Living-resource & Ecosystem Dynamics on the Slope of the South China Sea (LEDS)

Summary of the project

Mesopelagic fish is one of potential marine living resources and its vertical migration is one of major vertical carbon-transport processes in the global ocean.  The northern slope region of the South China Sea (SCS) is the breeding and nursing ground for commercially-valuable fish species such as octopus and tuna.  The large amount of mesopelagic fish in the slope region is one of primary prey items for bottom and pelagic fish species. Their vertical migration behavior potentially plays a key link between lower and higher trophic levels as predators on zooplankton and as prey for bottom and pelagic fishes, and between surface and deep layer ecosystems by feeding in the surface layer during the night and resting and excreting in the deep layer (400-1000 m) during the day.  Understanding the functions of mesopelagic fish in ecosystems and carbon export is critical in understanding shelf-slope marine ecosystem, resource protection and utilization, and carbon sequestration in the ocean.  The project “Living-resource & Ecosystem Dynamics on the Slope of the South China Sea (LEDS)” is funded by the 973 Plan Program under the Chinese Ministry of Science and Technology to address these primary scientific questions,

  • how the physical, biogeochemical and biological processes are coupled to support a highly productive slope ecosystem, and
  • how mesopelagic fish affect the biomass flow between trophic levels and ecosystem stability in the slope region.

The interdisciplinary project team consists of 1) physical oceanography, 2) biogeochemical oceanography, 3) microbial oceanography, 4) marine plankton, 5) fisheries oceanography and 6) fish acoustics and vertical process groups addressing mesoscale physical processes, nutrient and trace metal transport and limitations on primary production, microbial recycling, plankton community structure and abundance, fish species compositions, distribution and behaviour, and trophic dynamics.  The project period is between Jan 2014 and Dec 2018.

The project intends to address the research theme “Ecosystem dynamics and sustainability of marine resources in the tropical and South China Sea” in the Chinese 973 Plan Program.  The project objectives are to understand:

  • Seasonal variability in productivity and biomass transfer efficiencies between trophic levels
  • Effects of mesoscale processes on ecosystem structure and functioning
  • Effect of prey-predator relationships and vertical migration behavior of mesopelagic fish on ecosystem functions and biomass transport and transformation

The specific tasks of this project include:

  1. Developing mesoscale physical models to understand generation and decay mechanisms of mesoscale eddies in the slope region
  2. Developing biogeochemical models to understand transport, transformation and recycling of nutrients and organic matters
  3. Developing microbial dynamic model to understand microbial processes in metabolic pathway and functioning responding to dissolved and particular organic carbon
  4. Developing plankton models to understand plankton community structures, primary production, coupling between plankton and mesopelagic fish, and their seasonality
  5. Developing foodweb models to understand biomass paths from primary production to mesopelagic fish, and ecosystem productivity
  6. Developing horizontal and vertical migration behavior models of mesopelagic fish to understand their effects on biomass transport and mesopelagic ecosystem
  7. Developing an interdisciplinary team to address emerging environmental, ecosystem and climate questions.

The project research plan includes:

  1. Retrospective analysis of physical, biogeochemical, biological, fisheries and remote sensing data which will provide guidance for cruise and experimental designs, and long term trends and variations of environment and ecosystems in the northern slope region of the SCS;
  2. Physical and ecosystem models which will provide real-time predictions of hydrographic and biogeochemical fields for guiding in-situ field studies and tools to synthesize in-situ observed, experimental and lab analyzed data;
  3. Remote sensing models to analyze sea surface temperature, ocean color and altimetry data for understanding seasonal and interannual variability, episodic events, and Lagrangian Coherent Structures,
  4. In-situ observations and experiments in 3 cruises (fall 2014, spring-summer 2015, and winter -spring 2017), including in each cruise:


  • A large scale survey
  • A time series process study station


  • Temperature, salinity and ADCP current fields
  • Nutrients, trace metals, radium isotopes, POC, DOC, DO, and oxygen isotopes from water samples,
  • Phytoplankton, bacteria, zooplankton and POC from water samples, net tows and in-situ optical packages
  • O2/Ar ratio and trace metal continuous measurements from underway systems
  • Underway fish acoustics at 2 frequencies (38 and 120 kHz)
  • Mesopelagic and bottom fish compositions from midwater and bottom trawls

onboard experiments:

  • Primary production
  • Trace metal runout experiments
  • Dilution experiments of microzooplankton

5. Synthesis of physical, biogeochemical, biological and fish data through physical, biogeochemical and fish behavior models.

Area of study

Northern slope of the South China Sea (figure)

Time Table for activities

January 2014 – December 2018