Stable isotope ratios in Cape gannets around the southern coasts of Africa reveal penetration of biogeographic patterns in oceanic signatures
International audience The southern coasts of Africa are influenced by two major oceanic currents, leading to biogeographic patterns in inshore and offshore species assemblages, and in the stable isotope signatures of suspended particulate matter and filter-feeding mussels. We used the stable isotop...
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ftunivreunion:oai:HAL:hal-00866232v1 2024-04-28T08:14:46+00:00 Stable isotope ratios in Cape gannets around the southern coasts of Africa reveal penetration of biogeographic patterns in oceanic signatures Jaquemet, Sébastien Mcquaid, Christopher Laboratoire d'Ecologie Marine (ECOMAR) Université de La Réunion (UR) Rhodes University, Grahamstown 2008 https://hal.science/hal-00866232 https://doi.org/10.1016/j.ecss.2008.08.019 en eng HAL CCSD Elsevier info:eu-repo/semantics/altIdentifier/doi/10.1016/j.ecss.2008.08.019 hal-00866232 https://hal.science/hal-00866232 doi:10.1016/j.ecss.2008.08.019 ISSN: 0272-7714 EISSN: 1096-0015 Estuarine, Coastal and Shelf Science https://hal.science/hal-00866232 Estuarine, Coastal and Shelf Science, 2008, 80 (3), pp.374--380. ⟨10.1016/j.ecss.2008.08.019⟩ Agulhas Benguela Morus capensis seabirds upwelling δ13C δ15N [SDE.BE]Environmental Sciences/Biodiversity and Ecology info:eu-repo/semantics/article Journal articles 2008 ftunivreunion https://doi.org/10.1016/j.ecss.2008.08.019 2024-04-11T00:07:15Z International audience The southern coasts of Africa are influenced by two major oceanic currents, leading to biogeographic patterns in inshore and offshore species assemblages, and in the stable isotope signatures of suspended particulate matter and filter-feeding mussels. We used the stable isotope ratios of carbon (13C/12C) and nitrogen (15N/14N) from the blood and feathers of adult and chick Cape gannets (Morus capensis) to investigate whether the geographic differences observed at the lower levels in the marine communities are deep penetrating effects that reach top predators. Additionally, we evaluated whether trophic segregation occurs between adult and reared chick gannets, and whether a shift to wintering habitat occurs in adults. The study was conducted during the 2006 breeding season on Bird Island in the Agulhas system, and on Malgas and Ichaboe Islands, in the south and north Benguela respectively. Our results showed significant differences in the isotope ratios of members of different colonies, but no intra-colony differences between tissues or age groups. These results indicate that there is neither age-related nor temporal segregation in the diet of members of the same colony. Feather isotopic values suggest that adults remain all year round in the same habitats, and do not undertake long migration after reproduction. Since all gannets tend to target similar prey, we attributed among-colony differences in isotope signatures mostly to the oceanic conditions experienced by the main prey of birds rather than substantial differences in diet composition. Overall, isotopic signatures segregate the two current systems, with depleted carbon values in the Agulhas and enriched nitrogen values in the upwelled waters of the Benguela. Within the Benguela birds from Ichaboe in the north had higher δ15N values than those from Malgas in the south, which we attributed to differences in the functioning of the upwelling cells in the vicinity of the two colonies. Finally, slight variation in the proportion of main ... Article in Journal/Newspaper Bird Island Université de la Réunion: HAL Estuarine, Coastal and Shelf Science 80 3 374 380 |
institution |
Open Polar |
collection |
Université de la Réunion: HAL |
op_collection_id |
ftunivreunion |
language |
English |
topic |
Agulhas Benguela Morus capensis seabirds upwelling δ13C δ15N [SDE.BE]Environmental Sciences/Biodiversity and Ecology |
spellingShingle |
Agulhas Benguela Morus capensis seabirds upwelling δ13C δ15N [SDE.BE]Environmental Sciences/Biodiversity and Ecology Jaquemet, Sébastien Mcquaid, Christopher Stable isotope ratios in Cape gannets around the southern coasts of Africa reveal penetration of biogeographic patterns in oceanic signatures |
