PRIMARY PRODUCTION IN POLAR WATERS - RELATION TO NUTRIENT AVAILABILITY

Temperature, light and dissolved nutrients arc considered the "master" abiotic properties controlling primary production in the ocean. Each of these properties, in turn, is influenced by water column stability and vertical mixing. Sustained research over the past several decades has endeavored to ascertain which of these properties is most important in regulating phytoplankton growth. In no region has this research effort been more evident than at high latitudes. For both polar regions, extremes in each of these properties is the rule in surface waters where phytoplankton grow: the lowest ocean temperatures, the greatest seasonal excursion in incident solar radiation, and thc highest dissolved nutrient concentrations. Based largely on indirect evidence, early researchers speculated that polar primary production was high relative to production at lower latitudes. This was commonly attributed to the abundant surface "macronutrients" (NO3, PO4, H4SiO4) since physiological adaptations to thc suboptimum temperatures and light were thought to characterise these high latitude populations. Intensification of polar research since the late 1960's has in many respects modified this view. Current perspectives arc that important differences exist between the Arctic and Antarctic with regard to the availability and role nutrients play in regulating primary production. In general much less emphasis is now placed on the significance of the macronutrients in the Antarctic although there is speculation and some evidence that "micronutrients" (Fe) may be important. Macronutrient availability appears to play a more important, though secondary, role in the Arctic, that of sustaining rather than initiating phytoplankton growth. This paper reviews early, contemporary. and present research addressing the question. "What role does nutrient availability play in the distribution and magnitude of primary production in Arctic and Antarctic waters?" Emphasis is placed on new research on under-ice communities as well as on the historically studied pelagic communities.