Rose Atoll: an Annotated Bibliography
Total Page:16
File Type:pdf, Size:1020Kb
ISSN 103J-8062 ISBN 0131001362 Rose Atoll: an Annotated Bibliography K.A. Rodgers, I.A. W. MeAllan, Carol Cantrell & Bonnie J. Ponwith Technical Reports oj the Australian Museum Number 9 Technical Reports of the Australian Museum (1993) ISSN 1031-8062 Rose Atoll: an Annotated Bibliography 'Department of Geology. University of Auckland Private Bag, Auckland, New Zealand l46 Yeramba St, Turramurra, NSW 2074, Australia 'Australian Museum, PO Box A285, Sydney South, NSW 2000, Australia 'Department of Marine and Wildlife Resources Pago Pago, American Samoa ABSTRACT. Over 290 citations of published monographs, articles from learned journals, periodical features, official reports, letters, notes, some limited circulation andlor unpublished documents, and unofficial reports, concerned with the geology, geography, pedology, biology, meteorology, oceanography and history of Rose Atoll, American Samoa, are indexed and annotated. RODGERS,K.A., I.A.W. MCALLAN,C. CANTRELL& B.J. PONWITH. 1992. Rose Atoll: an annotated bibliography. Technical Reports of the Australian Museum 9: 1-37. Rose Atoll lies at the extreme eastern end of the impoverishment in hard species (Itano, 1987, cited in Samoan island volcanic chain (14'32's 168"08'W), 240 United Nations Environment Programme, 1988). The km east-south-east of Pago Pago Harbor (Fig.1). It is atoll has been established as a National Wildlife Refuge of a roughly square shape. The fringing reef and since 5 July 1973, and annual resource surveys are lagoon together cover just 640 ha making it one of the carried out by US Fish and Wildlife Service and smallest atolls in the world. The fetch of the lagoon is American Samoan Government personnel. These about 2 km and the maximum depth about 20 m. The include both the lagoon and outer reef as well as coralline algal reef has a uniform, 500 m width and the islets, thus affording an invaluable scientific baseline is largely submerged at low tide. A single channel in for biological and geological studies of low Pacific the north-east, 1.8-15 m deep, links the lagoon to the islands. sea. Excellent summary reviews of the history and natural The atoll is one of the least disturbed areas of the history of the atoll are given by Setchell (1924) and world. Its benthic community is unique in Samoa, being Sachet (1954). A highly detailed, up-to-date account of dominated by encrusting coralline algae, and having a the terrestrial biology is contained in Amerson et al. relative abundance of soft corals with a comparable (1982a,b). 2 Technical Reports of the Australian Museum (1993) Geological and Biological Notes of them and he and Setchell (1924) dismissed the earlier reports as incorrect identifications of weathered limestone. However, Schultz (1940, 1943), located and The Samoan Islands are part of a chain of searnounts, collected from a dozen basalt boulders lying loose on shallow banks and drowned atolls which extend 1700 the reef flat. Sachet (1954) reported that Gilbert Corwin km to the north-west. All are volcanic in origin and lie of the US National Museum had identified the samples in a line with the correct orientation to have been as olivine basalt. generated by the present motion of the Pacific plate over There are only two islets upon the reef (Fig.l,2): Rose a fixed hot spot (Natland, 1980; Menard, 1986). Both Island in the east and Sand Island to the north. Total the size of the islands, and the proportion of them land area is 7.77 ha. Aggradation and degradation are covered by Quaternary lava flows, increases to the west, active around the islets' margins and published in contrast to the Hawaiian, Society, and Marquesas descriptions of the atoll indicate that variation has chains. In these lineaments, submerged volcanic mounds, occurred in area, shape and even position of the islets both drowned and capped by atoll reefs, occur at the within historic times (e.g., Mayor, 1921b; Setchell, 1924; western end, but in the Samoan chain Rose Atoll lies Bryan, 1938; Schultz, 1943; Amerson et al., 1982a; to the east. The age of Rose's volcanic substrate is not Ludwig, 1982a; cf. Sachet, 1954: 1-2; and see Figs 1,3a- known, but it could be very young (Natland, 1980 but cpa-d). Rose displays the dynamic character so typical cf. Menard, 1986). Unlike the seemingly more mature, of low islands in general, and atolls in particular. drowned atolls and flat banks to the west, Rose lacks Perhaps, the small size of the atoll has helped heighten wide offshore banks. different observers's awareness of its active physical In his studies of the petrology of the Samoan chain, environment. The following descriptions are taken in Natland seems to have been unaware that basalt rocks large part from