«Marine Plants of Pohnpei and Ant Atoll: Chlorophyta, Phaeophyta and Magnoliophyta LYNN M. HODGSON University of Hawai‘i - West O‘ahu 96-129 Ala ...»
Micronesica 32(2):289-307, 2000
Marine Plants of Pohnpei and Ant Atoll: Chlorophyta, Phaeophyta
LYNN M. HODGSON
University of Hawai‘i - West O‘ahu 96-129 Ala Ike,
Pearl City, Hawai‘i 96782
KARLA J. MCDERMID1
Marine Science Department, University of Hawai‘i at Hilo
200 W. Kawili St., Hilo, Hawai‘i 967201
Abstract—A study of marine benthic plants collected from Pohnpei
Island and Ant Atoll, Federated States of Micronesia, between 1994 and 1997 documented the occurrence of 59 species of green algae (Division Chlorophyta), 16 species of brown algae (Division Phaeophyta), and 3 species of seagrasses (Division Magnoliophyta). Based on these collec- tions and a review of the literature, the marine flora of Pohnpei now comprises 52 Chlorophyta species, 22 Phaeophyta species, and 3 sea- grass species; and the list for Ant Atoll currently stands at 60 Chlorophyta species, 11 Phaeophyta species, and 2 seagrasses. New records include 20 species from Pohnpei, and 30 from Ant. Of these, 8 were taxa previously unknown from Micronesia: Caulerpa microphysa (Weber-van Bosse) J. Feldmann, Derbesia fastigiata Taylor, Dictyota acutiloba J. Agardh, Enteromorpha flexuosa (Roth) J. Agardh, Padina boergesenii Allender & Kraft, Percursaria dawsonii Hollenberg & Abbott, Ulothrix flacca (Dillw.) Thuret, and Ulvella setchellii Dangeard.
Red algae (Division Rhodophyta) were also collected, and will be reported in a future paper.
Introduction The early marine algal checklists that spanned vast expanses of the Pacific, i.e., the Caroline Islands (Okamura 1916), western Oceania (Schmidt 1928), and Micronesia (Tokida 1939) gave the first sparse records of marine plants of Pohnpei Island (previously spelled Ponape) (6°55'N, 158°15'E). Glassman (1952) compiled a list of the non-vascular plants of Pohnpei, and included relatively few marine algae. Yamada was the first phycologist to spend time on Pohnpei and its closest neighbor, Ant Atoll (32 km southwest), and to focus on their marine flora.
He added to the list of recorded species, and also described several new taxa of Address for correspondence 1 290 Micronesica 32(2), 2000 Table 1. Collecting site information for Pohnpei Island and Ant Atoll.
Site # Location Habitat Depth Collecting Dates Municipality Pohnpei Island 1 Nankepkep en Parem intertidal reef flat 1m 11/24/94 Nett 2 Mesenpal nearshore 1-2 m 9/18/97 Uh 3 Dehbehk Island
Caulerpa, Dictyosphaeria, Halimeda, Rhipilia, Centroceras, Crouania, Dasya, and Wrangelia from these islands (Yamada 1940, 1941, 1944a, 1944b). Pohnpei and Ant are mentioned in various taxonomic papers as localities of “materials examined” (Colinvaux 1968; Hollenberg 1968a, 1968b, 1968c; Trono 1968, 1969; DeWreede 1973; Taylor 1977; Itono 1980; Meneses & Abbott 1987). The most recent studies on marine plants of Pohnpei (Best & Pendleton 1980) and of Ant (Enomoto et al. 1986) are limited in scope and over twelve years old.
Hodgson & McDermid: Pohnpei and Ant marine plants 291 Figure 1. Collecting sites around Pohnpei Island. The scale bar in the upper right is 4 km.
In the mean time, Pohnpei and Ant have become part of the independent Federated States of Micronesia with a burgeoning human population that is increasingly dependent on marine resources for subsistence, as well as capital income. The nearshore marine waters of Pohnpei and Ant are the site of reef fishing, sponge farming, sea cucumber harvesting, Trochus snail collecting, sand mining, coral dredging for roads, and tourist recreation (U.S. Army Corps of Engineers 1985), yet little is known of the diversity, distribution or ecology of the primary producers.
292 Micronesica 32(2), 2000
Figure 2. Collecting sites at Ant Atoll. The scale bar in the upper right is 2 km.
