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Showing papers in "Journal of Phycology in 2001"


Journal ArticleDOI
TL;DR: Findings indicate that some Symbiodinium species may have global biogeographic distributions and there is evidence, based on the lack of phylogenetic congruency with allelic variability, that sexual recombination occurs at some frequency among Symbiod inium populations.
Abstract: The internal transcribed spacer (ITS) regions from 47 Symbiodinium (Freudenthal) isolates cultured from 34 different host species and two populations sampled from nature were sequenced and compared. Of these, 17 distinct ITS types were identified. The described species Symbiodinium goreaui, S. kawagutii, S. pilosum (Trench and Blank), S. microadriaticum (Freudenthal), and S. (=Gymnodinium) linucheae (Trench and Thinh) had ITS sequences distinct from each other. Four of these species share identical ITS sequences with uncharacterized isolates. Sequence differences among other isolates indicate that at least seven other cultured types await formal species descriptions, whereas numerous others most likely exist in nature. The Symbiodinium phylogeny is positively correlated with cell size, mycosporine-like amino acid production (UV protection), and host infectivity, whereas the production of water-soluble peridinin–chl a–protein homodimer and monomer apoproteins and isoenzyme similarity do not correlate. There is evidence, based on the lack of phylogenetic congruency with allelic variability, that sexual recombination occurs at some frequency among Symbiodinium populations. Symbiodinium isolates from the Caribbean possess identical ITS sequences to isolates originating from the Red Sea or the western Pacific. These findings indicate that some Symbiodinium species may have global biogeographic distributions.

658 citations


Journal ArticleDOI
TL;DR: By adopting integrated polytrophic practices, the aquaculture industry should find increasing environmental, economic, and social acceptability and become a full and sustainable partner within the development of integrated coastal management frameworks.
Abstract: The rapid development of intensive fed aquaculture (e.g. finfish and shrimp) throughout the world is associated with concerns about the environmental impacts of such often monospecific practices, especially where activities are highly geographically concentrated or located in suboptimal sites whose assimilative capacity is poorly understood and, consequently, prone to being exceeded. One of the main environmental issues is the direct discharge of significant nutrient loads into coastal waters from open-water systems and with the effluents from land-based systems. In its search for best management practices, the aquaculture industry should develop innovative and responsible practices that optimize its efficiency and create diversification, while ensuring the remediation of the consequences of its activities to maintain the health of coastal waters. To avoid pronounced shifts in coastal processes, conversion, not dilution, is a common-sense solution, used for centuries in Asian countries. By integrating fed aquaculture (finfish, shrimp) with inorganic and organic extractive aquaculture (seaweed and shellfish), the wastes of one resource user become a resource (fertilizer or food) for the others. Such a balanced ecosystem approach provides nutrient bioremediation capability, mutual benefits to the cocultured organisms, economic diversification by producing other value-added marine crops, and increased profitability per cultivation unit for the aquaculture industry. Moreover, as guidelines and regulations on aquaculture effluents are forthcoming in several countries, using appropriately selected seaweeds as renewable biological nutrient scrubbers represents a cost-effective means for reaching compliance by reducing the internalization of the total environmental costs. By adopting integrated polytrophic practices, the aquaculture industry should find increasing environmental, economic, and social acceptability and become a full and sustainable partner within the development of integrated coastal management frameworks.

600 citations


Journal ArticleDOI
TL;DR: It is concluded that changes to the enrichment portion of the recipe have significantly improved this artificial seawater medium and that it can be used to grow an even wider range of coastal and open ocean species.
Abstract: Although most phycologists use natural seawater for culturing marine species, artificial media continue to play important roles in overcoming problems of supply and seasonal variability in the quality of natural seawater and also for experiments involving manipulation of micro- and macronutrients. Several artificial media have been developed over the last 90 years; enriched seawater, artificial water (ESAW) is among the more popular recipes. ESAW has the advantage of an ionic balance that is somewhat closer to that of normal seawater. The original paper compared the growth of 83 strains of microalgae in natural seawater (ESNW) versus ESAW and determined that 23% grew more poorly in the artificial water. Since 1980, however, the composition of ESAW, as used by the original authors, has changed considerably. In particular, the added forms of phosphate, iron, and silicate have been changed and the trace metal mixture has been altered to include nickel, molybdenum, and selenium. We tested whether these changes improved the ability of the artificial medium to grow previously difficult to grow phytoplankton species. To test this, we selected eight species that had been shown to grow better in ESNW than in ESAW and compared their growth again, using the currently used recipe with all the above modifications. For all but one species (Apedinella spinifera), growth rate and final yield was no different between the media but in one case (Emiliania huxleyi) was slightly higher in ESAW. No differences in cell morphology or volume were found in any case. We conclude that changes to the enrichment portion of the recipe have significantly improved this artificial seawater medium and that it can be used to grow an even wider range of coastal and open ocean species.

