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1. Carbon and nitrogen stocks in sediment at Península Valdés Biosphere Reserve: novel insights into the potential contribution of large marine vertebrates to carbon sequestration

Author

Rocío Jiménez-Ramos, Luis G. Egea, Valeria C. D’Agostino, Mariana Degrati, and Rocío Loizaga

Subjects
blue carbon, Eubalaena australis, nitrogen sequestration, Otaria flavescens, salt marshes, southern right whales, Science, General. Including nature conservation, geographical distribution, QH1-199.5
Abstract

Although policymakers and stakeholders are beginning to acknowledge the importance of the marine biosphere in blue carbon services, the role of large marine vertebrates in the marine carbon and nitrogen cycle and especially in carbon sequestration has not yet been fully understood. Large marine vertebrates store only a small percentage of total oceanic carbon in their bodies, but they can provide important and lasting contributions to the oceanic carbon flux. The Península Valdés Biosphere Reserve in southwestern Argentina was partially established to conserve these large marine vertebrates, including the South American sea lion (Otaria flavescens) and southern right whale (Eubalaena australis). Three locations in Peninsula Valdés were sampling for the proximity of marine vertebrate populations in the area and the presence of salt marshes to assess the organic carbon (OC) and total nitrogen (TN) stocks in the top 1 m of sediment. Our work provides the first quantitative data on the OC and TN sequestered in the coastal sediments of Península Valdés and shows that this protected area contributes significantly to blue carbon by storing relevant quantities of OC (140 to 317 Mg OC ha-1) and nitrogen (7.3 to 22.9 Mg TN ha-1). Specifically, we found that salt marshes and terrestrial plants were the main C sources in each sediment core, but a non-negligible proportion (from 0.8 to 6.8% dry weight) of the OC stocks showed an isotopic signal from the large vertebrates that usually inhabit the area. Therefore, our results provide novel hypotheses about the potential contribution of large marine vertebrates as an OC vector in coastal systems and may serve as a basis for further investigation about their role into coastal blue carbon.

Published
2025
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3. Integrating Multiple Techniques to Estimate Population Size of an Impacted Dusky Dolphin’s Population in Patagonia, Argentina

Author

Mariana Degrati, Rocio Loizaga, Mariano A. Coscarella, Nicolás Sueyro, Enrique A. Crespo, and Silvana L. Dans

Subjects
effective population size, abundance, genetic, photo-identification, dusky dolphins, conservation, Science, General. Including nature conservation, geographical distribution, QH1-199.5
Abstract

Successful conservation strategies require an accurate estimation of population size, and this parameter is one of the most important factors that determine the rate of various evolutionary processes. In this study, we integrated information from genetic, photo-identification, and aerial surveys of dusky dolphins to determine the effective population size and the number of dolphins that inhabit the gulfs of Península Valdés [Golfo Nuevo (GN) and Golfo San José (GSJ)] and are exposed to tourism vessel traffic. Photo-identification sessions and biopsies samples were collected from a research vessel between 2004 and 2013 to estimate the number of dolphins in the area by capture–recapture methods and the effective population size using mtDNA data. In addition, four aerial surveys were carried out using line transects to estimate density via distance sampling. The long-term effective size estimated was 992.87–1,103.19 individuals. During the photo-identification period and by applying a mark rate of 0.416, the total estimated individuals in GN was 374 (95% CI: 237–511). For GSJ, the estimated individuals in the area were 55 (95% CI: 2–108, mark rate 0.692). From aerial surveys, the overall density estimate was D⌢ = 0.13 dolphins/km2 (95% CI: 0.052–0.35; CV: 49.60). The estimation for GN was 325 (95% CI: 130–875), whereas for GSJ, it was 104 (95% CI: 42–280) individuals. These are the first estimations of the number and the effective population size for dusky dolphins in a small-scale area along north Patagonia. Dusky dolphins groups are impacted by anthropogenic activities; therefore, the information reported here contributes population information to help to the species management and conservation.

