Bangiales Research Articles

Integrative analyses of transcriptomes and metabolomes provide insight into salinity adaption in Bangia (Rhodaphyta)

The salinity of the external environment poses a serious threat to most land plants. Although seaweeds can adapt to this, intertidal species are subject to wide fluctuations in salinity, including hypo- and hyper-saline conditions. The red algal genus Bangiales is a typical example; it is one of the oldest eukaryotes with sexual reproduction and has successfully adapted to both marine and freshwater environments. However, there is a dearth of research focused on elucidating the mechanism by which marine Bangia (Bangia fuscopurpurea) adapts to hypo-salinity, as well as the mechanism by which freshwater Bangia (Bangia atropurpurea) adapts to hyper-salinity. The objective of this study is to employ third-generation full-length transcriptome data and untargeted metabolome data, to provide insights into the salinity adaptation mechanism of as well as the evolutionary relationship between both Bangia species. B. fuscopurpurea and B. atropurpurea exhibited 9112 and 8772 differentially expressed genes (DEGs), respectively, during various periods of hyper-saline condition. These genes were primarily enriched in secondary metabolites and energy-related metabolic pathways. Additionally, B. fuscopurpurea displayed 16,285 DEGs during different periods of hypo-saline condition, which were mainly enriched in metabolic pathways related to ion transport and membrane proteins. In the hyper- and hypo-saline adapt response processes of B. fuscopurpurea, a total of 303 transcription factors were identified, which belonged to 26 families. Among these, 85 and 142 differential transcription factors were identified, respectively, mainly belonging to the C2H2 and MYB family. Similarly, in the response process of B. atropurpurea to hyper-saline condition, a total of 317 transcription factors were identified, mainly belonging to 17 families. Among these, 121 differential transcription factors were identified, mainly belonging to the C2H2 and bZIP family. Furthermore, a correlation analysis was conducted to examine the relationship between the transcriptional and metabolic levels of both species under saline adaptation. The findings demonstrated that Bangia exhibits intricate adaptations to salinity, which involve swift regulation of its photosynthetic processes, alternations in membrane contents, and a robust anti-oxidation system to mitigate the effects of excess redox energy during exposure to varying salinity. Notably, the unsaturated fat and glutathione metabolic pathways were found to be significantly enriched in this context.

Heat-Stress Responses Differ among Species from Different 'Bangia' Clades of Bangiales (Rhodophyta).

The red alga ‘Bangia’ sp. ESS1, a ‘Bangia’ 2 clade member, responds to heat stress via accelerated asexual reproduction and acquires thermotolerance based on heat-stress memory. However, whether these strategies are specific to ‘Bangia’ 2, especially ‘Bangia’ sp. ESS1, or whether they are employed by all ‘Bangia’ species is currently unknown. Here, we examined the heat-stress responses of ‘Bangia’ sp. ESS2, a newly identified ‘Bangia’ clade 3 member, and Bangia atropurpurea. Intrinsic thermotolerance differed among species: Whereas ‘Bangia’ sp. ESS1 survived at 30 °C for 7 days, ‘Bangia’ sp. ESS2 and B. atropurpurea did not, with B. atropurpurea showing the highest heat sensitivity. Under sublethal heat stress, the release of asexual spores was highly repressed in ‘Bangia’ sp. ESS2 and completely repressed in B. atropurpurea, whereas it was enhanced in ‘Bangia’ sp. ESS1. ‘Bangia’ sp. ESS2 failed to acquire heat-stress tolerance under sublethal heat-stress conditions, whereas the acquisition of heat tolerance by priming with sublethal high temperatures was observed in both B. atropurpurea and ‘Bangia’ sp. ESS1. Finally, unlike ‘Bangia’ sp. ESS1, neither ‘Bangia’ sp. ESS2 nor B. atropurpurea acquired heat-stress memory. These findings provide insights into the diverse heat-stress response strategies among species from different clades of ‘Bangia’.