502 citations


Journal ArticleDOI
TL;DR: Rhodoliths are widely distributed in the worlds' oceans and have an excellent fossil record, and their external morphology and internal growth bands are potential archives of environmental variation at scales of within years to tens of years.
Abstract: Rhodoliths (maerl) are widely distributed in the worlds' oceans and have an excellent fossil record. Individuals are slow growing, may be long lived (>100 years), and are resilient to a variety of environmental disturbances. Their external morphology and internal growth bands are potential archives of environmental variation at scales of within years to tens of years. At high densities, these free-living non-geniculate coralline algae form rhodolith beds, communities of high diversity that can be severely impacted by resource extraction.

485 citations


Journal ArticleDOI
TL;DR: To resolve the uncertainty about Fv/Fm as a diagnostic of nutrient stress, the neritic diatom Thalassiosira pseudonana (Hustedt) Hasle et Heimdal was grew under nutrient‐replete and nutrient‐stressed conditions, using replicate semicontinuous, batch, and continuous cultures.
Abstract: In biological oceanography, it has been widely accepted that the maximum quantum yield of photosynthesis is influenced by nutrient stress. A closely related parameter, the maximum quantum yield for stable charge separation of PSII, (φPSII)m, can be estimated by measuring the increase in fluorescence yield from dark-adapted minimal fluorescence (Fo) to maximal fluorescence (Fm) associated with the closing of photosynthetic reaction centers with saturating light or with a photosynthetic inhibitor such as 3′-(3,4-dichlorophenyl)-1′,1′-dimethyl urea (DCMU). The ratio Fv/Fm (= (Fm− Fo)/Fm) is thus used as a diagnostic of nutrient stress. Published results indicate that Fv/Fm is depressed for nutrient-stressed phytoplankton, both during nutrient starvation (unbalanced growth) and acclimated nutrient limitation (steady-state or balanced growth). In contrast to published results, fluorescence measurements from our laboratory indicate that Fv/Fm is high and insensitive to nutrient limitation for cultures in steady state under a wide range of relative growth rates and irradiance levels. This discrepancy between results could be attributed to differences in measurement systems or to differences in growth conditions. To resolve the uncertainty about Fv/Fm as a diagnostic of nutrient stress, we grew the neritic diatom Thalassiosira pseudonana (Hustedt) Hasle et Heimdal under nutrient-replete and nutrient-stressed conditions, using replicate semicontinuous, batch, and continuous cultures. Fv/Fm was determined using a conventional fluorometer and DCMU and with a pulse amplitude modulated (PAM) fluorometer. Reduction of excitation irradiance in the conventional fluorometer eliminated overestimation of Fo in the DCMU methodology for cultures grown at lower light levels, and for a large range of growth conditions there was a strong correlation between the measurements of Fv/Fm with DCMU and PAM (r2 = 0.77, n = 460). Consistent with the literature, nutrient-replete cultures showed consistently high Fv/Fm (∼0.65), independent of growth irradiance. Under nutrient-starved (batch culture and perturbed steady state) conditions, Fv/Fm was significantly correlated to time without the limiting nutrient and to nutrient-limited growth rate before starvation. In contrast to published results, our continuous culture experiments showed that Fv/Fm was not a good measure of nutrient limitation under balanced growth conditions and remained constant (∼0.65) and independent of nutrient-limited growth rate under different irradiance levels. Because variable fluorescence can only be used as a diagnostic for nutrient-starved unbalanced growth conditions, a robust measure of nutrient stressed oceanic waters is still required.

481 citations


Journal ArticleDOI
TL;DR: The theory of endosymbiosis describes the origin of plastids from cyanobacterial‐like prokaryotes living within eukaryotic host cells, and morphological, biochemical, and molecular studies provide clear evidence of a proKaryotic ancestry for plastid ancestry.
Abstract: The theory of endosymbiosis describes the origin of plastids from cyanobacterial-like prokaryotes living within eukaryotic host cells. The endosymbionts are much reduced, but morphological, biochemical, and molecular studies provide clear evidence of a prokaryotic ancestry for plastids. There appears to have been a single (primary) endosymbiosis that produced plastids with two bounding membranes, such as those in green algae, plants, red algae, and glaucophytes. A subsequent round of endosymbioses, in which red or green algae were engulfed and retained by eukaryotic hosts, transferred photosynthesis into other eukaryotic lineages. These endosymbiotic plastid acquisitions from eukaryotic algae are referred to as secondary endosymbioses, and the resulting plastids classically have three or four bounding membranes. Secondary endosymbioses have been a potent factor in eukaryotic evolution, producing much of the modern diversity of life.

