Systematics of the marine microfilamentous green algae Uronema curvatum and Urospora microscopica (Chlorophyta)

The microfilamentous green alga Uronema curvatum is widely distributed along the western and eastern coasts of the north Atlantic Ocean where it typically grows on crustose red algae and on haptera of kelps in subtidal habitats. The placement of this marine species in a genus of freshwater Chlorophyceae had been questioned. Molecular phylogenetic analysis of nuclear-encoded small and large subunit rDNA sequences reveal that U. curvatum is closely related to the ulvophycean order Cladophorales, with which it shares a number of morphological features, including a siphonocladous level of organization and zoidangial development. The divergent phylogenetic position of U. curvatum, sister to the rest of the Cladophorales, along with a combination of distinctive morphological features, such as the absence of pyrenoids, the diminutive size of the unbranched filaments and the discoid holdfast, warrants the recognition of a separate genus, Okellya, within a new family of Cladophorales, Okellyaceae. The epiphytic Urospora microscopica from Norway, which has been allied with U. curvatum, is revealed as a member of the cladophoralean genus Chaetomorpha and is herein transferred to that genus as C. norvegica nom. nov.     

Species-specific oligonucleotide probes for macroalgae: molecular discrimination of two marine fouling species of Enteromorpha (Ulvophyceae)

The green seaweeds Enteromorpha intestinalis and E. compressa are important fouling organisms commonly found in polluted and nutrient-enriched marine and brackish water habitats, where they are used in environmental monitoring. Discrimination of the two species is extremely difficult because of overlapping morphological characters. In this study a quick molecular method for species identification was developed based on the nuclear rDNA ITS2 sequence data of 54 E. intestinalis samples and 20 E. compressa samples from a wide geographical range. Oligonucleotide probes were designed for species-specific hybridization to dot-blots of the PCR-amplified ITS1, 5.8S gene and ITS2 fragment of both E. intestinalis and E. compressa. Specificity of the oligonucleotide probes was confirmed by tests with taxonomically diverse species that could morphologically be confused with E. intestinalis or E. compressa. This is the first use of species-specific probes for macroalgae. The restriction endonuclease NruI digested specifically the amplified PCR product from E. compressa into two fragments detectable on agarose gels, but no suitable restriction sites were identifiable in the PCR product of E. intestinalis.     

Fatty acid composition of ten marine algae from australian waters

Detailed fatty acid analyses are reported for ten benthic algae from Australian waters of which the data for Cladophora fascicularis (Chlorophyta); Polysiphonia pungens, Porphyra sp., Centroceras clavatum (Rhodophyta); Hormosira banksii, Ralfsia sp., and Dictyota dichomota (Phaeophyta) are presented for the first time. The analyses report the exact molecular structure of component acids which is essential for taxonomic and food chain studies. The acid 16:4ω3 could be taxonomically distinguishing for species of the Chlorophyta. The occurrence of cis-vaccenic acid (18:1ω7) in the algae reported here suggests a distribution in marine benthic algae which is wider than hitherto realised, with particular taxonomic importance for Chlorophyta species in which it occurs in high levels. Corallina officinalis was found to contain the non-methylene interrupted acids 20:2 and 22:2.     

Diterpenoid metabolites from pacific marine algae of the order Caulerpales (Chlorophyta)

Chemical investigations of two new species of Udotea, reinvestigation of Tydemania expeditionis and Chlorodesmis fastigiata from Guam and Saipan, Marianas Islands, as well as studies of Caulerpa brownii from Southern Australia, have led to the isolation of four new related diterpenoids and several previously described metabolites. These metabolites possess antimicrobial activities and inhibit cell division in the fertilized sea urchin egg bioassay.     

A multi-locus time-calibrated phylogeny of the siphonous green algae

The siphonous green algae are an assemblage of seaweeds that consist of a single giant cell. They comprise two sister orders, the Bryopsidales and Dasycladales. We infer the phylogenetic relationships among the siphonous green algae based on a five-locus data matrix and analyze temporal aspects of their diversification using relaxed molecular clock methods calibrated with the fossil record. The multi-locus approach resolves much of the previous phylogenetic uncertainty, but the radiation of families belonging to the core Halimedineae remains unresolved. In the Bryopsidales, three main clades were inferred, two of which correspond to previously described suborders (Bryopsidineae and Halimedineae) and a third lineage that contains only the limestone-boring genus Ostreobium. Relaxed molecular clock models indicate a Neoproterozoic origin of the siphonous green algae and a Paleozoic diversification of the orders into their families. The inferred node ages are used to resolve conflicting hypotheses about species ages in the tropical marine alga Halimeda.     

