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

GIUDICI P; GARAFFO G; DANS S; CRESPO E; DEGRATI M; GAGLIARDINI A

Puerto Madryn, Chubut

Workshop; 4th Aquarius/SAC-D Science Workshop; 2008

Comisión Nacional de Actividades Espaciales (CONAE)

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:ES; mso-fareast-language:ES;} @page Section1 {size:595.3pt 841.9pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:35.4pt; mso-footer-margin:35.4pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> 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. High-resolution satellite systems (LANDSAT-TM and ETM+) can provide valuable information for the identification and study of coastal small-scale oceanographic processes. Their capability to estimate the sea surface temperature and to detect suspended matter at the upper layer in addition to their high spatial resolution makes them excellent tools for observing small scale oceanographic processes (e.g. studying fronts and upwellings) in coastal regions. These processes produce a greater productivity and are very important for marine mammals feeding. In Nuevo Gulf, dusky dolphins (Lagenorhynchus obscurus) are common small cetaceans. We qualitatively describe the dynamics of main oceanographic features within the Nuevo Gulf, specifically circulation and seasonal distribution of water temperature, and analyze its influence on spatial patterns of dusky dolphin’s distribution. Random transects were done by a boat (2001-2007) in Nuevo Gulf. All transects and dolphin positions were recorded by a GPS. Also, 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, depending of the season of the year. 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. Dolphins preferred the coldest areas of the gulf and avoided the central zone during the warm season. Therefore, these results allow to say that satellite information, integrated with in situ data has contributed also in a better understanding of the relations between physical and biological processes in this region.