Ecology of the tube-building polychaete Diopatra leuckarti Kinberg, 1865 (Onuphidae) in Hawaii: community structure, and sediment stabilizing properties*

Large numbers of the tube-building polychaete Diopatra leuckarti Kinberg form extensive mounds of sand on a Hawaiian reef-fiat, providing a stable environment with plentiful resources to support a diverse invertebrate community. The vertically oriented tubes reach densities of 21 800 m−2 and the projecting tubes trap drift algae and sediments which are sources of food and tube-building materials for the associated community. There are 22 polychaete species, six crustacean species and eight of other taxa represented, with Leptochelia dubia (tanaid) and Capitella capitala (capitellid) as the dominant organisms, reaching densities of 32 800 m−2 and 11600 m−;2, respectively. Both species form fine mud tubes on the sediment surface among the Diopatra tubes. Other numerically abundant taxa are the deposit feeders comprising orbiniid, capitellid and cirratulid polychaetes, small crustaceans and a holothurian. Crustaceans, fishes and polychaetes are the primary predators. Both low salinities (15–26%, at low tides) due to ground water seepage and fine sediments are probably major factors affecting the species composition of the Diopatra mounds. They also act as a buffer between the reef-flat and the beach, serving to reduce beach erosion.