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Skinner C, Pei YD, Morimoto N, Miyajima T, Wyatt ASJ. Stable isotopes elucidate body-size and seasonal fluctuations in the feeding strategies of planktivorous fishes across a semi-enclosed tropical embayment. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.942968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Reef fish may switch feeding strategies due to fluctuations in resource availability or through ontogeny. A number of studies have explored these trophodynamics using carbon (δ13C) and nitrogen (δ15N) stable isotopes, but additional tracers such as sulfur isotopes (δ34S) show strong potential in systems, where δ13C and δ15N results are ambiguous. We tested the utility of adding δ34S to conventional δ13C and δ15N analysis to detect seasonal and body size changes in resource use of two planktivorous damselfish, Dascyllus reticulatus and Dascyllus trimaculatus across the Puerto Galera embayment in the Philippines. We analyzed stable isotope ratios (δ13C, δ15N, and δ34S) in multiple fish tissues (liver, eye, and muscle) to represent different dietary time frames. We then compared fish tissue isotopes against particulate organic matter (POM) (δ13C and δ15N) and POM suspension feeder (the tunicate Polycarpa aurata: δ13C, δ15N, and δ34S) across the same sites. There were size-based and seasonal differences in damselfish resource use, the latter of which was most pronounced in the fast-turnover liver. Small fish (<70 mm) demonstrated significant seasonality, appearing to switch their resource use between the rainy season and the dry season, while there was no seasonal variation in larger fish (>70 mm). This suggests that smaller fish across the embayment employ an opportunistic feeding strategy to take advantage of fluctuating resource availability, while larger fish exhibits more consistent resource use. Isotope ratios of tunicates and POM further confirmed strong seasonality in this system and a lack of a spatial isotopic gradient. δ15N did not seem to contribute to consumer resource use patterns, while by contrast, δ34S fluctuated significantly between sampling periods and was crucial for demonstrating seasonality in resource use. We recommend including δ34S when attempting to disentangle seasonal differences in resource use in aquatic food webs using stable isotopes.
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Cybulski JD, Skinner C, Wan Z, Wong CKM, Toonen RJ, Gaither MR, Soong K, Wyatt ASJ, Baker DM. Improving stable isotope assessments of inter- and intra-species variation in coral reef fish trophic strategies. Ecol Evol 2022; 12:e9221. [PMID: 36172294 PMCID: PMC9468908 DOI: 10.1002/ece3.9221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 07/03/2022] [Accepted: 07/22/2022] [Indexed: 11/23/2022] Open
Abstract
Fish have one of the highest occurrences of individual specialization in trophic strategies among Eukaryotes. Yet, few studies characterize this variation during trophic niche analysis, limiting our understanding of aquatic food web dynamics. Stable isotope analysis (SIA) with advanced Bayesian statistics is one way to incorporate this individual trophic variation when quantifying niche size. However, studies using SIA to investigate trophodynamics have mostly focused on species- or guild-level (i.e., assumed similar trophic strategy) analyses in settings where source isotopes are well-resolved. These parameters are uncommon in an ecological context. Here, we use Stable Isotope Bayesian Ellipses in R (SIBER) to investigate cross-guild trophodynamics of 11 reef fish species within an oceanic atoll. We compared two- (δ 15N and δ 13C) versus three-dimensional (δ 15N, δ 13C, and δ 34S) reconstructions of isotopic niche space for interpreting guild-, species-, and individual-level trophic strategies. Reef fish isotope compositions varied significantly among, but also within, guilds. Individuals of the same species did not cluster together based on their isotope values, suggesting within-species specializations. Furthermore, while two-dimensional isotopic niches helped differentiate reef fish resource use, niche overlap among species was exceptionally high. The addition of δ 34S and the generation of three-dimensional isotopic niches were needed to further characterize their isotopic niches and better evaluate potential trophic strategies. These data suggest that δ 34S may reveal fluctuations in resource availability, which are not detectable using only δ 15N and δ 13C. We recommend that researchers include δ 34S in future aquatic food web studies.
