Size-fractionated chlorophyll a and primary productivity in the Chukchi Sea and its northern Chukchi Plateau

Abstract

Investigations on chlorophyll a and primary productivity were carried out in the Chukchi Sea and its northern Chukchi Plateau during the 2 nd Chinese National Arctic Research Expedition in the summer of 2003. The results showed that chlorophyll a concentrations were 0.009–30.390 μg/dm 3 at the surveyed waters; the surface chlorophyll a concentrations were 0.050–4.644 μg/dm 3 and the average value was (0.875±0.981) μg/dm 3 in the surveyed area. In the Chukchi Sea Shelf, chlorophyll a concentrations at the depth from 10 m to bottom were higher than that in the surface water, and the concentrations were lower at the depth below 75 m in the Chukchi Plateau. Chlorophyll a concentrations descended in 3 sequential samplings on Transect R, with average values of (2.564±1.496) μg/dm 3, (1.329±0.882) μg/dm 3 and (0.965±0.623) μg/dm 3, respectively. The potential primary productivity ((2.305± 1.493) mgC/(m 3·h)) in the Chukchi Sea was higher than that ((0.527±0.374) mgC/(m 3·h)) in the Chukchi Plateau. The results of the size-fractionated chlorophyll a and primary productivity showed that microplankton accounted for the majority of the total chlorophyll a (63.13%) and primary productivity (65.16%) at the survey stations. The contributions of the nanoplankton and picoplankton to the total chlorophyll a and primary productivity were roughly the same.