Lichens as bioindicators of temporal variations in air quality around Thessaloniki, northern Greece

The epiphytic lichen vegetation of 20 sites around Thessaloniki (Macedonia, northern Greece) surveyed in 1987 was sampled again in 1997 to monitor any changes in lichen communities and consequently in air quality. A general impoverishment in lichen communities was recorded in the 10-year period, presumably chiefly due to changes in the air pollution status. A small increase in lichen species diversity was recorded in some stations, probably as a result of the buffering capacity of airborne dust.     

Neogene stratigraphy of the Eastern basin,Samos island,Greece

Revision of the stratigraphy and depositional environmentsin the Eastern Neogene basin of Samos. Mapping, structural analysis together with new K/Ar dates provide the following general pattern: two fluvial-lacustrine cycles separated by a disconformity. Basal cycle is Astaracian-Vallesian, the disconformity occured between 9 and 8.5 MY, upper cycle is Turolian and has yielded the famous «Samos mammal fauna wich is between 8.5 and 7.0 MY old.     

Aurearenophyceae classis nova, a new class of Heterokontophyta based on a new marine unicellular alga Aurearena cruciata gen. et sp. nov. inhabiting sandy beaches

A new heterokontophyte alga, Aurearena cruciata gen. et sp. nov., was isolated from sandy beaches in Japan. Isolates were characterized by light and electron microscopy, spectroscopy of pigment composition, and molecular phylogenetic analyses using 18S rDNA and rbcL. The alga usually possessed a cell wall but also retained two heterokont flagella beneath the cell wall. Each walled cell first produced only a single flagellate cell that subsequently divided into two flagellate cells. Electron-opaque vesicles, possibly associated with cell wall formation, were observed beneath the cell membrane. The chloroplast consisted of two compartments, each enclosed by a chloroplast envelope and the inner membrane of the chloroplast endoplasmic reticulum; these two compartments were surrounded by a common outer membrane of chloroplast endoplasmic reticulum. Molecular phylogenetic trees suggested that this alga was a new and independent member of the clade that included the Phaeophyceae and Xanthophyceae (PX clade). A new class, Aurearenophyceae classis nova was proposed for A. cruciata.     

The molecular systematics of some agar- and carrageenan-containing marine red algae based on rbcL sequence analysis

A hypothesis of phylogenetic relationships inferred by parsimony analysis of plastid-encoded rbcL sequences is presented for red algae containing agar- and carrageenan-like phycocolloids; rbcL encodes the large subunit of ribulose 1,5 bisphosphate carboxylase/oxygenase. Previous studies have shown that Floridean families that contain sulfated galactans as cell wall components are resolved as a monophyletic clade sister to the agarophyte order Ahnfeltiales. Families that have been identified as containing kappa-type carrageenans, often in addition to lambda-type carrageenans, are resolved in three clades: (1) a complex containing the families Solieriaceae, Cystocloniaceae, Hypneaceae, Caulacanthaceae, Tichocarpaceae, Furcellariaceae, and the genera Turnerella and Opuntiella; (2) the Gigartinaceae and Phyllophoraceae, and (3) the genus Endocladia. Except for Tichocarpus and Endocladia, these are all members of the Gigartinales sensu Kylin (1956). Most of the families previously placed in the Cryptonemiales by Kylin appear to contain only lambda-type carrageenans. These fall into two groups, one that clusters with typical carrageenophyte- and the other with typical agarophyte-taxa. The first of these includes the families Polyideaceae, Kallymeniaceae, Dumontiaceae, and Rhizophyllidaceae. The second includes the type family of the Cryptonemiales, the Halymeniaceae, which is divisible into two well-supported clades, one of which possesses special lambda-like carrageenans, the aeodans, and the Schizymeniaceae, a recently created family containing two former gigartinalean genera. The agarophyte orders Gelidiales, Gracilariales and Ceramiales are well resolved as monophyletic clades, but their topological positions are poorly resolved. The Gelidiales and Ceramiales are associated, but the Gracilariales is included in a clade that contains families belonging to the Rhodymeniales, a possible agarophyte order. Finally, two groups that may contain lambda-like carrageenans, the Plocamiales and the Sarcodiaceae, are resolved as separate clades.     