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Affiliation(s)
- Jonathan D. Cybulski
- The Swire Institute of Marine ScienceThe University of Hong KongShek OHong Kong SAR
- School of Biological SciencesThe University of Hong KongPok Fu LamHong Kong SAR
| | - Christina Skinner
- Department of Ocean ScienceThe Hong Kong University of Science and TechnologyClear Water BayHong Kong SAR
| | - Zhongyue Wan
- School of Biological SciencesThe University of Hong KongPok Fu LamHong Kong SAR
| | - Carmen K. M. Wong
- State Key Laboratory of Marine PollutionCity University of Hong KongKowloonHong Kong SAR
| | - Robert J. Toonen
- Hawai‘i Institute of Marine Biology, School of Ocean & Earth Sciences & TechnologyUniversity of Hawai‘i at MānoaKaneoheHawaiiUSA
| | | | - Keryea Soong
- Department of OceanographyNational Sun Yat‐sen UniversityKaohsiungTaiwan
| | - Alex S. J. Wyatt
- Department of Ocean ScienceThe Hong Kong University of Science and TechnologyClear Water BayHong Kong SAR
| | - David M. Baker
- The Swire Institute of Marine ScienceThe University of Hong KongShek OHong Kong SAR
- School of Biological SciencesThe University of Hong KongPok Fu LamHong Kong SAR
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Letessier TB, Johnston J, Delarue J, Martin B, Anderson RC. Spinner dolphin residency in tropical atoll lagoons: Diurnal presence, seasonal variability and implications for nutrient dynamics. J Zool (1987) 2022. [DOI: 10.1111/jzo.13000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- T. B. Letessier
- Institute of Zoology, Zoological Society of London Regent's Park London UK
- School of Biological Sciences University of Western Australia Perth SA Australia
| | - J. Johnston
- Institute of Zoology, Zoological Society of London Regent's Park London UK
- University College London London UK
| | - J. Delarue
- JASCO Applied Sciences The Roundel, St Clair's Farm Droxford UK
| | - B. Martin
- JASCO Applied Sciences The Roundel, St Clair's Farm Droxford UK
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Brown K, Monk J, Williams J, Carroll A, Harasti D, Barrett N. Depth and benthic habitat influence shallow and mesophotic predatory fishes on a remote, high-latitude coral reef. PLoS One 2022; 17:e0265067. [PMID: 35324946 PMCID: PMC8947262 DOI: 10.1371/journal.pone.0265067] [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: 08/27/2021] [Accepted: 02/22/2022] [Indexed: 11/18/2022] Open
Abstract
Predatory fishes on coral reefs continue to decline globally despite playing key roles in ecosystem functioning. Remote atolls and platform reefs provide potential refugia for predator populations, but quantitative information on their spatial distribution is required to establish accurate baselines for ongoing monitoring and conservation management. Current knowledge of predatory fish populations has been derived from targeted shallow diver-based surveys (<15 m). However, the spatial distribution and extent of predatory fishes on outer mesophotic shelf environments has remained under described. Middleton Reef is a remote, high-latitude, oceanic platform reef that is located within a no-take area in the Lord Howe Marine Park off eastern Australia. Here we used baited remote underwater stereo video to sample predatory fishes across lagoon and outer shelf habitats from depths 0–100 m, extending knowledge on use of mesophotic depths and habitats. Many predatory fish demonstrated clear depth and habitat associations over this depth range. Carcharhinid sharks and Carangid fishes were the most abundant predators sampled on Middleton Reef, with five predatory fishes accounting for over 90% of the predator fish biomass. Notably, Galapagos shark (Carcharhinus galapagensis) and the protected black rockcod (Epinephelus daemelii) dominated the predator fish assemblage. A higher richness of predator fish species was sampled on reef areas north and south of the lagoon. The more exposed southern aspect of the reef supported a different suite of predator fish across mesophotic habitats relative to the assemblage recorded in the north and lagoonal habitats, a pattern potentially driven by differences in hard coral cover. Biomass of predatory fishes in the more sheltered north habitats was twice that of other areas, predominantly driven by high abundances of Galapagos shark. This work adds to the growing body of literature highlighting the conservation value of isolated oceanic reefs and the need to ensure that lagoon, shallow and mesophotic habitats in these systems are adequately protected, as they support vulnerable ecologically and economically important predator fish assemblages.
