Reproductive phenology and growth rates in two species of Gracilaria from Hawaii

Observations on wild populations of Gracilaria bursapastoris (Gmelin) Silva and G. coronopifolia J. Ag. showed significant differences in gametophyte: tetrasporophyte ratios from the expected 1: 1 ratio. As in many other perennial red algae, the proportion of tetrasporic individuals in a population of these two Gracilaria spp. dominates the combined male and female gametophytc stage. There were significantly more male than female thalli in the G. cornopifolia population whereas the gametophytes of G. bursapastoris occurred in the expected 1: 1 ratio. In addition, there are seasonal changes in the proportions of tetrasporic and gametophytic individuals within the populations. Tetrasporic thalli of G. coronopifolia evinced a biphasic seasonal pattern with high proportions in winter and summer. The tetrasporic phase of G. bursapastoris, on the other hand, showed a low proportion in winter. Maximum biomass does not necessarily correlate with maximum proportion of the tetrasporophyte generation. Seasonal patterns in the proportion of male and female gametophytes differed for each stage as well as for each species. The proportion of male thalli in G. bursapastoris and G. coronopifolia showed high peaks in winter and autumn, respectively. Cystocarpic thalli were most abundant in the former in late winter and summer and in the latter in winter and spring. In both species the female gametophytes grew significantly slower than did the male gametophytic or tetrasporophytic stages. Practical applications regarding seasonal cycles in the various reproductive stages and their differential growth rates are discussed.     

ITS1 sequences of type specimens of Gigartina and Sarcothalia and their significance for the classification of South African Gigartinaceae (Gigartinales,Rhodophyta)

Uncertainties about the identity of type specimens of red algae have frequently led to taxonomic and nomenclatural confusion. A procedure for extracting PCR-amplifiable DNA from formalin-fixed material and herbarium specimens was used to investigate the taxonomic status of several South African Gigartinaceae. We compared nucleotide sequences in the internal transcribed spacer 1 (ITS1) region in type specimens and other historically important collections presently referred to Gigartina bracteata, G. radula and G. stiriata. The following opinions are supported: (1) Fucus bracteatus S.G. Gmelin, Chondrodictyon capense Kützing and Iridaea clathrata Decaisne represent a single species of South African Gigartina (G. bracteata (S.G. Gmelin) Setchell & Gardner) in which the disintegration of tetrasporangial sori results in a reticulate thallus. (2) Mastocarpus polycarpus Kützing, M. incrassatus Kützing and Iridaea lapathifolia Kützing represent a single species of South African Gigartina (G. polycarpa (Kützing) Setchell & Gardner) that has often, but erroneously, been called G. radula (Esper) J. Agardh. (3) Mastocarpus verrucosus Kützing is a later heterotypic synonym of Iridaea papillosa Bory (Sarcothalia papillosa (Bory) Leister) and was based on material that probably came from southern South America rather than from South Africa, the provenance given by Kützing. (4) Fucus stiriatus Turner and Sphaerococcus burmannii C. Agardh represent a single species of South African Sarcothalia (S. stiriata (Turner) Leister).     

Pedobesia simple (Kützing) comb. nov. (Chlorophyta), a new name for P. lamourouxii and its first report from the Indian Ocean

The green alga Pedobesia lamourouxii (J. Agardh) Feldmann et al. (Bryopsidales) is reported from the northern Arabian Sea on the basis of collections from the Sultanate of Oman and Socotra Island (Yemen). Vegetative and sporangial plants as well as the ecology are described. These collections constitute the first record of this widely distributed species for the Indian Ocean. In the course of this study we discovered that Bryopsis simplex Kützing is an older taxonomic synonym, and thus we propose Pedobesia simplex (Kützing) comb. nov. as the correct name for this species. A specimen of Bryopsis simplex in the Leiden Herbarium (L) is designated as lectotype.     

