| Constancea 83, 2002 University and Jepson Herbaria P.C. Silva Festschrift |
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The Samoan Archipelago represents the easternmost natural extension of mangroves in the Indo-Pacific, with mangrove communities composed of two main species Bruguiera gymnorhiza (L.) Lamx. and Rhizophora mangle L.; the associated macroalgal flora has not been previously described. Mangrove associated macroalgae are documented from the island of Upolu, Samoa. A total of 25 taxa were found: 6 Cyanophyta, 10 Rhodophyta, and 9 Chlorophyta. Twelve of these taxa are newly recorded for the Samoan flora (2 Cyanophyta, 5 Rhodophyta, and 5 Chlorophyta). Cystocarpic and spermatangial plants of Caloglossa adhaerens King & Puttock are reported for the first time. Mangrove communities of predominantly Bruguiera gymnorhiza were endowed with bostrychietum algae (Bostrychia tenella subsp. tenella, Caloglossa leprieurii and Murrayella periclados). In communities dominated by Rhizophora mangle, two algal assemblages were noted; one having a mixture of Caloglossa spp. and Murrayella periclados, and the other consisting primarily of Polysiphonia, Murrayella and Cladophora species. Both assemblages lacked Bostrychia species. There was a notable absence of Phaeophyta from the mangrove communities of Samoa.
The small and inconspicuous size of mangrove-associated algae, coupled with a lack of understanding of their role in the mangrove ecosystem may be a reason why they are frequently overlooked when mangrove flora assessments are undertaken. They are the main food source for a variety of fishes and invertebrates, such as crabs (Wada and Wowor 1989). Some algae are unique to certain mangrove habitats and an understanding of their diversity and biomass may indicate the health of mangroves (Chihara and Tanaka 1988). Algal mats (consisting largely of Cyanophyta and Chlorophyta) associated with mangrove habitats play an important role in building and trapping sediments and/or in carbonate precipitation (Golubic 1973, Hoffmann 1999). Furthermore, many mangrove-associated cyanophytes (e.g., Scytonema) are important nitrogen fixers (Hoffmann 1999).
The diversity and distribution of mangroves is centred in the Indo-Pacific region, notably southeast Asia (McNae 1968). Aunu'u mangroves in the Samoan Archipelago represent the easternmost limit of the Indo-Pacific distribution of mangroves (Woodroffe 1987). Two main kinds of mangrove communities are found distributed throughout the islands of the Samoan Archipelago. One is dominated by Bruguiera gymnorhiza (Linnaeus) Lamouroux and the other by Rhizophora mangle Linnaeus. In studies of mangrove forests in Samoa by Vodonaivalu (1983), Pearsall and Whistler (1991), Schuster (1993) and Boon (1997) algae were not treated. Genera associated with mangroves, however, have been recorded by Setchell (1924; Bostrychia spp.) and by Hollenberg (1968a; Murrayella periclados) from American Samoa. We provide here the first survey of mangrove-associated algae from the Samoan Archipelago, based on collections made on Upolu Island of independent Samoa.
The algae were washed and mounted in 30–60 percent Karo solution (corn syrup in distilled water with a few thymol crystals) and stained with 1% aqueous aniline blue. The slides were sealed with nail varnish for long-term storage. Portions of algae were hand-sectioned for anatomical examination. Specimens were observed under an Olympus CH-2 compound and an Olympus SZ40 stereomicroscopes. Photographs were taken using a NIKON Coolpix 990 digital camera, and enhanced and arranged into plates using Adobe Photoshop® 6 software.
Three Lyngbya taxa were found to be significant members of the mangrove communities, tentatively described as Lyngbya sp. 1–3.
Lyngbya sp. 1.
Voucher: A'anapu (Skelton and South, 5.i.1998. SUVA-A S39:8)
Plants epilithic; filaments 40–42.5µm diam.; cells 27.5µm diam., 5–7µm long; rarely constricted at cell walls; filaments wavy; sheath clear, not striated, to 10µm thick.
Lyngbya sp. 2.
Voucher: Moata'a (Skelton and South, 26.viii.2000. SUVA-A S41:8)
Plants epilithic, entangled with other algae; filaments 50–52.5µm diam., cells 27.5–32.5µm diam., 5–7.5µm long, slightly constricted at cross walls; filaments straight; sheath double striated to 17.5µm thick.
Lyngbya sp. 3.
Voucher: A'anapu (Skelton and South, 5.i.1998. SUVA-A S39:5)
Plants growing on volcanic rock, forming dark green masses; filaments 45–97.5µm diam., cells 22.5–25µm diam., 2.5µm long; sheath clear to multi-striated.
