Search

Two trawl samples of natural sunken wood collected near Vanuatu were identified based on histological studies. Detailed descriptions were made and microphotographs of the cell types were taken, using the three classical sections (cross, tangential and radial). The botanical characters were compared first to the native flora of Vanuatu, then also to the introduced species. The possibility of transportation by ocean currents with a mainly southern and eastern direction is discussed. The first sample lacks apparent colonization marks. Its main histologic character is the presence of `paedomorphic type I rays' which relates it to the shrubby genera Fitchia (Asteraceae) and Fuchsia (Onagraceae): both are known in Polynesia but they seem not to be recorded from Vanuatu. The second wood sample is densely colonized by molluscs and other fauna. It comes from a tree close to the Fabaceae-Mimosoideae, possibly belonging to the genera Leucaena or Serianthes, both known from Vanuatu. Our work shows for the first time that, even after prolonged submergence in water at substantial depth (> 500 m), the wood structure may be well preserved. Therefore, the botanical identification and the determination of the origin of the sunken wood were possible. The two selected samples show completely different colonization patterns, which could be related to differences in chemical composition or to time elapsed since sinking.

Sunken woods are abundant in deep oceanic environments, housing a huge faunal diversity. Studies on that substrate firstly focused on the associated organisms, but since a few years, identification of wood is a further aim. The purpose is to appreciate its degradation state, diversity, geographical origin and to identify specific associations between colonizing organisms and substrates. The first determinations were made on sunken woods from Taiwan/Philippines, the Vanuatu Archipelago, and the Mediterranean Sea. Samples’ identification was based on histological studies. Different preparation techniques were used, depending on their degradation state. Detailed anatomy descriptions were made and compared to the native flora and the introduced species. Wood samples were well preserved. Diversified species were encountered, seemingly originating from local floras. In situ settlements of known wood species will enhance the knowledge of degradation and colonization degrees.