Preliminary investigation of Okhotsk Sea ice algae; taxonomic composition and photosynthetic activity

Abstract

Okhostsk Sea pack ice from Shiretoko in northern Hokkaido,March 2007, contained microalgal communities dominated by the centric diatoms Thalassiosira nordenskioeldi and Thalassiosira punctigera. Domination by this genus is very unusual in sea ice. Communities from nearby fast ice at Saroma-ko lagoon were dominated by Detonula conferavea and Odontella aurita. Average microalgal biomass of the Okhotsk Sea pack ice (surface and bottom) was 1.59±1.09 µg chla l-1 and for fast ice (bottom only) at nearby Saroma-ko lagoon, 16.5±3.2 µg l-1 (= 31.1±5.0 mg chla m-2). Maximum quantum yield of the Shiretoko pack ice algal communities was 0.618±0.056 with values from different species ranging between 0.211 and 0.653. These community values are amongst the highest recorded for sea ice algae. Rapid light curves (RLC) on individual cells indicated maximum relative electron transfer rates (relETR) between 20.8 and 60.6, photosynthetic efficiency values (α) between 0.31 and 0.93 and onset of saturation values (Ek) between 33 and 91 µmol photons m-2 s-1. This data implies that the pack ice algal community at Shiretoko was healthy and actively photosynthesising. Maximum quantum yield of the Saroma-ko fast ice community was 0.401±0.086, with values for different species between 0.361 and 0.560. RLC data from individual Saroma-ko fast ice algal cells indicated relETR between 55.3 and 60.6, α values between 0.609 and 0.816 and Ek values between 74 and 91 µmol photons m-2 s-1. This data is consistent with measurements of these parameters in previous years.