Chlorophyll, bacteria and picophytoplankton in ecological provinces of the North Atlantic

A comparative ecology of chlorophyll, bacteria and picophytoplankton is presented for seven ecological provinces in the North Atlantic. Depth-integrated standing stocks of these biota were measured from boreal polar to subtropical gyral regions. Averaging over all sampling times and locations within each province, it appeared that the integrated biomass of bacteria did not exceed that of phytoplankton in any province. Although this biomass ratio often exceeded unity in surface waters of the subtropical gyral provinces, the ratio for the upper water column as a whole was lowered by the subsurface chlorophyll layer. Bacteria and picophytoplankton, as the potential food resource of micrograzers, appeared to complement each other such that their total biomass did not vary much more than 2-fold amongst the seven provinces. Characteristic parameters of the biotic depth profiles, namely surface concentrations, integrated stocks and depth of maximum, were used to cluster the provinces. The original classification of provinces based on surface chlorophyll fields and characteristic regional physics was reinforced by the inclusion of bacteria and picophytoplankton. Crown Copyright (C) 2001 Published by Elsevier Science Ltd. All rights reserved.