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Affiliation(s)
- Kristy Brown
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
| | - Jacquomo Monk
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
- * E-mail:
| | - Joel Williams
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
- Fisheries Research, Port Stephens Fisheries Institute, NSW Department of Primary Industries, Taylors Beach, NSW, Australia
| | | | - David Harasti
- Fisheries Research, Port Stephens Fisheries Institute, NSW Department of Primary Industries, Taylors Beach, NSW, Australia
| | - Neville Barrett
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
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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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Birt MJ, Cure K, Wilson S, Newman SJ, Harvey ES, Meekan M, Speed C, Heyward A, Goetze J, Gilmour J. Isolated reefs support stable fish communities with high abundances of regionally fished species. Ecol Evol 2021; 11:4701-4718. [PMID: 33976841 PMCID: PMC8093692 DOI: 10.1002/ece3.7370] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 12/22/2020] [Accepted: 02/18/2021] [Indexed: 12/31/2022] Open
Abstract
Anthropogenic impacts at isolated and inaccessible reefs are often minimal, offering rare opportunities to observe fish assemblages in a relatively undisturbed state. The remote Rowley Shoals are regarded as one of the healthiest reef systems in the Indian Ocean with demonstrated resilience to natural disturbance, no permanent human population nearby, low visitation rates, and large protected areas where fishing prohibitions are enforced. We used baited remote underwater video systems (BRUVS) to quantify fish assemblages and the relative abundance of regionally fished species within the lagoon, on the slope and in the mesophotic habitat at the Rowley Shoals at three times spanning 14 years and compared abundances of regionally fished species and the length distributions of predatory species to other isolated reefs in the northeast Indian Ocean. Fish assemblage composition and the relative abundance of regionally fished species were remarkably stable through time. We recorded high abundances of regionally fished species relative to other isolated reefs, including globally threatened humphead Maori wrasse (Cheilinus undulatus) and bumphead parrotfish (Bolbometopon muricatum). Length distributions of fish differed among habitats at the Rowley Shoals, suggesting differences in ontogenetic shifts among species. The Cocos (Keeling) Islands typically had larger-bodied predatory species than at the Rowley Shoals. Differences in geomorphology, lagoonal habitats, and fishing history likely contribute to the differences among remote reefs. Rowley Shoals is a rare example of a reef system demonstrating ecological stability in reef fish assemblages during a time of unprecedented degradation of coral reefs.
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Affiliation(s)
- Matthew J. Birt
- The Australian Institute of Marine ScienceIndian Ocean Marine Research Centre, Cnr of Fairway and Service Road 4PerthWA6009Australia
| | - Katherine Cure
- The Australian Institute of Marine ScienceIndian Ocean Marine Research Centre, Cnr of Fairway and Service Road 4PerthWA6009Australia
| | - Shaun Wilson
- Marine Science ProgramDepartment of Biodiversity, Conservation and AttractionsGovernment of Western Australia17 Dick Perry AveKensingtonWA6151Australia
- Oceans InstituteThe University of Western AustraliaIndian Ocean Marine Research Centre, Cnr of Fairway and Service Road 4PerthWA6009Australia
| | - Stephen J. Newman
- Western Australian Fisheries and Marine Research LaboratoriesDepartment of Primary Industries and Regional DevelopmentGovernment of Western AustraliaP.O Box 20North BeachWA6920Australia
| | - Euan S. Harvey
- School of Molecular and Life SciencesCurtin UniversityPerthWAAustralia
| | - Mark Meekan
- The Australian Institute of Marine ScienceIndian Ocean Marine Research Centre, Cnr of Fairway and Service Road 4PerthWA6009Australia
| | - Conrad Speed
- The Australian Institute of Marine ScienceIndian Ocean Marine Research Centre, Cnr of Fairway and Service Road 4PerthWA6009Australia
| | - Andrew Heyward
- The Australian Institute of Marine ScienceIndian Ocean Marine Research Centre, Cnr of Fairway and Service Road 4PerthWA6009Australia
- Oceans InstituteThe University of Western AustraliaIndian Ocean Marine Research Centre, Cnr of Fairway and Service Road 4PerthWA6009Australia
| | - Jordan Goetze
- Marine Science ProgramDepartment of Biodiversity, Conservation and AttractionsGovernment of Western Australia17 Dick Perry AveKensingtonWA6151Australia
- School of Molecular and Life SciencesCurtin UniversityPerthWAAustralia
| | - James Gilmour
- The Australian Institute of Marine ScienceIndian Ocean Marine Research Centre, Cnr of Fairway and Service Road 4PerthWA6009Australia
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7
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Skinner C, Mill AC, Fox MD, Newman SP, Zhu Y, Kuhl A, Polunin NVC. Offshore pelagic subsidies dominate carbon inputs to coral reef predators. SCIENCE ADVANCES 2021; 7:7/8/eabf3792. [PMID: 33608282 PMCID: PMC7895429 DOI: 10.1126/sciadv.abf3792] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 01/04/2021] [Indexed: 05/04/2023]
Abstract
Coral reefs were traditionally perceived as productive hot spots in oligotrophic waters. While modern evidence indicates that many coral reef food webs are heavily subsidized by planktonic production, the pathways through which this occurs remain unresolved. We used the analytical power of carbon isotope analysis of essential amino acids to distinguish between alternative carbon pathways supporting four key reef predators across an oceanic atoll. This technique separates benthic versus planktonic inputs, further identifying two distinct planktonic pathways (nearshore reef-associated plankton and offshore pelagic plankton), and revealing that these reef predators are overwhelmingly sustained by offshore pelagic sources rather than by reef sources (including reef-associated plankton). Notably, pelagic reliance did not vary between species or reef habitats, emphasizing that allochthonous energetic subsidies may have system-wide importance. These results help explain how coral reefs maintain exceptional productivity in apparently nutrient-poor tropical settings, but also emphasize their susceptibility to future ocean productivity fluctuations.