Published
2020
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4. Morphology of the mandibular gnathobases of the copepods Calanus australis and Calanoides carinatus: Evidence of omnivory

Author

Monica Susana Hoffmeyer, Mariana Degrati, and Valeria Carina D'agostino

Subjects
0106 biological sciences, CALANOID COPEPODS, CALANUS AUSTRALIS, 010607 zoology, Zoology, Morphology (biology), Biology, OMNIVOROUS, 010603 evolutionary biology, 01 natural sciences, Ciencias Biológicas, CALANOIDES CARINATUS, Calanus australis, Calanoides carinatus, Animal Science and Zoology, Otros Tópicos Biológicos, NORTHERN PATAGONIAN GULFS, MANDIBULAR GNATHOBASES, CIENCIAS NATURALES Y EXACTAS
Abstract

In spite of the worldwide ecological relevance of Calanus australis and Calanoides carinatus, little is known on the morphology of their mandibular gnathobase edges (MGEs). Thus, in order to further learn about the relationship between MGEs and diet, adults and copepodites of C. australis and C. carinatus collected from northern Patagonian coasts, Argentina, were morphologically analyzed using confocal laser scanning microscopy in transmission mode and scanning electron microscopy. In C. australis males as well as in C. australis and C. carinatus females, MGEs were found to end in one dorsal seta and to have one ventral tooth, four central teeth and three dorsal teeth. In contrast, in C. carinatus males, MGEs were observed to be rudimentary and with no dorsal seta, and −contrary to published data− they were found to have three cone-shaped, short and small tooth-like structures and three-four tooth-like structures that were long and pointed. The main differences between MGEs from copepodites and adults of C. australis and C. carinatus females lied in the number of cuspids observed on the different teeth and the presence of a short inner lateral peak found only in C. australis ventral tooth. Overall, the evidence gathered from our study leads us to classify C. australis and C. carinatus as omnivores. Fil: D'Agostino, Valeria C.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina Fil: Hoffmeyer, Mónica S.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Universidad Tecnológica Nacional. Facultad Regional Bahía Blanca; Argentina Fil: Degrati, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina

Published
2020

5. Potentially toxic Pseudo-nitzschia species in plankton and fecal samples of Eubalaena australis from Península Valdés calving ground, Argentina

Author

Mariana Degrati, Valeria Carina D'agostino, Monica Susana Hoffmeyer, Gaston Osvaldo Almandoz, and Viviana Sastre

Subjects
Eubalaena australis, Otras Ciencias Biológicas, Ice calving, Aquatic Science, Oceanography, Ciencias Biológicas, purl.org/becyt/ford/1 [https], chemistry.chemical_compound, Phytoplankton, purl.org/becyt/ford/1.6 [https], Ecology, Evolution, Behavior and Systematics, Domoic Acid, Phycotoxin, biology, Ecology, Domoic acid, Eubalaena Australis, Plankton, biology.organism_classification, chemistry, Right Whales, Right whale, Pseudo-nitzschia, CIENCIAS NATURALES Y EXACTAS, Península Valdés, Pseudo-Nitzschia Blooms
Abstract

Península Valdés (PV) in Argentina is an important calving ground for the southern right whale Eubalaena australis. However, a high mortality of calves has been observed in the last years, which could be associated with phycotoxin exposure. During a sampling program conducted late in the calving seasons of 2004, 2005 and 2010, potentially toxic species of the genus Pseudo-nitzschia were observed to be an important component of the phytoplankton community and they were also found in fecal samples of two live whales and three stranded whales. In line with this, in the present study Pseudo-nitzschia australis, Pseudo-nitzschia fraudulenta, Pseudo-nitzschia pungens and the complex Pseudo-nitzschia pseudodelicatissima were identified in fecal samples and phytoplankton samples by light and electron microscopy. Although no toxin analysis was carried out in the present study, our findings suggest that E. australis could be exposed to domoic acid in their calving ground. Fil: D'agostino, Valeria Carina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina Fil: Hoffmeyer, Monica Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Universidad Tecnológica Nacional. Facultad Regional Bahía Blanca; Argentina Fil: Almandoz, Gaston Osvaldo. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Sastre, Viviana. Universidad Nacional de la Patagonia ; Argentina Fil: Degrati, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina. Universidad Nacional de la Patagonia. Facultad de Ciencias Naturales. Sede Puerto Madryn; Argentina