*Schizothrix sp. cf. tenerrima (Gomont) Drouet 1968: 135
Voucher: A'anapu, (Skelton and South, 5.i.1998. SUVA-A S39:14)
Plants consist of a mass of intertwining trichomes; filaments unbranched and lacking sheath; cells square to slightly rectangular, 5µm diam., 5–8µm long, faint constrictions between cells; apex attenuated, apical cells to 12µm long; heterocytes absent.
Remarks: The lack of granulated cells and the thin apical cell separates it from Microcoleus and Oscillatoria, respectively. The lack of a distinct sheath and the attenuate terminal cells separate this species from two other similar cosmopolitan species (S. calcicola and S. arenaria); it is tentatively aligned to S. tenerrima on the basis of size, but the lack of clear spaces (see Lindstedt 1943: 90, pl. 11, fig. 8' as Microcoleus tenerrimus) between the cells is a character not seen in the Samoan material.
*Calothrix confervicola (Dillwyn) C. Agardh 1824: 70.
Type locality: Aberystwyth, Cardigan, Wales
Voucher: Vaitoloa, (Skelton, 25.vi.2000. SUVA-A S40:5); Mulinu'u Point, (Skelton SUVA-A S40: 5. Mulinu'u Point, (Skelton, 25.vi.2000. S40:5, S38:17)
Trichome unbranched; filaments 1–1.5mm high, 27.5µm wide, growing freely not entangled, continuing past tapering trichome cells; trichomes to 12.5–15µm diam., tapering distally in the last few cells; sheath hyaline; cells disc-shaped, 5–7.5µm, with no to slight constrictions between cells, occasionally cells separate; heterocytes intercalary, ovate, squarish to rectangular, 12.5–13.7µm diam., 12.5–25µm long, separated from cells on either side; subterminal meristematic zones common, causing a slight thickening of the trichome.
Remarks: Growing on the bark of Rhizophora mangle.
Calothrix crustacea Thuret in Bornet and Thuret 1876: 13–16, pl. IV: figs. 1–6.
Type locality: Tangier, Morocco
Voucher: A'anapu, (Skelton and South, 5.i.1998. SUVA-A S38:17, S38:8).
Filaments to 0.5 mm tall, 10–12.5µm wide; unbranched or with false branching (Scytonema-like); trichomes to 7.5µm wide, width uniform, tapering distally; cells rectangular, disc-shaped or bead-like, with a lens-shaped gap between some cells, 5–10µm diam., 5–12.5µm long; sheath hyaline, narrow; heterocytes mostly basal, inconspicuous, 5–10µm diam., 5µm high.
Remarks: Growing on the bark of Bruguiera gymnorhiza.
*Caulacanthus ustulatus (Turner) Kützing 1843: 395
Type locality: Cádiz, Spain
Voucher: Moata'a (Skelton and South, 26.viii.2000. Sa 278)
Plants gregarious or tangled with other algae, epiphytic or epilithic; axes of compressed prostrate system 250–300µm wide, expanded at node to 500µm wide (at the widest margins), giving rise to erect subterete to terete laterals to 4mm high, 250µm diam.; laterals tapering terminally, each with a distinct domed apical cell, 7.5µm high, 10µm wide; attached by clumped multicellular, branched rhizoids arising from the ventral cortical cells of the prostrate system, 87.5–125µm wide, 100–175µm long; secondary holdfast developed from axes reclining toward the substratum; two pericentral cells cut off from axial cell, giving rise to 4–5 layers of rounded and elongated cells, gradually diminishing in size toward the surface. Reproductive material not found.
Remarks: Growing with Gelidiella pannosa and Gelidium pusillum on pneumatophores and other solid substrata. This alga may be confused morphologically with Hypnea spinella, with its acute laterals. It is anatomically distinct in having only two pericentral cells compared to five in H. spinella. Other features useful for distinguishing the two are that C. ustulatus is less robust, and has narrower axes (Abbott 1999: 104). Recent molecular analyses and culture work by Zuccarello et al. (2002) has shown two distinct C. ustulatus lineages: a Pacific lineage and an Atlantic lineage. The morphological plasticity shown by cultured plants has reaffirmed West and Calumpong's (1990) view not to recognise C. okamurae Yamada and C. indicus Weber-van Bosse.
*Gelidium sp. aff. Gelidium pusillum (Stackhouse) Le Jolis 1863: 139.
Type locality: Sidmouth, Devon, England.