377 citations


Journal ArticleDOI
TL;DR: It is demonstrated that a variety of selectable markers and reporter genes can be expressed in P. tricornutum, enhancing the potential of this organism for exploring basic biological questions and industrial applications.
Abstract: A general purpose transformation vector, designated pPha-T1, was constructed for use with the diatom Phaeodactylum tricornutum Bohlin. This vector harbors the sh ble cassette for primary selection on medium containing the antibiotic zeocin, and a multiple cloning site flanked by the P. tricornutum fcpA promoter. pPha-T1 was used to establish the utility of three selectable marker genes and two reporter genes for P. tricornutum transformation. The nat and sat-1 genes confer resistance to the antibiotic nourseothricin, and nptII confers resistance to G418. Each of these genes was effective as a selectable marker for identifying primary transformants. These markers could also be used for dual selections in combination with the sh ble gene. The reporter genes uidA and gfp were also introduced into P. tricornutum using pPha-T1. Gus expression in some transformants reached 15 μg·μg−1 of total soluble protein and permitted excellent cell staining, while GFP fluorescence was readily visible with standard fluorescence microscopy. The egfp gene, which has optimal codon usage for expression in human cells, was the only version of gfp that produced a strong fluorescent signal in P. tricornutum. The codon bias of the egfp gene is similar to that of P. tricornutum genes. This study suggests that codon usage has a significant effect on the efficient expression of reporter genes in P. tricornutum. The results presented here demonstrate that a variety of selectable markers and reporter genes can be expressed in P. tricornutum, enhancing the potential of this organism for exploring basic biological questions and industrial applications.

365 citations



Journal ArticleDOI
TL;DR: The results suggested that reoxidation of Fe(II) produced by reduction may be a necessary part of the Fe internalization reaction, relevant to phytoplankton nutrition in the open sea where organic Fe complexes dominate the dissolved speciation and where the concentration of inorganic Fe is limiting.
Abstract: Thalassiosira oceanica (Hustedt) Hasle et Heimdal (clone 1003) attained rapid rates of growth in low Fe seawater containing the siderophore ferrioxamine B (FeDFB) as the sole Fe source. Short-term rates of Fe uptake were 109 times faster than those predicted from the equilibrium concentration of inorganic Fe, suggesting that FeDFB was the substrate for the Fe transport system. An extracellular reduction step, mediated by a cell surface reductase, preceded Fe transport from FeDFB and was induced under Fe limitation. The half-saturation constant for the reduction was 0.68 μM. Iron reduction rates were two times faster than uptake rates, so that the activities of the reductase and the transporter were tightly coupled. The rates of Fe reduction of a number of Fe chelators, including synthetic organic ligands (nitrilotriacetate, diethylenetriaminepentaacetate, and EDTA) and fungal siderophores (desferrioxamine B and desferrioxamine E), were inversely proportional to the ratio of the stability constants of their Fe(III) and Fe(II) complexes and varied by a factor of two times, like the redox potentials of the Fe complexes. Platinum (II), a known inhibitor of Fe reductase activity, appeared to reduce the rates of Fe uptake from FeDFB but not from inorganic complexes. The results suggested that reoxidation of Fe(II) produced by reduction may be a necessary part of the Fe internalization reaction. Ferric reductase could be relevant to phytoplankton nutrition in the open sea where organic Fe complexes dominate the dissolved speciation and where the concentration of inorganic Fe is limiting.

284 citations


Journal ArticleDOI
TL;DR: This study demonstrates that the relative proportions of the major macromolecules contained in microalgal cells and their changes in response to external stimuli can be determined rapidly, simultaneously, and inexpensively using FT‐IR.
Abstract: Fourier Transform Infrared (FT-IR) spectroscopy was used to study carbon allocation patterns in response to changes in nitrogen availability in the diatom Chaetoceros muellerii Lemmerman. The results of the FT-IR measurements were compared with those obtained with traditional chemical methods. The data obtained with both FT-IR and chemical methods showed that nitrogen starvation led to the disappearance of the differences in cell constituents and growth rates existing between cells cultured at either high [NO3−] or high [NH4+]. Irrespective of the nitrogen source supplied before nitrogen starvation, a diversion of carbon away from protein, chlorophyll, and carbohydrates into lipids was observed. Under these conditions, cells that had previously received nitrogen as nitrate appeared to allocate a larger amount of mobilized carbon into lipids than cells that had been cultured in the presence of ammonia. All these changes were reversed by resupplying the cultures with nitrogen. The rate of protein accumulation in the N-replete cells was slower than the rate of decrease under nitrogen starvation. This study demonstrates that the relative proportions of the major macromolecules contained in microalgal cells and their changes in response to external stimuli can be determined rapidly, simultaneously, and inexpensively using FT-IR. The technique proved to be equally reliable to and less labor intensive than more traditional chemical methods.

