Chlorophyll a and primary production in the northeastern Pacific Ocean

The primary production and chlorophyll a concentration of picoplankton (0.2～2μm),nanoplankton (2～20 μm) and micro- plankton (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/m3from 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 na- noplankton 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.