Materials and Methods This study is based on several collections by the authors on Pohnpei and Ant spanning the years 1994 to 1997, plus a smattering of dried specimens collected by students of the College of Micronesia-FSM. Collections were made at 20 locations around the island of Pohnpei and 11 sites at Ant Atoll. The authors collected seaweeds and seagrasses at depths ranging from less than 1 m deep to 27 m deep by SCUBA diving, snorkeling, or wading. Fresh specimens were hand-picked, placed in plastic bags with ambient seawater, and preserved within 6 hours of collection as dried material or in 4% formalin-seawater solution. Studies of anatomical and reproductive structures were made later. Thalli were stained in 1% aqueous aniline blue solution and mounted on glass slides in 25% corn syrup (Karo®) solution. Identification was made by L. M. Hodgson, K. J. McDermid and I. A. Abbott using a variety of references on marine plants from Micronesia, as well as specific references on Caulerpa (Coppejans 1992, Coppejans & Prud’homme van Reine 1992), Codium (Jones and Kraft 1984), Halimeda (HillisColinvaux 1980), Rhipilia (Gilbert 1978, N’Yeurt & Keats 1997), and the Hodgson & McDermid: Pohnpei and Ant marine plants 293 Dictyotales (Allender & Kraft 1983). Distribution records of species in Micronesia were checked using Tsuda et al. (1977), Tsuda & Wray (1977), and Tsuda (1981a). Dried specimens are deposited as vouchers in the herbarium at Bernice P. Bishop Museum (BISH) in Honolulu, Hawai‘i.
COLLECTING SITESTable 1 gives the complete list of collecting sites, including names, dates and information on the habitats. The site numbers and letters correspond to locations on the maps of Pohnpei Island (Fig. 1) and Ant Atoll (Fig. 2), respectively.
Results The taxa collected and identified from Pohnpei Island and Ant Atoll are documented in Table 2 which includes author citations. The site numbers and letters refer to locations in Table 1 and Figures 1 and 2. New records for Micronesia, Pohnpei and Ant are indicated in the first column of Table 2.
Fifty-nine species of the Division Chlorophyta were identified in this study.
The flora of Pohnpei and Ant is particularly rich in species of Caulerpa and Halimeda. Eleven species of Caulerpa were recognized, including 2 species which are new records for Pohnpei and/or Ant Atoll: C. filicoides, and C.
microphysa. The microscopic examination of Caulerpa specimens, particularly their pyrenoid characteristics, proved to be essential to accurate identification of species. Several of the Caulerpa species displayed multiple growth forms, recognized as “ecads” (Coppejans 1992, Coppejans & Prud’homme van Reine 1992). Although ecad is a descriptive category and not a taxonomic unit, we included ecad distinctions in this study in order to document the great morphological (and perhaps genetic) variation that exists within this genus in Pohnpei and Ant. More studies are needed to clarify the taxonomic and ecological significance of ecads and the biodiversity they represent. Fifteen species of Halimeda were identified in this study, including several new records for this area: H.
bikinensis, H. cylindracea, H. distorta, H. fragilis, H. gracilis, H. minima, H.
renschii, H. simulans, and H. taenicola. Five species of Rhipilia, a genus frequently underestimated in terms of its diversity, were collected. Rhipilia geppii and R. orientalis are new records for Ant Atoll, and R. diaphana was not previously reported from Pohnpei.
Sixteen species of brown algae were found. This collection was dominated by specimens of Dictyota and Padina. One immature Sargassum specimen, unidentifiable to species, was collected from Ant Atoll. However, even this small sprig is noteworthy because Tsuda (1976) points out that Sargassum is rarely found on atolls.
Three species of seagrasses were found on Pohnpei: Cymodocea rotundata, Enhalus acoroides, and Thalassia hemprichii. Only Cymodocea rotundata and T. hemprichii were present on Ant, and these two species are new records for Ant Atoll.
Table 2. Species, sites, and references for collections from Ant Atoll and Pohnpei Island.
The site numbers refer to locations in Table 1. New 294 records for species are indicated in the first column: M=Micronesia, A=Ant, P=Pohnpei. The authors who previously reported the species from Ant or Pohnpei are listed in the last column. Abbreviations for references: BP80 = Best & Pendleton 1980, EJA86 = Enomoto et al. 1986, G52 = Glassman 1952, ME99 = McDermid & Edward 1999, O16 = Okamura 1916, S28 = Schmidt 1928, T39 = Tokida 1939, T68 = Trono 1968, T69 = Trono 1969, TRC74 = Tsuda et al. 1974, TFS77 = Tsuda et al. 1977, Y44 = Yamada 1944a.
Fig. 3. Avrainvillea amadelpha, a widespread species with thick, felted, irregular blades. New record for Pohnpei and Ant, specimen #22187, scale bar = 1.2 cm. Fig. 4. Bryopsis pennata with characteristic pinnate branches which are non-septate when vegetative, but become septate when reproductive. New record for Ant, specimen #22616a, scale bar = 55µm. Fig. 5.
