Possible ecological implications of floating microbial assemblages lifted from the lakebed on an Antarctic lake
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Microbial assemblages can be found drifting/floating in lake water and being washed ashore in continental Antarctica. Two field studies in early and late January 2008 measured the light utilization properties and photosynthetic responses of these assemblages, which were then compared with those of pelagic and benthic microbial communities to evaluate the ecological implications of this phenomenon. The nutrient concentrations were low in the lake water, indicating oligotrophic conditions. Based on microscopic and pigment analysis, both the floating and benthic communities were mainly composed of Oedogonium sp. (Chlorophyceae), followed by cyanobacteria, diatoms, and dinoflagellates. Floating assemblages had a firmer and denser structure, and possessed more rich carotenoids than the benthic community. Measurements of photosynthesis conducted in early January indicated that the activities of the floating assemblages were considerably low. In late January almost all floating assemblages on the lakeshore turned white because of freezing and drying by the ambient temperature decrease, and had no photosynthetic signals. These results suggest that the floating assemblages could spontaneously lift off from the lakebed because of the bubbles created by photosynthesis and then repeatedly roll, flip, sink, or float depending on buoyancy. In addition, this phenomenon seemed to greatly change the cycling of matter by transporting the lake’s photosynthetic products to the surrounding ecosystems, then give the benthic subsurface communities in dark regions a chance to reactivate such as gap regeneration in the case of climax forest, and also allow the floating assemblages to restart photosynthesis at the top of the lakebed by resinking.
KeywordsLake Oligotrophic Photosynthesis Material cycling Production Ecosystem Antarctica Arctic Polar
The authors acknowledge all the members of the 49th Japanese Antarctic Research Expedition, especially its summer party leader, Dr. S. Imura, for their support. The authors also thank Ms. A. Sugimoto for assistance with nutrient analysis.
- Kudoh S, Tsuchiya Y, Ayukawa E, Imura S, Kanda H (2003a) Ecological studies of aquatic moss pillars in Antarctic lakes 1. Macro structure and carbon, nitrogen and chlorophyll a contents. Polar Biosci 16:11–22Google Scholar
- Kudoh S, Watanabe K, Imura S (2003b) Ecological studies of aquatic moss pillars in Antarctic lakes. 2: temperature and light environment at the moss habitat. Polar Biosci 16:33–42Google Scholar
- Kudoh S, Tanabe Y, Matsuzaki M, Imura S (2009) In situ photochemical activity of the phytobenthic communities in two Antarctic lakes. Polar Biol 3:262–271Google Scholar
- Matsumoto GI, Tani Y, Seto K, Tazawa T, Yamamuro M, Watanabe T, Nakamura T, Takemura T, Imura S, Kanda H (2010) Holocene paleolimnological changes in Lake Skallen Oike in the Syowa Station area of Antarctica inferred from organic components in a sediment core (Sk4C-2). J Paleolimnol 44:677–693CrossRefGoogle Scholar
- Quesada A, Vincent WF (1997) Strategies of adaptation by Antarctic cyanobacteria to ultraviolet radiation. Eur J Phycol 32(4):335–342Google Scholar