Phytoplankton phenology in the East Sea: the effect of environmental forcing on seasonal cycles (1998-2014)

Abstract

The phytoplankton seasonality controls the recruitment success of higher trophic levels and drives the carbon export production. We investigated the change in phytoplankton seasonality in the East Sea using the long-term time series of chlorophyll a concentration derived from satellite ocean color for the years 1998-2014. The phytoplankton phenology was analyzed using a shifted Gaussian function to estimate bloom initiation, peak timing, duration and peak magnitude. The phytoplankton seasonality showed spatially different patterns. The variability of seasonality parameters in the southern area is much higher than that in the northern area. In the southwestern area of the East Sea, in spring, the bloom timing was delayed and bloom duration was shortened, whereas in autumn, the bloom was advanced and lasted longer. The bloom peak was the most variable parameter in both spring and autumn. The bloom initiation in spring showed a positive relationship with the peak timing, but a negative correlation with the bloom duration. The bloom initiation in spring were more strongly correlated with environmental factors than peak timing and duration, especially wind stress.orophyll a concentration derived from satellite ocean color for the years 1998-2014. The phytoplankton phenology was analyzed using a shifted Gaussian function to estimate bloom initiation, peak timing, duration and peak magnitude. The phytoplankton seasonality showed spatially different patterns. The variability of seasonality parameters in the southern area is much higher than that in the northern area. In the southwestern area of the East Sea, in spring, the bloom timing was delayed and bloom duration was shortened, whereas in autumn, the bloom was advanced and lasted longer. The bloom peak was the most variable parameter in both spring and autumn. The bloom initiation in spring showed a positive relationship with the peak timing, but a negative correlation with the bloom duration. The bloom initiation in spring were more strongly correlated with environmental factors than peak timing and duration, especially wind stress.