Caulerpa microphysa outwardly indistinguishable from Caulerpa racemosa, but microscopically can be recognized by single pear-shaped pyrenoids in each chloroplast. New record for Pohnpei, Ant and Micronesia, specimen #KM4135, scale bar = 1.7 cm. Fig. 6. Caulerpella ambigua, showing vegetative branches which will become entirely reproductive, as distinguished from members of the genus Caulerpa in which individual ramuli become reproductive. New record for Ant, specimen #22616b, scale bar = 60µm. Fig. 7. Cladophora vagabunda, showing branches that originate as protrusions from distal corners of cells which are later cut off by a cell wall. The cells contain a diffuse reticulate chloroplast. New record for Pohnpei and Ant, specimen #22614, scale bar = 150µm.
Hodgson & McDermid: Pohnpei and Ant marine plants 299 Fig. 8. Derbesia fastigiata, showing tubular erect branches with no septa at the branch points. Cells contain small discoid chloroplasts. New record for Ant and Micronesia, specimen #22629, scale bar = 150µm. Fig. 9. Halimeda fragilis with a small holdfast region, branching in multiple planes as in Halimeda opuntia, but characteristically shiny white with heavy calcification. Internally, distinguished by separated filaments at nodes and separated peripheral utricles. New record for Pohnpei and Ant, specimen #22297, scale bar = 2.2 cm. Fig. 10.
Halimeda minima, a bushy, erect plant with cylindrical or trilobed segments longer than broad, and several segments fused at the base of the thallus. New record for Pohnpei and Ant, specimen #KM4175b, scale bar = 1.0 cm. Fig. 11. Halimeda taenicola with a small holdfast region and trapezoidal segments slightly raised at the margins. The lowermost 1 or 2 segments compressed-cylindrical, similar to, but lacking the swollen utricles of, Halimeda discoidea. New record for Pohnpei and Ant, specimen #KM4164, scale bar = 2.0 cm. Fig. 12.
Percursaria dawsonii, a close relative of Ulva with band-shaped plastids, distinguished by a slender, unbranched thallus with 2 sligthly staggered, longitudinal rows of isodiametric cells.
New record for Pohnpei and Micronesia, specimen #22583, scale bar = 37µm.
Overall, 20 species are new records for Pohnpei, and 30 species are new records for Ant Atoll. Several of these new records are highlighted in Figs. 3–12 to show the characteristic morphology or distinguishing traits of the species. Eight taxa are previously unknown or unreported from Micronesia: Caulerpa microphysa, Derbesia fastigiata, Dictyota acutiloba, Enteromorpha flexuosa, Padina boergesenii, Percursaria dawsonii, Ulothrix flacca, and Ulvella setchellii.
Caulerpa microphysa is distinguished by the single, large, pyriform pyrenoid 300 Micronesica 32(2), 2000
present in its chloroplasts, and is known from Indonesia and New Guinea.
Derbesia fastigiata is reported from Hawai‘i and California. The type locality of Dictyota acutiloba is Hawai‘i, and it has been recorded as far south as Lord Howe Island in Australia. Enteromorpha flexuosa, whose type locality is Yugoslavia, is also known from Hawai‘i, British Columbia to Central America, and the Galápagos Islands. Padina boergesenii has blades 3-cell layers thick, and is based on specimens from the West Indies and Australia. Wynne (1998) describes this Padina as “broadly distributed in the tropics,” and agrees with Allender & Kraft (1983) that specimens of P. gymnospora from India, the Phillipines and Vietnam need to be examined to determine their relation to P. boergesenii. Schmidt (1928) reported P. gymnospora from the Marianas Islands in northern Micronesia, but Hodgson & McDermid: Pohnpei and Ant marine plants 301
without voucher material to compare to our specimens from Pohnpei, and in light of the taxonomic questions raised by other authors, we list P. boergesenii here as a new record for Micronesia. The type locality of Percursaria dawsonii is Pacific Grove in Central California, and it was recently reported from Baja California, Mexico (Aguilar-Rosas & Aguilar-Rosas 1998). Ulothrix flacca is known from Japan, Alaska, California, with a type locality of Wales. Ulvella setchellii is reported from the coast of Washington to Baja California, as well as France (type locality).
None of the species were found at all 31 sites. The most frequently occurring species, Halimeda opuntia, was collected from 18 sites; Tydemania expeditionis from 11 locations; H. macroloba from 8 localities on Pohnpei (but was noticeably absent on Ant Atoll); Thalassia hemprichii and Caulerpa filicoides ecad andamanensis from 7 sites each; and Caulerpa racemosa ecad peltata, Cymodocea rotundata, Dictyota friabilis, H. micronesica, Microdictyon okamurae and Ventricaria ventricosa were each reported from 6 of the sites.