The marine algae of Berwickshire: a detailed checklist

Summary

Details are given of the distribution of 197 species of seaweed in Berwickshire. These include previous records from herbaria and the published literature, together with records gathered in a programme of field work carried out between 1987 and 1991.     

Analysis of the distribution of epiphytic lichens within homogeneousFagus sylvatica stands along an altitudinal gradient (Mount Olympos,Greece)

Epiphytic lichen vegetation onFagus sylvatica sas studied in 4 sites along an altitudinal gradient from 930 to 1500 m on SE facing slopes of Mount Olympos (Greece). The crucial factor determining the spatial heterogeneity of epiphytic lichens onF. sylvatica is the altitude and not the height on the trunk at which lichen community is established. 17 out of 26 taxa are confined to a particular elevation range, while another three are clearly ubiquitous in their distribution. The number of lichen species at breast height is higher than at the base of the trunks. The results were compared with those gathered earlier in an analogous study on the vertical distribution of epiphytic lichens onPinus nigra along an altitudinal gradient from 750 to 1510 m of the same mountain. Comparison suggests that spatial heterogeneity of epiphytic lichens onF. sylvatica is different from the one onP. nigra.     

The effects of initial population density on the competition for limiting nutrients in two freshwater algae

Eighteen long-term competition experiments were performed on two freshwater algae, a blue-green alga, Anabaena flos-aquae, and a diatom, Cyclotella sp., under controlled light and temperature conditions and various nutrient limitations. As predicted, Anabaena displaced Cyclotella when nitrate was in short supply to both species, whereas Cyclotella became dominant when both species were phosphate-limited. The two species stably coexisted when phosphate and silicate were limited. Anabaena either displaced or coexisted with Cyclotella when nitrate and phosphate or nitrate, phosphate and silicate were limited, depending on their initial density ratios. This study revealed strong effects of initial population densities on the outcomes of algal competition for limiting nutrients.     

A long-term comparison of the benthic algal flora of Clare Island, County Mayo, western Ireland

The marine benthic algal flora of Clare Island, off County Mayo, western shore of Ireland, was investigated; collections of intertidal and subtidal marine algae were made at 16 sites along the eastern and southern shores in the years 1990, 1993 and 2000–2002. The data and observations obtained were compared with the results of a similar survey conducted by Arthur Disbrowe Cotton in 1910–1911. Considering the results of the original survey and the new survey together, the marine algal flora of the island currently totals 293 species; 224 species were recorded by Cotton in the original survey, whereas 223 species were identified in the present study. Most species are common to the original and the new list and the main differences are easily explainable; the new survey used SCUBA diving, which allowed the collection of several subtidal species not collected in 1910, and Cotton reported several microscopic green and brown algae, usually difficult to recognise in the field, which were not rediscovered. The most remarkable differences consist in the current presence of some large intertidal brown algae (Bifurcaria bifurcata, Cystoseira foeniculacea and Cystoseira nodicaulis) that were not reported in the survey of 1910. Two algae, Codium fragile subsp. tomentosoides and Asparagopsis armata, were introduced in Europe after the original survey. At present, the benthic algal assemblages of Clare Island still have basically the same structure and distribution as in 1910 and, if compared with other coastal areas of Europe, the intertidal marine environment of Clare Island appears remarkably well conserved.     

