Effects of temperature, irradiance and photoperiod on growth and pigment content in some freshwater red algae in culture

The responses of relative growth rate (% day‐1) and pigment content (chlorophyll a, phycocyanin and phycoerythrin) to temperature, irradiance and photoperiod were analyzed in culture in seven freshwater red algae: Audouinella hermannii (Roth) Duby, Audouinella pygmaea (Kützing) Weber‐van Bosse, Batrachospermum ambiguum Montagne, Batrachospermum delicatulum (Skuja) Necchi et Entwisle,‘Chantransia’ stages of B. delicatulum and Batrachospermum macrosporum Montagne and Compsopogon coeruleus (C. Agardh) Montagne. Experimental conditions included temperatures of 10, 15, 20 and 25°C and low and high irradiances (65 and 300 μmol photons m^?2 s^?1, respectively). Long and short day lengths (16:8 and 8:16 LD cycles) were also applied at the two irradiances. Growth effects of temperature and irradiance were evident in most algae tested, and there were significant interactions among treatments. Most freshwater red algae had the best growth under low irradiance, confirming the preference of freshwater red algae for low light regimens. In general there was highest growth rate in long days and low irradiance. Growth optima in relation to temperature were species‐specific and also varied between low and high irradiances for the same alga. The most significant differences in pigment content were related to temperature, whereas few significant differences could be attributed to variation in irradiance and photoperiod or interactions among the three parameters. The responses were species‐specific and also differed for pigments in distinct temperatures, irradiances and photoperiods in the same alga. Phycocyanin was generally more concentrated than phycoerythrin and phycobiliproteins were more concentrated than chlorophyll a. The highest total pigment contents were found in two species typical of shaded habitats: A. hermannii and C. coeruleus. The expected inverse relationship of pigment with irradiance was observed only in C. coeruleus. In general, the most favorable conditions for growth were not coincident with those with highest pigment contents.     

The extensive development of the turf-forming red alga Womersleyella setacea (Hollenberg) R. E. Norris (Rhodophyta,Ceramiales) in the Bay of Boka Kotorska,Montenegro (southern Adriatic Sea)

Abstract

In August 2003, dense turfs formed by the filamentous red alga Womersleyella setacea (Hollenberg) R. E. Norris were found in the open part of the Bay of Boka Kotorska, on the shore of Montenegro (southern Adriatic Sea). The habitat and morphology of the alga are described and the impact of the massive development of this species on the structure of the algal communities is discussed.     

UPTAKE OF METHYLAMINE (AN AMMONIUM ANALOGUE) BY MACROCYSTIS PYRIFERA (PHAEOPHYTA)1

The ammonium analogue, methylamine, is taken up rapidly from dilute solution by Macrocystis pyrifera (L.) C. A. Agardh. ¹⁴C-methylamine was used to characterize the transport system, with respect to dependence on external concentration, temperature, pH and substrate specificity. The results suggest that methylamine enters the algal tissue via a specific mediated transport system. Uptake of methylamine showed no consistent relation to the N content of the plant tissue, but was highly dependent on the portion of plant sampled and severely affected by cutting the tissue. The strong inhibition of methylamine uptake by ammonium and lesser inhibition by other alkylamines suggests that the uptake system functions as an “ammonium permease”. Uptake of ¹⁴C-methylamine can be used as a highly sensitive measure of NH₄⁺ uptake activity and should be a useful tool for studying NH₄⁺ uptake in the laboratory and field.     

Reduction in omega-3 fatty acids by UV-B irradiation in microalgae

UV-B irradiation reduced the levels of omega-3 fatty acid, eicosapentaenoic acid (EPA, 20:53) and docosahexaenoic acid (DHA, 22:63), in microalgae; the degree of reduction varied with species.Chaetoceros calcitrans andSkeletonema costatum were high UV-B tolerant species, followed byPhaeodactylum tricornutum, Chroomonas salina, Pavlova lutheri, andThalassiosira pseudonana.Isochrysis galbana (T.ISO) andProrocentrum micans were UV- B sensitive. Cells in logarithmic phase were most sensitive to UV- B irradiation. Nitrate-, phosphate-, or sulphate-starved cells were more UV-B sensitive than non-starved cells grown in a complete basal medium. A relatively short exposure to high UV-B was more damaging than a longer exposure to lower irradiance. Visible light intensity levels had a profound impact on the sensitivity of microalgal cultures to UV-B, with high levels decreasing UV-B dependent damage. Addition of polyamines (putrescine, spermidine or spermine) or an amino acid (cysteine) to the culture medium minimized the reduction of omega-3 fatty acid content in microalgae caused by UV-B irradiation.Author for correspondence     

