ASSESSING THE EFFECTIVENESS OF USING BENTHIC INVERTEBRATES AS INDICATORS OF STREAM QUALITY; HOW UNIQUE ARE THE HAWAIIAN ISLANDS?

A.M.D. Brasher, R.H. Wolff, and C.D. Luton. U.S. Geological Survey, 677 Ala Moana Blvd. Suite 415, Honolulu, Hawaii 96813

In 1999, the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) program collected invertebrate and habitat data at ten sites on the island of Oahu to evaluate associations among land use, habitat characteristics, and stream invertebrate communities. Although invertebrate metrics developed for streams in the continental U.S. may not be appropriate for Hawaii, benthic invertebrate communities on Oahu did vary with land use and habitat characteristics and such associations may serve as a basis for the development of Hawaii-specific metrics. On Oahu, invertebrate abundance was greatest in streams associated with forested land use, while diversity was greatest in urban streams. Owing to the rarity or absence of members of the orders Ephemeroptera and Plecoptera, EPT-based metrics (Ephemeroptera, Plecoptera, Trichoptera) cannot be developed for Hawaiian streams; however, other invertebrate metrics may eventually prove to be useful. For example, the ratio of Diptera to Trichoptera was shown to vary with urbanization and could potentially be used as an indicator of stream quality. One notable characteristic of invertebrate assemblages in Oahu streams is that they are dominated by non-native species. Native species represented only 5% of the total taxa richness, and at least 84% of the total invertebrate abundance consisted of non-native species.