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

• Published in: Biogeosciences
• Main Authors: J. Martin, J. É. Tremblay, N. M. Price
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2012
• Subjects: Ecology; QH540-549.5; Life; QH501-531; Geology; QE1-996.5; Arctic
• Online Access: https://doi.org/10.5194/bg-9-5353-2012; https://doaj.org/article/728eb0f4ee5844be9c86dc7a8c0d08a2

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 (NO 3 − ) 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 NO 3 − , with an average f -ratio (i.e., relative contribution of NO 3 − uptake to total N uptake) of 0.74 ± 0.26. The seasonal decrease in NO 3 − availability and irradiance, coupled to the build up of ammonium (NH 4 + ), 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.