MEPS 412:69-84 (2010)  -  DOI:

Prevalence, structure and properties of subsurface chlorophyll maxima in Canadian Arctic waters

Johannie Martin1,*, Jean-Éric Tremblay1, Jonathan Gagnon1, Geneviève Tremblay2, Amandine Lapoussière2, Caroline Jose2, Michel Poulin3, Michel Gosselin2, Yves Gratton4, Christine Michel5

1Québec-Océan & Département de biologie, Université Laval, Québec, Québec G1V 0A6, Canada
2Institut des sciences de la mer (ISMER), Université du Québec à Rimouski, Rimouski, Québec G5L 3A1, Canada
3Canadian Museum of Nature, Ottawa, Ontario K1P 6P4, Canada
4Institut National de Recherche Scientifique, Centre Eau, Terre et Environnement, Québec, Québec G1K 9A9, Canada
5Freshwater Institute, Fisheries and Oceans Canada, Winnipeg, Manitoba R3T 2N6, Canada

ABSTRACT: Comprehensive investigations of the Canadian Arctic during late summer and early fall revealed the widespread occurrence of long-lived subsurface chlorophyll maxima (SCM) in seasonally ice-free waters. The vertical position of the SCM corresponded with the depth of the subsurface biomass maximum (SBM), at least in Baffin Bay, suggesting that SCM could be an important source of carbon for the food web. Most of these SCM were located well below the pycnocline in close association with the nitracline, implying that their vertical position was driven mainly by a shortage of inorganic nitrogen in the upper euphotic zone. The diversity of SCM configurations with respect to physical properties of the water column complicates the estimation of euphotic-zone chlorophyll and primary production from surface properties. High photosynthetic yields (Fv/Fm) showed the phytoplankton to be photosynthetically competent and well acclimated to conditions of irradiance and nutrient supply near the surface and at the SCM. A well-defined primary nitrite maximum was associated with the SCM in the southwest Canadian Arctic, but not in the northeast where nitrite concentrations were highest much below the euphotic zone. This contrast is consistent with differences in vertical stratification, the light–dark cycle and, possibly, the physiological state and taxonomic composition of the phytoplankton community at the SCM. This study demonstrates that the SCM, once regarded as anecdotal due to under-sampling, are a dominant feature of the Arctic Ocean that should be considered in remote sensing studies and biogeochemical models. 

KEY WORDS: Subsurface chlorophyll maximum · Deep chlorophyll maximum · Subsurface biomass maximum · Phytoplankton · Arctic · Nutrients · Nitrogen · Photosynthetic yield

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Cite this article as: Martin J, Tremblay JÉ, Gagnon J, Tremblay G and others (2010) Prevalence, structure and properties of subsurface chlorophyll maxima in Canadian Arctic waters. Mar Ecol Prog Ser 412:69-84.

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