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Biological Productivity in the Coastal Arctic Ocean
Tremblay, J.-E., Belanger, S., Barber, D.G., Asplin, M., Martin, J., Darnis, G.;, Fortier, L., Gratton, Y., Link, H., Archambault, P., Sallon, A., Michel, C., Williams, W.J., Philippe, B. and Gosselin, M. 2011. Climate forcing multiplies biological productivity in the coastal Arctic Ocean. Geophysical Research Letters 38: 10.1029/2011GL048825.

The authors set the stage for their study by noting that the Canadian Beaufort Shelf and adjacent bays make up a small part of the Arctic Ocean, but that they are of "prime social, economical and cultural importance" for coastal communities, in that they are "hotspots of marine productivity and staging," as well as "feeding areas for large aggregations of resident and migrant marine birds and mammals," citing the work of Carmack and MacDonald (2002).

What was done
Wondering what would happen to the productivity of this important coastal region if it were to warm any further than it already has, Tremblay et al. compared time series of ice cover, wind forcing and satellite-based assessments of photosynthetic carbon production for the years 2002-2008 with corresponding in situ measurements of salinity, nutrients, new production, biological stocks and biogenic fluxes obtained during overwintering surveys in 2003-2004 and 2007-2008.

What was learned
What the fifteen researchers discovered was truly amazing. They report, first of all, that in 2007-2008 -- in areas where ice was no longer present, due to enhanced seasonal warming -- there was significant wind-induced upwelling of growth-promoting nitrates, which were brought up from deep and dark waters into the euphotic zone, where photosynthesis occurs. And as a result of this fertilization effect, the herbivorous copepod Calanus glacialis -- which they say is "the key link between diatom production and apex consumers on Arctic shelves," citing Soreide et al. (2010) -- experienced a total abundance that was "3 to 33 times higher than in 2003 during mid-fall and 1.6 to 13 fold higher than in 2004 during early summer." Also, on the region's central shelf, they observed that "sedimentary chlorophyll a was over 20-fold higher than at any station not influenced by upwelling," and they likewise found that "benthic carbon demand was among the highest ever observed in the Arctic ocean," citing Clough et al. (2005). Therefore, it was not surprising that the end result of these related phenomena was that the "repeated instances of ice ablation and upwelling during fall 2007 and summer 2008 multiplied the production of ice algae, phytoplankton, zooplankton and benthos by 2 to 6 fold."

What it means
Tremblay et al. conclude that the phenomena they observed are "likely to prevail with the increasingly deep and frequent seaward retreat of the central ice pack and the greater incidence of upwelling-favorable winds," as described in detail by Yang (2009); and they state that "new production is also bound to rise as winds gain in intensity and upwelling draws deeper into the nutrient-rich, upper Pacific halocline." These developments should be good news, indeed, for the large aggregations of resident and migrant marine birds and mammals that frequent these important coastal marine communities, as well as for local marine food industries.

Carmack, E. and MacDonald, R.W. 2002. Oceanography of the Canadian Shelf of the Beaufort Sea: A setting for marine life. Arctic 55: 29-45.

Clough, L.M., Renaud, P.E. and Ambrose, W.G. 2005. Impacts of water depth, sediment pigment concentration, and benthic macrofaunal biomass on sediment oxygen demand in the western Arctic Ocean. Canadian Journal of Fisheries and Aquatic Sciences 62: 1756-1765.

Soreide, J.E., Leu, E., Graeve, M. and Falk-Petersen, S. 2010. Timing of blooms, algal food quality and Calanus glacialis reproduction and growth in a changing Arctic. Global Change Biology 16: 3154-3163.

Yang, J.Y. 2009. Seasonal and interannual variability of downwelling in the Beaufort Sea. Journal of Geophysical Research 114: 10.1029/2008JC005084.

Reviewed 7 December 2011