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Sanchez CL, Casale P, Bunbury N, A'Bear L, Banane V, Benstrong F, Bielsa M, Jones CW, Koester A, Murasko S, van Rooyen MC, Fleischer-Dogley F, Ceriani SA. Fine-scale foraging ecology and habitat use of sympatric green and hawksbill turtles in the Western Indian ocean. MARINE ENVIRONMENTAL RESEARCH 2024; 198:106529. [PMID: 38688109 DOI: 10.1016/j.marenvres.2024.106529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2023] [Revised: 04/01/2024] [Accepted: 04/26/2024] [Indexed: 05/02/2024]
Abstract
Using stable isotope analysis of carbon and nitrogen of turtle tissues and putative prey items, we investigated the diet of immature green turtles and hawksbill turtles foraging in the lagoon of Aldabra Atoll, a relatively undisturbed atoll in the southern Seychelles. Aldabra offers a unique environment for understanding sea turtle ecology. Green turtles mostly consumed seagrass and brown algae while hawksbill turtles mainly consumed mangroves and invertebrates. Green turtles showed a dietary shift with size (a proxy for age). There was minimal niche overlap between species and evidence of small-scale foraging site fidelity with turtle tissue reflecting site-specific prey. This highlights the ecological importance of seagrass and mangrove habitats and suggests that turtles play a role in controlling algal biomass at Aldabra. This study is the first to closely examine the foraging ecology of these sympatric turtle species in the Western Indian Ocean, a globally important region for both species.
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Affiliation(s)
- Cheryl L Sanchez
- Department of Biology, University of Pisa, Via A. Volta 6, 56126 Pisa, Italy; Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, Saint Petersburg, FL, USA; Seychelles Islands Foundation, Mahé, P.O. Box 853, Victoria, Seychelles
| | - Paolo Casale
- Department of Biology, University of Pisa, Via A. Volta 6, 56126 Pisa, Italy.
| | - Nancy Bunbury
- Seychelles Islands Foundation, Mahé, P.O. Box 853, Victoria, Seychelles; Centre for Ecology and Conservation, University of Exeter, Cornwall Campus, Penryn TR10 9FE, UK
| | - Luke A'Bear
- Seychelles Islands Foundation, Mahé, P.O. Box 853, Victoria, Seychelles
| | - Veronique Banane
- Seychelles Islands Foundation, Mahé, P.O. Box 853, Victoria, Seychelles
| | - Frances Benstrong
- Seychelles Islands Foundation, Mahé, P.O. Box 853, Victoria, Seychelles
| | - Maria Bielsa
- Seychelles Islands Foundation, Mahé, P.O. Box 853, Victoria, Seychelles
| | | | - Anna Koester
- Seychelles Islands Foundation, Mahé, P.O. Box 853, Victoria, Seychelles
| | - Susan Murasko
- Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, Saint Petersburg, FL, USA
| | | | | | - Simona A Ceriani
- Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, Saint Petersburg, FL, USA
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Appoo J, Bunbury N, Jaquemet S, Graham NA. Seabird nutrient subsidies enrich mangrove ecosystems and are exported to nearby coastal habitats. iScience 2024; 27:109404. [PMID: 38510135 PMCID: PMC10952037 DOI: 10.1016/j.isci.2024.109404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Revised: 01/19/2024] [Accepted: 02/29/2024] [Indexed: 03/22/2024] Open
Abstract
Eutrophication by human-derived nutrient enrichment is a major threat to mangroves, impacting productivity, ecological functions, resilience, and ecosystem services. Natural mangrove nutrient enrichment processes, however, remain largely uninvestigated. Mobile consumers such as seabirds are important vectors of cross-ecosystem nutrient subsidies to islands but how they influence mangrove ecosystems is poorly known. We assessed the contribution, uptake, cycling, and transfer of nutrients from seabird colonies in remote mangrove systems free of human stressors. We found that nutrients from seabird guano enrich mangrove plants, reduce nutrient limitations, enhance mangrove invertebrate food webs, and are exported to nearby coastal habitats through tidal flow. We show that seabird nutrient subsidies in mangroves can be substantial, improving the nutrient status and health of mangroves and adjacent coastal habitats. Conserving mobile consumers, such as seabirds, is therefore vital to preserve and enhance their role in mangrove productivity, resilience, and provision of diverse functions and services.
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Affiliation(s)
- Jennifer Appoo
- UMR ENTROPIE, Université de La Réunion, 97744 Saint Denis Cedex 9, La Réunion, France
- Seychelles Islands Foundation, Victoria, Mahé, Seychelles
| | - Nancy Bunbury
- Seychelles Islands Foundation, Victoria, Mahé, Seychelles
- Centre for Ecology and Conservation, University of Exeter, Cornwall TR10 9FE, UK
| | - Sébastien Jaquemet
- UMR ENTROPIE, Université de La Réunion, 97744 Saint Denis Cedex 9, La Réunion, France
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Horne JB, Frey A, Gaos AR, Martin S, Dutton PH. Non-random mating within an Island rookery of Hawaiian hawksbill turtles: demographic discontinuity at a small coastline scale. ROYAL SOCIETY OPEN SCIENCE 2023; 10:221547. [PMID: 37206959 PMCID: PMC10189603 DOI: 10.1098/rsos.221547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 04/26/2023] [Indexed: 05/21/2023]
Abstract
Hawksbill sea turtles (Eretmochelys imbricata) from the Hawaiian archipelago form a small and genetically isolated population, consisting of only a few tens of individuals breeding annually. Most females nest on the island of Hawai'i, but little is known about the demographics of this rookery. This study used genetic relatedness, inferred from 135 microhaplotype markers, to determine breeding sex-ratios, estimate female nesting frequency and assess relationships between individuals nesting on different beaches. Samples were collected during the 2017 nesting season and final data included 13 nesting females and 1002 unhatched embryos, salvaged from 41 nests, of which 13 had no observed mother. Results show that most females used a single nesting beach laying 1-5 nests each. From female and offspring alleles, the paternal genotypes of 12 breeding males were reconstructed and many showed high relatedness to their mates. Pairwise relatedness of offspring revealed one instance of polygyny but otherwise suggested a 1 : 1 breeding-sex ratio. Relatedness analysis and spatial-autocorrelation of genotypes indicate that turtles from different nesting areas do not regularly interbreed, suggesting that strong natal homing tendencies in both sexes result in non-random mating across the study area. Complexes of nearby nesting beaches also showed unique patterns of inbreeding across loci, further indicating that Hawaiian hawksbill turtles have demographically discontinuous nesting populations separated by only tens of km.
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Affiliation(s)
- John B. Horne
- Southwest Fisheries Science Center, NOAA-Fisheries, La Jolla, CA, USA
| | - Amy Frey
- Southwest Fisheries Science Center, NOAA-Fisheries, La Jolla, CA, USA
| | - Alexander R. Gaos
- Pacific Islands Fisheries Science Center, NOAA-Fisheries, Honolulu, HI, USA
| | - Summer Martin
- Pacific Islands Fisheries Science Center, NOAA-Fisheries, Honolulu, HI, USA
| | - Peter H. Dutton
- Southwest Fisheries Science Center, NOAA-Fisheries, La Jolla, CA, USA
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