Strategy of photo-protection in phytoplankton assemblages in the Kongsfjorden, Svalbard, Arctic

Photo-protective functions were investigated in phytoplankton assemblages at Kongsfjorden,Svalbard in spring,using their UV-absorbing compounds(mycosporine-like amino acids(MAAs)),xanthophyll pigments(diadinoxanthin(DD) and diatoxanthin(DT)) and < beta >- dimethylsulphoniopropionate(<beta>- DMSP). The dominant phytoplankton species in the inner bay were dominated by Phaeocystis spp. and nanoflagellates,while the offshore waters were dominated by Thalassiosira spp. In the inner bay,UVabsorbing compounds and xanthophyll pigments exhibited higher ratios of MAA to chlorophyll a(MAA:chl a ratio),and both DD and DT to chlorophyll a(DD:chl a ratio and DT:chl a ratio),respectively.Thus,the photoprotective-pigments such as DD and DT appear to complement MAAs in the natural phytoplankton assemblage. However,the ratio of<beta>- DMSP to chlorophyll a(<beta>-DMSP:chl a ratio) did not show a distinct spatial distribution according to environmental factors or interspecies differences. In this study,we found that photoprotective compounds occurred in a manner dependent on the phytoplankton species composition in Kongsfjorden Bay,where Phaeocystis is the dominant species.

Photo-protective functions were investigated in phytoplankton assemblages at Kongsfjorden, Svalbard in spring, using their UV-absorbing compounds （mycosporine-like amino acids （MAAs））, xanthophyllpigments （diadinoxanthin （DD） and diatoxanthin （DT）） and〈beta〉-dimethylsulphoniopropionate （〈beta〉-DMSP）. The dominant phytoplankton species in the inner bay were dominated by Phaeocystis spp. and nanoflagellates, while the offshore waters were dominated by Thalassiosira spp. In the inner bay, UV- absorbing compounds and xanthophyll pigments exhibited higher ratios of MAA to chlorophyll a （MAA：chl a ratio）, and both DD and DT to chlorophyll a （DD：chl a ratio and DT：chl a ratio）, respectively. Thus, the photoprotective-pigrnents such as DD and DT appear to complement MAAs in the natural phytoplankton assemblage. However, the ratio of 〈beta〉-DMSP to chlorophyll a （〈beta〉-DMSP：chl a ratio） did not show a distinct spatial distribution according to environmental factors or interspecies differences. In this study, we found that photoprotective compounds occurred in a manner dependent on the phytoplankton species composition in Kongsfjorden Bay, where Phaeocystis is the dominant species.