On Bangia atropurpurea (Bangiales, Rhodophyta), the strictly protected red alga in Serbia

The first observation of the red alga Bangia atropurpurea (Bangiales, Rhodophyta) in Serbia was in 1991 in the Trgoviski Timok River (Eastern Serbia). From 1991 to 2017, the species was sporadically observed at four more locations in three hillmountain rivers in Southwestern (the Gvozdacka River and the Raska River) and Eastern (the Nisava River - two localities) Serbia. More intensive research on this alga was carried out from 2017 to 2020, and a total of 220 localities in 132 hillmountain watercourses were studied. Bangia atropurpurea was recorded at six locations in Southwestern and Eastern Serbia. Five of these locations represent new B. atropurpurea localities in Serbia (the Brusnicka River, the Golijska Moravica River, the Panjica River, the Resava River, and the second locality in the Trgoviski Timok River), while one of them is already known from previous studies (the Raska River). The species was found in running, moderately hard and very hard, well-oxygenated, slightly alkaline waters, mainly low in inorganic nutrients, and in highly variable values of temperature and conductivity. Despite the long period since its first observation in Serbian rivers, the species is still known in a small number of localities. The small number of localities, low relative abundance, and various anthropogenic influences affecting its habitats have led the species to be recognized as endangered and strictly protected in Serbia. The intensive development of small hydropower plants which have emerged in recent years may threaten B. atropurpurea habitats.

Photoprotection properties of marine photosynthetic organisms grown in high ultraviolet exposure areas: Cosmeceutical applications

Seaweeds have been identified as promising sources of bioactive substances for the cosmeceutical industry, especially by their photoprotection capacity. Accordingly, this study aimed to evaluate the photoprotective properties of extracts from macroalgae and one marine lichen. Samples of 22 species of macroalgae and one marine lichen, were collected along the southern Iberian Peninsula. Hydroethanolic extracts were prepared from algal and marine lichen lyophilized biomass. Ultraviolet (UV) and visible absorption spectra, polyphenol content, antioxidant activity, mycosporine-like amino acid content and composition were analyzed. In order to quantify the photoprotection capacity of the extracts against different biological effects, two new indices were used, i.e., effective solar absorption radiation (%ESAR) and extract photoprotection index (EPI), considering the radiation absorbed and transmitted by the extract, respectively. In the ultraviolet spectrum, Porphyra umbilicalis and Pyropia elongata presented the highest absorbance values at 330 nm, while Ulva lactuca showed a prominent peak at 290 nm. In the visible spectrum, a fucoxanthin peak (450 nm) was strongly evident in extracts from the brown algal species, while green algal extracts presented characteristic chlorophyll a and b peaks at 447, 620 and 664 nm. Polyphenol content and antioxidant activity were much higher in Sargassum vulgare, Carpodesmia tamariscifolia, P. umbilicalis and Lichina pygmaea in comparison to the other species. P. umbilicalis and Bangia atropurpurea showed the highest amount of mycosporine-like amino acids. S. vulgare and P. umbilicalis extracts presented the highest values of potential photoprotection against all analyzed biological response according to the different action spectra. S. vulgare and P. umbilicalis showed an increase in %ESAR values associated with an increase in the concentration of their extracts. Considering the analyzed species, our results suggest that S. vulgare and P. umbilicalis could be potential sources of photoprotective extracts. The potential use of these species in cosmeceutical products is discussed.

Photosynthetic performance of two freshwater red algal species

Abstract Photosynthetic performances of two freshwater red algal populations from freshwaters of the Carpathian basin were measured in this study. Populations were collected from different habitats: Bangia atropurpurea from Lake Balaton and Batrachospermum gelatinosum from the Tapolca stream. Their photosynthesis was studied in a wide range of temperature (5–35 °C) and light intensity (0–1150 μmol m−2 s−1) in a photosynthetron. We found both species’ photosynthesis maxima at 25 °C but B. atropurpurea had significantly higher photosynthetic production. Low and medium values were calculated for the species’ photoadaptation parameters. Compensation light intensities determined in this study were similar to those obtained in previous studies. Both species utilized light efficiently; photoinhibition was detected only at two measuring temperatures for Bangia and at four measuring temperatures for Batrachospermum. P-T characteristics of the species revealed that both have temperature optima at 25 °C under high and medium light intensities but there are no such remarkable optima at low irradiance. The biomass specific respiration of both species increased with increasing temperature. We confirmed the good light utilization of these red algal species but found temperature optima higher than reported previously.

