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centre of origin, which may be linked to e.g. ocean currents or artificial dispersal agents. This knowledge can in turn broaden our appreciation of world-wide algal distribution patterns over geological time. Also, endemism rates can indicate evolutionary rates of algal species. Secondly, the study of algal distribution patterns on islands can yield useful information about the state of the particular reef systems they are associated with. Tropical reefs are very delicate and balanced ecological systems, exhibiting surprising productivity in otherwise nutrient-poor tropical oceanic waters. Peculiar macro-algal distribution patterns (e.g. sudden algal blooms) often reflect damaged or polluted reef environments. Phycological knowledge is therefore one of the essential prerequisites when undertaking such activities as environmental impact assessments or other baseline ecological surveys. Thirdly, there is an intrinsic value in any inventory of a new flora, as it contributes to a documentation of the world's biota. Rotuma Island is the most northerly island in the Fijian Island group and has been neglected in surveys of the Fijian algal flora. Few aspects of the island have received any scientific attention. Snow (1969) published a bibliography of Fiji, Tonga and Rotuma which includes several historical, sociological, and scientific entries for Rotuma. To the author's knowledge, however, no phycological survey of the algal flora of the island has yet been undertaken, despite fairly extensive surveys of nearby Fiji. The only previous records of Rotuman algae that could be traced by the author are two collections of Meristotheca by W. E. Booth in October, 1975 and August, 1977, housed in the phycological herbarium at the Bernice P. Bishop Museum, Honolulu, Hawaii (F. M. Norris, pers. comm.). Owing to its isolation from the rest of the Fiji group (and for that matter any other island group), it could be expected that there might be noticeable differences in the macroalgal species composition and distribution of that island. Being 6" north of Fiji, Rotuma also possesses a more equatorial climate than the remainder of the island group, leading to interesting speculations about floristic comparisons with the rest of Fiji and the Pacific in general. In addition, the fringing Rotuman reefs are essentially non-polluted, and a study of these could offer a useful means of comparison with other reef systems in the region. In order to address some of the above questions, it was decided to conduct a phycological survey of Rotuma and compile a preliminary checklist, as well as to make observations on the local habitats, species composition and distributions, and ecological interactions on the island's reefs and other marine habitats. Historical Background The earliest reports of marine benthic algae from the Fijian island group were by Gmnow (1874), who listed 37 species from Ovalau. In 1876, Dickie listed nine species, including four new records, from the same locality. Askenasy (1888) published a list of 10 species from Matuku Island collected during the H.M.S. 'Gazelle' Expeditions. It was almost 85 years later before Chapman (1971) published a checklist of some 79 species for Fiji, to which he added a further 17 in 1977. Further additions to the Fijian flora were published by Kapraun and Bowden (1978), and the early history of algal collecting in Fiji, together with biogeographic and ecological aspects, was reviewed by McRaild (1978). Five years later, Booth et al. (1983) made some preliminary attempts at culturing Eucheuma striatum in Fiji. In 1984, Itono and Ajisaka published taxonomic notes on the Fijian marine algae, while Itono (1985a, 1985b) described some Fijian Rhodophyta. In 1984, Kraft documented a deep- water form of Callophycus serratus from Fiji. The most detailed recent reports of Fiji algae have been by Kasahara (1985, 1988), who studied collections made by two Kagoshima Maru Expeditions to Fiji in 1982 as part of a scientific survey of the South Pacific by Kagoshima University in Japan, as well as extensive collections that he made on Viti Levu. Kasahara's 1985 thesis listed 76 Chlorophyta and Rhodophyta (including 37 new records), while his profusely illustrated 1988 report listed 43 Chlorophyta. Unfortunately, he did not publish his Phaeophyta collections, although duplicates were donated to the South Pacific Regional Herbarium and are awaiting identification. In 1991, Garbary et al. listed many new distribution records for Fijian algae (82 species listed, based on collections made in August 1980, August 1981 and February 1982). Later that same year, South (1991) published a
