Photoadaptation of sea-ice microalgae in the Barents Sea

Abstract

Variations in under-ice scalar irradiance, P vs I parameters and the CHL a C-1 ratio of natural assemblages of sea-ice microalgae from the Barents Sea growing at -1.8°C in May and September 1988 are described, including one diurnal station. CHL a C-1 ratios of 0.031-0.071 mg mg-1 indicate shade adaptated assemblages both in May and September. Values for αB (photosynthetic efficiency) were generally low, e.g. 0.0025-0.0078 mg C (mg CHL a)-1 h-1 (μmol m-2 s-1)-1, and should be typical for self-shaded algae in mats or aggregates of about 4 mm thickness. Provided no self shading and the typical spectral distribution of light under ice without algae, αB would, however, be about 2.5 times higher. Photoinhibition of the photosynthetic response was negligible. Maximum carbon uptake PmBwas 0.15-0.24 and 0.032-0.088 mg C (mg CHLa)-1 h-1 in May and September, respectively. Diurnal variations were small, particularly for PmB. Calculations of the maximum specific gross growth rate yielded an upper limit of 0.20-0.24 and 0.01-0.04 d-1 for assemblages in May and September, respectively; the latter may have been in a resting stage. © 1991 Springer-Verlag.