First Concurrent Measurement of Primary Production in the Yellow Sea, the South Sea of Korea, and the East/Japan Sea, 2018

Hyo-Keun Jang,Jae-Joong Kang,Sang-Heon Lee,Yejin Kim,Dabin Lee,Seok-Hyun Youn,Myung-Joon Kim,Naeun Jo,Huitae Joo,Kwanwoo Kim,Soohyun Kim

doi:10.3390/jmse9111237

Abstract

Dramatic environmental changes have been recently reported in the Yellow Sea (YS), the South Sea of Korea (SS), and the East/Japan Sea (EJS), but little information on the regional primary productions is currently available. Using the 13C-15N tracer method, we measured primary productions in the YS, the SS, and the EJS for the first time in 2018 to understand the current status of marine ecosystems in the three distinct seas. The mean daily primary productions during the observation period ranged from 25.8 to 607.5 mg C m−2 d−1 in the YS, 68.5 to 487.3 mg C m−2 d−1 in the SS, and 106.4 to 490.5 mg C m−2 d−1 in the EJS, respectively. In comparison with previous studies, significantly lower (t-test, p < 0.05) spring and summer productions and consequently lower annual primary productions were observed in this study. Based on PCA analysis, we found that small-sized (pico- and nano-) phytoplankton had strongly negative effects on the primary productions. Their ecological roles should be further investigated in the YS, the SS, and the EJS under warming ocean conditions within small phytoplankton-dominated ecosystems.

Highlights

Marine phytoplankton as primary producers play an important role as the base of the ecological pyramid in the ocean and are responsible for nearly a half of global primary production [1,2]
Seasonal water temperatures and salinities in the Yellow Sea (YS), the South Sea of Korea (SS), and the East/Japan Sea (EJS) were evenly distributed within the euphotic zone except in August
The mean temperatures within the euphotic zone in the YS, the SS, and the EJS were lowest in February, with means of 5.9 (S.D. = ± 2.3), 13.6 (± 1.3), and 9.9 (± 1.7) ◦ C, respectively, and gradually increased to their highest in August, with means of

Summary

Introduction

Marine phytoplankton as primary producers play an important role as the base of the ecological pyramid in the ocean and are responsible for nearly a half of global primary production [1,2]. Some notable changes in physicochemical conditions were reported, such as increasing limitation of nutrients in the YS and rapid ocean acidification and shoaling of the mixed layer depth in the EJS [16,17,18,19]. These recent environmental changes could result in alterations in biological characteristics, including community structure and bloom pattern of phytoplankton and subsequently higher-trophiclevel organisms [12,20,21,22]. We still have a lack of information on regional primary productions of phytoplankton for understanding the current status of the marine ecosystems in the YS, the SS, and the EJS

Methods

Results

Conclusion