Remote Sensing identification of Nuevo Gulf dynamics and environmental characteristics: its influence on dusky dolphin’s distribution.

PAULA GIUDICI; GRISELDA V. GARAFFO; SILVANA L. DANS; ENRIQUE A. CRESPO; MARIANA DEGRATI; GAGLIARDINI ANTONIO

Puerto Madryn

Workshop; 4to WORKSHOP DE CIENCIA SAC-D/AQUARIUS; 2008

The knowledge of coastal waters dynamic and their environmental characteristics such as the temperature is urgently needed to help understand their influence on marine biodiversity behavior. LANDSAT-TM/ETM+ satellite missions capability to estimate the sea surface temperature and to detect suspended matter at the upper layer with high spatial resolution make them excellent tools for identification of small scale coastal  processes (e.g. fronts, upwellings and eddies). We qualitatively describe the dynamics of main oceanographic features within the Nuevo Gulf, specifically circulation and seasonal distribution of water temperature. 22 high-resolution images, 10 corresponded to Landsat 5 (TM) and 12 to Landsat 7 (ETM+) from 1999 to 2007 were processed and analyzed. Channel 1 of all images allowed inferring the circulation within the gulf, and Channel 6 permitted to recognized specifics areas of colder and warmer waters. The central zone of the gulf presented the highest temperatures during the warm months. The coldest waters appeared in the southern zone on the gulf’s entrance, were water flows into the gulf as it was observed media the Channel 1. Even though different characteristics may appear between days or years, it was possible to infer a general patron for this study area: in the cold season water homogenize the surfer temperatures, and the only distinctive characteristic recognizable is the entrance flow current. In the warm season surfer water is heterogeneous, finding the warmest water in the central zone and the coldest in the southern zone on the gulf’s entrance, the rest of the gulf has lower temperatures than the center. These characteristics of Nuevo Gulf were compared with spatial distribution pattern of dusky dolphin (Lagenorhynchus obscurus), a common small cetacean of the region.  Dolphin positions were obtained by random transects done on boat (2001-2007) recorded by a GPS. It can be observed that dolphins preferred the coldest areas of the gulf and avoided the central zone during the warm season. Therefore, these results show that satellite information integrated with in situ data has contributed to a better understanding of dolphin’s distribution, which could be a first step of deeper studies of biological and environmental characteristic in Nuevo Gulf.