南極大陸カスミ岩露岩地帯のケイ藻植生

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The Kasumi Rock Ice-Free Area is located at 68°21'5"1.S. and 42°15'13"1.E. This area seems to have experienced not so many years since the glacial epoch, as no evidence of weathering nor weathered rocks were found there. Moss and lichen were not seen either. Only moraines were found in some places. 30 algae samples from 8 ponds were collected in polyethylene bottles. The time available for detailed investigation of the environmental factors was too short. The result is outlined in Table 1. The investigated ponds are 10-100 meters in diameter and less than 60cm in depth. The contents of nutritious salts (P, NH_3, N0_2) in these ponds are so small that a quantitative analysis was impossible, just like the case of the Shin-nan Rock Area. The SiO_2 content was 19-20 mg/l (standard). Ponds in the Kasumi Rock Area can be classified into two groups, one is of fresh water ponds and the other is of brackish water ponds. The former includes Stations 1 and 8, and the other has 5 stations (Stations 2-7). Concerning PH, the former was a little acidic and the latter was alkaline. The Kasumi Rock fresh water ponds contain much more Chlor ion than those of the Shin-nan Rock Area. Station 1 has 358 mg/l Chlor ion. In the brackish water ponds, the Chlor ion content varies with pond, and ranges from 4,959 to 9,523 mg/l. This is ca. 1/2-1/4 of Chlor ion in sea water. Almost all these brackish water ponds contain hydrogen sulfide and have a smell. Their bottom mud is black. In the ponds of the Kasumi Rock Area, blue-green algae and diatoms are predominant, whereas in the Shin-nan Rock Area only blue-green algae are found. The algal vegetation at Kasumi Rock is characterized by diatoms: Diatoms flora of the fresh water ponds differs from that of the brackish water ponds. The former belongs to the Navicula muticopsis association, and the latter to the Navicula cryptocephala var. intermedia-Navicula cryptocephala-Tropidoneis laevissima association. The writer found 46 taxon of diatoms in these ponds. Among 34 taxon already identified, 24 taxon were salt water species. The rest 12 taxon have not yet been identified. Station 1 (Fresh water pond). 6 samples: Navicula muticopsis and 6 other taxon. Navicula muticopsis association. Station 2 (Brackish water pond). 6 samples: Navicula cryptocephala var. intermedia and 16 other taxon. Navicula cryptocephala var. intermedia association. Station 3 (Brackish water pond). 2 samples: Navicula cryptocephala var. intermedia, N. cryptocephala, Tropidoneis laevissima and 16 other taxon. Navicula cryptocephala var. intermedia -N. cryptocephala- Tropidoneis laevissima association. Station 4 (Brackish water pond). 2 samples: Navicula cryptocephala, N. c. var. intermedia, and 4 other taxon. Navicula cryptocephala-N. c. var. intermedia association. Station 5 (Brackish water pond). 2 samples: Navicula cryptocephala var. intermedia and 15 other taxon. Navicula cryptocephala var. intermedia association. Station 6 (Brackish water pond). 2 samples: Navicula cryptocephala var. intermedia, Tropidoneis laevissima and 8 other taxon. Navicula cryptocephala var. intermedia-Tropidoneis laevissima association. Station 7 (Brackish water pond). 9 samples: Tropidoneis laevissima, Navicula cryptocephala var. intermedia, Navicula cryptocephala and 28 other taxon. Tropidoneis laevissima-Navicula cryptocephala var. intermedia-Navicula cryptocephala association. Station 8 (Fresh water pond). 1 sample: Navicula muticopsis and 2 other taxon. Comparing the diatom from the Shin-nan Rock Ice-Free Area with those from the Kasumi Rock Ice-Feee Area, it is known that the kinds and the number of individuals are less in the former area. The writer found that the latter area had many more salt water diatoms than in the former, probably due to the brackish pond existing there.
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南極大陸カスミ岩露岩地帯のケイ藻植生

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