Hawaiian Freshwater Polychaeta: A Potentially Substantial Trophic Component of Stream Depositional Habitats

In this paper we report the widespread occurrence of large annelids (Polychaeta: Nereididae) in Hawaiian stream depositional habitats, drawing attention to the lack of knowledge of Hawaiian stream energetics. Specimens of Namalycastis sp. were collected from five Hawaiian Islands from May–July 1995 and from the island of Maui from July–December 1999 and April–July 2000. Most specimens collected were N. hawaiiensis, while two specimens of N. abiuma were collected from a single site on the island of Molokai. Specimens were collected from elevations ranging from 3–240 m; several collections were from sites above at least one major (\u3e 15 m high) waterfall. Habitats were characterized by slow-moving or stagnant water, water temperatures ranging from \u3c 18–29 C, mixed gravel and sand substrates with organic detritus. Specimens were found among roots of vegetation along stream edges, in small lava pockets, buried in loose gravel, and in depressions between, under, and inside porous rocks. Body lengths of preserved specimens ranged from ~ 9 to 150 mm among islands and streams between years and seasons. Polychaetes were usually abundant in these habitats indicating a nearly ubiquitous distribution of Namalycastis, and suggesting ecological importance for stream benthic trophic dynamics throughout the Hawaiian archipelago