Dear colleagues, My co-authors and I would like to share with you our work recently published in Marine Ecology Progress Series:
Lübcker N, Reisinger RR, Oosthuizen WC, de Bruyn PJN, van Tonder A, Pistorius PA, Bester MN. 2017. Low trophic level diet of juvenile southern elephant seals Mirounga leonina from Marion Island: a stable isotope investigation using vibrissal regrowths. Mar Ecol Prog Ser 577: 237250. Article available at https://doi.org/10.3354/meps12240. ABSTRACT: Insight into the trophic ecology of marine predators is vital for understanding their ecosystem role and predicting their responses to environmental change. Juvenile southern elephant seals (SES) Mirounga leonina are considered generalist predators within the Southern Ocean. Although mesopelagic fish and squid dominate their stomach lavage samples, the stable isotope profile captured along the length of sampled vibrissae of young SES at Macquarie Island, southwest Pacific Ocean (54.5° S, 158.9° E) recently emphasized the contribution of crustaceans to their diet (likely Euphausia superba). Herein, we used the stable isotope values of sampled vibrissal regrowths with known growth histories to assess the diet of juvenile SES at Marion Island, southern Indian Ocean (46.8° S, 37.8° E) on a temporally integrated basis. We specifically aimed to quantify the possible contribution of crustaceans to the diet of juvenile SES. Sequentially (chronologically) sampled vibrissal regrowths of 14 juvenile SES produced fine-scale dietary information spanning up to 9 mo. The depleted stable isotope signatures of nitrogen (d15N) (8.5 ± 0.6) and carbon (d13C) (-20.3 ± 0.1) measured during the period of independent foraging suggested the use of a lower trophic level diet within the Polar Frontal Zone. A mixing model predicted that up to 76% of juvenile SES diet comprised crustaceans, consisting of 2 crustacean groups, each contributing 26% (credible interval, CI: 13 - 39%) and 50% (CI: 35 - 64%) to their diets, presumably representing subantarctic krill species. This first utilisation of the isotopic signature captured along the length of vibrissal regrowths confirms the inclusion and importance of crustaceans in the diet of juvenile SES. See (https://www.researchgate.net/project/Low-trophic-level-diet-of-juvenile-southern-elephant-seals-Mirounga-leonina-from-Marion-Island-a-stable-isotope-investigation-using-vibrissal-regrowths/) for more information regarding this project, or (http://www.marionseals.com/) for more information regarding our research group. Sincerely, Nico Lubcker PhD. Zoology Candidate Mammal Research Institute Old Botany Building Room 1.16.5 Department of Zoology and Entomology University of Pretoria Hatfield South Africa 0028 Cell: + 27 72 0370130 ---------------------------- Original Message ---------------------------- Subject: New article: Vibrissal growth parameters of southern elephant seals Mirounga leonina From: "Nico Lubcker" <nlubc...@zoology.up.ac.za> Date: Thu, January 5, 2017 09:35 To: "marmam@lists.uvic.ca" <marmam@lists.uvic.ca> -------------------------------------------------------------------------- Dear colleagues, My co-authors and I would like to share with you our work recently published in Marine Ecology Progress Series: Lübcker N, Condit R, Beltran RS, de Bruyn PJN, Bester MN. 2016. Vibrissal growth parameters of southern elephant seals Mirounga leonina: obtaining fine-scale, time-based stable isotope data. Marine Ecology Progress Series 559: 243-255. doi: 10.3354/meps11899. Article available at http://www.int-res.com/abstracts/meps/v559/p243-255/ ABSTRACT: Stable isotopes provide a powerful, indirect approach to assess the trophic ecology of individuals on a spatial and temporally integrated basis (especially when combined with telemetry). However, using stable isotopes requires accurate, species-specific quantification of the period of biomolecule deposition in the sampled tissue. Sequentially sampled vibrissae (whiskers) provide a chronology of biogeochemical data, although knowledge of vibrissal growth is required for temporal interpretations. We sampled vibrissae from southern elephant seals Mirounga leonina (hereafter SES) at Marion Island, southern Indian Ocean, to address the following aims: (1) define the prevalence and timing of their vibrissal replacement, (2) determine the vibrissal regrowth rate and temporal resolution of isotopic data captured along the length of sequentially sampled vibrissae, and (3) explore assumptions regarding their vibrissal growth. Contrary to the previously described asynchronous vibrissal shedding pattern of SES, 71.1% of individuals displayed vibrissal shedding during the annual pelage moult. Furthermore, vibrissal growth ceased once the asymptotic length was reached, and the vibrissae were retained before being replaced. Vibrissae with known growth histories were resampled at multiple known intervals to control for unknown growth starting dates. Vibrissae followed a von Bertalanffy growth function as the growth rate decreased near the asymptotic length. The resolution of the isotopic data obtainable per 2 mm section ranged from 3.5 d at the vibrissal tip to >40 d at the base. Using these defined growth rates and shedding patterns, researchers can prudently apply timestamps to stable isotope values along vibrissae. https://www.researchgate.net/publication/310330776_Vibrissal_growth_parameters_of_southern_elephant_seals_Mirounga_leonina_Obtaining_fine-scale_time-based_stable_isotope_data Sincerely, Nico Lubcker nlubc...@zoology.up.ac.za PhD Zoology Candidate Mammal Research Institute Department of Zoology and Entomology University of Pretoria South Africa --------------------------------------------------------------------- This message and attachments are subject to a disclaimer. Please refer to http://www.it.up.ac.za/documentation/governance/disclaimer/ for full details. / Hierdie boodskap en aanhangsels is aan 'n vrywaringsklousule onderhewig. Volledige besonderhede is by http://www.it.up.ac.za/documentation/governance/disclaimer/ beskikbaar. --------------------------------------------------------------------- This message and attachments are subject to a disclaimer. Please refer to http://www.it.up.ac.za/documentation/governance/disclaimer/ for full details. / Hierdie boodskap en aanhangsels is aan 'n vrywaringsklousule onderhewig. Volledige besonderhede is by http://www.it.up.ac.za/documentation/governance/disclaimer/ beskikbaar. _______________________________________________ MARMAM mailing list MARMAM@lists.uvic.ca https://lists.uvic.ca/mailman/listinfo/marmam
