Pacific Science

Twenty-three stream segments (seven on O‘ahu, eight on Kaua‘i, and eight on Hawai‘i) were sampled for macroalgae in the Hawaiian Islands. Stream segments ranged greatly in size from 1.2 to 40 m in width. Water temperature was uniformly warm (17–24°C), but other chemical parameters differed from site to site (pH 5.5–8.9, specific conductance 20–200 mS · cm-1). Mean species richness per site was 3.9 with one to eight species collected per stream segment. Ninety populations of 42 infrageneric taxa were identified from the Cyanobacteria (19), Chlorophyta (17), Rhodophyta (3), and Chrysophyta (3). The most abundant taxa were Spirogyra sp. 1, Audouinella pygmaea, and Phormidium retzii. All three of these taxa are widespread among the Islands. Other species collected on all three islands were Cloniophora plumosa and Hildenbrandia angolensis. Eighteen taxa are new records for streams and 15 of these for aquatic habitats. Ten of the new records for the Hawaiian Islands were collected on Kaua‘i, six on O‘ahu, and one on Hawai‘i (two new records shared for Kaua‘i and O‘ahu). The large percentage (36%) of new taxa reported in this study suggests that more research is needed to fully catalog the Hawaiian stream macroalgal diversity. This study extends the number of micro- and macroalgal taxa known from streams in the Hawaiian Islands to 299 infrageneric taxa.