A survey of the marine algae of Milos Island,Greece

The composition of the benthic macroflora was studied in an area of shallow-water gas-hydrothermal vents in the Palaeochori Bay (Milos Island, Aegean Sea). Some species, both taxonomically and biogeographically remarkable, were collected Tribonema marinum J. Feldmann, Stypopodium schimperi (Buchinger ex Kützing) Verlaque et Boudouresque, Amphiroa rubra (Philippi) Woelkerling, Cutleria cf. chilosa (Falkenberg) Suva, Womersleyella setacea (Hollenberg) R.E. Norris). The large number of species with warm-water affinities [Halopithys incurva (Hudson) Batters, Jania adhaerens Lamouroux, Laurencia microcladia Kützing, Tricleocarpa fragilis (Linnaeus) Huisman et Townsend, Stypopodium schimperi (Buchinger ex Kützing) Verlaque et Boudouresque, Zonaria toumefortii (Lamouroux) Montagne, Anadyomene stellata (Wulfen) C. Agardh, Dasycladus vermicularis (Scopoli) Krasser, Microdictyon tenuius Decaisne ex J. Gray] is mainly due to the southern location of the Milos Island but could be also related to a homogeneous influence of vent activity throughout the bay.     

SYSTEMATICS OF THE GRACILARIACEAE (GRACILARIALES,RHODOPHYTA): A CRITICAL ASSESSMENT BASED ON RBCL SEQUENCE ANALYSES1

Generic concepts in the economically important agarophyte red algal family Gracilariaceae were evaluated based on maximum parsimony, Bayesian likelihood, and minimum evolution analyses of the chloroplast‐encoded rbc L gene from 67 specimens worldwide. The results confirm the monophyly of the family and identify three large clades, one of which corresponds to the ancestral antiboreal genera Curdiea and Melanthalia, one to Gracilariopsis, and one to Gracilaria sensu lato, which contains nine distinct independent evolutionary lineages, including Hydropuntia. The species currently attributed to Hydropuntia comprise a single well‐supported clade composed of two distinct lineages. The two most basal clades within Gracilaria sensu lato deserve generic rank: a new genus centered around G. chilensis Bird, McLachlan et Oliveira and G. aff. tenuistipitata Chang et Xia and a resurrected Hydropuntia encompassing primarily Indo‐Pacific (G. urvillei [Montagne] Abbott, G. edulis [S. Gmelin] P. Silva, G. eucheumatoides Harvey, G. preissiana [Sonder] Womersley, and G. rangiferina [Kützing] Piccone) and western Atlantic species (G. cornea J. Agardh, G. crassissima P. et H. Crouan in Mazé et Schramm, G. usneoides [C. Agardh] J. Agardh, G. caudata J. Agardh, and G. secunda P. et H. Crouan in Mazé et Schramm). Cystocarpic features within the Gracilaria sensu lato clades appear to be more phylogenetically informative than male characters. The textorii‐type spermatangial configuration is represented in two distinct clusters of Gracilaria. The rbc L genetic divergence among the Gracilariaceae genera ranged between 8.46% and 16.41%, providing at least 2.5 times more genetic variation than does the 18S nuclear rDNA. rbc L also resolves intrageneric relationships, especially within Gracilaria sensu lato. The current number of gracilariacean species is underestimated in the western Atlantic because of convergence in habit and apparent homoplasy in vegetative and reproductive anatomy.     

广州市景观湖微囊藻的分类学研究

于2008年3月至2009年4月,对广州市区若干景观湖水体的微囊藻属(Microcystis)进行分类学研究。共观察到11种微囊藻,分别是铜绿微囊藻(M. aeruginosa Kützing)、放射微囊藻(M. botrys Teiling)、坚实微囊藻(M. firma Kützing)、水华微囊藻(M. flosaquae Wittrock)、鱼害微囊藻(M. ichthyoblabe Kützing)、挪氏微囊藻(M. novacekii Komárek)、苍白微囊藻(M. pallida (Farlow) Lemm.)、假丝微囊藻(M. pseudofilamentosa Crow)、史密斯微囊藻(M. smithii Komárek & Anagnostidis)、绿色微囊藻(M. viridis A. Braun)和惠氏微囊藻(M. wesenbergii Komárek),对它们的形态学特征进行描述,并比较这些种类间的形态区别。     

Distribution of diatom species on an estuarine mud flat and experimental analysis of the selective effect of stress

