Impact of ENSO events on phytoplankton over the Sulu Ridge

Xiaoyan Dang; Xiaoyan Chen; Yan Bai; Xianqiang He; Chen-Tung Arthur Chen; Teng Li; Delu Pan; Zhenke Zhang

doi:10.1016/j.marenvres.2020.104934

Impact of ENSO events on phytoplankton over the Sulu Ridge

Mar Environ Res. 2020 May:157:104934. doi: 10.1016/j.marenvres.2020.104934. Epub 2020 Mar 4.

Authors

Xiaoyan Dang¹, Xiaoyan Chen², Yan Bai³, Xianqiang He³, Chen-Tung Arthur Chen⁴, Teng Li⁵, Delu Pan⁵, Zhenke Zhang⁶

Affiliations

¹ School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing, 210023, China; Collaborative Innovation Center for the South China Sea Studies, Nanjing University, Nanjing, 210023, PR China; State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, 310012, China.
² State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, 310012, China. Electronic address: chenxy@sio.org.cn.
³ State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, 310012, China; Institute of Oceanography, Shanghai Jiao Tong University, Shanghai, 200240, China.
⁴ Department of Oceanography, National Sun Yat-Sen University, Kaohsiung, 80424, Taiwan.
⁵ State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, 310012, China.
⁶ School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing, 210023, China.

PMID: 32275514
DOI: 10.1016/j.marenvres.2020.104934

Abstract

Phytoplankton response to interannual climate variability has an important regulatory effect on the regional marine ecological environment and carbon cycle. In this study, we focused on the phytoplankton response in the upwelling region of the Sulu Ridge to the El Niño-Southern Oscillation (ENSO) based on monthly remote sensing chlorophyll-a concentration (Chl-a) and physical parameters from various sources from September 1997 to December 2017. We selected two El Niño events in 1997/1998 and 2015/2016 and two La Niña events in 1998/1999 and 2010/2011 to examine the response of Chl-a to ENSO events in this region. Results showed that El Niño and La Niña could enhance and inhibit the growth of phytoplankton in the Sulu Ridge in winter, respectively. For other seasons, the influence of ENSO on the Chl-a was inconsistent. Specifically, during El Niño events, the largest Chl-a increases occurred in winter, and the low sea surface temperature (SST) center appeared northwest of Sulu Ridge. The significant decrease of SST (~1.5 °C) during El Niño events in winter in the northeastern Sulu Ridge was mainly caused by the increase in Ekman transport (ET) and Ekman pumping velocity (EPV), which brought nutrient-rich subsurface water to the surface layer through the thin barrier layer and enhanced Chl-a. During La Niña events, the SST was higher (~0.8 °C) than the average and the high SST center generally appeared in the middle of the Sulu Ridge with the east-west direction in winter, which was resulted from the intensification of barrier layer thickness (BLT) and the decrease of ET, thus reducing the Chl-a. The different responses to El Niño and La Niña events indicate the high sensitivity of Chl-a in this region to the ENSO.

Keywords: ENSO events; Phytoplankton; Remote sensing; Sulu ridge.

MeSH terms

Chlorophyll A / analysis
El Nino-Southern Oscillation*
Philippines
Phytoplankton / growth & development*
Seasons

Substances

Chlorophyll A