Association of picophytoplankton distribution with ENSO events in the equatorial Pacific between 145 degrees E and 160 degrees W

作者：Matsumoto K^*; Furuya K; Kawano T

来源：Deep Sea Research Part I: Oceanographic Research Papers , 2004, 51(12): 1851-1871.

DOI：10.1016/j.dsr.2004.07.015

• picophytoplankton
• Prochlorococcus
• Synechococcus
• picoeukaryotes
• equatorial Pacific
• ENSO

Climatological variability of picophytoplankton populations that consisted of >64% of total chlorophyll a concentrations was investigated in the equatorial Pacific. Flow cytometric analysis was conducted along the equator between 145degreesE and 160degreesW during three cruises in November-December 1999, January 2001, and January-February 2002. Those cruises were covering the La Nina (1999, 2001) and the pre-El Nino (2002) periods. According to the sea surface temperature (SST) and nitrate concentrations in the surface water, three regions were distinguished spatially, viz., the warm-water region with > 28 degreesC SST and nitrate depletion (< 0.1 mumol kg(-1)), the upwelling region with < 28 degreesC SST and high nitrate (>4 mumol kg(-1)) water, and the in-between frontal zone with low nitrate (0.1-4 mumol kg(-1)). Picophytoplankton identified as the groups of Prochlorococcus, Synechococcus and picocukaryotes showed a distinct spatial heterogeneity in abundance corresponding to the watermass distribution. Prochlorococcus was most abundant in the warm-water region, especially in the nitrate-depleted water with > 150 x 10(3) cells ml(-1), Synechococcus in the frontal zone with > 15 x 10(3) cells ml(-1), and picoeukaryotes in the upwelling region with > 8 x 10(3) cells ml(-1). The warm-water region extended eastward with eastward shift of the frontal zone and the upwelling region during the pre-El Nino period. On the contrary, these regions distributed westward during the La Nina period. These climatological fluctuations of the watermass significantly influenced the distribution of picophytoplankton populations. The most abundant area of Prochlorococcus and Synechococcus extended eastward and picoeukaryotes developed westward during the pre-El Nino period. The spatial heterogeneity of each picophytoplankton group is discussed here in association with spatial variations in nitrate supply, ambient ammonium concentration, and light field.

• 出版日期2004-12