Hydrography of the Inner Continental Shelf along the Southwest Buenos Aires Province, Argentina: Influence of an Estuarine Plume on Coastal Waters

Estuarine plumes have a significant influence on the characteristics and biology of the adjacent inner shelf. In the sector occupied by the plume, several transformations occur to the sediment and nutrients exported from the continent to the oceans. The coastal zone of Pehuen Co (PC) and Monte Hermoso (MH) is located in a highly complex oceanographic and ecological regional system, which creates the basis of one of the most valuable Argentinean habitats for fishing of commercial species. In this work, the physical oceanographic characteristics of the inner shelf of the southwest Buenos Aires Province and the influence of the Bahia Blanca estuarine (BBE) waters are introduced. The in situ data obtained from oceanographic cruises included vertical profiles of water temperature, salinity, and turbidity. The spatial variability of the parameters was studied with a multivariate statistical analysis. Temperature and salinity presented high seasonal variability (6.1-22.9 degrees C; 33.5-36, respectively). Maximum turbidity occurred throughout the summer (64 nephelometric turbidity units [NTU]) and showed a minimum during spring (24 NTU). The study area was characterized by a significant spatial variability, especially in terms of salinity and turbidity, while water temperature showed a more homogeneous pattern. Salinity and turbidity values decreased from PC (closer to BBE) to MH (further from BBE) stations, with the highest values located near the mouth of the BBE. The PC and MH (to a lesser extent) inner shelves are transitional environments between the estuary and the open beaches of Buenos Aires Province, creating a habitat where benthic and zooplankton estuarine and marine species are found.