The distribution patterns of seven dominant diatom species on an estuarine mud flat transect were related to salinity gradients and organic pollution. The temporal distribution of species can be explained partly by the seasonal variation in irradiance and temperature, and partly by the large discharges of organically polluted fresh water during the late autumn. The selective effects of stress factors, such as low or high salinity, high concentrations of ammonia and free sulphide, and high temperatures were studied by measuring: (1) the tolerance of natural diatom populations isolated from the sediment; (2) the tolerance and capacities of unialgal cultures: and (3) the effects of the stress factors on the species composition of the populations in sediment samples incubated in the laboratory. A low salinity (1‰), but not a high salinity (20‰), markedly altered the species composition of natural diatom populations kept in the laboratory. Navicula salinarum Grunow and N. cf. cryptocephala Kützing outcompete other species only at a salinity of 1‰, which is below the optimum salinity for growth of these species. High concentrations (2–4 mM) of ammonia inhibited the photosynthesis of N. phyllepta Kützing and N. flanatica Grunow and decreased the cell numbers of these species in mixed populations kept in the laboratory. N. salinarum and Gyrosigma fasciola (Ehr) Cleve were relatively ammonia-tolerant and reached their highest abundance during periods of large discharges of organically polluted water. The populations on the mud-flat stations that had black, sulphide-containing layers 1 mm below the surface of the sediment, were dominated by the relatively sulphide-tolerant Navicula salinarum and N. pygmaea Kützing.High values of irradiance and temperature were a selective factor explaining the absence of N. flanatica in summer. Uptake of organic substrates and the inhibitory effect of high population densities are discussed in regard to their possible modifying influence on the distribution of diatom species on the mud flat.     

Contribution to the seaweed flora of Namibia: new records of Chlorophyta and Phaeophyceae

Six species of benthic marine Chlorophyta and Phaeophyceae are recorded for the first time from the coast of Namibia: Ectocarpus fasciculatus Harvey, Feldmannia irregularis (Kützing) G. Hamel, Bachelotia antillarum (Grunow) Gerloff, Straguloria clavata (Harvey in Hooker) Hamel, Entocladia leptochaete (Huber) Burrows and Ulvella lens P. Crouan & H. Crouan. Data concerning local and world distribution of these species as well as some taxonomical remarks are provided.     

Agars fromGracilaria chilensis (Gracilariales)

The chemical composition of the agars extracted with water at 95 °C fromGracilaria chilensis of Estero de Lenga (43.2% of yield) and of Bahia de Coquimbo (43.4% of yield) were determined. The gel strength, gel melting and gelation temperature of the agars were also measured. Polysaccharides obtained by extraction with cold water and by extraction of the alkali pre-treatedG. chilensis of Bahia de Coquimbo were also analyzed. The physical constants and the contents of sulfate and 3,6-anhydrogalactose of the alkali-modified agar fromG. chilensis of Estero de Lenga were comparable to those of commercial agar. This algae represents an excellent potential commercial resource of agar.G. chilensis of Bahia de Coquimbo gave hydrocolloids with low gel strength values more suitable for use in the food industry. Anion exchange chromatography of the agars obtained by extraction with water at 95 °C indicated that the whole polysaccharides and all of the acidic fractions were not homogeneous. Neutral fractions comprised only about 25% of the agars.     

Seasonal growth dynamics of Laurencia papillosa and Gracilaria coronopifolia from a highly eutrophic reef in southern Taiwan: temperature limitation and nutrient availability

