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Baletaud F, Lecellier G, Gilbert A, Mathon L, Côme JM, Dejean T, Dumas M, Fiat S, Vigliola L. Comparing Seamounts and Coral Reefs with eDNA and BRUVS Reveals Oases and Refuges on Shallow Seamounts. BIOLOGY 2023; 12:1446. [PMID: 37998045 PMCID: PMC10669620 DOI: 10.3390/biology12111446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Revised: 11/13/2023] [Accepted: 11/13/2023] [Indexed: 11/25/2023]
Abstract
Seamounts are the least known ocean biome. Considered biodiversity hotspots, biomass oases, and refuges for megafauna, large gaps exist in their real diversity relative to other ecosystems like coral reefs. Using environmental DNA metabarcoding (eDNA) and baited video (BRUVS), we compared fish assemblages across five environments of different depths: coral reefs (15 m), shallow seamounts (50 m), continental slopes (150 m), intermediate seamounts (250 m), and deep seamounts (500 m). We modeled assemblages using 12 environmental variables and found depth to be the main driver of fish diversity and biomass, although other variables like human accessibility were important. Boosted Regression Trees (BRT) revealed a strong negative effect of depth on species richness, segregating coral reefs from deep-sea environments. Surprisingly, BRT showed a hump-shaped effect of depth on fish biomass, with significantly lower biomass on coral reefs than in shallowest deep-sea environments. Biomass of large predators like sharks was three times higher on shallow seamounts (50 m) than on coral reefs. The five studied environments showed quite distinct assemblages. However, species shared between coral reefs and deeper-sea environments were dominated by highly mobile large predators. Our results suggest that seamounts are no diversity hotspots for fish. However, we show that shallower seamounts form biomass oases and refuges for threatened megafauna, suggesting that priority should be given to their protection.
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Affiliation(s)
- Florian Baletaud
- ENTROPIE, Institut de Recherche pour le Développement (IRD), UR, UNC, IFREMER, CNRS, Centre IRD de Nouméa, 98848 Noumea, New Caledonia, France; (F.B.); (G.L.); (L.M.); (M.D.); (S.F.)
- GINGER SOPRONER, 98000 Noumea, New Caledonia, France;
- GINGER BURGEAP, 69000 Lyon, France;
- MARBEC, University of Montpellier, CNRS, IFREMER, 34000 Montpellier, France
| | - Gaël Lecellier
- ENTROPIE, Institut de Recherche pour le Développement (IRD), UR, UNC, IFREMER, CNRS, Centre IRD de Nouméa, 98848 Noumea, New Caledonia, France; (F.B.); (G.L.); (L.M.); (M.D.); (S.F.)
- ISEA, University of New Caledonia, 98800 Noumea, New Caledonia, France
| | | | - Laëtitia Mathon
- ENTROPIE, Institut de Recherche pour le Développement (IRD), UR, UNC, IFREMER, CNRS, Centre IRD de Nouméa, 98848 Noumea, New Caledonia, France; (F.B.); (G.L.); (L.M.); (M.D.); (S.F.)
- CEFE, University of Montpellier, CNRS, EPHE-PSL, IRD, 34000 Montpellier, France
| | | | | | - Mahé Dumas
- ENTROPIE, Institut de Recherche pour le Développement (IRD), UR, UNC, IFREMER, CNRS, Centre IRD de Nouméa, 98848 Noumea, New Caledonia, France; (F.B.); (G.L.); (L.M.); (M.D.); (S.F.)
| | - Sylvie Fiat
- ENTROPIE, Institut de Recherche pour le Développement (IRD), UR, UNC, IFREMER, CNRS, Centre IRD de Nouméa, 98848 Noumea, New Caledonia, France; (F.B.); (G.L.); (L.M.); (M.D.); (S.F.)
| | - Laurent Vigliola
- ENTROPIE, Institut de Recherche pour le Développement (IRD), UR, UNC, IFREMER, CNRS, Centre IRD de Nouméa, 98848 Noumea, New Caledonia, France; (F.B.); (G.L.); (L.M.); (M.D.); (S.F.)
