because the overall bloom can be constituted of several, sequential blooms of different
species. Estimates of grazing and phytoplankton sinking would also be good, but
harder to obtain.
Fig. 11.7 Average annual cycling of phytoplankton biomass (solid line) at two North
Atlantic sites. Cycles include a spring bloom, fall bloom, and extreme winter low.
Estimates are from color of 240 mm continuous plankton recorder “silks” after towing
through the regions neighboring the points indicated in all seasons of many different
years (based on Robinson 1970). Peak stock at the more northern site occurs later.
Relative irradiance (short dashes) and nitrate (long dashes) curves are hypothetical.
The standard explanation of the schematic (Fig. 11.7) goes as follows: in winter,