Phytoplankton pigment patterns in the California Current as determined by satellite l

The satellite images of phytoplankton pigments off California show a high degree of heterogeneity. However, recurrent phytoplankton pigment structures can be identified in the California Current. The major ones are: two sharp boundaries several hundreds of kilometers long; low pigment eddies far offshore interwoven with higher pigment structures immediately inshore; a low pigment intrusion in the Southern California Bight, and a higher pigment region farther offshore; eddies “attached” to shallow coastal areas; and California Current rings spawned far offshore. The larger scale structures of phytoplankton pigments show a remarkable continuity throughout a year, but there is shifting, wobbling, and erosion of these structures. The structures are strong and distinct in spring and summer, weaken through fall (except for a slight intensification in October), and become weakest and poorly defined in late fall-early winter. The patterns of distribution of phytoplankton pigments for a given season tend to reappear from one year to another in the 3 years analyzed. Such recurrency is significant because these patterns may change, and some disappear, within any given year. Clear similarities of the phytoplankton pigment distributions to the field of dynamic height and to an infrared image of sea surface temperature indicate the very important role of ocean circulation, and of phytoplankton nutrient content of the waters, in the generation and maintenance of the observed patterns. The California Current is an eastern boundary current (Wooster and Reid 1963; Smith 1968) that has been extensively studied (e.g. Reid et al. 1958; Hickey 1979; Bernal and McGowan 198 1; Chelton et al. 1982; for an early study using satellite infrared sensors, see Bernstein et al. 1977). Since 1949 the region has been regularly surveyed by the California Cooperative Oceanic Fisheries Investigations (CalCOFI), a multiagency project sponsored by the Marine Research Committee of the State of California. Large spatial scale monthly or quarterly CalCOFI cruises have measured physical, biological, and in some cases chemical properties, but phytoplankton pigments were measured only every third year since 1969 (see Owen 1974). To understand the biology of this region, it is important to have a better knowledge of the content and distribution of phytoplankton in its waters. Furthermore, the asl This work was supported by the Marine Life Research Program of the Scripps Institution of Oceanography. 2 To whom reprint requests should be addressed. sessment of phytoplankton heterogeneity and the identification of its spatial structure constitute important information in biological oceanography, because of the well known nonuniform distribution of marine organisms (Steele 1978), i.e. the so-called patchiness problem. The availability of data obtained by the Coastal Zone Color Scanner (CZCS) onboard the Nimbus-7 satellite (Austin 1980; Hovis et al. 1980) has greatly increased the possibilities of analyzing the patterns of distribution of phytoplankton pigments, both in space and in time (Smith and Baker 1982; Gordon et al. 1983). Here, we use a 34-month CZCS data set, available at the Scripps Satellite-Oceanography Facility, to describe the major phytoplankton pigment patterns in the California Current in time and space. The degree to which CZCS data represent the state of the phytoplankton community, its biomass, and production is uncertain (Cullen 1982). Because light attenuates rapidly with depth, the depths from which the signal is received are thought to vary, depending on the amount and vertical distribution of materials (including plant cells)