Voucher: Moata'a, (Skelton and South, 28.viii.2000([tetrasporangial]). SUVA-A S41:5).
Plants wiry, tangled and gregarious on Rhizophora mangle bark or other solid substrata; attached by a dense holdfast comprising compacted multicellular rhizoids, 300µm wide, 450µm long; secondary holdfasts arising from laterals that come in contact with the substratum; thallus variable throughout, mostly terete to subterete and expanded to clavate above, to 550µm wide at the most expanded part; branches irregular, initially subterete, compressed in upper mid-part forming clavate blades, tapering towards the apex; cross section showing dense medullary cells with rhizines, the cortex having smaller pigmented cells which are irregularly arranged; tetrasporangial stichidia in mid portions of expanded blades; tetrasporangia irregularly arranged in sori, spherical to 35µm diam., in mature sporangia, cruciately divided.
Remarks: A fairly common alga that is found in mangrove habitat as well as shallow intertidal areas (< 3m depth) where it is consumed by marine animals (Skelton pers. obs.). Molecular analyses by Freshwater and Rueness (1994) and Freshwater et al. (1995) have concluded that Gelidium pusillum is strictly found in Wales, France, and Norway. The status of this species in tropical seas needs to be re-evaluated. Norris (1992) expressed concern about the frequent referral of tropical specimens to this species, which is a morphologically variable entity found in the British Isles (Dixon and Irvine 1977).
*Gelidiella pannosa (J. Feldmann) J. Feldmann and G. Hamel 1934: 534–535.
Type locality: Biarritz, Pyrénées-Atlantiques, France.
Voucher: Mulinu'u Point (Skelton, 24.vi.2000. SUVA-A S39:2)
Plants growing on Rhizophora mangle pneumatophores or other hard substrata, consisting of prostrate and erect systems; erect thallus terete to subterete, 1.5–6mm high, 60–130µm diam., rarely branching; prostrate system terete, 80–110µm diam.; attached by non-aggregated unicellular rhizoids issuing from cortical cells on ventral side of prostrate systems; cross section showing small medullary cells and 2 layers of cortical cells; rhizines lacking; tetrasporangial stichidia terminal on erect thallus, 250–500µm long, 80–130µm wide, 4–6 tetrasporangia per segment; tetrasporangia spherical, to 27.5µm diam., tetrahedrally divided.
Remarks: Several diminutive species of Gelidiella have been reported from the tropical Pacific: G. adnata Dawson (= G. antipai Celan), G. bornetii (Weber-van Bosse) J. Feldmann & Hamel, G. tenuissima J. Feldmann & Hamel (= G. pannosa), G. myrioclada (Børgesen) J. Feldmann & Hamel, G. womersleyana Kraft & Abbott, and G. machirisiana Dawson (see Kraft and Abbott 1998, Abbott 1999). The compressed and ribbon-like erect thalli of G. bornetii, G. machirisiana, and G. womersleyana separate them from G. pannosa. The greater size of G. myrioclada, to 20mm compared to 5mm in local material is a distinguishing character. Gelidiella adnata differs from G. pannosa by the rhizoids which are ‘short unicellular non-aggregated rhizoids that develop along the entire under surface’ (Shimada and Masuda 2000: 99). Furthermore, G. adnata has tetrasporangia borne on ‘short slender pedicels’ (Dawson 1954).
Ceramium flaccidum (Harvey ex Kützing) Ardissone 1871: 40. South and Skelton 2000: 65, figs. 32–39, 41–44.
Type locality: Kilkee, County Clare, Ireland
Voucher: Moata'a, (Skelton and South, 26.viii.2000. SUVA-A S41:8)
Plants growing with Polysiphonia howei, to 6mm high, consisting of creeping axes, giving rise to erect branches; attached by unicellular rhizoids terminating in digitate or blunt tips; branching irregular to alternate, occasionally subdichotomous; pericentral cells 6–7, triangular or rounded, 8–15µ m wide, 20–30µ m long, producing basipetal and acropetal cortical cells; basipetal cells transversely elongate, to 10µ m wide, 30µ m long; acropetal cells spherical or dome-shaped, dividing further to form a total of four acropetal cells resembling a ‘V’ shape; gland cells produced irregularly on nodal bands, to 10µ m diam.; hairs on acropetal cortical cells; tetrasporangia tetrahedrally divided, 37–58µ m diam., surrounded by an involucral branch of two cells when mature. Sexual material not seen.
