Ōike | |
---|---|
大池 ( Japanese) | |
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.
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]
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]