A sea bottom classification of the Robredo area in the Northern San Jorge Gulf (Argentina)

Abstract

Benthic habitats are primarily determined by the nature of the substrate (i.e., the type of sediment or rock) and by the bathymetry (e.g., light availability, current, or waves exposition) both determining the viability of infaunal organisms. In this sense multibeam (MB) echosounders provide more data about the sea bottom than any other acoustic technique. During the 2014 Argentine-Canadian survey of the RV Coriolis II in the Gulf of San Jorge, MB data were acquired in the area of Robredo, west of the Marine Protected Area (MPA) Parque Interjurisdiccional Marino Costero Patagonia Austral (PIMCPA, Patagonia, Argentine). Acoustic data were affected by acquisition artifacts, so an ad hoc algorithm was required to restore the data. Moreover, during the survey, dredge samples were also acquired where acoustic data suggested changes in substrate properties, and two later scientific surveys acquired video transects of the sea bottom that allowed also a basic classification. A non-supervised classification of the seabed was performed, using a subsampling and voting algorithm, with the acoustic and bathymetric data. The final classification is in agreement with groundtruthing (dredge samples and video transects), showing that bottom structure complexity leads to a meaningful picture of the sea bottom classes in the area. Our results reveal that Robredo has two subareas, one with a fine substrate (west) and another with a coarse substrate (east), the latter being also characterized by outcropping rock formations of marked relief. Despite the small spatial coverage of the survey, the resulting sea bottom classification presented in this paper has described, for the first time, some important features of the benthic geohabitats in the PIMCPA.