Published
2015

6. Seabird and dolphin associations: do seabirds benefit from feeding in association with dusky dolphins in Patagonia?

Author

Griselda Valeria Garaffo, Enrique Alberto Crespo, Mariana Degrati, and Silvana Laura Dans

Subjects
FEEDING ASSOCIATION, COMMENSALISM, biology, Ecology, PENINSULA VALDÉS, Zoología, Ornitología, Entomología, Etología, Aquatic Science, Commensalism, SEABIRD-CETACEAN INTERACTION, Ciencias Biológicas, Geography, biology.animal, Seabird, CIENCIAS NATURALES Y EXACTAS
Abstract

The objective of this study was to describe associations between several species of seabirds and dusky dolphins. We investigated during what dolphin activities seabirds were most commonly associated, and the size of flock in relation to the number of dolphins in a group. Since both seabirds and dolphins may display different feeding strategies, we also investigated if benefits differed among seabird species. Data were collected in Golfo Nuevo (42820′S, 65800′W) onboard a research vessel between 2001 and 2008. A total of 224 mixed groups of seabirds were encountered during this study. The seabird?dolphin associations were mainly observed during dusky dolphin surface feeding. Shearwaters and kelp gulls were mainly observed in flocks that were associated with dolphins, while Magellanic penguins and cormorants were mainly observed without dolphins. Seabirds may be conditioned to the foraging strategy of dolphins, since birds are associated with dolphins only during dolphin surface feeding. This association probably helped seabirds to find prey, but there were no obvious benefits to dolphins. Fil: Degrati, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina Fil: Dans, Silvana Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina Fil: Garaffo, Griselda Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Subsede Instituto Nacional de Investigación y Desarrollo Pesquero; Argentina Fil: Crespo, Enrique Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina

Published
2013

7. Modeling habitat use for dusky dolphin and Commerson's dolphin in Patagonia

Author

Griselda Valeria Garaffo, Enrique Alberto Crespo, Susana N. Pedraza, Mariana Degrati, Silvana Laura Dans, Raúl González, and Adrián Schiavini

Subjects
Aerial survey, Species distribution, Aquatic Science, Spearman's rank correlation coefficient, purl.org/becyt/ford/1 [https], Ciencias Biológicas, Cephalorhynchus, GENERALIZED LINEAR MODEL, DOLPHINS, Lagenorhynchus, HABITAT SELECTION, purl.org/becyt/ford/1.6 [https], Ecology, Evolution, Behavior and Systematics, geography.geographical_feature_category, Ecology, biology, Estuary, DISTRIBUTION MODELING, Biología Marina, Limnología, biology.organism_classification, Fishery, PATAGONIA, Geography, Habitat, Dusky dolphin, CIENCIAS NATURALES Y EXACTAS
Abstract

Several species of small cetaceans inhabit the coastal area of Patagonia (Argentina), but little is known about their distribution and the degree of overlap between them. The goal of the present study was to build habitat-selection models for small cetaceans in order to assess areas of particular importance for the different species. These models were constructed using physiographic and remotely sensed variables. From 1994 to 2007, 13 aerial surveys were conducted along the Patagonian coast (from Golfo San Matías: 40° 40'-42°14' S, 65° 00'-63°47' W to Bahía de los Nodales: 48°00' S, 65°35' W). A grid of 0.5° × 0.5° cells was constructed for the study area. Each cell was characterized by environmental variables and by the encounter rate (ER) for each cetacean species. The ER of each species was investigated in relation to environmental variables using generalized linear models, and model averaging (multimodel inference) was used to obtain a predicted ER for the different species. The correlation between the ER of different species was analyzed by Spearman rank correlation. The environmental variables that were found to be significant predictors of species distribution differed between species. The ERs of dusky dolphin Lagenorhynchus obscurus and Peale's dolphin L. australis showed a positive relationship. Commerson's dolphin Cephalorhynchus commersonii presented a more coastal distribution than the other species, and individuals were more often found feeding in estuarine zones. Knowledge of the patterns of distribution of small cetaceans along the Patagonian coast provides baseline knowledge of how these species interact with each other and their environment. Such information should be considered when managing potential areas of conflict between coastal small cetaceans and human activities. Fil: Garaffo, Griselda V.. Universidad Nacional de Mar del Plata; Argentina Fil: Dans, Silvana Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina Fil: Pedraza, Susana N.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina Fil: Degrati, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina Fil: Schiavini, Adrian Carlos Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Wildlife Conservation Society Argentina; Argentina Fil: González, Raul Alberto Candido. Universidad Nacional del Comahue. Instituto de Biología Marina y Pesquera Almirante Storni; Argentina Fil: Crespo, Enrique Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina

