Distributions of chlorophyll and primary productivity in relation to water column structure in the eastern North Atlantic Ocean


  • Denis W. Frazel,

  • G. Berberian


Latitudinal variations in the megascale (103 km) distribution of biological properties are described in relation to water column structure between 60° and 7°N in the eastern North Atlantic Ocean. Stations were occupied along a meridional transect of stations at 20°W in August-September, 1988, during the third leg of the National Oceanic and Atmospheric Administration Global Change Expedition. An additional transect to the south (38°N to 7°N) was occupied to extend the total range of latitudinal observations. Chlorophyll a concentrations were highest in the northern latitudes (<2.51 mg m−3) , decreasing to >0.2 mg m−3 in the vicintiy of the subtropical gyre, south of 40°N. The nitracline was associated with a shoaling of the pycnocline in the northern latitudes. At 7°N, high chlorophyll concentrations (approximately 0.5 mg m−3), and enhanced primary productivity (375.5 mg C m−2 d−1) were associated with a lens of fresh Amazon River Water. Primary productivity rates were variable throughout the transect, ranging from 646.10 mg C m−2 d−1 to 138.26 mg C m−2 d−1. Productivity maxima were located south of Iceland, at 46°N (646.10 mg C m−2 d−1) and in the vicinity of the Azores Front at 35°N (259.85 mg C m−2 d−1). Latitudinal distributions of primary productivity corresponded closely to a model of productivity along a transect at 40°N by Yentsch (1990).