Both field and laboratory studies were used to investigate the effects of temperature limitation and nutrient availability on seasonal growth dynamics of Laurencia papillosa and Gracilaria coronopifolia from a nearshore coral reef in the southern tip of Taiwan during 1999-2000. L. papillosa was a summer blooming alga abundant in August-November and G. coronopifolia was abundant year round except April-May. L. papillosa blooms in the summer were attributed to its preference for high temperatures and highly sensitivity to low temperatures. A wider temperature range and a significant stimulation of growth by high N inputs can explain the appearance of G. coronopifolia year round and also its maximum growth in November-March. Levels of dissolved inorganic nitrogen (DIN) and soluble reactive phosphorus (SRP) in water column were extremely high, but the growth of these two rhodophytes still suffered nutrient limitation that the type and severity of nutrient limitation were variable over time and also between two species. The growth of L. papillosa was limited by P in the early growth stage (August-September) as indicated by decreased tissue P contents, increased C/P and N/P molar ratios and increased alkaline phosphatase activity (APA) and in the later growth stage, it was subjected to N-limitation, evidenced by decreased tissue N contents and C/P and N/P molar ratios and increased tissue P contents. The growth of G. coronopifolia was also P-limited as indicated by increased tissue N contents and concomitantly decreased tissue P contents, while marked drops in tissue P contents below the subsistence level in mid September and December 1999 reveal severe P limitation, which was supported by increased alkaline phosphatase activity. Higher critical nutrient contents and nutrient thresholds for maximum growth of G. coronopifolia suggest that G. coronopifolia faced more frequent nutrient limitation compared to L. papillosa. In conclusion, the results from these laboratory and field studies provide evidence that the seasonal abundance of L. papillosa and G. coronopifolia from southern Taiwan was determined by seasonal variations in seawater temperatures and nutrient concentrations as well as different physiological growth strategies. Seawater temperature and nutrient availability were important determinants of seasonal abundance of L. papillosa while the seasonal abundance of G. coronopifolia was influenced by nutrient availability.     

The Ecological Perspective of Microbial Communities in Two Pairs of Competitive Hawaiian Native and Invasive Macroalgae

Marine macroalgae are known to harbor large populations of microbial symbionts, and yet, microbe symbiosis in invasive macroalgae remains largely unknown. In this study, we applied molecular methods to study microbial communities associated with two invasive algae Acanthophora spicifera and Gracilaria salicornia and the two native algae Gracilaria coronopifolia and Laurencia nidifica at spatial and temporal scales in Hawaiian coral reef ecosystems. Bacterial communities of both the invasive and native macroalgae displayed little spatial and temporal variations, suggesting consistent and stable bacterial associations with these macroalgae. Results of this study identified three types of bacterial populations: nonspecific (present in both algal and water samples); algae-specific (found in all algal species); and species-specific (only found in individual species). The bacterial diversity of invasive algae was lower than that of their native counterparts at phylum and species levels. Notably, the vast majority (71 %) of bacterial communities associated with the invasive algae G. salicornia were representatives of Cyanobacteria, suggesting a potential ecological significance of symbiotic Cyanobacteria.     

Physiological ecology studies on chilean gelidiales

In the exposed rocky habitats of Central Chile, four species of Gelidium occur along the vertical distance extending from the upper intertidal to the shallow subtidal. The present study was undertaken to characterize taxonomically confused species of Gelidium by differential responses to key ecological factors. In so doing, it was expected to better characterize ecophysiological differences between upper and lower intertidal species and to establish experimental bases on which to compare physiological responses of temperate and subtropical species of Gelidiaceae. The effects of temperature, water movement, salinity, photon flux density and photoperiod were tested on the growth rates of Gelidium pusillum (Stackh.) Le Jol., G. filicinum Bory, G. lingulatum (C. Agardh) J. Agardh and G. spinulosum Kützing prox. With the exception of salinity, specific differences are evident under the effects of all other factors tested.     

New finds of charophytes in Iceland with an update on the distribution of the charophyte flora

Charophyte species new to the flora of Iceland are reported and an update on the distribution of the previously known species is given. Four species are new to Iceland; Chara aspera Willdenow, Chara contraria Braun ex Kützing, Tolypella canadensis Sawa and Tolypella glomerata (Desvaux) Leonhardi, while four species were previously known: Chara globularis Thuiller, Chara virgata Kützing, Nitella flexilis (L.) Agardh and Nitella opaca (Agardh ex Bruzelius) Agardh. The finding of the species new to Iceland add to the hitherto known worldwide distribution of those species, including a significant extension to the north.     

