Articles | Volume 9, issue 12
Biogeosciences, 9, 5353–5371, 2012
Biogeosciences, 9, 5353–5371, 2012

Research article 21 Dec 2012

Research article | 21 Dec 2012

Nutritive and photosynthetic ecology of subsurface chlorophyll maxima in Canadian Arctic waters

J. Martin1, J. É. Tremblay1, and N. M. Price2 J. Martin et al.
  • 1Québec-Océan & Département de Biologie, Université Laval, Québec, QC, G1V 0A6, Canada
  • 2Department of Biology, McGill University, Montréal, Québec, QC, H3A 1B1, Canada

Abstract. Assessments of carbon and nitrogen (N) assimilation in Canadian Arctic waters confirmed the large contribution of subsurface chlorophyll maxima (SCM) to total water-column production from spring to late fall. Although SCM communities showed acclimation to low irradiance and greater nitrate (NO3) availability, their productivity was generally constrained by light and temperature. During spring–early summer, most of the primary production at the SCM was sustained by NO3, with an average f-ratio (i.e., relative contribution of NO3 uptake to total N uptake) of 0.74 ± 0.26. The seasonal decrease in NO3 availability and irradiance, coupled to the build up of ammonium (NH4+), favoured a transition toward a predominantly regenerative system (f-ratio = 0.37 ± 0.20) during late summer and fall. Results emphasize the need to adequately consider SCM when estimating primary production and to revisit ecosystem model parameters in highly stratified Arctic waters.

Final-revised paper