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Genomic insights into the historical and contemporary demographics of the grey reef shark. Heredity (Edinb) 2022; 128:225-235. [PMID: 35296830 PMCID: PMC8987070 DOI: 10.1038/s41437-022-00514-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 02/11/2022] [Accepted: 02/13/2022] [Indexed: 11/08/2022] Open
Abstract
Analyses of genetic diversity can shed light on both the origins of biodiversity hotspots, as well as the conservation status of species that are impacted by human activities. With these objectives, we assembled a genomic dataset of 14,935 single nucleotide polymorphisms from 513 grey reef sharks (Carcharhinus amblyrhynchos) sampled across 17 locations in the tropical Indo-Pacific. We analysed geographic variation in genetic diversity, estimated ancient and contemporary effective population size (Ne) across sampling locations (using coalescent and linkage disequilibrium methods) and modelled the history of gene flow between the Coral Triangle and the Coral Sea. Genetic diversity decreased with distance away from the Coral Triangle and north-western Australia, implying that C. amblyrhynchos may have originated in this region. Increases in Ne were detected across almost all sampling locations 40,000-90,000 generations ago (approximately 0.6-1.5 mya, given an estimated generation time of 16.4 years), suggesting a range expansion around this time. More recent, secondary increases in Ne were inferred for the Misool and North Great Barrier Reef sampling locations, but joint modelling did not clarify whether these were due to population growth, migration, or both. Despite the greater genetic diversity and ancient Ne observed at sites around Australia and the Coral Triangle, remote reefs around north-western New Caledonia had the highest contemporary Ne, demonstrating the importance of using multiple population size assessment methods. This study provides insight into both the past and present demographics of C. amblyrhynchos and contributes to our understanding of evolution in marine biodiversity hotspots.
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Morais RA, Siqueira AC, Smallhorn-West PF, Bellwood DR. Spatial subsidies drive sweet spots of tropical marine biomass production. PLoS Biol 2021; 19:e3001435. [PMID: 34727097 PMCID: PMC8562822 DOI: 10.1371/journal.pbio.3001435] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 10/04/2021] [Indexed: 11/18/2022] Open
Abstract
Spatial subsidies increase local productivity and boost consumer abundance beyond the limits imposed by local resources. In marine ecosystems, deeper water and open ocean subsidies promote animal aggregations and enhance biomass that is critical for human harvesting. However, the scale of this phenomenon in tropical marine systems remains unknown. Here, we integrate a detailed assessment of biomass production in 3 key locations, spanning a major biodiversity and abundance gradient, with an ocean-scale dataset of fish counts to predict the extent and magnitude of plankton subsidies to fishes on coral reefs. We show that planktivorous fish-mediated spatial subsidies are widespread across the Indian and Pacific oceans and drive local spikes in biomass production that can lead to extreme productivity, up to 30 kg ha-1 day-1. Plankton subsidies form the basis of productivity "sweet spots" where planktivores provide more than 50% of the total fish production, more than all other trophic groups combined. These sweet spots operate at regional, site, and smaller local scales. By harvesting oceanic productivity, planktivores bypass spatial constraints imposed by local primary productivity, creating "oases" of tropical fish biomass that are accessible to humans.
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Affiliation(s)
- Renato A. Morais
- Research Hub for Coral Reef Ecosystem Functions, College of Science and Engineering, James Cook University, Townsville, Australia
- ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Australia
| | - Alexandre C. Siqueira
- Research Hub for Coral Reef Ecosystem Functions, College of Science and Engineering, James Cook University, Townsville, Australia
- ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Australia
| | - Patrick F. Smallhorn-West
- ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Australia
- WorldFish, Bayan Lepas, Malaysia
| | - David R. Bellwood
- Research Hub for Coral Reef Ecosystem Functions, College of Science and Engineering, James Cook University, Townsville, Australia
- ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Australia
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Guillaume MMM, Séret B. Observations of sharks (Elasmobranchii) at Europa Island, a remote marine protected area important for shark conservation in the southern Mozambique Channel. PLoS One 2021; 16:e0253867. [PMID: 34610033 PMCID: PMC8491881 DOI: 10.1371/journal.pone.0253867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 06/15/2021] [Indexed: 11/19/2022] Open
Abstract
Sharks have declined worldwide and remote sanctuaries are becoming crucial for shark conservation. The southwest Indian Ocean is a hotspot of both terrestrial and marine biodiversity mostly impacted by anthropogenic damage. Sharks were observed during surveys performed from April to June 2013 in the virtually pristine coral reefs around Europa Island, a remote Marine Protected Area located in the southern Mozambique Channel. Observation events comprised 67 1-hour scientific dives between 5 – 35m depth and 7 snorkeling inspections, as well as 4 dinghy-based observations in the shallow lagoon. In a period of 24 days, 475 sharks were tallied. Carcharhinus galapagensis was most encountered and contributed 20% of the abundance during diving, followed by C. albimarginatus (10%). Both species were more abundant between 11-14h, and on the exposed sides of the island. Numbers of Sphyrna lewini were highest with 370 individuals windward and leeward, mostly schooling. S. lewini aggregations in the area are hypothesized to be attracted to the seamount archipelago offering favorable conditions for deep incursions and of which Europa Island forms part. C. amblyrhynchos, Galeocerdo cuvier and S. mokarran were uncommon, while there was an additional observation of Rhincodon typus. The lagoon of Europa was a nursery ground for C. melanopterus where it was the only species present. A total of 8 species was recorded, contributing to the shark diversity of 15 species reported from Europa since 1952 in the scientific and gray literature. Overall, with the occurrence of several species of apex predators in addition to that of R. typus, large schools of S. lewini, fair numbers of reef sharks and a nursery of C. melanopterus, Europa’s sharks constitute a significant reservoir of biodiversity, which contributes to preserve the functioning of the ecosystem. Our observations highlight the relevance of Europa Island for shark conservation and the need for shark-targeted management in the EEZ of both Europa and Bassas da India.