Benthic Marine Algae of Rotuma Island 363 checklist of marine benthic algae from Dravuni Island, in the Astrolabe Reef region, listing a total of 71 species, 5 of which were new records for Fiji. South (1992) also published an illustrated catalogue of the Halimeda species reported from Fiji, and in 1993 reported on the edible seaweeds of these islands. The most comprehensive overview of Fijian algae to date is the 1992 checklist by South and Kasahara, listing a total of 314 species including 11 Cyanophyceae, 99 Chlorophyceae, 36 Phaeophyceae and 168 Rhodophyceae. Since then, further additions to the flora were made by a number of researchers (Raj 1993; South 1993; South and N'Yeurt 1993; South et al. 1993; N'Yeurt et al. 1995, 1996a, 1996b), bringing the total Fijian macroalgal flora (including Rotuma) to 422 taxa. In addition, recent visits by D. S., and M. M. Littler, from the Smithsonian Institution in Washington, DC., to the Great Astrolabe Reef, Kadavu, have yielded many new records of benthic algae that await publication. However, most of the Fijian algal flora is still poorly known, as much of the Lau Group, Kadavu, Lomaiviti Group, Yasawas, Taveuni and Vanua Levu have yet to be investigated in detail. Materials and Methods Field Survey Methods An initial survey of the island was carried out, from January to May 1992. A further survey was conducted from December 1992 to February 1993, with additional specimens collected between September 1993 and January 1994, and between November 1994 and January 1995. A preliminary visual survey of the coastline was carried out, and 19 representative sites around the island were chosen for inspection (Fig. 1). Surveys were carried out either by wading or snorkelling. Considering the sparse distribution of the algae, and the turbulent and exposed conditions on the often very narrow fringing reefs, it was deemed impractical to lay transects. Instead, the area was visually inspected for algal growth, with salient distribution and reef profile features being recorded on an underwater writing board. Owing to the exposed nature of the reefs and the lack of diving facilities and trained partners, it was considered dangerous to sample subtidal habitats. Consequently, all collections were from the intertidal region, imposing obvious limitations on the overall results obtained. Photographs of algae in situ and of the general habitats were taken using an Olympus 35 mm camera and a Pentax SLR variable-focus camera. Algal specimens were hand-collected or scraped off the substratum using a knife, put into polyethylene plastic bags or vials, promptly preserved in 5% formaldehyde in seawater, and stored in light-proof plastic containers for eventual shipment back to Fiji. Laboratoiy Methods Hand-sections or freezing-microtome sections were made for general observation of internal anatomy. Slides were stained with either crystal violet or 1% acidified aniline blue, and made permanent if necessary by embedding in glycerine jelly (Drury et al. 1967) following impregnation of the material in 50% glycerol water solution for 2-3 h. Slides were examined using a Zeiss compound microscope. A camera-lucida attachment (Abb6 Drawing Tube, Carl Zeiss) was used to make pencil drawings of the specimens. Observations on larger specimens and general sorting of the collections were performed using a Labova dissecting microscope. Slides are housed in the South Pacific Regional Herbarium in a numbered series prefixed by 'S' (slide). Voucher specimens of larger algae were first dried using an algal press, then mounted onto herbarium paper. Specimens were deposited into the South Pacific Regional Herbarium housed at the University of the South Pacific in Suva. Collection numbers are preceded by 'USP'. Ektachromes and black-and-white photographs of identified algae were obtained in the laboratory, either using formalin- preserved or pressed specimens. Macrophotography was undertaken with a Nikon F2A using a 55 mm 1 : 3.5 lens, and a ring flash (Sunpak GX8R ring flash attachment, Sunpak Corporation, Tokyo, Japan) in conjunction with Kodak EClOO (Ektachromes) or Kodak PX125 (Black-and-white) film. Photomicrographs were taken with a Zeiss Photoscope I11 (*I S = slide collections. Accession numbers refer to specimens housed at the Phycological Herbarium, South Pacific Regional Herbarium, The University of the South Pacific (SUVA) and are preceded by 'USP' to distinguish them from the angiosperm collection). Taxonomy and Nomenclature Nomenclature used in identification of the algae follows that of Silva et al. (1987) unless stated otherwise. The lists of Tsuda and Wray (1977) and of Dawson (1954, 1956, 1957) were used as references for the region. Taylor's Bikini atoll flora (1950) was also widely used, as were Womersley and Bailey's (1970) Solomon Islands list, Tsuda and Ganigue's (1988) New Caledonia list, Payri and
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Benthic Marine Aigae of Rotuma Isla
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Fig. 122. Peyssonnelia sp. Cross-se
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A. D. R. N'Yeurt Fig. 136. Hypnea n
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A. D. R. N'Yeurt Fig. 148. Centroce
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A. D. R. N'Yeurt Fig. 156. Ceramium
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A. D. R. N'Yeurt Fig. 168. Grzffith
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Fig. 181. Heterosiphonia crispella
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Fig. 188. (a, b) Chorzdria dasyphyl
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Fig. 200. Herposiphonia secunda f.
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Rotuman Algal Flora Composition At
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CENTRAL AND SOUTHWESTERN PACIFIC RE
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