Photophysiological responses of phytobenthic communities to the strong light and UV in Antarctic shallow lakes

Yukiko Tanabe, Shuji Ohtani, Nobue Kasamatsu, Mitsuo Fukuchi, Sakae Kudoh

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

Light environment, community structure, pigments, and photophysiological properties of mat-forming phytobenthos were studied in four shallow Antarctic lakes in 2007 at maximum water depths of 1.7-2.5 m. All lakes were oligotrophic, and water transparencies were high, enabling 45-60% of photosynthetically active radiation (PAR, 400-700 nm) and 20-40% of ultraviolet radiation (300-400 nm) to reach the lake beds. Phytobenthic mats were dominated by cyanobacteria and green algae. Little PARL (500-700 nm) penetrated through the firm mat in the shallowest lake, while in the other lakes more (>20%) PARL got through the mats to the subsurface mat layers. Photochemical activities indicated almost no photoinhibition but low photosynthetic efficiency in all mat surface layers. Non-photochemical quenching was rarely detected, suggesting excess energy dissipation may not be efficient in the UV-rich environment. There was a positive correlation between photo-protective substances and incident radiation in the mats, and an inverse correlation between such substances and photochemical efficiency, suggesting that the phytobenthos survive by changing a light-protection/utilization balance. The communities under strong UV-B and PAR had firm mat textures and were characterized by high UV/photo-protective substance ratios that make them less transparent. Maximum relative electron transportation rates (rETRmax) and photochemical efficiencies, however, were low, possibly because the protective substances prevent efficient light usage. In contrast, communities under mild light were characterized by lower substance ratios and softer textures, while rETRmax values and photochemical efficiencies were greater. The phytobenthic mat surface seems to act as a filter for strong and harmful light, typically penetrating through the clear water of Antarctic lakes, and produces a milder light environment for the subsurface mat organisms.

Original languageEnglish
Pages (from-to)85-100
Number of pages16
JournalPolar Biology
Volume33
Issue number1
DOIs
Publication statusPublished - 2010

Keywords

  • Algae
  • Antarctic lakes
  • Photosynthesis
  • Phytobenthos
  • Pigments

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)

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