Chlorophyll a and primary production in the northeastern Pacific Ocean

The primary production and chlorophyll a concentration of picoplankton (0.2~2 μm), nanoplankton (2~20 μm) and microplankton (20~200 μm) are described in the northeastern Pacific Ocean near the Hawaii Islands during the six survey cruises from 1996 to 2003:DY85-4, DY95-7, DY95-8, DY95-10, DY105-11 and DY105-12.14. The primary production of carbon was in range from 76.8 to 191.9 mg/(m²·d) with an average of 116.1 mg/(m²·d) in the east region, and from 73.1 to 222.5 mg/(m²·d) with an average of 127.1 mg/(m²·d) in the west region, similar to the other oligotrophic regions of the Pacific Ocean investigated. The chlorophyll a concentration was about 0.1 mg/m³ from the surface to the 50 m depth, about 0.2~0.4 mg/m³ from 50 to 100 m, and gradually decreased below the 100 m depth. The picoplankton accounted for more than 70% of the total chlorophyll a in the upper layer (surface to 125 m), but it decreased to less than 50% in depth below 125 m. The nanoplankton and microplankton combined only accounted for less than 30% of the total chlorophyll a in the upper layer, but showed a more even vertical distribution.