Evaluation of antioxidant properties of phycobiliproteins and phenolic compounds extracted from Bangia atropurpurea

Bangia atropurpurea is a freshwater red filamentous alga. In this study, we report on the recovery yield of purified phycobiliproteins, total phenolic content (TPC) and their antioxidant capacity. B. atropurpurea suspended in phosphate buffer (pH 7.2), saturated with ammonium sulphate and further isolated R-phycoerythrin and phycocyanin from phycobilisome structure by gel filtration with Sephadex G-200. Phenolic compounds extracted by variable polarity solvents to exhibit optimum yield. Folin–Ciocalteu method was used to determine the TPC, while 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and ferric-reducing antioxidant power (FRAP) assays were used to quantitate the antioxidant activity of phycobiliproteins and phenolic compounds. B. atropurpurea predominantly contains R-phycoerythrin 54.80 % of the total protein extracted at purity ratio A562 to A280 of 4.45 while, phycocyanin displayed 16 % recovery yield at purity ratio A615 to A280 of 2.18. The purified R-phycoerythrin exhibited better antioxidant activity than phycocyanin extract and BHT synthetic antioxidant by exhibiting (IC50%=7.66 ±0.81µg/mL) and 54.74 ± 0.11 mg GAE/1g extract for, DPPH scavenging and FRAP assay, respectively. The sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of purified R-phycoerythrin and phycocyanin proteins have showed apparent single band at molecular weight of 19.6 kDa and 17.5 kDa, respectively. The methanol-soluble extract displayed the utmost TPC, 80.97±0.53 mg GAE/1g extract compared to phenolic content in other organic solvents used for extraction. In accordance with TPC, methanol-soluble extract exhibited as the most effective DPPH radical scavenging and ferric reduction, (IC50%=14.63±0.79 µg/mL) and 37.79±0.27 mg GAE/1g extract, respectively. The presence of R-phycoerythrin, phycocyanin and phenolic compounds in an array, amplifies the antioxidant property of B. atropurpurea.

Uranium sorption by native and nitrilotriacetate-modified Bangia atropurpurea biomass: kinetics and thermodynamics

In this study, the red alga Bangia atropurpurea was modified with nitrilotriacetate (NTA) ligand and used for removal of U(VI) ions from aqueous solution using native form as a control system. The modification of B. atropurpurea biomass was realized by sequential treatment of algal biomass with glutaraldehyde and NTA ligand. Influence of U(VI) sorption parameters, such as contact time, adsorbent amount, medium pH and ionic strength, initial U(VI) ions concentration, and temperature on the removal performance of both algal biomasses were studied from aqueous solution. The hydroxyl, amino, carbonyl, and carboxyl groups were the main adsorptive groups of the biomasses as observed in FTIR data, and these groups can bind to U(VI) ions via electrostatic interactions. More than 78% of total sorption took place within 40 min, and equilibrium was established about 60 min. Maximum sorption capacities of the native and NTA-modified algal biomasses were found to be 190.2 and 328.8 mg g−1, respectively, at pH 5.5 and at 30 °C. The presence of other ionic species slightly decreased the U(VI) sorption capacity except that in Fe(III) ions. The sorption processes of U(VI) on the algal biomasses were described by the Langmuir and Temkin isotherms and pseudo-second-order kinetic models. The thermodynamic parameters, such as ΔH°, ΔS°, and ΔG°, show that the process is exothermic and spontaneous. It should be stated that the NTA-modified algal biomass has a high potential for the removal of U(VI) ions from aqueous solution.

