Intrinsic tracers for the analysis of habitat use by large marine vertebrates
[eng] The use of the stable isotopes of different chemical elements as intrinsic biogeochemical tracers offers a unique opportunity to infer information about the foraging and spatial ecology of large marine vertebrates from small tissue samples of alive or dead individuals. Historically, the most c...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2025 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/222521 |
| Acceso en línea: | https://hdl.handle.net/2445/222521 http://hdl.handle.net/10803/694930 |
| Access Level: | acceso abierto |
| Palabra clave: | Fauna marina Hàbitat (Ecologia) Nínxol ecològic Isòtops estables en ecologia Marine fauna Habitat (Ecology) Niche (Ecology) Stable isotopes in ecological research |
| Sumario: | [eng] The use of the stable isotopes of different chemical elements as intrinsic biogeochemical tracers offers a unique opportunity to infer information about the foraging and spatial ecology of large marine vertebrates from small tissue samples of alive or dead individuals. Historically, the most commonly used tracers to study the trophic ecology of marine species have been the stable isotope ratios of carbon (δ13C) and nitrogen (δ15N), since they allow to identify the contribution of different primary producers with distinct isotopic signatures to the diet of a consumer and to estimate the trophic position of species and individuals within an ecosystem. More recently, the use of these isotopic tracers to analyse the habitat use of marine animals has led to the inclusion of other chemical elements to explore new dimensions of the isotopic niche. Such is the case of the sulphur stable isotope ratio (δ34S) to differentiate between inshore/benthic habits from offshore/pelagic habits, and the oxygen stable isotope ratio (δ18O) to study migration patterns across areas with distinct salinity. Nevertheless, the advantages of using additional isotopic tracers to improve the definition of the isotopic niche will depend on the ecosystem and species involved and, particularly, on the existence and scale of environmental isotopic gradients that affect the stable isotope ratios in primary producers and along the respective food webs. Therefore, this thesis aims to assess the suitability of the δ34S and δ18O ratio as habitat tracers for two different aspects, (1) to evaluate the isotopic niche partitioning among species of the same community and (2) to identify individual movement patterns among isotopically distinct foraging grounds. To do this, the δ13C, δ15N, δ34S and/or δ18O ratios were analysed in two types of consumer tissues, bone of marine mammals and sea turtles and epidermis of sea turtles, inhabiting ecosystems with marked environmental isotopic gradients such as the Río de la Plata estuary, the Mauritanian coast and the North Atlantic Ocean-Mediterranean Sea system. On one hand, the addition of the δ18O and δ34S ratios to the δ13C and δ15N ratios allowed to better characterize the isotopic niche partitioning among marine consumers in an ecosystem with important inputs of freshwater and terrestrial particulate organic matter, since the spatial scale of the environmental isotopic gradients covered the area used by the species. However, this did not occur everywhere and hence, the inclusion of more tracers does not necessarily translate into an improvement of the characterization of the isotopic niche partitioning among species. On the other hand, the use of at least three of these intrinsic tracers allowed to identify individual specialization in habitat within populations, as well as to trace individual movements among isotopically distinct areas. Furthermore, accounting for as many physical and chemical processes as possible, both environmental and metabolic, is critical when using stable isotopes to assess the habitat use and trophic ecology of large marine vertebrates, as the isotopic ratios of the consumers can be jointly affected by many processes. Finally, results should be validated with other complementary research techniques, such as direct observations, satellite telemetry and genetic analysis. |
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