Spectral Properties of the Green Alga Trebouxia,a Phycobiont of Cryptoendolithic Lichens in the Antarctic Dry Valley

An algologically pure culture of the green alga Trebouxia, a phycobiont of cryptoendolithic lichens, was isolated from sandstone samples collected in the high-altitude polar regions of Antarctica. The absorption and second-derivative absorption spectra of acetone extract of the Antarctic phycobiont cells were studied in comparison with those of a Trebouxia phycobiont isolated recently from a Parmeliaceae lichen in the Mid-European climatic zone. The cells of the Antarctic phycobiont were characterized by a lower content of chlorophyll a and a higher ratio of chlorophyll b and carotenoids to chlorophyll a as compared to the Mid-European phycobiont. Furthermore, the carotenoids of the Antarctic phycobiont were more diverse. The low-temperature fluorescence spectra of the Antarctic phycobiont were characterized by an increased intensity of the short-wavelength fluorescence peak of chlorophyll aand a diminished intensity of fluorescence in the long-wavelength spectral region.     

Isolation and characterization of rapidly-growing,marine, nitrogen-fixing strains of blue-green algae

Five strains of heterocystous blue-green algae capable of high rates of growth and nitrogenase activity were isolated from shallow coastal environments. Growth of the organisms was characterized with respect to temperature, NaCl concentration in the medium, and nitrogen source. The temperature optima ranged from 35–42°C, and all but one of the strains displayed a requirement for added NaCl. The generation times under N₂-fixing conditions were 5.1–5.9 h, and were as low as 3.4 h for growth on NH₄Cl. Nitrogenase activity (C₂H₂ reduction) was high throughout the logarithmic growth phase of each strain. The maximum value observed for one strain was 65.5 nmoles C₂H₄ produced/mg protein x min, and the average values for the five strains ranged from 24.5–46.7 nmoles C₂H₄/mg protein x min. The organisms all belong to the genusAnabaena. The growth and nitrogenase activity of these strains are much higher than those of the heterocystous blue-green algae commonly used for investigation of nitrogen metabolism, and they thus should prove to be useful physiological tools. Their prevalence, as judged by the ease of their enrichment and isolation, in bay and estuarine environments suggests that they are important contributors of combined nitrogen.     

Priority effects, taxonomic resolution, and the prediction of variable patterns of colonisation of algae in littoral rock pools

This study focuses on succession of macroalgae in littoral rock pools on the west coast of Italy. Previous studies in this system indicated that either canopy algae or turf-forming algae may dominate late in succession. Priority effects and non-hierarchical interactions have been proposed as possible explanations for these patterns. From previous knowledge on the timing of reproduction and recruitment of the two groups of algae and their interactions, I predicted that: (1) canopy algae would dominate patches of substratum cleared during their main period of recruitment (between April and July); (2) the turf-forming algae, although initially present, would be replaced by canopies in these patches; (3) turf-forming algae would characterise both the early stages of colonisation and the mature assemblage in patches cleared before or after the main period of recruitment of canopy algae, and (4) succession would be more consistent in space (i.e. canalised) in the presence of canopy algae than when the turf-forming plants achieve dominance. These predictions were tested in a multifactorial experiment where patches of substratum were cleared in three different periods (before, during and after the main period of recruitment of canopy algae), on three dates within each period and in two replicate pools in each date. Univariate and multivariate analyses indicated that variability at early stages of colonisation dictated much of the subsequent dynamics in this system. Predictions 1–3 were supported by the results, but only at a gross level of taxonomic resolution. Patterns of colonisation of individual species of turf-forming algae were unpredictable due to large small-scale spatial and temporal variation in abundance. Prediction 4 was not supported by the results. This study indicated that knowledge of the life-histories and ecology of individual populations is crucial to increase the accuracy and precision of ecological models that attempt to predict succession in variable systems. Received: 4 May 1999 / Accepted: 8 November 1999     

Nest site selection of loggerhead sea turtles: The case of the island of Zakynthos, W Greece

The sandy beaches of Zakynthos Island support the largest single nesting aggregation in the Mediterranean Region of the endangered loggerhead turtle Caretta caretta. The present study attempts to determine possible correlations between a series of habitat variables and nest site selection. Nesting activities, including total and nesting emergences were examined in response to the recorded biotic and abiotic variables. The results of the analysis indicate that beach width is the most critical habitat variable affecting nest site selection. Further analysis of nesting performance implies that sea turtles use multiple environmental cues for nest site selection during the different steps of the nesting processes such as emergence from the surf and nesting. Nevertheless, we caution that a detailed study needs to be conducted over a more extensive period of time to verify these suggestions.