Macroalgae from 23 Stream Segments in the Hawaiian Islands

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 IlS . cmI ). 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 microand macroalgal taxa known from streams in the Hawaiian Islands to 299 infrageneric taxa. THE HAWAIIAN ISLANDS are at least 3700 Ian from the continental landmasses of Asia, Australia, North America, and South America (Maciolek 1969). Volcanic oceanic islands, such as the Hawaiian Archipelago, derive their entire flora and fauna from immigrants capable of long-distance dispersal or their descendents (Pielou 1979). Typically, islands such as these have lower species richness than continental landmasses due to difficulties of long-distance dispersal (Schoener 1988). For freshwater algae to colonize these islands, wind or bird dispersal must be relied upon, which may limit taxon richness. However, a I Manuscript accepted 18 March 2003. 2 Department of Environmental and Plant Biology, Ohio University, Athens, Ohio 45701 (E-mail: nf160798@ ohio.edu and [email protected]). 3 Department of Botany, University of Hawai'i at Manoa, Honolulu, Hawai'i 96822 (E-mail: asherwoo@