Estimation of the Annual Primary Production and Sea Surface Nitrate Concentration with Remote Sensing at the Iedo Ocean Research Station

Abstract

The new production of phytoplankton based on nitrate is very important to understand how much portion of primary production passes on to higher trophic levels and sinks into deeper ocean. In this study, inter-annual variation of the annualprimary production and contribution of small-sized phytoplankton were analyzed at the Iedo Ocean Research Station with MODIS-Aqua satellite datasets from 2012 to 2017. Moreover, sea surface nitrate (SSN) concentration was also estimated with satellite datasets. Annual primary production in the study site ranged from 299.0 g C m-2 yr-1 to 328.1 g C m-2 yr-1 during the study period. Contribution of small-sized phytoplankton to the annual primary production ranged from 8.52 % to 10.30 %. The estimation of SSN concentration was performed with a regional empirical algorithm which is based on sea surface temperature (SST) and chlorophyll-a concentration. However, we found some disagreements between satellite-derivedSSN concentrations and in-situ SSN concentrations. Generally, the nutrient concentration in the East China Sea is closely related with the sea surface salinity (SSS) due to the existence of the Changjiang River. It suggests that the algorithm for the SSN concentration in the East China Sea should be considered for the sea surface salinity. An improvement of the SSN algorithm will allow us to estimate annual new production at the Iedo Ocean Research Station.