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Affiliation(s)
- Mireille M. M. Guillaume
- Laboratoire BOrEA MNHN-SU-CNRS-IRD-UCN-UA EcoFunc, Aviv, Muséum National d’Histoire Naturelle, Paris, France
- Laboratoire d’Excellence CORAIL, Perpignan, France
- * E-mail:
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Nolan MKB, Schmidt-Roach S, Davis AR, Aranda M, Howells EJ. Widespread bleaching in the One Tree Island lagoon (Southern Great Barrier Reef) during record-breaking temperatures in 2020. ENVIRONMENTAL MONITORING AND ASSESSMENT 2021; 193:590. [PMID: 34417871 PMCID: PMC8379602 DOI: 10.1007/s10661-021-09330-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 07/22/2021] [Indexed: 06/13/2023]
Abstract
The global marine environment has been impacted significantly by climate change. Ocean temperatures are rising, and the frequency, duration and intensity of marine heatwaves are increasing, particularly affecting coral reefs. Coral bleaching events are becoming more common, with less recovery time between events. Anomalous temperatures at the start of 2020 caused widespread bleaching across the Great Barrier Reef (GBR), extending to southern, previously less affected reefs such as One Tree Island. Here, nine video transects were conducted at One Tree Island, in the Capricorn Bunker Group, and analysed for community composition and diversity, and the extent of bleaching across taxa. Average live hard coral cover across the area was 11.62%, and almost half of this was identified as severely bleached. This bleaching event is concerning as it occurred in an area previously considered a potential refuge for corals and associated fauna from the risks of climate warming. Due to the global impacts of COVID-19 during 2020, this report provides one of potentially few monitoring efforts of coral bleaching.
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Affiliation(s)
- Megan K B Nolan
- Red Sea Research Centre, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia.
| | - Sebastian Schmidt-Roach
- Red Sea Research Centre, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
| | - Andrew R Davis
- Centre for Sustainable Ecosystem Solutions and School of Earth, Atmospheric and Life Sciences, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Manuel Aranda
- Red Sea Research Centre, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
| | - Emily J Howells
- Centre for Sustainable Ecosystem Solutions and School of Earth, Atmospheric and Life Sciences, University of Wollongong, Wollongong, NSW, 2522, Australia
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Van Houtan KS, Reygondeau G, Gagné TO, Tanaka KR, Jorgensen SJ, Palumbi SR. Narrowing the niche of shark fin harvests in the global ocean. Biol Lett 2021; 17:20210206. [PMID: 34256578 PMCID: PMC8278037 DOI: 10.1098/rsbl.2021.0206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Kyle S Van Houtan
- Monterey Bay Aquarium, Monterey, CA 93940, USA.,Nicholas School of the Environment, Durham, NC 27708, USA
| | - Gabriel Reygondeau
- Changing Ocean Research Unit, Institute for the Oceans and Fisheries, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z4
| | | | | | - Salvador J Jorgensen
- Monterey Bay Aquarium, Monterey, CA 93940, USA.,Institute of Marine Science, University of California, Santa Cruz, CA 95060, USA
| | - Stephen R Palumbi
- Department of Biology, Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950, USA
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Recent expansion of marine protected areas matches with home range of grey reef sharks. Sci Rep 2021; 11:14221. [PMID: 34244536 PMCID: PMC8270914 DOI: 10.1038/s41598-021-93426-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 06/17/2021] [Indexed: 02/06/2023] Open
Abstract
Dramatic declines in reef shark populations have been documented worldwide in response to human activities. Marine Protected Areas (MPAs) offer a useful mechanism to protect these species and their roles in coral reef ecosystems. The effectiveness of MPAs notably relies on compliance together with sufficient size to encompass animal home range. Here, we measured home range of 147 grey reef sharks, Carcharhinus amblyrhynchos, using acoustic telemetry in New Caledonia. The distribution of home range was then compared to local MPA sizes. We report a home range of 12 km2 of reef for the species with strong differences between adult males (21 km2), adult females (4.4 km2) and juveniles (6.2 km2 for males, 2.7 km2 for females). Whereas local historic MPA size seemed adequate to protect reef shark home range in general, these were clearly too small when considering adult males only, which is consistent with the reported failure of MPAs to protect sharks in New Caledonia. Fortunately, the recent implementation of several orders of magnitude larger MPAs in New Caledonia and abroad show that recent Indo-Pacific MPAs are now sufficiently large to protect the home ranges of this species, including males, across its geographical range. However, protection efforts are concentrated in a few regions and cannot provide adequate protection at a global scale.
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