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, K_d(l), 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 K_d(l). 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 K_d(l). During the post-bloom period (27 August to 25 September 1999), POC contributed from 57 to 83% of the K_d(l). Under stratification conditions, an inverse relationship was observed in the UVR and PAR ranges, between K_d(l) 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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Published in MEPS Vol. 252 (2003) on April 30
Print ISSN: 0171-8630; Online ISSN: 1616-1599. Copyright © Inter-Research, Oldendorf/Luhe, 2003