Javier E Ciancio1, Carina Righi2, Adrián Faiella3, Esteban Frere4. 1. IBIOMAR Centro Nacional Patagónico--CONICET, Blvd. Brown 2915, CP 9120, Puerto Madryn, Chubut, Argentina. 2. Fundacion Temaikèn Departamento de Conservación e Investigación, Ruta 25, Km 0.7 Belén de Escobar, CP, 1625, Buenos Aires, Argentina. 3. Aquarium Mar del Plata, Av. Martínez de Hoz 5600, CP 7600, Mar del Plata, Buenos Aires, Argentina. 4. Centro de investigaciones Puerto Deseado (UNPA-CONICET) and BirdLife International (Marine Programme), Costanera Lotufo s/n, CP 9050, Puerto Deseado, Santa Cruz, Argentina.
Abstract
RATIONALE: The use of stable isotopes for ecological studies has increased exponentially in recent years. Isotopic trophic studies are based on the assumption that animals are what they eat plus a discrimination factor. The discrimination factor is affected by many variables and can be determined empirically. The Magellanic penguin is a highly abundant marine bird that plays a key role in the southern oceans. This study provides the first estimation of the Magellanic penguin blood discrimination factor for (13) C and (15) N. METHODS: A two and a half month feeding experiment was performed, in which ten captive penguins were fed their main natural prey (anchovy Engraulis anchoita). The discrimination factors were estimated by comparing anchovy δ(13) C and δ(15) N values (obtained with isotope ratio mass spectrometry using lipid-extracted and bulk anchovy muscle) with penguin blood δ(13) C and δ(15) N values. RESULTS: Penguin blood was shown to be enriched, compared with anchovies, for (13) C and (15) N. No changes were observed in the stable isotope ratios of anchovies and discrimination factors during the experiment. The overall discrimination factors were 0.93 ± 0.12 (bulk) and 0.41 ± 0.12 (lipid-free) for (13) C; and 2.81 ± 0.17 (bulk) and 2.31 ± 0.17 (lipid-free) for (15) N. CONCLUSIONS: Having an accurate discrimination factor for the studied species is key in any trophic or food web isotopic study. Comparisons of estimated diet-to-blood discrimination factors with published values of aquatic piscivore birds showed that the (13) C discrimination factor is particularly variable, and therefore ecologists should be cautious when using a surrogate value from other species. In this study, the Magellanic penguin discrimination factor of a tissue that does not require euthanasia was obtained, a fundamental input for trophic isotopic modeling of the species.
RATIONALE: The use of stable isotopes for ecological studies has increased exponentially in recent years. Isotopic trophic studies are based on the assumption that animals are what they eat plus a discrimination factor. The discrimination factor is affected by many variables and can be determined empirically. The Magellanic penguin is a highly abundant marine bird that plays a key role in the southern oceans. This study provides the first estimation of the Magellanic penguin blood discrimination factor for (13) C and (15) N. METHODS: A two and a half month feeding experiment was performed, in which ten captive penguins were fed their main natural prey (anchovy Engraulis anchoita). The discrimination factors were estimated by comparing anchovy δ(13) C and δ(15) N values (obtained with isotope ratio mass spectrometry using lipid-extracted and bulk anchovy muscle) with penguin blood δ(13) C and δ(15) N values. RESULTS: Penguin blood was shown to be enriched, compared with anchovies, for (13) C and (15) N. No changes were observed in the stable isotope ratios of anchovies and discrimination factors during the experiment. The overall discrimination factors were 0.93 ± 0.12 (bulk) and 0.41 ± 0.12 (lipid-free) for (13) C; and 2.81 ± 0.17 (bulk) and 2.31 ± 0.17 (lipid-free) for (15) N. CONCLUSIONS: Having an accurate discrimination factor for the studied species is key in any trophic or food web isotopic study. Comparisons of estimated diet-to-blood discrimination factors with published values of aquatic piscivore birds showed that the (13) C discrimination factor is particularly variable, and therefore ecologists should be cautious when using a surrogate value from other species. In this study, the Magellanic penguin discrimination factor of a tissue that does not require euthanasia was obtained, a fundamental input for trophic isotopic modeling of the species.
Authors: Samanta Dodino; Nicolás A Lois; Luciana Riccialdelli; Michael J Polito; Klemens Pütz; Andrea Raya Rey Journal: PLoS One Date: 2021-08-20 Impact factor: 3.240
Authors: Nathalie Almeida; Jaime A Ramos; Isabel Rodrigues; Ivo Dos Santos; Jorge M Pereira; Diana M Matos; Pedro M Araújo; Pedro Geraldes; Tommy Melo; Vitor H Paiva Journal: PLoS One Date: 2021-06-21 Impact factor: 3.240