Tonga

Five seagrass species are confirmed from Tonga, Halodule pinifolia, Halodule uninervis, Halophila ovalis, Syringodium isoetifolium and Ruppia maritima.

Seagrass meadows occur in the shallow sheltered bays and lagoons of many of Tonga’s islands. The earliest record of seagrass was in July 1874 when the Challenger expedition dredged flowering Halophila ovalis in abundance off Tongatapu in 33 m.

The most extensive meadows occur in the Tongatapu Island group, with its extensive coral reefs to the north which includes large shallow bays and sheltered lagoons. On the western side of Tongatapu lagoon, seagrass meadows dominate the coastal reef flat around Ha’atafu. Intertidal and shallow subtidal meadows cover much of the nearshore reefs fringing Nuku’alofa harbour, and extensive meadows occur between the islands of Makaha’a, Manima and ‘Oneata. Along the south western shores of Pangaimotu Island, Nuku’alofa harbour, the meadows extend to 20 m depth on coarse sandy substrate. Nearby, Halodule uninervis and Halophila ovalis meadows cover large areas of the shallow enclosed Fanga’uta Lagoon, bordering Nuku’alofa. On the north east of the main island, shallow-reef habitat meadows occur off Manuka. Located on the eastern side of the lagoon, opposite Manuka, are extensive and dense meadows to the north west of Onevai island. Seagrass meadows are also scattered across the large number of bays and coves located in Ha’apai and Vava’u Island groups. Extensive meadows have been reported across the western reef flat of Lifuka, the main island of the Ha’apai Island group¹