Biological-Physical spatial analysis of a plume frontal zone at El Rincón Area, Argentina

HOFFMEYER, M. S.; CUADRADO, M. D.; BIANCALANA, F.; MENÉNDEZ, M. C.; TORRES, E. R; PÍCCOLO, M. C.

Mar del Plata, Buenos Aires, Argentina.

Simposio; IAPSO/ IADO- Symposium: An Ocean Odyssey; 2001

IAPSO-IABO

BIOLOGICAL - PHYSICAL SPATIAL ANALYSIS OF A PLUME FRONTAL ZONE AT EL RINCÓN AREA, ARGENTINA Hoffmeyer, M. S., D. Cuadrado, F. Biancalana, M. C. Menéndez, E. R. Torres and  M. C. Píccolo Instituto Argentino de Oceanografía. Cno. La Carrindanga Km 7.5. 8000, Bahía Blanca. Argentina E mail: bmhoffme@criba.edu.ar This study constitutes a significant contribution to understand the complex relationships existing between physical and biological processes in coastal zones. The study area was the inner shelf zone named “El Rincón” between 39°-40° 30´S and 61°-62° W. Physical and biological data (suspended matter, salinity, temperature, nutrients, chlorophyl a, particulate organic matter, phaeopigments and zooplankton – ichthyoplankton) were obtained from 30 sampling stations aboard the cruise El Austral on November 1993, and analyzed in order to obtain front spatial evidences. Spearman’s rank correlation coefficient was applied to data taking into account the non- lineal character of distribution of the variables. Principal Components and Clusters Analysis were performed.  Statistical results demonstrated the existence of two distinct frontal zones orientated in the NE-SW direction. In the surrounding coasts and mouths of the Bahía Blanca estuary, Colorado River and Anegada bay there is a zone characterized by high values of temperature, particulate organic matter, suspended sediments, silicates, chlorophyll a and phaeopigments. Eastward of that zone, there is an area that is characterized by high values of salinity, zooplankton and ichthyoplankton (eggs and larvae) densities. Between both zones, a buffering area with spatial mixed features was observed. Although this is in general an eutrophic area, results from this study allows to establish a clear distinction between an autotrophic front constructed on the basis of the terrestrial, river and estuary bay inputs on the inshore coast and a heterotrophic front offshore. Spatial plume frontal features are demonstrating why this area is mentioned as nursery ground for some coastal fishes.