Chlorophyll and zooplankton in microbasins along the Strait of Magellan - Beagle Channel passage

Abstract

Distributions of chlorophyll and zooplankton were compared to temperature and salinity distributions along previously defined microbasins. Results were consistent for chlorophyll: 1.- Paso Ancho-Seno Magdalena showed a shallow chlorophyll maximum (ca. 5 mg m^-3 at 0 - 20 m) in a vertically homogeneous cold and brackish water column, 2.- Canal Magdalena-Canal Cockburn-Canal Brecknock had relatively lower chlorophyll concentrations (2-3 mg m^-3 at 0-50 m), minor stratification of salinity and a surface lens of warmer water, 3.- Canal Ballenero-Brazo Noroeste had a subsurface layer of high chlorophyll concentration (> 4 mg m^-3) in a vertically stratified water column of 2 salinity layers and 3 temperature layers, 4.- Canal Beagle presented a subsurface chlorophyll maximum (> 4 mg m^-3) extending to the bottom, and vertically homogeneous salinity and temperature distribution. Chaetoceros spp.-dominated phytoplankton was a common feature in the entire area. Zooplankton distributions did not match the above mentioned subdivision of microbasins despite some trends along the passage. High relative abundance of invertebrate larvae in the zooplankton was associated with a matching response to the spring bloom and implies a strong bentho-pelagic coupling.