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Affiliation(s)
- C Skinner
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
- Department of Ocean Science and Hong Kong Branch of the Southern Marine Science and Engineering, Guangdong Laboratory (Guangzhou), The Hong Kong University of Science and Technology, Kowloon, Hong Kong
| | - A C Mill
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
| | - M D Fox
- Woods Hole Oceanographic Institution, 266 Woods Hole Rd, Woods Hole, MA 02543, USA
| | - S P Newman
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
- Banyan Tree Marine Lab, Vabbinfaru Resort, North Malé Atoll, Republic of Maldives
| | - Y Zhu
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
| | - A Kuhl
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - N V C Polunin
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
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8
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Skinner C, Mill AC, Newman SP, Newton J, Cobain MRD, Polunin NVC. Novel tri-isotope ellipsoid approach reveals dietary variation in sympatric predators. Ecol Evol 2019; 9:13267-13277. [PMID: 31893024 PMCID: PMC6936247 DOI: 10.1002/ece3.5779] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 10/01/2019] [Accepted: 10/04/2019] [Indexed: 11/21/2022] Open
Abstract
Sympatric species may partition resources to reduce competition and facilitate co-existence. While spatial variation and specialization in feeding strategies may be prevalent among large marine predators, studies have focussed on sharks, birds, and marine mammals. We consider for the first time the isotopic niche partitioning of co-occurring, teleost reef predators spanning multiple families. Using a novel tri-isotope ellipsoid approach, we investigate the feeding strategies of seven of these species across an atoll seascape in the Maldives. We demonstrate substantial spatial variation in resource use of all predator populations. Furthermore, within each area, there was evidence of intraspecific variation in feeding behaviors that could not wholly be attributed to individual body size. Assessing species at the population level will mask these intraspecific differences in resource use. Knowledge of resource use is important for predicting how species will respond to environmental change and spatial variation should be considered when investigating trophic diversity.
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Affiliation(s)
- Christina Skinner
- School of Natural and Environmental SciencesNewcastle UniversityNewcastleUK
| | - Aileen C. Mill
- School of Natural and Environmental SciencesNewcastle UniversityNewcastleUK
| | - Steven P. Newman
- School of Natural and Environmental SciencesNewcastle UniversityNewcastleUK
- Banyan Tree Marine LabVabbinfaruRepublic of the Maldives
| | - Jason Newton
- NERC Life Sciences Mass Spectrometry FacilityScottish Universities Environmental Research CentreEast KilbrideUK
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Skinner C, Newman SP, Mill AC, Newton J, Polunin NVC. Prevalence of pelagic dependence among coral reef predators across an atoll seascape. J Anim Ecol 2019; 88:1564-1574. [PMID: 31264204 PMCID: PMC6852557 DOI: 10.1111/1365-2656.13056] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Accepted: 06/06/2019] [Indexed: 12/11/2022]
Abstract
Coral reef food webs are complex, vary spatially and remain poorly understood. Certain large predators, notably sharks, are subsidized by pelagic production on outer reef slopes, but how widespread this dependence is across all teleost fishery target species and within atolls is unclear. North Malé Atoll (Maldives) includes oceanic barrier as well as lagoonal reefs. Nine fishery target predators constituting ca. 55% of the local fishery target species biomass at assumed trophic levels 3–5 were selected for analysis. Data were derived from carbon (δ13C), nitrogen (δ15N) and sulphur (δ34S) stable isotopes from predator white dorsal muscle samples, and primary consumer species representing production source end‐members. Three‐source Bayesian stable isotope mixing models showed that uptake of pelagic production extends throughout the atoll, with predatory fishes showing equal planktonic reliance between inner and outer edge reefs. Median plankton contribution was 65%–80% for all groupers and 68%–88% for an emperor, a jack and snappers. Lagoonal and atoll edge predators are equally at risk from anthropogenic and climate‐induced changes, which may impact the linkages they construct, highlighting the need for management plans that transcend the boundaries of this threatened ecosystem.
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Affiliation(s)
- Christina Skinner
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Steven P Newman
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, UK.,Banyan Tree Marine Lab, Vabbinfaru, Republic of the Maldives
| | - Aileen C Mill
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Jason Newton
- NERC Life Sciences Mass Spectrometry Facility, Scottish Universities Environmental Research Centre, East Kilbride, UK
| | - Nicholas V C Polunin
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, UK
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