Topic outline

  • General

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    • Prof. Yamaguchi's Laboratory of Marine Biology and Biodiversity, Division of Marine Bioresource and Environmental Science

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      Prof. Atsushi Yamaguchi Page

  • Plankton community as structured by size and major taxon

  • Methods


  • Sampling sites

  • Vertical distribution of plankton biomass


  • Biomass-depth regression



  • Community structure of whole plankton

  • Deep-Sea copepods: species diversity

  • Vertical partitioning within Metridia species

    • Four Metridia species dominate in the western subarctic Pacific. 

      Their vertical distributions are well separated within the 0-4000 m water column. 


  • Life cycle of Gaetanus variabilis

  • Gut contents of Gaetanus variabilis (SEM)

  • Vertical POC flux and copepod ingestion/egestion

  • Conclusion

      • Plankton biomass of whole taxa (from phytoplankton to metazooplankton) was evaluated for whole water column (0-5800 m) at four stations covering from subarctic to subtropical western North Pacific Ocean

      • Throughout the taxa, plankton biomass density decreased with increasing depth, while their decreasing rate is varied with taxa: heterotrophic bacteria < protozooplankton < phytoplankton < metazooplankton

      • Latitudinal changes in taxonomic composition of planktonic biomass were present.  Thus, metazooplankton dominated in the subarctic region, while heterotrophic bacteria and protozooplankton dominated in the subtropical region

      • For calanoid copepods (dominant component of metazooplankton), species diversity formed peaks at mesopelagic (200-1000 m) layers. 

      • Within the same genus, vertical distribution was separated with species down to the greater depths. 

      • Life cycle of suspension feeding copepods living at 500-1000 m had clear seasonal pattern, with their reproduction corresponded with the spring phytoplankton bloom at surface later. 

      • This correspondence of reproduction timing of deep-sea copepods may related with seasonal changes in their food which provided by sinking particles from surface layer. 

      • Calanoid copepods are estimated to be consume 32% of sinking particule flux throughout the water column.

  • Others