Remarks: A very common alga with a widespread distribution throughout the tropical Pacific Islands. The distinctive transversely elongated basipetal cells are a diagnostic feature of this species. Ceramium species from Samoa and Fiji have been treated by South et al. (2001) and Skelton (2001). Ceramium flaccidum with its European type locality appears to be cosmopolitan in cold temperate to tropical seas. Whether the same entity is truly represented outside of its type locality, needs to be clarified, perhaps with the aid of molecular studies.
Ceramium upolense South & Skelton 2000: 82, figs. 80–88
Type locality: Palolo Deep Marine Reserve, Samoa.
Voucher: Vaitoloa, (Skelton, 25.vi.2000. SUVA-A5563, SUVA-A S38:6, SUVA-A S40:7); A'anapu, (Skelton and South, 5.i.1998. SUVA-A S39:3).
Plants caespitose to 1 cm tall, consisting of branched prostrate axes bearing simple erect branches with more or less straight tips; attached by uniseriate rhizoids, terminating in branched tips; cortical bands symmetrical, the acropetal and basipetal margins straight, with 4–6 cell rows; axial cells ellipsoidal, 50–100µm diam.; pericentral cells 5–7, rounded to polygonal, 22.5–35µm diam., 22.5–35µm long; pericentral cells cutting off 2 acropetal and 2 basipetal cortical initials, which in turn cut off 1 or 2 acropetal and basipetal cortical cells respectively. Fertile material not found.
Remarks: A common alga collected in intertidal situations. Although this has only been reported from Samoa and Australia (Price and Scott 1992: 113 as Ceramium sp.), it is probably much more widespread like C. flaccidum. These specimens agree well with the holotype (SUVA-A 5025!).
*Caloglossa adhaerens King & Puttock 1994a: 103–106, figs. 3d, 5, 6e.
Type locality: Ballina, New South Wales, Australia
Voucher: Moata'a, (Skelton and South, 26.viii.2000. Sa:314, S41:7); Vaitoloa, (Skelton, 25.vi.2000. SUVA-A 5556, 5564, 5575
[tetrasporangial],
SUVA-A S40:13, [spermatangial],
[tetrasporangial].
S38:14. S40:10, [cystocarpic]); A'anapu, (Skelton and South, 5.i.1998. SUVA-A S38: 18, S38: 20)
Plants forming mats, individual plants to 20 mm long, monostromatic except at the midrib; attached by random, solitary rhizoids cylindrical to 50µm diam., tapering distally, 20–25µm diam., and issued from second and third-order cells, terminating in haptera or blunt tips; mature blades to 2mm wide, tapering towards apices; branching pseudo-dichotomous, the widest part near dichotomy; adventitious branches formed from initials on the thallus margin; pericentral cells elongate, to 190µm long, to 35µm wide; only first or second cells of the second-order cell rows bearing third-order cells, all reaching the thallus margin; cystocarps solitary, spherical, dorsal, to 1 mm diam.; carposporangia ellipsoid, obovoid to subspherical, to 60µm wide, 75µm long; spermatangial sori subterminal on main branch or on adventitious branches; spermatangial mother cells initially cut off from all cells except 1–2 marginal cells, later spermatangia development ceasing on dorsal and ventral pericentral cells as well as on the upper 5 cells from the apex; spermatia rounded ca. 5µm diam.; tetrasporangial sori in slightly swollen or enlarged part of the thallus and usually near the apex, and on both sides, but not protruding onto the midrib, to 2.5mm long, 2mm wide; tetrasporangia arranged in regular tiers, up to 10 (–12) on each side of the midrib; tetrasporangia subspherical, decussately or cruciately divided to 90µm wide.
Remarks: This is a fairly common species found from the three mangrove sites, often dominating over C. leprieurii. It is morphologically distinct from C. leprieurii by the lack of obvious node-internode structure and the scattered rhizoids. Caloglossa adhaerens can be confused with Caloglossa bengalensis (G. Martens) King & Puttock, but the latter is separated by the slight constrictions at the node, and rhizoids assembling near the nodes (King and Puttock 1994a: table 2).
Male and female reproductive structures of this species apparently have been recorded by West et al. (2001) (West pers. comm. 2002). The reproductive structures of local material are similar to those reported in other Caloglossa species: C. ogasawaraensis (Tanaka and Kamiya 1993), C. continua subsp. continua (Tanaka 1992) and C. postiae Kamiya and King (Kamiya et al. 1999). King and Puttock (1994a: 100–102) spermatangial sori cover the whole of the blade with the exception of marginal cells, some lateral cells and all transverse pericentral cells. Caloglossa adhaerens, however, initially exhibits 1 or 2 sterile marginal cells, but at maturity all cells including marginal cells and pericentral cells are covered with spermatangia except the very top and very basal cells.
