Distribución potencial de mamíferos marinos durante el verano austral en el Golfo San Jorge, Argentina

Abstract

Resumen.-El Golfo San Jorge (GSJ) es una región oceanográfica importante debido a la influencia de dos frentes de marea, siendo uno de los sectores más productivos y con alta biodiversidad marina del Mar Argentino. El objetivo de este estudio fue identificar cuáles variables oceanográficas explican la presencia de mamíferos marinos y explorar el solapamiento de la riqueza predicha con las áreas frontales del GSJ durante el verano austral. La distribución potencial de las 9 especies (Balaenoptera sp., Cephalorhynchus commersonii, Globicephala melas, Grampus griseus, Lagenorhynchus australis, L. obscurus, Mirounga leonina, Orcinus orca, Otaria flavescens) fue modelada con Maxent utilizando 6 variables ambientales (batimetría, pendiente del fondo marino, distancia a la costa, distancia al frente de marea, temperatura superficial y concentración de clorofila). Los mamíferos marinos se encontraron más cerca de las áreas frontales que al azar (9,48 km y 13,34 km, respectivamente). La profundidad, la distancia a la costa y la pendiente fueron las variables más importantes en la distribución de todas las especies. Balaenoptera sp., G. melas, G. griseus, L. australis y O. orca mostraron una distribución costera (< 10 km), principalmente al noroeste del golfo. M. leonina, O. flavescens y C. commersonii siguieron la isobata de los 80 m, mientras que L. obscurus se distribuyó en todo el golfo. Las áreas de mayor riqueza predicha se solaparon un 75% con las áreas frontales localizadas al noroeste y sudeste del golfo. Este trabajo provee información de base para el diseño de futuros muestreos que pueden explicar la influencia de los procesos y variación estacional de la distribución de los mamíferos marinos del GSJ. Palabras clave: Modelos de distribución, frentes de marea, mamíferos marinos, Maxent, Golfo San JorgeAbstract.-The San Jorge Gulf (SJG) is an important oceanographic region due to the influence of two tidal fronts, being one of the most productive sectors and with greater marine biodiversity in the Argentine Sea. The aim of this study was to identify which oceanographic variables best explained the presence of marine mammals and to explore the overlap of the predicted richness with the frontal areas of the SJG during the austral summer. The potential distribution of 9 species (Balaenoptera sp., Cephalorhynchus commersonii, Globicephala melas, Grampus griseus, Lagenorhynchus australis, L. obscurus, Mirounga leonina, Orcinus orca, Otaria flavescens) was modeled with Maxent using 6 environmental variables (bathymetry, seafloor slope, distance to the coast, distance to the frontal area, sea surface temperature and chlorophyll a concentration). Marine mammals were found closer to the frontal area than expected by chance (9.48 km and 13.34 km, respectively). Bathymetry, distance to the coast and seafloor slope were the most important variables in the distribution of all the species. Balaenoptera sp., G. melas, G. griseus, L. australis and O. orca showed a coastal distribution (<10 km), mainly in the northwest of the gul...

Spatial Analysis of Benthic Functional Biodiversity in San Jorge Gulf, Argentina

“…The area close to Cape Tres Puntas was characterized by coarse sediments with low concentrations of organic matter and bottom water exhibiting high temperatures, oxygen availability, and chlorophyll a concentrations. This might be associated with the presence of fronts in the south where the primary productivity was high (Glembocki et al, 2015;Retana and Lewis, 2017). The abundance of filterfeeding species in assemblages close to Cape Tres Puntas suggests a more direct dependence on primary productivity.…”

Using Landsat Image Series to Identify and Characterize Persistent Oceanographic Structures in a Dynamic Marine Protected Area (North of San Jorge Gulf, Argentinian Patagonia)

“…In the northern area of this gulf, the Marine Protected Area Parque Interjurisdiccional Marino Costero Patagonia Austral (PIMCPA) was established in 2007 and the trawl fishing was interdicted in 2013 (Figure 1). It is one of the most relevant areas of the Argentine coast in terms of biodiversity and productivity [37,38,57,58] and currently a management plan is being developed in it, involving government and scientific staff. The region encompasses a shallow ecosystem unit of the inner Patagonian Shelf in the Southwestern Atlantic Ocean, an area with depths up to 90 m [59] and including several coastal islands, headlands, and steep slopes, about which detailed information is lacking [36].…”

“…It is influenced by the North Patagonian Frontal System which is forced by seasonal thermal stratification and high energy dissipation of semi-diurnal tides. Semidiurnal tides constitute one of the main ocean forcings of this region, having a typical intertidal range around 4 m [37,60], and due to their seasonality, homogeneous coastal waters remain vertically separated in a stratified water column up to long distances from tshe coast [61,62]. current vector (u,v components) based on the global barotropic model TPXO9-atlas.…”

“…San Jorge Gulf (GSJ) is the biggest of Argentinean Patagonian Gulfs, covered by coldtemperate shelf waters resulting from the mixing process between pure sub-Antarctic waters, coastal waters of continental origin and sea-air fluxes. Due to the influence of two tidal fronts it is one of the most productive sectors, and with the highest marine biodiversity in the Argentine Sea [37]. Its Northern part was established in 2007 as marine protected area by the federal and provincial governments, through an agreement between the National Parks Administration and the Government of the Province of Chubut (Law 26446/2008) because it is one of the most relevant areas of the Argentine in terms of biodiversity and productivity [38].…”

“…Because of its ecological relevance and high dynamism, this area has been previously studied from different perspectives: seabirds and marine mammals communities [37,[39][40][41], bottom characterization (Sánchez-Carnero et al, 2020 [42]), biological and chemical oceanography [43][44][45][46][47][48], physical oceanography [45,[49][50][51], even submesoscale processes characterization [32,36]. However, due to its large size, no systematic study of the submesoscale processes of the entire protected area of the northern San Jorge Gulf has been carried out so far.…”