278 citations


Journal ArticleDOI
TL;DR: A mouse bioassay did not show lethal toxicity when tested at doses up to 1500 mg dry weight cells·kg−1 body weight within 96 h, demonstrating that production of primarily deoxy‐CYN does not lead to significant mouse toxicity by strain HB1, and suggests that Raphidiopsis belongs to the Nostocaceae, but this requires confirmation by molecular systematic studies.
Abstract: A strain of Raphidiopsis (Cyanobacteria) isolated from a fish pond in Wuhan, P. R. China was examined for its taxonomy and production of the alkaloidal hepatotoxins cylindrospermopsin (CYN) and deoxy-cylindrospermopsin (deoxy-CYN). Strain HB1 was identified as R. curvata Fritsch et Rich based on morphological examination of the laboratory culture. HB1 produced mainly deoxy-CYN at a concentration of 1.3 mg(.)g(-1) (dry ut cells) by HPLC and HPLC-MS/MS. CYN was also detected in trace amounts (0.56 mug(.)g(-1)). A mouse bioassay did not show lethal toxicity when tested at doses up to 1500 mg dry weight cells(.)kg(-1) body weight within 96 h, demonstrating that production of primarily deoxy CYN does not lead to significant mouse toxicity by strain BB I. The presence of deoxy-CYN and CYN in R curvata suggests that Raphidiopsis belongs to the Nostocaceae, but this requires confirmation by molecular systematic studies. Production of these cyanotoxins by Raphidiopsis adds another genus, in addition to Cylindrospemopsis, Aphanizomenon, and Umezakia, now known to produce this group of hepatotoxic cyanotoxins. This is also the first report from China of a CYN and deoxy-CYN producing cyanobacterium.

Journal ArticleDOI
TL;DR: Three aspects of EPS production have been identified: production during rapid growth, which differs in composition from (2) EPS directly produced as a result of photosynthetic overflow during growth limiting conditions and (3) EPS produced for up to 3 days in the dark using intracellular storage reserves (glucans).
Abstract: Epipelic diatoms are important constituents of estuarine microphytobenthic biofilms. Field-based investigations have shown that the production of carbohydrates by such taxa is ecologically important. However, limited information exists on the dynamics of carbohydrate production by individual species of epipelic diatoms. The production of low and high molecular weight extracellular carbohydrates in axenic cultures of five species of benthic estuarine diatoms, Cylindrotheca closterium (Ehrenberg), Navicula perminuta (Grun.) in Van Heurck, Nitzschia frustulum (Kutz.) Grunow, Nitzschia sigma (Kutz.) Grunow, and Surirella ovata (Kutz.) Grunow, were investigated. All species produced colloidal (water-soluble) carbohydrates during growth, with maximal production occurring during stationary phase. During logarithmic growth, approximately 20% of extracellular carbohydrates consisted of polymeric material (extracellular polymeric substances [EPS]), but during stationary phase, EPS content increased to 34%–50%. Pyrolysis–mass spectrophotometry analysis showed differences in the composition of EPS produced during logarithmic and stationary phase. All species synthesized glucan as a storage carbohydrate, with maximum glucan accumulation during the transition from log to stationary phase. Short-term labeling with 14C-bicarbonate found that between 30 and 60% of photoassimilates were released as colloidal carbohydrate, with EPS consisting of approximately 16% of this colloidal fraction. When cells were placed in darkness, EPS production increased, and between 85 and 99% of extracellular carbohydrate produced was polymeric. Glucan reserves were utilized in dark conditions, with significant negative correlations between EPS and glucan for N. perminuta and S. ovata. Under dark conditions, cells continued to produce EPS for up to 3 days, although release of low molecular weight carbohydrates rapidly ceased when cells were dark treated. Three aspects of EPS production have been identified during this investigation: (1) production during rapid growth, which differs in composition from (2) EPS directly produced as a result of photosynthetic overflow during growth limiting conditions and (3) EPS produced for up to 3 days in the dark using intracellular storage reserves (glucans). The ecological implications of these patterns of production and utilization are discussed.