Origin and evolutionary history of freshwater Rhodophyta: further insights based on phylogenomic evidence

Freshwater representatives of Rhodophyta were sampled and the complete chloroplast and mitochondrial genomes were determined. Characteristics of the chloroplast and mitochondrial genomes were analyzed and phylogenetic relationship of marine and freshwater Rhodophyta were reconstructed based on the organelle genomes. The freshwater member Compsopogon caeruleus was determined for the largest chloroplast genome among multicellular Rhodophyta up to now. Expansion and subsequent reduction of both the genome size and GC content were observed in the Rhodophyta except for the freshwater Compsopogon caeruleus. It was inferred that the freshwater members of Rhodophyta occurred through diverse origins based on evidence of genome size, GC-content, phylogenomic analysis and divergence time estimation. The freshwater species Compsopogon caeruleus and Hildenbrandia rivularis originated and evolved independently at the inland water, whereas the Bangia atropurpurea, Batrachospermum arcuatum and Thorea hispida are derived from the marine relatives. The typical freshwater representatives Thoreales and Batrachospermales are probably derived from the marine relative Palmaria palmata at approximately 415–484 MYA. The origin and evolutionary history of freshwater Rhodophyta needs to be testified with more organelle genome sequences and wider global sampling.

Complete nuclear ribosomal DNA sequence amplification and molecular analyses of Bangia (Bangiales, Rhodophyta) from China

Filamentous Bangia, which are distributed extensively throughout the world, have simple and similar morphological characteristics. Scientists can classify these organisms using molecular markers in combination with morphology. We successfully sequenced the complete nuclear ribosomal DNA, approximately 13 kb in length, from a marine Bangia population. We further analyzed the small subunit ribosomal DNA gene (nrSSU) and the internal transcribed spacer (ITS) sequence regions along with nine other marine, and two freshwater Bangia samples from China. Pairwise distances of the nrSSU and 5.8S ribosomal DNA gene sequences show the marine samples grouping together with low divergences (00.003; 0–0.006, respectively) from each other, but high divergences (0.123–0.126; 0.198, respectively) from freshwater samples. An exception is the marine sample collected from Weihai, which shows high divergence from both other marine samples (0.063–0.065; 0.129, respectively) and the freshwater samples (0.097; 0.120, respectively). A maximum likelihood phylogenetic tree based on a combined SSU-ITS dataset with maximum likelihood method shows the samples divided into three clades, with the two marine sample clades containing Bangia spp. from North America, Europe, Asia, and Australia; and one freshwater clade, containing Bangia atropurpurea from North America and China.

Distribution, seasonality and putative origin of the non-native red alga Bangia atropurpurea (Bangiales, Rhodophyta) in the Laurentian Great Lakes

Bangia atropurpurea was first observed in Lake Erie in 1964 and subsequently spread to the lower Laurentian Great Lakes by the mid to late 1970s. The present study was initiated to examine the recent distribution of B. atropurpurea in the Great Lakes, the seasonal variation of the alga and the putative origin of this species based on DNA sequence analysis. From surveys in 1995 and 2002, this species has clearly spread, with newly identified populations observed in Lakes Huron, Michigan, Georgian Bay and the St. Lawrence River. Morphological analyses showed that Great Lakes populations from individual lakes or neighboring populations did not group together in cluster analyses. Correlation analysis, however, revealed significant relationships between the presence or absence of Bangia among the studied sites with pH and specific conductance as those locations that had stable populations had a mean pH and conductance of 8.2 and 353μS·cm−1 respectively. Seasonal variation in morphology of a population from Burlington, Ontario (Lake Ontario, Canada) was examined monthly for one year. Maximum filament length occurred in April, with the greatest diameter and archaeospore production observed in May. Significant correlations were also noted for many morphological characteristics with water temperature, population height on the shoreline relative to the waterline and total phosphorus. Collections of B. atropurpurea analyzed from the Great Lakes were observed to be identical in sequence to collections of European freshwater Bangia in the cox2–3 gene spacer, the nuclear internal transcribed spacers (ITS 1 and 2) and the 5.8S rRNA gene (between the small and large subunits of the rRNA gene). These results suggest a recent European origin; however, further global collections of B. atropurpurea and microsatellite analyses are necessary to confirm this hypothesis.

