Variability in phytoplankton biomass and effects of sea surface temperature based on satellite data from the Yellow Sea, China.

Chunli Liu,Danling Tang,Qiwei Sun,Sufen Wang,Donghe Zhu,Qianguo Xing,Xiang Xing,Hui Zhao

doi:10.1371/journal.pone.0220058

Abstract

A time series of satellite data on Chlorophyll-a concentration (Chl-a) that used ocean color was studied to determine mechanisms of phytoplankton variation in recent decade in the Yellow Sea, China during 2003–2015. The variability patterns on seasonal and inter-annual oscillation periods were confirmed using the Empirical Orthogonal Function (EOF), and Morlet wavelet transform analyses, respectively. The first EOF mode for Chl-a was dominated by obvious spring and fall blooms in a spatial pattern that was related to the strong mixing of the water masses from the Yellow Sea Cold Warm Mass (YSCWM) and the Yellow Sea Warm Current (YSWC) in winter. The second EOF mode for Chl-a showed an opposite spatial pattern between the northern and southern regions. The temporal coefficient showed differences in the timing of blooms. On an inter-annual scale, Chl-a indicated variation at periods of 2–4 years during 2003–2015. Chl-a showed a significantly negative correlation with the sea surface temperature (r = -0.21, p<0.01), with time lags of 4 months (Chl-a ahead). Chl-a was coupled with El Niño Southern Oscillation (ENSO) events, with a positive correlation (r = 0.46, p<0.01) at a lag of 3–5 months (ENSO ahead). The present study demonstrated that the variation in phytoplankton biomass was controlled primarily by water mass seasonally, and it was influenced by ENSO events on an inter-annual scale.

Highlights

Marine phytoplankton is responsible for almost half of the primary productivity in the world [1]
In this study, combined the updated satellite datasets, we examined the variation in Chl-a seasonality during 2003–2015 in the Yellow Sea (30–40 ̊ N, 118–126 ̊ E), using the empirical orthogonal function (EOF)
Chl-a variability based on standard deviations (STD) of annual mean temporal values showed that the lowest STDs (~0.02 mg m3) (Fig 2B) in coastal waters were observed where the highest Chl-a values occurred (Fig 2A)

Summary

Introduction

Marine phytoplankton is responsible for almost half of the primary productivity in the world [1]. What controls their abundance is a key issue for understanding the ocean’s biogeochemical cycle. Recent research has shown that global phytoplankton biomass has decreased since the past century, probably due to increased sea surface temperatures [2]. Phytoplankton biomass is affected by different factors at the regional scale [3,4].

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Results

Conclusion