Journal ArticleDOI
TL;DR: The Kylin system is tested based on phylogenetic parsimony and distance analyses inferred from two molecular data sets and morphological evidence, and a new subfamily, Phycodryoideae, is proposed.
Abstract: The present classification of the Delesseriaceae retains the essential features of Kylin's system, which recognizes two subfamilies Delesserioideae and Nitophylloideae and a series of “groups” or tribes. In this study we test the Kylin system based on phylogenetic parsimony and distance analyses inferred from two molecular data sets and morphological evidence. A set of 72 delesseriacean and 7 additional taxa in the order Ceramiales was sequenced in the large subunit rDNA and rbcL analyses. Three large clades were identified in both the separate and combined data sets, one of which corresponds to the Delesserioideae, one to a narrowly circumscribed Nitophylloideae, and one to the Phycodryoideae, subfam. nov., comprising the remainder of the Nitophylloideae sensu Kylin. Two additional trees inferred from rbcL sequences are included to provide broader coverage of relationships among some Delesserioideae and Phycodryoideae. Belonging to the Delesserioideae are the Caloglosseae with Caloglossa; an expanded Hemineureae that includes Hemineura, Patulophycus, Marionella, Laingia, Botryocarpa, and Pseudophycodrys; the Delesserieae with Delesseria and Membranoptera; the Apoglosseae with Apoglossum and a group of southern hemisphere species presently placed in Delesseria that belong in Paraglossum; the Hypoglosseae with Hypoglossum, Branchioglossum, Zellera, and Bartoniella; and the Grinnellieae with Grinnellia. The revised Nitophylloideae contains the Nitophylleae with Nitophyllum, Valeriemaya, Polyneuropsis, and Calonitophyllum and the Martensieae with Opephyllum and Martensia. A new subfamily, Phycodryoideae, is proposed to include the Phycodryeae with Phycodrys, Polyneura, Nienburgia, Cladodonta, Heterodoxia, and Womersleya; the Cryptopleureae with Cryptopleura, Hymenena, Acrosorium, and Botryoglossum; the Myriogrammeae with Myriogramme and Haraldiophyllum; and the Schizoserideae with Schizoseris, Neuroglossum, Drachiella, Abroteia, and species from South America placed in Platyclinia. This research promotes the correlation of molecular and morphological phylogenies.

Journal ArticleDOI
TL;DR: Results showed little variation in the size range of the silica particles within a particular frustule component (valve or girdle band), but there may be differences in particle size between these components within a diatom frustule and significant differences are found between species.
Abstract: The cell wall (frustule) of the freshwater diatom Pinnularia viridis (Nitzsch) Ehrenberg is composed of an assembly of highly silicified components and associated organic layers. We used atomic force microscopy (AFM) to investigate the nanostructure and relationship between the outermost surface organics and the siliceous frustule components of live diatoms under natural hydrated conditions. Contact mode AFM imaging revealed that the walls were coated in a thick mucilaginous material that was interrupted only in the vicinity of the raphe fissure. Analysis of this mucilage by force mode AFM demonstrated it to be a nonadhesive, soft, and compressible material. Application of greater force to the sample during repeated scanning enabled the mucilage to be swept from the hard underlying siliceous components and piled into columns on either side of the scan area by the scanning action of the tip. The mucilage columns remained intact for several hours without dissolving or settling back onto the cleaned valve surface, thereby revealing a cohesiveness that suggested a degree of cross-linking. The hard silicified surfaces of the diatom frustule appeared to be relatively smooth when living cells were imaged by AFM or when field-emission SEM was used to image chemically cleaned walls. AFM analysis of P. viridis frustules cleaved in cross-section revealed the nanostructure of the valve silica to be composed of a conglomerate of packed silica spheres that were 44.8 ± 0.7 nm in diameter. The silica spheres that comprised the girdle band biosilica were 40.3 ± 0.8 nm in diameter. Analysis of another heavily silicified diatom, Hantzschia amphioxys (Ehrenberg) Grunow, showed that the valve biosilica was composed of packed silica spheres that were 37.1 ± 1.4 nm and that silica particles from the girdle bands were 38.1 ± 0.5 nm. These results showed little variation in the size range of the silica particles within a particular frustule component (valve or girdle band), but there may be differences in particle size between these components within a diatom frustule and significant differences are found between species.

Journal ArticleDOI
TL;DR: RFLP data suggest that, in most cases, cultures are a subset of the original in hospite population, and reexamination of the literature revealed examples of zooxanthella cultures being nonrepresentative of in Hospite populations.
Abstract: Zooxanthellae, algal symbionts in divergent marine invertebrate hosts, are a genetically heterogeneous group. All species descriptions and most physiological and infectivity studies of zooxanthellae have been conducted using cultured material. However, few studies have attempted to quantify the representation of cultures isolated from cnidarians to the in hospite zooxanthella populations of the individual host or host species from which they were established. RFLPs of small subunit (18S) rDNA, internal transcribed spacer (ITS)rDNA sequence data, and microsatellite analyses were conducted to assess the relatedness between cultured zooxanthellae and the in hospite populations of the individual host or host species from which they were isolated. RFLP data demonstrated that cultures may represent either the numerically dominant symbiont or ones present in lower number. ITS-rDNA sequences from zooxanthella cultures were disconcordant with ITS-rDNA sequences identified from in hospite zooxanthellae of the same host species, and microsatellites present in in hospite zooxanthella populations were absent from the corresponding cultures. Finally, reexamination of the literature revealed examples of zooxanthella cultures being nonrepresentative of in hospite populations. These data suggest that, in most cases, cultures are a subset of the original in hospite population. Factors such as failing to homogenize bulk cultures before transfer, growth medium used, and the picking of single motile cells may contribute to many zooxanthella cultures being nonrepresentative.

