MEPS 252:1-13 (2003)  -  doi:10.3354/meps252001

Effects of bio-optical factors on the attenuation of ultraviolet and photosynthetically available radiation in the North Water Polynya, northern Baffin Bay: ecological implications

Christophe Vasseur1,*, Behzad Mostajir2, Christian Nozais1, Michel Denis3, Éric Fouilland4, Bert Klein5, Serge Demers1

1Institut des sciences de la mer de Rimouski, Université du Québec à Rimouski, 310 allée des Ursulines, Rimouski, Québec G5L 3A1, Canada
2Ecosystèmes lagunaires, CNRS, UMR 5119, Université Montpellier II, CP 093, Place Bataillon, 34095 Montpellier cedex 5, France
3Centre d'Océanologie de Marseille, Université de la Méditerranée, Laboratoire d¹Océanographie et de Biogéochimie, CNRS UMR 6535, Parc Scientifique et Technologique de Luminy, Case 901, 13288 Marseille cedex 09, France
4The Scottish Association for Marine Sciences (SAMS), Dunstaffnage Marine Laboratory, Dunbeg, Oban PA37 1QA, Scotland
5Département de biologie, Université Laval, 2503 des Hospitalières, Sillery, Québec G1T 1V6, Canada

ABSTRACT: Recently, the Arctic has experienced a recurrent springtime thinning of the stratospheric ozone layer resulting in increasing ultraviolet-B radiation (UVBR, 280 to 320 nm). However, little is known about the effect of such UVBR enhancement on the Arctic ecosystem. In spring-summer 1998 and fall 1999, 40 stations were investigated in the North Water Polynya (NOW), High Arctic. In the course of this study, 3 periods (pre-bloom, bloom and post-bloom) were distinguished based on chlorophyll a (chl a) concentrations. The attenuation of ultraviolet radiation (UVR) and photosynthetically available radiation (PAR) are reported here. Bio-optical factors, namely particulate organic carbon (POC), dissolved organic carbon (DOC) and chl a concentrations were related to the attenuation coefficient, Kd(λ), of both UVR and PAR. During the pre-bloom period (9 April to 12 May 1998), all bio-optical factors except chl a concentrations were unrelated to Kd(λ). However, the absorption of colored dissolved organic matter might prevail. During the bloom period (15 May to 29 June 1998), both chl a and POC were strongly correlated to Kd(λ). During the post-bloom period (27 August to 25 September 1999), POC contributed from 57 to 83% of the Kd(λ). Under stratification conditions, an inverse relationship was observed in the UVR and PAR ranges, between Kd(λ) and the depth of the subsurface chlorophyll maximum (SCM). This could be a consequence of cell migration below the penetration depth of UVR where they are protected from UVR-induced physiological damages.

KEY WORDS: UVR · PAR · NOW Polynya · Subsurface chlorophyll maximum · Bio-optical factors

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