Diversity, Ecology and Survivor of Freshwater Red Algae in Israel

From 1950s till now only seven species of Rhodophyta were recorded from continental waters of Israel. Among them, the most abundant are the species of Audouinella that inhabit fresh or brackish waters of lakes, pools and rivers. Our findings of two species of this genus inhabiting the fresh clear water Oren River, the middle reaches of the polluted Qishon River (A. pygmaea (Kutz.) Weber-van Bosse)), as well as the middle reaches of the strongly impacted Lower Jordan River (A. hermannii (Roth) Duby in De Candolle). These findings led us to conclude the latter species preferred low to moderate salinity and a high calcium concentration and is relatively resistant to organic pollution. Bangia atropurpurea (Mertens ex Roth) C. Agardh and Hildenbrandia rivularis (Liebmann) J. Agardh are the sensitive species sporadically observed in a few habitats only and preferring the slightly mineralized slow streaming carbonate waters with insignificant organic pollution. Batrachospermum gelatinosum (Linnaeus) De Candolle is only one new for Israel species that has been found in the Meshushim stream. The likewise sensitive Phragmonema sordidum Zopf is consider as a lost species because of the loss of habitat. We do not confirm finding of red algae Paralemanea catenata (Kutzing) Vis et Sheath in the Banias stream.

Distribución y ecología de algunas especies de rodófitos (Rhodophyta) en la cuenca del río Ebro

The implementation of the Water Framework Directive (2000/60/CE) in the Ebro River Basin and the evaluation of the ecological status of rivers, lakes and wetlands are increasing the knowledge about the distribution and ecology of aquatic organisms, including the red algae (Rhodophyta). In this work we show new data concerning the distribution, habitat and environmental ranges of five species of Rhodophyta in the Ebro River Basin with scarce records: Bangia atropurpurea, Chroodactylon ornatum, Chroothece rupestris, Compsopogon coeruleus and Thorea hispida. The former three species showed an optimum development in calcareous mountain streams while the latter two species did in lower reaches where salinity and eutrophication increase.

The Cryptogenic Red Alga <i>Bangia Atropurpurea</i> in Lough Derg, River Shannon, Ireland

The filamentous and euryhaline red alga Bangia atropurpurea (Rhodophyta, Bangiophyceae) is a littleknown member of the Irish aquatic flora. Although a common freshwater species in the northern hemisphere, it seems that the lower Shannon Navigation is one of the principal freshwater localities for the species in Ireland. It was recorded from thirteen sites in Lough Derg in 1972 and in the 2010 survey reported here at 40 sites including islands and navigation buoys as well as on lock gates. It attaches to rocks and other hard surfaces immediately above and below the waterline. It may have been introduced to Lough Derg on the hulls of commercial vessels. Changes in climatic conditions, eutrophication, competition from other filamentous algae and fluctuating lake levels are all pressures that could affect the sustainability of Bangia within the Shannon Navigation. Nevertheless, this study shows that B. atropurpurea has persisted for at least 40 years in Lough Derg and remains widespread despite highly variable environmental conditions.

THE CRYPTOGENIC RED ALGA BANGIA ATROPURPUREA IN LOUGH DERG, RIVER SHANNON, IRELAND

The filamentous and euryhaline red alga Bangia atropurpurea (Rhodophyta, Bangiophyceae) is a little-known member of the Irish aquatic flora. Although a common freshwater species in the northern hemisphere, it seems that the lower Shannon Navigation is one of the principal freshwater localities for the species in Ireland. It was recorded from thirteen sites in Lough Derg in 1972 and in the 2010 survey reported here at 40 sites including islands and navigation buoys as well as on lock gates. It attaches to rocks and other hard surfaces immediately above and below the waterline. It may have been introduced to Lough Derg on the hulls of commercial vessels. Changes in climatic conditions, eutrophication, competition from other filamentous algae and fluctuating lake levels are all pressures that could affect the sustainability of Bangia within the Shannon Navigation. Nevertheless, this study shows that B. atropurpurea has persisted for at least 40 years in Lough Derg and remains widespread despite highly variable environmental conditions.

