Distribución espacial del amonio en fiordos y canales comprendidos entre Puerto Montt y Laguna San Rafael en período de primavera

Abstract

An oceanographic expedition was carried out between October 18th and November 15th 1995 in the inlets region and fjords located between Puerto Montt (41° 20’S and San Rafael Lagoon (46° 40’ S) in Southern Chile. The main purpose of the present work is to characterise the spatial distribution of ammonium and its concentration range in the studied region during spring onset. Water samples were collected from a total of 101 oceanographic stations of the expedition Cimar-Fiordo 1. The main part of the water body showed concentrations lower than 1 µmol/L. The higher ammonium concentrations were found in the continental fjords, specially in the area situated south of the narrows of Meninea island, where subsurface maximums greater than 2 µmol/L were found. The vertical distribution of ammonium concentration presents a three layer structure for the whole area. The surface layer was 20 m thick and had concentrations lower than 0.5 µmol/L. This layer was followed in depth by one having a subsurface maximum of ammonium. Finally, a third deep and thicker layer with very low concentrations, even under the limit of detection was found. The continental fjords showed concentrations significantly higher than those of the inlet channels located westward of the main axis formed by the Corcovado gulf, Moraleda, Costa and Elefantes channels. This was particularly the case of the most superficial layer (less than 5 m depth). This difference is attributed to the organic nitrogen supply of land vegetal origin.