Biology and the Carbon Cycle

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biological production due to the year-round presence of ice and a short photo-

synthetic season. Past studies have postulated that the high concentrations of

dissolved organic carbon in surface waters result from the slow growth and

metabolism of bacteria at low temperatures. To determine if biological pro-

cesses play a significant role in the Arctic carbon cycle, the investigators of the

biology program measured nutrients, particulate and dissolved organic carbon,

standing stocks of algae, micro- and mesozooplankton, and rates of primary pro-

duction and bacterial production. Standing stocks and production rates are

described in reports by Gosselin et al., Sherr et al., and Thibault. In this sum-

mary, I describe major patterns in the distribution of nutrients and organic

carbon along the transect. Then, using biomass and rate measurements made

by other investigators, I estimate the turnover time for the pool of dissolved

organic carbon. The results clearly indicate that significant in-situ production

and utilization of organic carbon takes place in the central Arctic Ocean and

that biological processes play an important role in the Arctic carbon cycle.

Samples were collected at 16 major stations across the Arctic, starting in

the Chukchi Sea, proceeding to the North Pole and exiting on the Atlantic

side. Water samples were collected with a CTD/rosette, after moving ice away

from the ship when necessary. Water samples from 1224 depths in the upper

300 m were analyzed for nutrient concentrations, particulate carbon and ni-

trogen, and dissolved organic carbon and nitrogen. Nutrients were analyzed

onboard, while the other samples were stored for later analysis in our shore-

based laboratory.

In general, the major nutrients (nitrate, phosphate and silicate) were present

in sufficient concentrations in surface water (025 m) to support the primary

production of phytoplankton and ice algae. The one exception was low nitrate

concentrations at stations between 76 and 80N, 173 and 178W. In this

region, ice algae in particular may have been nitrogen-limited. Phosphate con-

centrations decreased from 1.0 to 0.6 M along the transect, while silicate

Patricia Wheeler is from the College of Oceanic and Atmospheric Sciences at Oregon State University in Corval-

lis, Oregon, U.S.A.