Niche partitioning, shape of species response, and diversity in the phytobenthos across the rocky shoreline of a large peri-Alpine lake

By colonizing a particular depth zone across the transition from aquatic to terrestrial habitats, littoral species may exhibit specific physiological and ecological adaptations, as well as characteristic responses to the gradient of conditions across the ecotone. The objectives of the study were: (i) to identify the depth zone (location in relation to average water level) where the replacement of species occurs most rapidly; (ii) to test whether and to what extent the occurrence of species, their abundance and their response to the gradient evolves over time; and (iii) to assess the shape of the species' response to the gradient, calculating the niche overlap of the dominant species. Results showed that the diversity of species peaked at a depth between 18 and 48cm, in a zone thought to be of intermediate disturbance (the transect depth was, on average, 103cm). The main macroalgal species (the red alga, Bangia atropurpurea and the green algae, Jaoa bullata, and Cladophora glomerata), showed a variety of response shapes to the gradient: monotonic, symmetrical and skewed, depending on the stage of seasonal growth. The efficient regulation of growth of B. atropurpurea along the fluctuating gradient was interpreted as an adaptive trait giving it an advantage over more slowly reacting species. The spatial and temporal niches of B. atropurpurea and Jaoa bullata overlapped widely only in early spring, whereas later their optimal habitats were clearly differentiated. This suggested partial niche segregation between these two species, and a potential seasonal interaction.

MOLECULAR EVOLUTION OF GLUTAMINE SYNTHETASE II AND III IN THE CHROMALVEOLATES(1).

Glutamine synthetase (GS) is encoded by three distinct gene families (GSI, GSII, and GSIII) that are broadly distributed among the three domains of life. Previous studies established that GSII and GSIII isoenzymes were expressed in diatoms; however, less is known about the distribution and evolution of the gene families in other chromalveolate lineages. Thus, GSII cDNA sequences were isolated from three cryptophytes (Guillardia theta D. R. A. Hill et Wetherbee, Cryptomonas phaseolus Skuja, and Pyrenomonas helgolandii Santore), and GSIII was sequenced from G. theta. Red algal GSII sequences were obtained from Bangia atropurpurea (Mertens ex Roth) C. Agardh; Compsopogon caeruleus (Balbis ex C. Agardh) Mont.; Flintiella sanguinaria F. D. Ott and Porphyridium aerugineum Geitler; Rhodella violacea (Kornmann) Wehrmeyer and Dixoniella grisea (Geitler) J. L. Scott, S. T. Broadwater, B. D. Saunders, J. P. Thomas et P. W. Gabrielson; and Stylonema alsidii (Zanardini) K. M. Drew. In Bayesian inference and maximum-likelihood (ML) phylogenetic analyses, chromalveolate GSII sequences formed a weakly supported clade that nested among sequences from glaucophytes, red algae, green algae, and plants. Red algal GSII sequences formed two distinct clades. The largest clade contained representatives from the Cyanidiophytina and Rhodophytina and grouped with plants and green algae. The smaller clade (C. caeruleus, Porphyra yezoensis, and S. alsidii) nested within the chromalveolates, although its placement was unresolved. Chromalveolate GSIII sequences formed a well-supported clade in Bayesian and ML phylogenies, and mitochondrial transit peptides were identified in many of the sequences. There was strong support for a stramenopile-haptophyte-cryptophyte GSIII clade in which the cryptophyte sequence diverged from the deepest node. Overall, the evolutionary history of the GS gene families within the algae is complex with evidence for the presence of orthologous and paralogous sequences, ancient and recent gene duplications, gene losses and replacements, and the potential for both endosymbiotic and lateral gene transfers.

Fine-Scale Spatial Patterns of Mature and Immature Filaments and Bioorganic Compounds of the Rhodophyte Bangia atropurpurea in the Supra- and Eulittoral Zones of a Large Lake(1).

