogenic disturbances and is considered a significant criterion in planning for MPAs. In this study, we provide insights into the delineation of ecologically connected MPA networks using larval dispersal modeling and network analysis. We characterized the network properties of the Philippine coral reefs, organized as 252 reef nodes, based on the larval connectivity networks of a branching coral, sea urchin, and grouper. We then evaluated the distribution of the existing 1,060 MPAs relative to the connectivity patterns. All reef nodes were found to be highly interconnected with a mean shortest path ranging from 1.96 to 4.06. Reef nodes were then ranked according to their relative importance in regional connectivity based on five connectivity indices. Despite the between-organism and between-index variability in rankings, there were reefs nodes, mostly located offshore and at major straits, which consistently ranked high. We found that the distribution of existing MPAs partially capture some of the regional connectivity functions but there is a spatial mismatch between the primarily coastal MPAs and the high-ranking reef nodes. Furthermore, network partitioning identified subnetworks and dispersal barriers. The existing MPAs were found to be disproportionately distributed to a few subnetworks and that the largest subnetworks do not contain the greatest number of MPAs. Considering these gaps, we suggest expanding the coverage of protected areas especially in underrepresented reef networks to meaningfully capture national-scale connectivity and meet global conservation objectives.
    We would like to thank Dr. Vera Horigue and Andrew Torres for constructive comments and suggestions during the early versions of this paper. We also thank the members of the Biological Oceanography and Modeling of Ecosystems (BiOME) Laboratory who assisted in running model simulations.
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    Two hidden mtDNA-clades of crown-of-thorns starfish in the Pacific Ocean
    Yasuda, Nina; Inoue, Jun; Hall, Michael R.; Nair, Manoj R.; Adjeroud, Mehdi; Fortes, Miguel D.; Nishida, Mutsumi; Tuivavalagi, Nat; Ravago-Gotanco, Rachel; Forsman, Zac H.; Soliman, Taha; Koyanagi, Ryo; Hisata, Kanako; Motti, Cherie A.; Satoh, Noriyuki (Frontiers Media SA, 2022-04-27)
    Recurring outbreaks of crown-of-thorns starfish (COTS) severely damage healthy corals, especially in the Western Pacific Ocean. To obtain a better understanding of population genetics of COTS and historical colonization across the Pacific Ocean, complete mitochondrial genomes were sequenced from 243 individuals collected in 11 reef regions. Our results indicate that Pacific COTS (Acanthaster cf. solaris) comprise two major clades, an East-Central Pacific (ECP) clade and a Pan-Pacific (PP) clade, separation of which was supported by high bootstrap value. The ECP clade consists of COTS from French Polynesia, Fiji, Vanuatu and the Great Barrier Reef (GBR). The Hawaii population is unique within this clade, while California COTS are included in EPC clade. On the other hand, the PP clade comprises multiple lineages that contain COTS from Vietnam, the Philippines, Japan, Papua New Guinea, Micronesia, the Marshall Islands, GBR, Vanuatu, Fiji and French Polynesia. For example, a lineage of the PP clade, which has the largest geographic distribution, includes COTS from all of these locations. These results suggest two alternative histories of current geographic distributions of COTS in the Pacific Ocean, an ECP clade ancestry or Western Pacific clade ancestry. Although further questions remain to be explored, this discovery provides an evolutionary context for the interpretation of COTS population structure which will aid future coral reef research in the Pacific Ocean, and ultimately improve reef management of COTS.
    We thank the following people for their help with sample collection: Dr. Hugh Sweatman and the AIMS Bioresources Library for GBR samples, Dr. Molly Timmers for Hawaiian samples, Geoff Jones and Jeff Kinch for Papua New Guinean samples, Monal Lal for Fijian samples, Christina Shaw for Vanuatu samples, Hoang Dinh Chieu for Vietnamese samples, and Hiromitsu Ueno for Japanese samples. The DNA Sequencing Section and IT section of OIST are acknowledged for its expert help with genome sequencing and bioinfomatic analysis. Last, but not least, we acknowledge the traditional owners of the lands and sea country on which this research took place.