*Caloglossa leprieurii (Montagne) G. Martens 1869: 234, 237. King and Puttock 1994a: 112–113. Silva et al. 1996: 450. Stegenga et al. 1997.
Type locality: near Cayenne, French Guiana.
Voucher: Vaitoloa, (Skelton, 25.vi.2000. SUVA-A 5562, S40:11, [tetrasporangial]
); A'anapu, (Skelton and South, 5.i.1998. S41:2, [tetrasporangial],
S38:19, [spermatangial]).
Plants forming mats spreading to 5cm diam.; individual plants monopodial, frequently displaying a rosette arrangement; attached by aggregation of intertwining, pit-connected multicellular rhizoids confined to the nodes, occasionally forming a stipe to 3mm long, 500µm wide; thallus monostromatic except the midrib (and the stipe); mature blades to 3 mm wide, tapering toward the node; branching pseudo-dichotomous; endogenous blades formed from nodes; pericentral cells 4; the laterals dividing horizontally, and dorsal and ventral cells remaining inactive, although occasionally with a single cell cut off from the dorsal pericentral cell; pericentral cells squarish to ovate, 75µm wide, 90µm long; other cells 75µm long diminishing in size toward the margin; axial cells elongate to 150µm long, 30µm diam., only the first 5–6 cells of the second-order cell rows bearing third-order cells, all reaching the margin; spermatangial sori on both sides of the midrib, to 3.5mm long, 1mm wide, involving all cells after the second cells of the second-order cell rows, except 1–2 cells from the margin; spermatia rounded 5–7.5µm diam.; tetrasporangial sori produced in a single layer, covering most cells including lateral pericentral cells, except 4–6 submarginal cells; mature tetrasporangia arranged in regular tiers, surrounded by involucral cells, spherical, cruciately or decussately arranged, 50–60µm diam. Female plants not seen.
Remarks: An important species of the bostrychietum turf, often entangled with Bostrychia tenella in the Bruguiera gymnorhiza-dominated mangrove, whereas mixed with C. adhaerens and M. periclados in Rhizophora mangle-dominated mangroves. This species closely resembles Hypoglossum caloglossoides Wynne and Kraft (1985) differing in that the latter has all second-order cells bearing third-order cell rows and is not found in mangrove habitats. Furthermore, the tetrasporangia are produced in two to many layers in H. caloglossoides, but in a single layer in C. leprieurii. According to Kamiya (pers. comm. 2002) there are three morphotypes of C. leprieurii, with the tropical Pacific entity representing a new species as yet unpublished. The Samoan material tentatively treated as C. leprieurii by Kamiya (pers. comm. 2001) has the characters of his new entity.
Bostrychia tenella subsp. tenella King & Puttock 1989: 34–37, fig. 15
Type locality: type locality: St Croix, Virgin Islands
Voucher: A'anapu, Skelton and South, 5.i.1998. SUVA-A S38:16; S39:1, S39:6,[tetrasporangial],
S39:7,
[tetrasporangial],
S39:9,[cystocarpic], S39:12, S40:15,
[tetrasporangial],
S40:18,[tetrasporangial]).
Plants forming mats, prostrate with erect laterals to 20mm long, densely branched, especially in distal portions; attached by a holdfast consisting of a mass of multicellular rhizoids issuing from cortical cells, or secondary attachments from tips of branched indeterminate axes; main axes polysiphonous, terete, to 0.5mm wide, with laterals arising mostly at every axial cell; laterals usually polysiphonous below becoming monosiphonous above; cystocarps terminal on polysiphonous branches, spherical to reniform, to 775µm wide; ostiole slight 50–80µm high, 150–220µm wide; carposporangia oblanceolate, 100–125µm long, 30µm wide; tetrasporangial stichidia sub-terminal on polysiphonous branches, to 500µm long, 200µm wide; 1-(4)–5 tetrasporangia in regular tiers, borne on pericentral cells, with 2–3 cover cells; tetrahedrally divided tetrasporangia, to 65µm diam. Male plants not seen (see remarks below).
