Surface distribution of size-fractionated chlorophyll a and participate organic matter in the Strait of Magellan

Abstract

The surface distribution of chlorophyll a (chl a) from size-fractionated phytoplankton and of particulate organic matter was studied along the Strait of Magellan during late austral summer (February 20th to March 2nd, 1991), in order to contribute an outline of the ecological characteristics of its pelagic compartment. Sampling of surface water was carried out at 2.5 mile intervals, yielding 152 sampling points for chl a and 104 for particulate organic carbon (POC). The Strait appeared as a system strongly controlled by land forcing. Its phytoplankton community was dominated by the picoplanktonic fraction along its entire length, with mean chl a concentrations of 0.74 and 1.17 μg dm−3 for pico- and total phytoplankton, respectively. The microphytoplankton never exceeded 0.02 μg dm−3. POC concentrations, with a maximum of 242.5 and a mean of 144.8 μg dm−3, were mainly of autotrophic origin, as indicated by a mean POC:chl a ratio of 138.4.