topic_facet |
Agulhas Benguela Morus capensis seabirds upwelling δ13C δ15N [SDE.BE]Environmental Sciences/Biodiversity and Ecology |
description |
International audience The southern coasts of Africa are influenced by two major oceanic currents, leading to biogeographic patterns in inshore and offshore species assemblages, and in the stable isotope signatures of suspended particulate matter and filter-feeding mussels. We used the stable isotope ratios of carbon (13C/12C) and nitrogen (15N/14N) from the blood and feathers of adult and chick Cape gannets (Morus capensis) to investigate whether the geographic differences observed at the lower levels in the marine communities are deep penetrating effects that reach top predators. Additionally, we evaluated whether trophic segregation occurs between adult and reared chick gannets, and whether a shift to wintering habitat occurs in adults. The study was conducted during the 2006 breeding season on Bird Island in the Agulhas system, and on Malgas and Ichaboe Islands, in the south and north Benguela respectively. Our results showed significant differences in the isotope ratios of members of different colonies, but no intra-colony differences between tissues or age groups. These results indicate that there is neither age-related nor temporal segregation in the diet of members of the same colony. Feather isotopic values suggest that adults remain all year round in the same habitats, and do not undertake long migration after reproduction. Since all gannets tend to target similar prey, we attributed among-colony differences in isotope signatures mostly to the oceanic conditions experienced by the main prey of birds rather than substantial differences in diet composition. Overall, isotopic signatures segregate the two current systems, with depleted carbon values in the Agulhas and enriched nitrogen values in the upwelled waters of the Benguela. Within the Benguela birds from Ichaboe in the north had higher δ15N values than those from Malgas in the south, which we attributed to differences in the functioning of the upwelling cells in the vicinity of the two colonies. Finally, slight variation in the proportion of main ... |
author2 |
Laboratoire d'Ecologie Marine (ECOMAR) Université de La Réunion (UR) Rhodes University, Grahamstown |
format |
Article in Journal/Newspaper |
author |
Jaquemet, Sébastien Mcquaid, Christopher |
author_facet |
Jaquemet, Sébastien Mcquaid, Christopher |
author_sort |
Jaquemet, Sébastien |
title |
Stable isotope ratios in Cape gannets around the southern coasts of Africa reveal penetration of biogeographic patterns in oceanic signatures |
title_short |
Stable isotope ratios in Cape gannets around the southern coasts of Africa reveal penetration of biogeographic patterns in oceanic signatures |
title_full |
Stable isotope ratios in Cape gannets around the southern coasts of Africa reveal penetration of biogeographic patterns in oceanic signatures |
title_fullStr |
Stable isotope ratios in Cape gannets around the southern coasts of Africa reveal penetration of biogeographic patterns in oceanic signatures |
title_full_unstemmed |
Stable isotope ratios in Cape gannets around the southern coasts of Africa reveal penetration of biogeographic patterns in oceanic signatures |
title_sort |
stable isotope ratios in cape gannets around the southern coasts of africa reveal penetration of biogeographic patterns in oceanic signatures |
publisher |
HAL CCSD |
publishDate |
2008 |
url |
https://hal.science/hal-00866232 https://doi.org/10.1016/j.ecss.2008.08.019 |
genre |
Bird Island |
genre_facet |
Bird Island |
op_source |
ISSN: 0272-7714 EISSN: 1096-0015 Estuarine, Coastal and Shelf Science https://hal.science/hal-00866232 Estuarine, Coastal and Shelf Science, 2008, 80 (3), pp.374--380. ⟨10.1016/j.ecss.2008.08.019⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1016/j.ecss.2008.08.019 hal-00866232 https://hal.science/hal-00866232 doi:10.1016/j.ecss.2008.08.019 |
op_doi |
https://doi.org/10.1016/j.ecss.2008.08.019 |
container_title |
Estuarine, Coastal and Shelf Science |
container_volume |
80 |
container_issue |
3 |
container_start_page |
374 |
op_container_end_page |
380 |
_version_ |
1797580680244232192 |