Bering Strait/Chukchi Sea>230 42
Barents Sea <20–200 136
Interior shelves
Beaufort Sea 30–70 8
Kara/Laptev/Siberian Sea 25–50 83
Out-flow
East Greenland Shelf 70 42
Canadian Archipelago 20–40 5
Total Arctic primary production
Sakshaug (2004) >26 >329
Pabi et al. (2008) 44 419
Total Southern Ocean primary production
Arrigo et al. (2008) 57 1949Microbial Food-Webs Are Net Heterotrophic
(^) Bacterial biomass and growth rates are lower in the polar regions than in other oceans.
Growth of heterotrophic bacteria has been thought to be limited by cold polar
temperatures, but a recent comparison of bacterial production in the polar oceans
(Kirchman et al. 2009) suggests that the major factor limiting bacterial growth is the
relatively low amount of labile DOC. In both polar regions, bacterial growth rates
increase with increasing levels of semi-labile DOC. The levels of DOC vary
seasonally and reflect the seasonal cycle of plankton production and consumption.
(^) The balance between autotrophy and heterotrophy can be determined by measuring
net changes in oxygen in incubated seawater samples. Cottrell et al. (2006) showed
both positive and negative net changes in oxygen. Repeated measurements across a
latitudinal gradient in the Chukchi Sea suggest that primary production on the shelf
can be transported to the basin, where respiration exceeds the local levels of
photosynthesis.
(^) Heterotrophic protists are an important component of the arctic plankton. Dilution
experiments in parallel with copepod grazing experiments in the Chukchi and
Beaufort Seas showed that ciliates and heterotrophic dinoflagellates consumed 22 ±
26% of phytoplankton daily growth (Sherr et al. 2009), while copepods consumed
13–28% of primary production (Campbell et al. 2009). In these shallow seas, meso-
and microzooplankton consume about 44% of water-column production, the rest
being available for export to depth.
(^) In comparison to the shelf seas, stocks of plankton are lower in the central arctic
basins, and there are differences in food-web interactions. During a year-long
sampling in the central Arctic, stocks of bacteria and protists doubled during the
growing season (Sherr et al. 2003). The central arctic mesozooplankton biomass is