SPATIAL AND TEMPORAL VARIABILITY OF PHYTOPLANKTON PIGMENT DISTRIBUTIONS IN THE CENTRAL EQUATORIAL PACIFIC-OCEAN

During the 1992 U.S. JGOFS Equatorial Pacific (EqPac) study, we partic ipated in survey (12 degrees N-12 degrees S, along 135 degrees-140 deg rees W) and time-series (0 degrees, 140 degrees W) cruises to identify the factors that control spatial and temporal Variations in phytoplan kton pigment biomass, taxonomic composition and size structure. To ach ieve this goal, we determined pigment marker distributions in conjunct ion with collaborative measurements performed by EqPac investigators. Distributions of phytoplankton pigments measured during early 1992 (EI Nino conditions) were different from those measured during late 1992 (''normal'' conditions). Most notably, the accessory pigment distribut ions revealed that the 1991-1992 EI Nino event produced a significant reduction in eukaryotic phytoplankton biomass, especially that contrib uted by prymnesiophytes, pelagophytes and diatoms. This Variability wa s most likely caused by a combination of physical (Kelvin waves, tropi cal instability waves and advection), chemical (iron limitation) and b iological (growth-grazing imbalances) processes. The results of this p igment study underscore the need for sampling biological properties on the appropriate time and space scales, and the necessity of physical measurements for interpreting their distributions. Copyright (C) 1996 Elsevier Science Ltd.