United Nations Environment Programme had been reported and recovered from Rose (e.g., (1988) report of Susan Wells. Natland, 1980; Natland & Turner, 1985). The nature of Rose Island is located on the lagoon half of the reef these particular rocks, and even their very existence, has in the windward corner of the atoll square (Fig.1). It been a subject of some confusion in the literature. They is a roughly oval islet about 180 X 200 m, covering 5.18 were first reported by members of the United States ha, having a 1.0 km shoreline, and a maximum altitude Exploring Expedition (e.g., Couthouy, 1844; Wilkes, of 3.0 m (Fig.2). It consists of raised reef rock and a 1844; Dana, 1851; Pickering, 1876). Mayor (1921b, coquina of worn fragments of lithothamnium, Favites, 1924b) specifically looked for but failed to find any trace Porites, Symphallia, Pocillopora, Acropora, Tridacna, Fig.1. Sketch map of Rose Atoll, after Amerson et al. (1982a). Insert indicates location of Rose within the Samoan island chain. Rodgers et al.: Rose Atoll, bibliography 3 gastropod shells and echinoderms. A phosphatic soil, rich he estimated weighed 46 tons. He argued (1921b, 1921c, in humus has developed on the coquina beneath a large 1924b) that the appearance of these boulders lent grove of Pisonia grandis. support to the rim of the atoll having once been 6 to Sand Island is a bank of coralgal sand with an 0.5 8 feet (1.8-2.4 m) higher than at present (cf. Stoddart, km shoreline and reaching about 5.2 m above sea level. 1969). The remainder of the reef flat is rubble-strewn It covers 2.59 ha and presently lies on the lagoon side and also heavily encrusted by coralline algae and of the reef, due east of the lagoon entrance channel, with scattered colonies of Acropora. The basalt boulders, a broad reef flat extending seawards. It is intermittently noted earlier, are part of the rubble of the flat. Their vegetated and following Humcane Ofa in February apparent comings and goings give further indication of 1990, it was swept clear save for one Messerschmidia the dynamic nature of the atoll environment. tree. It now hosts seedling growth of Boerhavia and The reef front extends from a depth of 4 m in a series Messerschmidia. of irregular steep steps to about 50 m depth. The upper The lagoon floor has an undulating sandy bottom portion is dissected by ridges and surge channels. The much of which is covered with algae and small scattered irregular, high magnesium calcite substrate is encrusted colonies of Acropora. Flat-topped, steep-sided pinnacles thickly with coralline algae. Corals, including Acropora jut up from the floor and are encrusted by coralline algae, and Pocillopora, are abundant and diverse but table and with both hard and soft corals on the vertical and staghorn varieties are lacking. No reports of the outer undercut sides. reef have been published at the time of writing. Descriptions of the reef and the reef flat are given Several authors (e.g., Setchell, 1924; Sachet, 1954) by Mayor (1921b) and Wass (n.d. a,b) which are have drawn attention to the number of native vascular summarised in United Nations Environment Programme plant species found on Rose being restricted to three: (1988). The upper surface of the reef is a hard, smooth- Pisonia grandis, Boerhavia tetrandra, and Portulaca floored flat, awash at low tide, and covered with vigorous lutea which form a small evergreen orthophyll softwood growths of Porolithon that form connected pink patches forest. At the time of their intensive survey of the atoll, and ridges up to 15 cm high and 15 cm to a metre or Amerson et al. (1982a,b) found the number of species more wide. The inner lagoon edge is covered by coral had increased to include Messerschmidia argentea, blocks, the larger of which have flattened tops, also Ipomoea macrantha, and Suriana rnaritima, the latter encrusted by coralline algae, and with both algae and having anived only very recently. Several attempts have soft corals coating their sides. Most of these blocks lie been made to introduce coconut palms Cocos nucifera. loose on the flat but some are attached by slender The number surviving varies (20 in 1938, 12 in 1953), pedicels. Mayor (1921b) noted one loose boulder which as do reports of their health (cf. Sachet, 1954:5,16). Fig.2. Aerial photograph of Rose Island about 1988. Department of Marine and Wildlife Resources, Pago Pago. 4 Technical Reports of the Australian Museum (1993) To Pacific ornithologists Rose means seabirds. All 1873; Sachet, 1954; Gray, 1960). observers have commented on the very large seabird Rose was chosen as a dive-bombing practice range population which dominates the life of the atoll. About during World War 11. It is unclear whether this was 97% of the total seabird population of American Samoa implemented.