Spatial and temporal variations of particulate organic carbon in the Yellow-Bohai Sea over 2002\u20132016

Hang Fan,Haibo Zhang,Zhitong Yu,Xiujun Wang

doi:10.1038/s41598-018-26373-w

Hang Fan, Haibo Zhang + Show 2 more

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https://doi.org/10.1038/s41598-018-26373-w

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Abstract

The Yellow-Bohai Sea (YBS) is a typical marginal sea in the Northwest Pacific Ocean; however, little is known about the dynamics of particulate organic carbon (POC) and underlying mechanisms. Here, we analyze the spatial and temporal variations of surface POC derived from MODIS-Aqua during 2002–2016. Overall, POC is higher in the Bohai Sea (315–588 mg m−3) than in the Yellow Sea (181–492 mg m−3), and higher in the nearshore than in the offshore. Surface POC is highest in spring in the YBS, and lowest in winter (summer) in the Bohai Sea (the Yellow Sea). The spatial and seasonal patterns of POC are due to combined influences of primary productivity, water exchange, sediment resuspension and terrestrial inputs. Surface POC shows an overall decreasing trend prior to 2012 followed by an upward trend until 2015 in the YBS, which is almost opposite to chlorophyll; the decrease (increase) may result from strengthened (weakened) water exchange with the East China Sea through the Yellow Sea Warm Current. Declined terrestrial runoff is also partly responsible for the decrease prior to 2012. Our study suggests that water exchange and sediment resuspension are dominant factors regulating the spatial and temporal variability of POC in the YBS.

Highlights

The concentration of carbon dioxide (CO2) in the atmosphere has increased from approximately 280 parts per million in the beginning of the Industrial Era to about 400 ppm in 20131
To explore the influence of large-scale climate modes on the dynamics of surface Particulate organic carbon (POC), we examine the correlations of surface POC with Pacific Decadal Oscillation (PDO), North Pacific Gyre Oscillation (NPGO) and El Niño-Southern Oscillation (ENSO) indices
Our study shows large spatial and temporal variations in the surface POC of the Yellow-Bohai Sea

Summary

Introduction

The concentration of carbon dioxide (CO2) in the atmosphere has increased from approximately 280 parts per million in the beginning of the Industrial Era to about 400 ppm in 20131. Limited studies have shown that the Yellow-Bohai Sea is a significant repository of sedimentary total organic carbon with large spatial variability[9,10]; there is a significant seasonal and spatial variability in the POC of the Yellow-Bohai Sea, which may be associated with anthropogenic perturbations and oceanic physical processes[10,11,12,13]. The main anthropogenic impacts in the Yellow-Bohai Sea may include terrestrial runoff and river discharge of nutrients and/or organic matters that promote biological activity[14,15] and lead to higher levels of POC nearshore. Addition, physical and biogeochemical processes in the Yellow-Bohai Sea are largely influenced by the current systems that are linked with the northwest Pacific Ocean through the East China Sea, which may be associated with large-scale climate modes. The Yellow Sea Warm Current, as a branch of the Kuroshio Current extension, may be affected by the El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO)[18,19,20]

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