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.
