General
Prof. Yamaguchi's Laboratory of Marine Biology and Biodiversity, Division of Marine Bioresource and Environmental Science
Topic outline
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.
Gut contents of Gaetanus variabilis (SEM)
Adult females collected from 600-700 m depth
Vertical POC flux and copepod ingestion/egestion
Average of 32% of the POC flux is consumed by copepods in the 0-4000 m water column
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.
