Lake Saroma is the third largest lake of Japan located on the north-eastern shore of Hokkaido about 30 km away from Abashiri City. The lake is very shallow for its size (maximum depth 19.5 m, mean depth 8.7 m), and is separated from the Sea of Okhotsk by a 20 km-long sandbar (only 150-500 m wide). A narrow opening through the sandbar makes the lake water brackish with a normal chloride concentration of 17-18%. The lake is mesotrophic, as indicated by a normal transparency value of about 6 m, and is known for various kinds of aquaculture (oyster, scallop, smelt, laver, etc.).

Extensive stands of a halophyte, Salicornia europaea, with succulent stems and small scale-like leaves turn coastal salt marsh of the lake into deep red with its autumnal color. The lake is surrounded by wide reed zone and deciduous forests with many oak trees. It is included in Abashiri Quasi-national Park, designated by the Prefectural Government of Hokkaido for its scarcely populated wild natural landscape (Q, 2).