Published
2011

8. Diurnal behavior of dusky dolphins, Lagenorhynchus obscurus, in Golfo Nuevo, Argentina

Author

Enrique A. Crespo, Griselda Valeria Garaffo, Mariana Degrati, Susana N. Pedraza, and Silvana Laura Dans

Subjects
Zoology, Cetacea, LAGENORHYNCHUS OBSCURUS, Research vessel, Ciencias Biológicas, Genetics, medicine, Age composition, Daylight, Lagenorhynchus, ACTIVITY PATTERNS, Ecology, Evolution, Behavior and Systematics, Nature and Landscape Conservation, Ecology, biology, Aquatic animal, Seasonality, Ecología, biology.organism_classification, medicine.disease, DUSKY DOLPHINS, PATAGONIA, Dusky dolphin, Animal Science and Zoology, human activities, CIENCIAS NATURALES Y EXACTAS
Abstract

Las medidas estandardizadas del comportamiento pueden ser una poderosa herramienta para predecir los efectos de las actividades humanas sobre poblaciones naturales de mamíferos. Cuantificamos el presupuesto diario de la actividad de los delfines oscuros (Lagenorhynchus obscurus) en el Golfo Nuevo, Argentina, examinando los cambios de actividad en función de la estación y de los tipos de grupos. Las observaciones fueron hechas desde una embarcación de investigación durante el verano y el otoño desde 2001 hasta 2005. Se utilizó una metodología de seguimiento de grupo focal. La actividad predominante de cada grupo fue registrada usando un muestreo instantáneo, con intervalos de 2 minutos. La actividad mas frecuentemente observada fue el traslado, seguido por nado errático y alimentación. Las madres con cría invirtieron más tiempo en nado errático y descanso, mientras que grupos grandes de adultos y juveniles y los grupos mixtos invirtieron más tiempo en traslado y alimentación. Aunque se encontró un patrón estacional en cuanto al tamaño y la composición de los grupos, poca variación estacional fue encontrada en los presupuestos de la actividad, que fueron casi constantes durante las horas del día. Los resultados generados en este estudio proporcionan información de base para poder detectar diferencias en el comportamiento asociadas al turismo y otras actividades humanas en la región. Standardized measures of behavior can be powerful tools for predicting effects of human activities on natural populations of mammals. We quantified the diurnal activity budget of dusky dolphins (Lagenorhynchus obscurus) in Golfo Nuevo, Argentina, by examining variation in activity as a function of season and age composition of social groups. Observations were made from a research vessel during summer and autumn from 2001 to 2005. Focal group-follow methodology was used. The predominant activity in each social group was recorded using instantaneous sampling, with a 2-min interscan interval. The main daytime activity of dusky dolphins was traveling, followed by milling and feeding. Mother and calf pairs spent more time milling and resting, whereas larger groups of adults and juveniles as well as mixed-age-class groups spent more time traveling and feeding. Although a seasonal pattern of variation in group size and composition was found, little seasonal variation was found in activity budgets, which were almost constant during daylight hours. The activity budget generated by this study provides a baseline for detection of behavioral differences associated with tourism and other human activity in the region. Fil: Degrati, Mariana. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina Fil: Dans, Silvana Laura. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina Fil: Pedraza, Susana Noemi. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina Fil: Crespo, Enrique Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina Fil: Garaffo, Griselda Valeria. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina

Published
2008

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