Dissolved and Particulate Primary Production and Subsequent Bacterial C Consumption in the Southern East China Sea

Tzong-Yueh Chen,Fuh-Kwo Shiah,Chao-Chen Lai,Gwo-Ching Gong

doi:10.3389/fmars.2020.00713

Abstract

Dissolved primary production (DPP), particulate primary production (PPP), and the subsequent bacterial production (BP) and respiration (BR) were reported for the first time in the NW Pacific. The study area of the subtropical southern East China Sea covers different water types, including oligotrophic Kuroshio and Taiwan Strait waters, as well as nutrient-rich China coastal and upwelled Kuroshio subsurface waters. On an areal basis, DPP and PPP ranged from 67-1649 and 160-1182 mgC m-2 d-1, respectively, showing high values in the upwelling area. The contribution of DPP to total primary production (percent extracellular release; PER) averaged 40.8+/-12.2%with >50% in the upwelling stations. The BP and BR ranged from 48-245 and 709-2822 mgC m-2 d-1, respectively, showing patterns similar to those of primary production. Bacterial growth efficiency (BGE) averaged 5.7+/-1.4%, representing in the lower end of the global ocean values. Phytoplankton and bacteria were well coupled in the upwelling area, whereas primary production could not sustain the bacterial carbon demand (BCD) at other stations. The slope of the log-log relationship between DPP and PPP was >1, indicating that the microbial loop may receive less organic carbon supply in the future warmer, less productive ocean.

Highlights

Photosynthesis is the most important organic carbon source in the ocean (Druffel et al, 1992)
Particulate primary production [particulate primary production (PPP); i.e., the carbon fixed in the particulate form] could be transported to higher trophic levels through grazing food webs, whereas dissolved primary production (dissolved primary production (DPP); i.e., photosynthetic carbon released by phytoplankton) fuels the microbial loop
Dissolved primary production (DPP) has long been recognized as a source of labile organic carbon for heterotrophic bacterial growth (e.g., Cole et al, 1982; Norrman et al, 1995)

Summary

Introduction

Photosynthesis is the most important organic carbon source in the ocean (Druffel et al, 1992). DPP has long been recognized as a source of labile organic carbon for heterotrophic bacterial growth (e.g., Cole et al, 1982; Norrman et al, 1995). DPP is often omitted or only roughly estimated in budgets of the marine organic carbon cycle (Thornton, 2014). Microbial Carbon Fluxes in ECS from

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Conclusion