Journal ArticleDOI
TL;DR: Molecular data obtained by a procedure for extracting PCR‐amplifiable nuclear and chloroplast DNA from old and formalin‐fixed red algal herbarium specimens were used to elucidate problems in the systematics of Pacific Gigartinaceae.
Abstract: Molecular data obtained by a procedure for extracting PCR-amplifiable nuclear and chloroplast DNA from old and formalin-fixed red algal herbarium specimens were used to elucidate problems in the systematics of Pacific Gigartinaceae. Correspondence between nucleotide sequences of the internal transcribed spacer 1 region or the RUBISCO spacer from type specimens and modern collections supports the following conclusions. (1) The type of Fucus cordatus Turner, now Iridaea cordata (Turner) Bory, came from the southern hemisphere (probably from Isla de los Estados, Argentina) rather than from Banks Island, B.C., Canada. (2) The type of Iridaea heterocarpa P. et R. [ Mazzaella heterocarpa (P. et R.) Fred.] represents the tetrasporangial phase of a species of Chondrus , possibly C. crispus Stackh. (3) The types of Iridaea lilacina P. et R., I. phyllocarpa P. et R., and Iridophycus furcatum S. et G. represent a single species from Alaska, Mazzaella phyllocarpa (P. et R.) Perest., currently but incorrectly called M. heterocarpa. (4) The type of Iridophycus oregonum Doty represents the tetrasporangial phase of the species from southern Alaska to southern California known incorrectly as M. heterocarpa . (5) Mazzaella splendens (S. et G.) Fred. is more closely related to M. linearis (S. et G.) Fred. than it is to M. flaccida (S. et G.) Fred. (6) Iridophycus coriaceum S. et G. is conspecific with M. splendens , whereas Rhodoglossum coriaceum E.Y. Dawson is an independent species: Mazzaella coriacea (E.Y. Dawson) Hughey. (7) Iridaea cornucopiae P. et R. is conspecific with Mazzaella laminarioides (Bory) Fred., and the type probably came from Chile rather than from the North Pacific. (8) Plants attributed to Iridaea cornucopiae in Pacific North America are referable to Mazzaella parksii (S. et G.) comb. nov. (9) Rhodoglossum parvum G. M. Smith et Hollenb. is an independent species: Mazzaella parva (G. M. Smith et Hollenb.) comb. nov. (10) Grateloupia squarrulosa S. et G., Grateloupia johnstonii S. et G., and Gigartina pectinata E.Y. Dawson represent a single species: Chondracanthus squarrulosus (S. et G.) comb. nov.

Journal ArticleDOI
TL;DR: An important role of DNA repair pathways in determining the UV sensitivity in red macrophytes is suggested, as the accumulation of DNA damage may have been responsible for the complete inhibition of growth in Phycodrys rubens and Polyneura hilliae.
Abstract: The sensitivity to UV-B radiation (UVBR: 280-315 nm) was tested for littoral (Palmaria palmata [L] O Kuntze, Chondrus crispus Stackhouse) and sublittoral (Phyllophora pseudoceranoides S. G. Gmelin, Rhodymenia pseudopalmata [Lamouroux] Silva, Phycodrys rubens [L.] Batt, Polyneura hilliae [Greville] Kylin) red macrophytes from Brittany, France. Algal fragments were subjected to daily repeated exposures of artificial UVBR that were realistic for springtime solar UVBR at the water surface in Brittany, Growth, DNA damage, photoinhibition, and UV-absorbing compounds were monitored during 2 weeks of PAR + UV-A radiation (WAR) + UVBR, whereas PAR + UVAR and PAR treatments were used as controls. The littoral species showed a higher UV tolerance than the sublittoral species. After 2 weeks, growth of P. palmata and C, crispus was not significantly affected by UVBR, and DNA damage, measured as the number of cyclobutane-pyrimidine dimers per 10(6) nucleotides, was negligible. Photoinhibition, determined as the decline in optimal quantum yield, was low and decreased during the course of the experiment, coinciding with the production of UV-absorbing compounds in these species. In contrast, no UV-absorbing compounds were induced in the sublittoral species. Growth rates of P. pseudoceranoides and R. pseudopalmata were reduced by 40% compared with the PAR treatment. Additionally, constant levels of DNA damage and pronounced photoinhibition were observed after the UVBR treatments. Growth was completely halted for Phycodrys rubens and Polyneura hilliae, whereas DNA damage accumulated in the course of the experiment. Because Phycodrys rubens and Polyneura hilliae showed the same degree of photoinhibition as the other sublittoral species, it appears that the accumulation of DNA damage may have been responsible for the complete inhibition of: growth. The results suggest an important role of DNA repair pathways in determining the UV sensitivity in red macrophytes.