Bangia atropurpurea (Mertens ex Roth) C. Agardh is a freshwater red alga species that is distributed worldwide. B. atropurpurea is highly adaptable due to its stress-tolerance, which ensures survival under desiccation periods and under radiation extremes typical of the supra- and upper eulittoral zones. Whereas a number of previous investigations addressed some of the physiological and biochemical traits involved in stress-tolerance, we studied the spatial arrangement of the mature (multiseriate) and immature (uniseriate) filaments and of selected bioorganic compounds along a gradient defined by distance from the waterline. Substantial physiological and biochemical differences were previously observed among phenological stages in the marine environment. In this study, we showed a nonrandom spatial structure of both phenological stages and photosynthetic pigments and photoprotective compounds, R-phycocyanin and R-phycoerythrin along the supralittoral-eulittoral gradient. This observed pattern strongly suggests a complex interplay between physio-morphological regulation and spatial arrangement of mature and immature filaments in conferring the typical stress tolerance of B. atropurpurea.

Stabilization and modulation of the phycobilisome by calcium in the calciphilic freshwater red alga Bangia atropurpurea

The bangiophycean filamentous red alga Bangia atropurpurea is distributed in freshwater habitats such as littoral and splash zones of lakes or rapid currents distant from the sea. In these habitats, the distribution and growth of this alga appear to be related to hard water rich in calcium ions. To characterize the eco-physiological properties of this calciphilic red alga, we examined the effects of long-term and short-term Ca2+ depletion on photosynthetic growth of the thallus and on the phycobilisome. Long-term culture experiments suggested that higher Ca2+ concentrations (>50mgL−1) were required to sustain thallus growth and pigmentation of cells. In short-term Ca2+-depletion treatments, fluorescence derived from phycoerythrin (PE) fluctuated, although the absorption spectra of the thalli did not change. After 30min of Ca2+ depletion, the fluorescence lifetime of PE became markedly longer, indicating that the energy transfer from PE to phycocyanin (PC) was suppressed. The fluorescence lifetime of PE returned to its original value within a short time after 4h of Ca2+ depletion, however, energy transfer from PE to PC was still suppressed. This suggested that the excitation energy absorbed by PE was quenched during prolonged Ca2+ depletion. The efficient energy transfer from PC and allophycocyanin were unchanged during these treatments.

Trace metals and radionuclides in macroalgae from Moroccan coastal waters

Macroalgae species Codium sp, Bangia atropurpurea, Membranoptera alata, Plocamium cartilagineum, Dictyota dichotoma, Fucus spiralis and Stypocaulon scoparia were collected from seven stations along the north coast of Morocco. Samples were analysed to determine activities of naturally occurring radionuclides ((210)Pb, U isotopes and (40)K) and concentrations of metals (Zn, Fe, Co, Cu, Ni, Mn, Pb, Cd, As and Cr) using radiometric and ICP-OES techniques, respectively. Metal concentrations were within ranges reported in the scientific literature, and concentrations of bio-essential elements were in the order Mn>Fe> Zn>Cu in all samples. Brown algae had the highest concentrations of almost all metals, and concentrations decreased in the order brown>red>green algae. With respect to radionuclides, the red alga P. cartilagineum had the highest activities of (210)Pb, in most cases an order of magnitude higher than for the green alga Codium sp. (234)U and (238)U activities in all algae samples were in the range 0.96- 7.61 and 1.16-6.14 Bq/kg dry weight, respectively. Our analyses of radionuclide activities and metal concentrations in marine macroalgae showed large differences among taxa. These results provide insights into which algal species should be used for biomonitoring programmes.

New record of endangered red alga Bangia atropurpurea (A. Roth) C. Agardh (Bangiales, Rhodophyta) in the Nisava river, Serbia

Bangia atropurpurea was found at two new localities in the Nisava River (Southern Serbia). In Serbia, this species is endangered. It has been found so far in the Trgoviski Timok River, the Gvozdovacka River and the Raska River. With the two new localities in the Nisava River, at present Bangia occupies four rivers (five localities). New findings are important for the protection of the biodiversity of red algal flora in the region, and provide useful information on the ecological preferences of the species in Serbia.