Chemical characteristics and gelling properties of agar from two Philippine Gracilaria spp. (Gracilariales, Rhodophyta)

The chemical structure of agars extracted from Philippine Gracilaria arcuata and G. tenuistipitata were determined by NMR and infrared spectroscopy. Agar with alternating 3-linked 6-O-methyl-β-D-galactopyranosyl and 4-linked 3,6-anhydro-2- O-methyl-α-L-galactopyranosyl units was isolated from G. arcuata, while the agar from G. tenuistipitata possesses the regular agarobiose repeating unit with partial methylation at the 6-position of the D-galactosyl residues. Both agars exhibit sulphate substitution at varying positions in the polymer. Chemical analyses reveal higher 3,6-anhydrogalactose and lower sulphate contents in alkali-modified than in native agar from both samples. Also, alkali modification enhanced agar gel strength and syneresis. Native G. arcuata agar produces a viscous solution (2000 cP at 75 °C) with a high gelling point (>60 °C) that forms a soft gel even after alkali modification (gel strength: <300 g cm⁻²). On the other hand, the agar from G. tenuistipitata exhibits gel qualities typical of most Gracilaria agars. This revised version was published online in June 2006 with corrections to the Cover Date.     

桥弯藻科和异极藻科（硅藻门）植物中国7种新记录

对采自黑龙江省东南部兴凯湖湿地的100余号硅藻标本进行分类研究,共发现桥弯藻科、异极藻科（硅藻门）中国新记录植物5种2变种,分别为亚粗糙桥弯藻（Cymbella peraspera Krammer）、尖头弯肋藻［Cymbopleura cuspidata (Kützing) Krammer］、不显内丝藻高山变种（Encyonema obscurum var.alpina Krammer）、西里西亚内丝藻翼形变种（Encyonema silesiacum var.lata Krammer）、耳状异极藻（Gomphonema auritum Braun & Kützing）、棍棒异极藻（Gomphonema clava Reichardt）、极细异极藻［Gomphonema exilissimum (Grunow) Lange-Bertalot & Reichardt］。对其分类学特征进行了详细的描述,与同属中相似的种类进行了比较与讨论,为今后该区域的藻类研究提供了基础的资料。     

dÉcologie des diatomées d'eau douce de la région centrale du Portugal

Tychoplanktonic and epilithic diatom samples were taken monthly during one year at 18 sites in small lowland rivers in the northern central region of Portugal. Canonical correspondence analysis was used to explore the relationships between measured environmental variables and patterns in the diatom assemblages. Conductivity, HCO₃⁻, and chemical oxygen demand (COD) were the most significant environmental variables influencing the structure of the tychoplankton and of the epilithon. Other less important variables, such as K⁺, Fe, N(NO₃⁻), and Na⁺ also explained significant (P < 0.05) amounts of variance. The ordination diagrams showed very similar distribution of the tychoplanktonic and epilithic diatom samples. At sites with similar geomorphology as in this study, it is possible to use only one of these samples for water quality evaluation. The optima and tolerances of some diatom taxa were calculated for the most influential variables. Although the diatoms showed high tolerances to some environmental parameters, it was possible to establish groups of taxa with defined and distinctive ecological preferences. Two species groups stood out depending on the alkalinity and mineralization of the water. With a moderate conductivity (> 600 μS·cm⁻¹), alkaline pH, HCO₃⁻ concentrations equal or higher than 150 mg·l⁻¹, the first group includes Achnanthes hungarica Grunow, Amphora pediculus (Kützing) Grunow, Bacillaria paxillifera (O. F. Müller) Hendey, Cymatopleura solea (Brébisson) W. Smith, Navicula accomoda Hustedt, Navicula lanceolata (Agardh) Ehrenberg, Navicula trivialis Lange-Bertalot, Nitzschia hungarica Grunow. In waters of lower conductivity (varying between 72 and 262 μS·cm⁻¹) slightly acid pH (6 to 6.5) and HCO₃⁻¹ lower than 46 mg·l⁻¹ the following species were common: Achnanthes oblongella Östrup, Achnanthes subatomoides (Hustedt) Lange-Bertalot, et Archibald, Cymbella gracilis (Ehrenberg) Kützing, Cymbella naviculiformis Auerswald, Diatoma mesodon (Ehrenberg) Kützing, and Eunotia exigua (Brébisson) Rabenhorst. Considering COD, two further groups were distinguished. At high values (> 40 mg·l⁻¹) the following taxa were observed: Achnanthes delicatula (Kützing) Grunow, Navicula capitata Ehrenberg var. hungarica (Grunow) Ross, Nitzschia nana Grunow, Pinnularia interrupta W. Smith, Thalassiosira pseudonana Hasle & Heimdal, Thalassiosira weisflogii (Grunow) Fryxell et Hasle. For lower values than 19 mg·l⁻¹, we found Cymbella naviculiformis Auerswald, Diatoma mesodon (Ehrenberg) Kützing, Eunotia exigua (Brébisson) Rabenhorst, Fragilaria arcus (Ehrenberg) Cleve, and Nitzschia epithemioides Grumow var. disputata (Carter) Lange-Bertalot.     

