Possibility of using the SBE profilometer data for calibration of satellite data on concentration of chlorophyll <i>a</i> in the Japan Sea

Abstract

Chlorophyll a (Chl) concentration in the upper 100 m layer of the northwestern Japan Sea is measured both by fluorimeter Wetlabs mounted on oceanographic sonde-profilometer SBE 911 and by standard spectrophotometric method in the 1st Russian-Chinese survey in the autumn of 2010. Biomass and species composition of phytoplankton at the seas surface are determined in the same time. For the whole area of measurements, the data on Chl defined by two methods correlate weakly (R2 = 0.22). However, after dividing the investigated area onto five local areas taking into account oceanographic patterns and satellite data on Chl concentration (8-day composite images), the correlation becomes higher for any local area (R2 from 0.57 to 0.91). Inclination of regression between the data measured by two methods (ratio fluorescence : concentration) varies between the areas, as well - from 0.76 above the continental slope of middle Primorye to 1.70 at Kito-Yamato Bank. This variability is reasoned by variations of both oceanographic conditions and species composition of phytoplankton. Instability of Chl fluorescent ability should be considered when satellite data on Chl concentration are used.

Keywords

• microalga
• chlorophyll
• phytoplankton biomass
• regression model
• satellite data