Remarks: The Samoan material conforms well to the description and illustrations of this species by King and Puttock (1989: 34, fig. 15). One specimen (S40:15) superficially resembles a male plant, with immature stichidia endowed with smaller cover cells; furthermore most stichidia are produced on monosiphonous and occasionally polysiphonous laterals. Closer examination of stichidia revealed no spermatia, but immature tetrasporangia present in some. Tetrasporangial stichidia of B. tenella are reported to be borne on polysiphonous laterals (King and Puttock 1989); although monosiphonous laterals bearing tetrasporangial stichidia are reported here. The possibility that this is a mixed phase plant, however, cannot be ruled out, as mixed phase plants have been reported in B. tenella from the Philippines and Puerto Rico (West and Calumpong 1988).
Murrayella periclados (C. Agardh) Schmitz 1893: 227, footnote. Hollenberg 1968a: 80.
Type locality: St Croix, Virgin Islands.
Voucher: Vaitoloa, (Skelton, 25.vi.2000. SUVA-A 5558, 5560, 5561, 5565, 5575[tetrasporangial],
S40:4[tetrasporangial],
S38:12[tetrasporangial];
S38:15). A'anapu, (Skelton and South, 5.i.1998.
SUVA-A S40:20[tetrasporangial],
S39:17[tetrasporangial]).
Plants caespitose, mixed with Caloglossa spp., and Polysiphonia howei; with a prostrate system giving rise to erect branches to 3cm tall; attached by numerous uniseriate rhizoids pit-connected to prostrate pericentral cells or scar cells, terminating in rounded or branched tips, to 1mm long, 30–50(–70)µm diam.; main indeterminate axes bearing branched, uniseriate determinate axes and indeterminate laterals on every segment, alternately arranged, 160–200µm diam.; determinate axes deciduous, uncorticated, pseudo-dichotomously branched below, unbranched terminally, 25–40µm diam., to 2mm long, up curved slightly; pericentral cells four, elongated, 50µm diam., 110–155µm long; determinate lateral cells rectangular to squarish, 25µm diam., 50µm long, tapering distally to a pyramidal apical cell; tetrasporangial stichidia 125–500µm diam., 250–2000µm long, terminal on short multiseriate branch, with or without uniseriate branchlets; secondary stichidium often developing above initial stichidium; tetrasporangia surrounded by involucral cells, 40–65µm diam. Sexual plants not found.
Type locality: Whale Cay, Berry Islands, Bahamas
Voucher: Vaitoloa, (Skelton, 25.vi.2000. SUVA-A S40:8, S40:9[tetrasporangial])
Plants matted; axes prostrate, decumbent, 130–180µm diam.; attached by unicellular rhizoids, these arising one to several per segment, cut off by a cross wall at the distal ends of the pericentral cells, terminating in digitate or multicellular tips; erect laterals to 5mm tall, 110–150µm diam., tapering terminally, and curving toward the prostrate apices; pericentral cells 9–14; branches arising irregularly and exogenously; trichoblasts abundant toward the tips of erect branches, to 750µm long, closely and repeatedly branched in a strictly dichotomous manner, arising one per segment, deciduous, leaving persistent scar-cells; tetrasporangia one per segment, 40–55µm in diameter in relatively long and slightly spiralled series in the tips of the erect branches; sexual material not seen.
Remarks: The Samoan material agrees well with the type description (Taylor 1945: 302) and plants reported by Abbott (1999: 419) from Hawaii and Littler and Littler (2000: 230) from the Caribbean. This alga appears to be widespread in tropical to subtropical regions, and may be found in southern Europe (Hollenberg 1968b: 204). The first record from the Samoan Archipelago was by Hollenberg who included W.A. Setchell's Samoan collection (UC 237032) under his new species (Taylor 1945: 303). Hollenberg's description of his type material clearly shows that it belongs to Neosiphonia sensu Kim and Lee (1999), with its spirally arranged tetrasporangia and the rhizoids being cut off from periaxial cells.
Type locality: Baltic Sea, Germany.
Voucher: Vaitoloa, (Skelton, 25.vi.2000. SUVA-A 5557, S38:11, S39:20).
(Plate V, Figs. 29–33, Plate VI, Fig. 34)
Plants free floating, entangled with Chaetomorpha brachygona and other algae; filaments mostly unbranched above, tubular to compressed, of more or less uniform size 875–1500µm wide, to 10cm long; numerous determinate proliferations occurring in the lower thallus, initially uniseriate, becoming multiseriate below; 2–4 pyrenoids per cell, cells 25–30µm long, not orderly arranged in mature thallus, but longitudinally arranged in branchlets.