MOLECULAR PHYLOGENY OF ANTARCTIC PRASIOLA (PRASIOLALES,TREBOUXIOPHYCEAE) REVEALS EXTENSIVE CRYPTIC DIVERSITY1

Trebouxiophytes of the genus Prasiola are well known in Antarctica, where they are among the most important primary producers. Although many aspects of their biology have been thoroughly investigated, the scarcity of molecular data has so far prevented an accurate assessment of their taxonomy and phylogenetic position. Using sequences of the chloroplast genes rbcL and psaB, we demonstrate the existence of three cryptic species that were previously confused under Prasiola crispa (Lightfoot) Kützing. Genuine P. crispa occurs in Antarctica; its presence was confirmed by comparison with the rbcL sequence of the type specimen (from the Isle of Skye, Scotland). Prasiola antarctica Kützing is resurrected as an independent species to designate algae with gross morphology identical to P. crispa but robustly placed in a separate lineage. The third species is represented by specimens identified as P. calophylla (Carmichael ex Greville) Kützing in previous studies, but clearly separated from European P. calophylla (type locality: Argyll, Scotland); this alga is described as P. glacialis sp. nov. The molecular data demonstrated the presence of P. crispa in Maritime and Continental Antarctica. P. antarctica was recorded from the Antarctic Peninsula and Shetland Islands, and P. glacialis from the Southern Ocean islands and coast. Such unexpected cryptic diversity highlights the need for a taxonomic reassessment of many published Antarctic records of P. crispa. The results also indicate that marine species of Prasiola form a well‐supported monophyletic group, whereas the phylogenetic diversity of freshwater species is higher than previously suspected (at least three separate lineages within the genus include species living in this type of environments).     

Superior quality agar from <Emphasis Type="Italic">Gracilaria</Emphasis> species (Gracilariales,Rhodophyta) collected from the Gulf of Mannar,India

Gracilaria edulis, G. crassa, G. foliifera, and G. corticata are naturally occurring agarophytes of Indian waters. These agarophytes were evaluated for their agar contents using an improved process recently reported by us (US Patent 2005/0267296A1). The effect of different concentrations of NaOH in the alkali treatment was studied for optimizing the extraction conditions. These Gracilaria species of Indian waters produced agars, both native and alkali treated, with different properties confirming the heterogeneity of the agar polymers in this genera, as one would expect. Among these, G. edulis and G. crassa produced agar polymers having high gel strengths of 490 ± 8.16 and 800 ± 15.4 g cm⁻², respectively, with 8% NaOH treatment as opposed the low gel strength agars that have been reported in the literature to date.     

SILICA,NITROGEN AND PHOSPHORUS REQUIREMENTS OF SOME SOUTHERN AFRICAN DIATOMS

SUMMARY

The yield coefficients and minimum cell concentrations of silica, nitrogen and phosphorus have been determined for four diatoms, Navicula pell iculosa (Brébisson ex Kützing) Hilse, Nitzschia elliptica Hustedt, N. palea (Kützing) W. Smith and N. perpusilla Rabenhorst. It was found that the three Nitzschia species require more Si > N > P whereas the Navicula species needs more N > Si >P. Where possible the results are evaluated in terms of the morphological and ecological characteristics of these diatoms.