PURIFICATION AND CHARACTERIZATION OF A LECTIN,BRYOHEALIN, INVOLVED IN THE PROTOPLAST FORMATION OF A MARINE GREEN ALGA BRYOPSIS PLUMOSA (CHLOROPHYTA) 1

When the coenocytic green alga Bryopsis plumosa (Huds.) Ag. was cut open and the cell contents were expelled, the cell organelles agglutinated rapidly in seawater to form protoplasts. Aggregation of cell organelles in seawater was mediated by a lectin–carbohydrate complementary system. Two sugars, N‐acetyl‐d ‐glucosamine and N‐acetyl‐d ‐galactosamine inhibited aggregation of cell organelles. The presence of these sugars on the surface of chloroplasts was verified with their complementary fluorescein isothiacyanate‐labeled lectins. An agglutination assay using human erythrocytes showed the presence of lectins specific for N‐acetyl‐d ‐galactosamine and N‐acetyl‐d ‐glucosamine in the crude extract. One‐step column purification using N‐acetyl‐d ‐glucosamine‐agarose affinity chromatography yielded a homogeneous protein. The protein agglutinated the cell organelles of B. plumosa, and its agglutinating activity was inhibited by the above sugars. Sodium dodecyl sulfate polyacrylamide gel electrophoresis results showed that this protein might be composed of two identical subunits cross‐linked by two disulfide bridges. Enzyme and chemical deglycosylation experiments showed that this protein is deficient in glycosylation. The molecular weight was determined as 53.8 kDa by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. The N‐terminal 15 amino acid sequence of the lectin was Ser–Asp–Leu–Pro–Thr–X–Asp–Phe–Phe–His–Ile–Pro–Glu–Arg–Tyr, and showed no sequence homology to those of other reported proteins. These results suggest that this lectin belongs to a new class of lectins. We named this novel lectin from B. plumosa“bryohealin.”     

Turbinaria foliosasp. nov. (Fucales, Phaeophyceae) from the Sultanate of Oman, with a census of currently recognized species in the genus Turbinaria

Turbinaria foliosasp. nov. is described on the basis of several collections made from Dhofar, Sultanate of Oman. The new species is known only from southern Oman, a region of the northern Arabian Sea that is strongly impacted by the upwelling from the summertime monsoon. It is distinguished from other species of the genus by the shape of the leaves and by their loose, non‐congested arrangement. Air vesicles, embedded in the leaves, may be present, but more often are absent. A census of the currently recognized species in the genus Turbinaria is provided. Reference is made to Sargassum turbinarioides and Sargassum turbinati‐folium. These species possess discrete blades and spherical vesicles and thus conform to Sargassum.     

Recent developments in the systematics of the Gigartinaceae (Gigartinales, Rhodophyta) based on rbcL sequence analysis and morphological evidence

The phylogenetic systematics of the Gigartinaceae is discussed for seven genera and three undescribed generic lineages and 65 taxa representing 62 species based on an analysis of rbcL sequences and morphological evidence. An examination of rbcL trees resulting from analyses of these taxa identifies seven lineages: (i) ‘Gigartina’ alveata; (ii) Rhodoglossum/Gigartina; (iii) Chondracanthus; (iv) Ostiophyllum; (v) Sarcothalia; (vi) ‘Gigartina’ skottsbergii; and (vii) a large clade containing Iridaea/‘Sarcothalia’, Mazzaella and Chondrus. These lineages and Chondrus are strongly supported; however, two groups, Iridaea/‘Sarcothalia’ and Mazzaella, receive no bootstrap support. The morphology of the female reproductive system is investigated with the aid of computer-generated, color-coded tracings of photographs of cystocarps seen in cross section at different developmental stages. Seven basic cystocarp types were found which corresponded to species groups seen in rbcL trees. These were: (i) a ‘Gigartina’ alveata group in which the carposporangia-bearing filaments develop apomictically from gametophytic cells; (ii) a Rhodoglossum/Gigartina group in which gonimoblast filaments penetrate the surrounding envelope fusing progessively with envelope cells; (iii) a Chondracanthus group in which gonimoblast filaments penetrate the envelope but fuse with envelope cells only at late developmental stages; (iv) a Sarcothalia group in which the gonimoblast filaments displace an envelope composed mainly of secondary gametophytic filaments and link to envelope cells by terminal tubular gonimoblast cells; (v) an Iridaea group similar to the Sarcothalia group, but with an envelope composed of a mixture of medullary cells and secondary gametophytic filaments; (vi) a Mazzaella group that lacks a true envelope and in which gonimoblast filaments connect to modified gametophytic cells by means of terminal tubular cells; (vii) a Chondrus group in which gonimoblast filaments penetrate the medulla and link to modified medullary cells by means of conjunctor cells forming secondary pit connections. The further separation of these groups into genera is based largely on tetrasporangial characters.     