Remarks: The Samoan material falls within the Clathrata group as recognised by Bliding (1963). The unordered cell arrangement in mature thalli as well as the smaller cell sizes (compared to Bliding's material, ‘cells large to very large 35–45µm’) may be a slight variation. Our material agrees in most respects with description of plants from Lord Howe Island (Kraft 2000), although slightly larger and lacking branchlets with bulbous endings.
Type localities: Key West, Florida, USA; mouth of Rio Bravo [Rio Grande], border of Mexico and Texas, USA.
Voucher: Vaitoloa, (Skelton, 25.vi.2000. SUVA-A S38:10).
Plants generally free-floating, entangled with other algae, light green in colour; cells square to rectangular, 130–180µm diam., (L:W ratio, 0.5–2).
Remarks: Specimens reported by Setchell (1924: 178) as Chaetomorpha restricta (Suhr) Kützing were later identified as C. brachygona by Blair (1975: 54, 164).
*Chaetomorpha mimima Collins and Hervey 1917: 41–42, pl. I: figs. 5–7
Type locality: Bermuda
Voucher: Vaitoloa, (Skelton, 25.vi.2000. SUVA-A S38:13)
Plants epiphytic or forming felted mats with other algae on firm substrata; colour bright green; filaments slender, 25–40µm diam., to 5mm tall; attached by tapering basal cells, 30–40µm diam., 150–200(–300)µm long.
Remarks: The filament sizes are well within the range of this species reported by Blair (1975: 55).
*Cladophora liebetruthii Grunow in Piccone 1884: 53. Kraft 2000: 564–566, fig. 22.
Type locality: Ionian Sea
Voucher: A'anapu, (Skelton and South, 5.i.1998. SUVA-A 5656)
Plants forming cushions to 1cm tall; main axes not obvious, attached by numerous rhizoids extending from ventral parts of creeping branches terminating in digitate tips; rhizoids 50–70µm diam., 375–1500µm long; branching secund, occasionally opposite; main thallus 70–100µm diam., laterals 60–70(–100)µm diam.; cells 600–1150µm long (L:W ratio, 6–12:1); apical cell rounded, 100–125µm diam., 1125–1925µm long.
Remarks: Identification of Cladophora species in the tropics is hindered by the lack of a good monograph, although the excellent treatment of Hoek (1963, 1982) of European and the North Atlantic Ocean provide an excellent starting point. This entity keys out to C. liebetruthii in Kraft (2000), but seems to align with C. laetevirens (Dillwyn) Kützing if Littler and Littler (2000) are consulted. The smaller cell sizes in C. laetevirens as reported by Littler and Littler (2000) separate that species from the local material. Although C. boodleoides Børgesen was synonymised with C. liebetruthii by Hoek (1963: 59), Trono (1968) and South et al. (2001) recognised the two as separate entities. Comparison of C. boodleoides reported by South et al. (2001) and the Samoan material revealed two very different entities. Cladophora boodleoides is characterised by its ‘Boodlea-type’ cells, which are about 3 times larger than those of C. liebetruthii. Furthermore, C. boodleoides has branched rhizoids, a character not reported in C. liebetruthii. We therefore concur with Børgesen (1925), Trono (1968) and South et al. (2001) that the two are separate species.
Plants tufted to 3cm tall, attached by blunt, colourless rhizoids; main axes undifferentiated from laterals, 90–125µm wide below, 175–180µm wide above; branching most proliferous at distal part of the thallus, secund to alternately arranged; cells 130–160µm diam., to 750µm long; apical cells 125–175µm, 1.5–5mm long.
Remarks: This is an important alga that dominates one of the two major algal assemblages in Rhizophora mangle communities, growing on discarded cloth and hard substrata in shaded places under mangrove trees.
*Rhizoclonium africanum Kützing 1853: 21, pl. 67 (2).
Type locality: Senegambia, Africa.
Voucher: A'anapu, (Skelton and South, 5.i.1998. SUVA-A S40:16)
Plants common, epiphytic or epilithic, forming an entangled mass; filaments slender, unbranched, 60–80µm diam.; attached by short, rarely branched rhizoids; cells rectangular and irregularly divided, 2 times longer than broad, 50µm diam., 100µm long; cell wall thick, stratified, 10–20µm thick.
Remarks: The genus Rhizoclonium is in need of a comprehensive monographic treatment as species are poorly delimited. Furthermore, its generic distinction from Chaetomorpha needs to be confirmed. Rhizoclonium is currently separated from Chaetomorpha by its finer filaments that form tangled free-living mats and lack branches except for the production of short rhizoids (Silva et al. 1996: 936).
Type locality: Mauritius.
Voucher: Moata'a, (Skelton and South, 26.viii.2000. SUVA-A S41:9).
