Temporal and spatial distribution of phytoplankton pigments in the central Pacific Ocean along 175° E during the boreal summers of 1992 and 1993
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文摘
The long meridional (175° E, 48° N-8° S) distribution of phytoplankton pigments was investigated in the central Pacific Ocean during the boreal summers of 1992 and 1993 by using high-performance liquid chromatography (HPLC). The sampling periods were under El Nino conditions. The distribution patterns of the chemotaxonomical pigments for eukaryotic phytoplankton were characterised: 19′-hexanoyloxyfucoxanthin (a prymnesiophyte marker) and 19′-butanoyloxyfucoxanthin (a pelagophyte marker) were detected throughout the whole study area, fucoxanthin (a diatom marker) was observed north of Kuroshio Extension, and peridinin (a dinoflagellate marker) was found at the stations both north of the Kuroshio Extension and the equatorial area, and the abundance of these pigments detected was not significantly changed (non-parametric one-way ANOVA, P↑0.05) in the whole study area during the two sampling periods. However, the abundance of prokaryotic photoautotrophs (prochlorophytes and cyanobacteria) at the North Pacific subtropical gyre and the equatorial region during the boreal summers of 1993 was significantly higher (P<0.001) than that during the boreal summer of 1992 as estimated by their chemotaxonomical marker, zeaxanthin. The high prokaryotic phytoplankton biomass during the boreal summer of 1993 was also calculated by using the algorithm of Letelier et al. (1993) for partioning total chlorophyll a biomass into contributions by major phytoplankton taxa. The North Pacific subtropical gyre has generally been thought to support a homogeneous, stable biological community, but our result suggests that the abundance of prokaryotic phytoplankton in this gyre may be spatially and temporally variable, and these change can affect primary production and zooplankton biomass.