Genetic and morphological variation in an ecosystem engineer,Lithophyllum byssoides (Corallinales,Rhodophyta)

Lithophyllum byssoides is a common coralline alga in the intertidal zone of Mediterranean coasts, where it produces biogenic concretions housing a high algal and invertebrate biodiversity. This species is an ecosystem engineer and is considered a target for conservation efforts, but designing effective conservation strategies currently is impossible due to lack of information about its population structure. The morphological and molecular variation of L. byssoides was investigated using morphoanatomy and DNA sequences (psbA and cox2,3) obtained from populations at 15 localities on the Italian and Croatian coasts. Lithophyllum byssoides exhibited a high number of haplotypes (31 psbA haplotypes and 24 cox2,3 haplotypes) in the central Mediterranean. The psbA and cox2,3 phylogenies were congruent and showed seven lineages. For most of these clades, the distribution was limited to one or a few localities, but one of them (clade 7) was widespread across the central Mediterranean, spanning the main biogeographic boundaries recognized in this area. The central Mediterranean populations formed a lineage separate from Atlantic samples; psbA pair‐wise divergences suggested that recognition of Atlantic and Mediterranean L. byssoides as different species may be appropriate. The central Mediterranean haplotype patterns of L. byssoides were interpreted as resulting from past climatic events in the hydrogeological history of the Mediterranean Sea. The high haplotype diversity and the restricted spatial distribution of the seven lineages suggest that individual populations should be managed as independent units.     

CULTURE OF THE TERRESTRIAL CYANOBACTERIUM,NOSTOC FLAGELLIFORME (CYANOPHYCEAE), UNDER AQUATIC CONDITIONS1

Both colonies and free‐living cells of the terrestrial cyanobacterium, Nostoc flagelliforme (Berk. & Curtis) Bornet & Flahault, were cultured under aquatic conditions to develop the techniques for the cultivation and restoration of this endangered resource. The colonial filaments disintegrated with their sheaths ruptured in about 2 days without any desiccating treatments. Periodic desiccation played an important role in preventing the alga from decomposing, with greater delays to sheath rupture with a higher frequency of exposure to air. The bacterial numbers in the culture treated with seven periods of desiccation per day were about 50% less compared with the cultures without the desiccation treatment. When bacteria in the culture were controlled, the colonial filaments did not disintegrate and maintained the integrity of their sheath for about 20 days even without the desiccation treatments, indicating the importance of desiccation for N. flagelliforme to prevent them from being disintegrated by bacteria. On the other hand, when free‐living cells obtained from crushed colonial filaments were cultured in liquid medium, they developed into single filaments with sheaths, within which multiple filaments were formed later on as a colony. Such colonial filaments were developed at 15, 25, and 30° C at either 20 or 60 μmol photons·m^?2·s^?1; colonies did not develop at 180 μmol photons·m^?2·s^?1, though this light level resulted in the most rapid growth of the cells. Conditions of 60 μmol photons·m^?2·s^?1 and 25° C appeared to result in the best colonial development and faster growth of the sheath‐held colonies of N. flagelliforme when cultured indoor under aquatic conditions.     

Bacterioplankton interactions with Daphnia and algae in experimental enclosures

Development of bacterioplankton was studied by manipulation of planktivorous fish and/or nutrients in experimental enclosures in a fish pond. Grazing pressure exerted by large zooplankton (Daphnia galeata and Daphnia pulicaria) strongly influenced the counts and size distribution of bacterial populations. Morphometric analyses by scanning electron microscope revealed a shift in size distribution from larger mainly rod-type bacteria under low grazing pressure towards smaller mainly coccus-type under strong grazing pressure. The metabolic activity of bacteria measured as glucose uptake was higher under strong grazing pressure. After removal of large daphnids, the increase in bacterial density was probably the result of two additive factors: low grazing pressure and high level of dissolved organic matter (DOM) due to photosynthetic activity of more abundant algae. Composition of bacterial populations shifted toward larger, rod-type bacteria, and their metabolic efficiency measured by uptake, was lowered. The basic dimensionality of the system and interactions between variables was describe by R-mode factor analysis. The manipulated enclosures were relate with factor score.