Plants forming spongy cushions; densely branched in a 3-dimensional network; branching opposite, unilateral to alternate; cells of main axes distinct from thinner laterals, to 500µm, up to 8 diameters longer than broad; laterals cylindrical, 100–140µm diam., tapering slightly to blunt rounded apices; attached by colourless rhizoids.
Remarks: Plants form extensive spongy cushions overlying the muddy substratum beneath the mangrove canopy. There is a lack of good morphological characters to differentiate species of this genus. The highly variable cell sizes and the degree of thallus branching are still being used to distinguish species, although rhizoidal disposition is used by Leliaert et al. (1998: 184) to separate B. composita from B. vanbosseae Reinbold.
* Cladophoropsis carolinensis Trono 1971: 48, pl. 3, figs. 1–5; Kraft 2000: 573–575, fig. 25A-D.
Type locality: Utwa Village, Kusaie Is. Caroline Islands
Voucher: A'anapu, (Skelton and South, 5.i.1998. SUVA-A 5559, S39:11).
Plants forming dense tufts to 10cm or more in diameter; main filaments 100–200µm diam., irregularly branched, secund, alternate to sub-opposite, slightly tapering distally; attached by 1–2 celled rhizoids terminating as lacerated hapteral tips; intercalary cell lengths 375–3000µm; laterals arising from the distal ends of main axes, maintaining an open connection with parent cell.
Remarks: Common forming cushion-like growths beneath Bruguiera gymnorhiza canopy; attached to volcanic rocks, infiltrated with sand. The Samoan material agrees in most respects with the description of the type of C. carolinensis and plants from Lord Howe Island (Kraft 2000). Cladophoropsis sundanensis Reinbold and C. carolinensis are two very similar entities. The main distinction is the clavate tips of the branches in C. sundanensis compared to distinctly tapering towards distal end in C. carolinensis (Trono 1971: 49). Samoan material has branches that are tapering, but never clavate.
Type locality: Malakal Is., Caroline Islands.
Voucher: A'anapu, (Skelton and South, 5.i.1998. SUVA-A S39:16).
Plants forming extensive felted mass on surface of substratum; filaments colourless below, dark green pigmented above; main axis indistinguishable from ramuli, width variable to 45µm diam., attached by branched rhizoids; branching irregular, mostly di-trichotomous, branches to 25µm diam.; ultimate laterals slightly constricted at base; sporangia subspherical, 57–62.5µm diam.
Remarks: Plants agree very well with the description and illustrations of Trono (1971) and West (1991), except that the basal filaments and sporangia are half the size. Trono (1971) separated B. carolinensis from B. siphonacea based on species “forming felted mass and compactly intricated filaments" compared to ”caespitose turfs and extensively and loosely intricated" ramuli. The taxonomic distinctiveness of B. carolinensis remains tenuous as the characters used by Trono are variable (West pers. comm., 2002). Modern treatment of the genus, including molecular work, is desirable.
Twenty-five algae (6 Cyanophyta, 10 Rhodophyta and 9 Chlorophyta) were enumerated, of which twelve are new records for Samoa. There was a notable absence of Phaeophyta from all sites surveyed, considered poor in other studies (King 1990, Prasad and South 1995). The high number of Chlorophyta may be attributed to the fact that other substrata within the mangrove communities (e.g., basaltic rocks and discarded objects) were sampled.
The typical bostrychietum algal community (those dominated by Bostrychia and Caloglossa) was observed only from Bruguiera gymnorhiza-dominated site (A'anapu), which also contained the highest diversity of species. In Rhizophora mangle-dominated sites the bostrychietum was replaced by two distinctive algal assemblages, both lacking Bostrychia. The first assemblage, found on pneumatophores, is of mixed Caloglossa adhaerens, Caloglossa leprieurii, and Murrayella periclados. The second assemblage is an extensive thick and muddy fuzz, growing on basaltic rock and other hard substrata and consists mostly of Polysiphonia howei, Murrayella periclados, Cladophora liebetruthii, and Cladophora sp. It is clear that the mangrove algal associated flora of Samoa is impoverished and contains species that are atypical of the bostrychietum.
The Bruguiera-dominated site is in relatively good condition (Boon 1997, Skelton and South, pers. obs.), whereas R. mangle sites found in the Apia District are heavily impacted by human activities (Schuster 1993). Documenting the algal flora of mangrove and related ecosystems provides a solid foundation for other scientific disciplines (e.g., ecology) to begin and the formulation of good management practice.