Scales of Variability in a Stable Environment: Phytoplankton in the Central North Pacific

Abstract

Since 1968, scientists from Scripps Institution of Oceanography (SIO) have been studying the structure and dynamics of the epipelagic ecosystem of the central North Pacific Ocean. This Central Pacific Study has its roots in the California Cooperative Oceanic Fisheries Investigations (CalCOFI), an interagency study originally established to understand the disappearance of the sardines from the California Current. Since 1949, CalCOFI has studied the physics, chemistry, and biology of this ecosystem through a series of regular cruises. The California Current is the eastern limb of the huge anticyclonic central North Pacific gyre (Figure 10-1). Current waters are derived from four distinct oceanographic environments and are supplemented locally by upwelling. Each water source has its own physical and chemical signature and its own complement of plankton species (Figure 10-2). The flow of the current is characterized by strong meanders, narrow eddies, and regions of rapid flow, squirts, and jets, embedded in a generally southward flow (Figure 10-3). These complex flow patterns mix and stir together disparate species assemblages, which, in turn, are continually responding to the changes in ambient conditions. Thus, ecosystem structure at any place or time is largely determined by the advective history of the water parcel.