Ōike
| Ōike | |
|---|---|
| 大池 (Japanese) | |
 | |
  Ōike | |
| Location | Minamidaitōjima, Okinawa Prefecture, Japan |
| Coordinates | 25°51′18″N 131°14′19″E / 25.85500°N 131.23861°E |
| Surface area | 0.31 km2 (0.12 sq mi) |
| Max. depth | 1.3 m (4 ft 3 in) |
| Shore length1 | 5.50 km (3.42 mi) |
| 1 Shore length is not a well-defined measure. | |
Ōike (大池) is a karst pond on Minamidaitōjima, Okinawa Prefecture, Japan. Ōike is the largest pond containing both freshwater and seawater.[clarification needed] It covers 0.31 square kilometres (0.12 sq mi), the circumference is 5.50 kilometres (3.42 mi), and it is 1.3 metres (4 ft 3 in) at its deepest point. Fresh water is mixed with seawater beneath.
Geology
The island is composed of elevated limestone from its atoll.[citation needed] Rainwater has dissolved the limestone leading to a depression in the ground (sinkhole). This has filled with water to become a pond.[citation needed]
Natural history
On the north of the pond extends an area of wetland with large communities of Bruguera gymnorrhiza, a mangrove plant, which was designated as a Natural monument since it is unique in freshwater on March 18, 1975.[citation needed] Other plants include Scirpus tabemaemontani C. C. Gemlin, Panicum repens L. Najas marina and Vallisneria natans.[citation needed][clarification needed]
Common carp and Carassius auratus langsdorfii were introduced in 1910 and tilapia in 1955.[citation needed] Birds include mallard, Pacific reef heron, common moorhen and cattle egret.[1]
Footnotes
- ^ Environmental AgencyThe 4th Reports on Japanese Lakes and Ponds- Chugoku, Shikoku, Kyushu and Okinawa 1993
References
- Ministry of the Environment, Environment of lakes and ponds in Japan part 2 1995, Nature and Environment Research Center, ISBN 4-915959-10-4
- Masaaki Tanaka, Lakes and ponds in Japan 2 2004, University of Nagoya Press, ISBN 4-8158-0492-3