Journal ArticleDOI
TL;DR: A time‐integrated thermogeographic model is developed to demonstrate conditions under which benthic marine algal assemblages evolve biogeographical patterns in their distribution and abundance and proposes that biogeographic patterns should be determined by the abundance of species assemblage rather than presence and absence or percent endemism as is commonly done.
Abstract: We developed a time-integrated thermogeographic model to demonstrate conditions under which benthic marine algal assemblages evolve biogeographic patterns in their distribution and abundance. The graphical model applies to rocky marine sublittoral zones in which seasonal temperatures, coastline area, isolation, and evolutionary time are primary factors. Time is treated by using the temperature/area/distributions for the present (interglacial period) integrated with that of 18,000 years before present (glacial period). These two alternate states characterize the global marine realm since the late Pliocene to Pleistocene time during which many extant species have evolved. The resulting abiotic “thermogeographic” model defines 20 regions that correspond with the cores of 24 recognized biogeographic regions and/or provinces determined by published distributions of organisms. Modern biogeographic regions conform closely with thermogeographic regions where temperature, area, and time are integrated. We also propose that biogeographic patterns should be determined by the abundance of species assemblages rather than presence and absence or percent endemism as is commonly done. We test the efficacy of thermogeographic regions with abundance-weighted patterns in the biogeography of crustose coralline red algae (Rhodophyta/Corallinales) in the colder part of the northern hemisphere. Based on abundance, rather than presence/absence, coralline red algal biogeographic regions correspond closely with the model's thermogeographic regions.

Journal ArticleDOI
TL;DR: In this volume, a multidisciplinary group of acknowledged experts fully intergrate the physical, chemical, and biological sciences to provide a complete understanding of the interrelationships between snow structure and life.
Abstract: In this volume, a multidisciplinary group of acknowledged experts fully intergrate the physical, chemical, and biological sciences to provide a complete understanding of the interrelationships between snow structure and life. This volume opens a new perspecitve on snow cover as a habitat for organisms under extreme environmental conditions and as a key factor in the ecology of much of the Earth's surface. The contributors describe the fundamental physical and small-scale chemical processes that characterize the evolution of snow and their influence on the life cycles of true snow organisms and the biota of cold regions with extended snow cover. The book further expands on the role of snow in the biosphere by the study of the relationship between snow and climate and the paleo-ecological evidence for the influence of past snow regimes on plant communities. Snow Ecology will form a main textbook on advanced courses in biology, ecology, geography, environmental science, and earth science where an important component is devoted to the study of the cryosphere. It will also be useful as a reference text for graduate students, researchers, and professionals at academic institutions and in government and nongovernmental agencies with environmental concerns.

Journal ArticleDOI
TL;DR: Results were interpreted as an indication that the frequently reported existence of free polyunsaturated fatty acids in live biomass is an analytical artifact.
Abstract: Acute grazer toxicity of freshwater diatom biofilms was determined using Thamnocephalus platyurus Packard, an anostracan grazer, as the bioassay organism. The diatoms exhibited toxicity when the cells of the biofilm were freeze–thawed before the assay. The toxicity could be extracted from the biofilms with methanol and acetone, and only minimal toxicity was left in the insoluble residue. Bioassay-guided HPLC separation of the methanolic extract was performed to trace the most toxic components. Analysis by UV spectrometry, gas chromatography, and mass spectrometry showed that 5,8,11,14,17-eicosapentaenoic acid was responsible for most grazer toxicity. The 24-h LC50 of this polyunsaturated fatty acid was 34 μM in the Thamnocephalus platyurus bioassay. The concentrations of other free fatty acids were not high enough to contribute significantly to the toxicity. Procedures that affected the integrity of the cells (e.g. solvent extraction, freezing and thawing, osmotic stress by addition of 20% NaCl, or grinding the cells in a mortar) were taken as model reactions for grazing and had the common effect of resulting in a dramatic increase of free polyunsaturated and saturated fatty acids. Under these conditions, about 30% of the total fatty acids of the diatoms was transformed from the bound into the free form. The time necessary for liberation was very short. With the exception of 5,8,11,14,17-eicosapentaenoic acid, which continued to be liberated, the hydrolysis of the other fatty acids was terminated less than 1 min after initiating the reaction. The classical extraction procedures using methanol and other solvents led to the appearance of a high percentage of free fatty acids in live cells. Treatment of biofilms with these solvents did not stop the hydrolysis of lipids initiated by the disintegration of the cells. However, boiling acetone completely suppressed the hydrolytic reactions, and free polyunsaturated fatty acids were not detected in live biofilm organisms, although nontoxic saturated fatty acids were present in moderate concentrations. These results were interpreted as an indication that the frequently reported existence of free polyunsaturated fatty acids in live biomass is an analytical artifact.

