The Pacific islands of Oceania cover almost 15% of the world’s surface and are characterised by a high degree of ecosystem and species diversity. The region is characterised by thousands of isolated small coral atolls and higher volcanic islands, which has led to the high diversity of species found today. In fact, the number of plants and animals found nowhere else on earth (endemic species) is extremely high - often up to 90% for particular groups. Often, these rare and endemic species are adapted to specialised habitats and limited to small areas of a few islands.

American Samoa invasive species strategy and action plan for the only US territory in the South Pacific being such is faced with unique threats with its location from a national perspective and has a need for both nation al and regional collaborations. The ecological integrity of American Samoa is of utmost importance in the face of invasive species. The cultural identity of American Samoans is also closely tied to the ecological integrity of its natural environment.

This is a continuation of the survey of islands in Micronesia and American Samoa for invasive plant species requested by the Pacific Islands Committee, Council of Western State Foresters. A survey of selected Micronesian islands was conducted in 1998 and was discussed in a previous report2. This report is based on perceptions gained from a trip to American Samoa from 16 to 23 July 1999, including the islands of Tutuila, Ofu, Olosega and Ta'u.

This study provides the latest, up-to-date information on the diversity of marine plants (algae and seagrasses) of American Samoa. A general introduction to marine plants is provided, with observations on the flora of the islands. An illustrated guide to 67 macroalgae and seagrasses is provided in this report. The surveys covered 26 sites from four inhabited islands Tutuila, Aunu’u, Ofu and Olosega and two smaller