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TL;DR: Sensory photoreceptors of algae and protists are exceptionally rich in structure and function; light-gated ion channels and photoactivated adenylate cyclases are unique examples.
Abstract: Only five major types of sensory photoreceptors (BLUF-proteins, cryptochromes, phototropins, phytochromes, and rhodopsins) are used in nature to regulate developmental processes, photosynthesis, photoorientation, and control of the circadian clock. Sensory photoreceptors of algae and protists are exceptionally rich in structure and function; light-gated ion channels and photoactivated adenylate cyclases are unique examples. During the past ten years major progress has been made with respect to understanding the function, photochemistry, and structure of key sensory players of the algal kingdom.

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TL;DR: The phylogenetic position of Koliella, a chlorophyte characterized by Klebsormidium type cell division, was inferred from analyses of partial 18S r DNA and partial 16S rDNA, and high decay indices and bootstrap values supported high affinity for Trebouxiophyceae, however, the genus appeared to be polyphyletic.
Abstract: The phylogenetic position of Koliella, a chlorophyte characterized by Klebsormidium type cell division, was inferred from analyses of partial 18S rDNA and partial 16S rDNA. Parsimony and distance analyses of separate and combined data sets indicated that the members of Koliella belonged to Trebouxiophyceae, and high decay indices and bootstrap values supported this affinity. However, the genus appeared to be polyphyletic. Koliella spiculiformis, the nomenclatural type of the genus, was allied with Nannochloris eucaryota and the “true” chlorellas (Chlorella vulgaris, C. lobophora, C. sorokiniana, and C. kessleri). The close relatives of Koliella longiseta (≡Raphidonema longiseta) and Koliella sempervirens appeared to be Stichococcus bacillaris and some species traditionally classified in Chlorella that were characterized by the production of secondary carotenoids under nitrogen-deficient conditions. This clade was also supported by the presence of a relatively phylogenetically stable group I intron (1506) in the 18S rRNA gene. Because of the presence of Klebsormidium type cell division, some authors regarded the members of Koliella as closely related to charophytes. Molecular analyses, however, did not confirm this affinity and suggested that a Klebsormidium type cell division is homoplastic in green plants.

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TL;DR: Macrocystis may be a monospecific genus (M. pyrifera), and a northern‐hemisphere‐to‐southern-hemisphere pattern of dispersal was inferred, because northern•hemisphere individuals were more diverse and displayed paraphyletic clades, whereas southern‐hem hemisphere individuals were less diverse and formed a monophyleticClade.
Abstract: Macrocystis (Lessoniaceae) displays an antitropical distribution, occurring in temperate subtidal regions along western North America in the northern hemisphere and throughout the southern hemisphere. We used the noncoding rDNA internal transcribed spacer regions (ITS1 and ITS2) to examine relatedness among (1) Macrocystis and several genera of Laminariales, (2) four species of Macrocystis (M. integrifolia Bory from the northern hemisphere, M. angustifolia Bory and M. laevis Hay from the southern hemisphere, and M. pyrifera [L.] C. Ag. from both hemispheres), and (3) multiple clones of several individuals. Of the taxa included in our phylogenetic analysis, the elk kelp, Pelagophycus porra (tem.) Setch., was the sister taxon to Macrocystis spp. Macrocystis individuals from the southern hemisphere (representing three species) formed a strongly to moderately supported clade, respectively, when the ITS1 and ITS2 sequences were analyzed separately. No distinction was detected between the two species in the northern hemisphere. Thus, Macrocystis may be a monospecific genus (M. pyrifera). A northern-hemisphere-to-southern-hemisphere pattern of dispersal was inferred, because northern-hemisphere individuals were more diverse and displayed paraphyletic clades, whereas southern-hemisphere individuals were less diverse and formed a monophyletic clade. High intraindividual variation in ITS I sequences was observed in one individual from Santa Catalina Island (CA), suggesting very recent and rapid mixing of genotypes from areas to the north and Baja California (Mexico) or introgressive hybridization with Pelagophycus.


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TL;DR: The challenge being addressed in current research on microalgae in Aquaculture food chains is to combine engineering and nutritional principles so that effective and economical production of microalgal feed cultures can be accomplished to support an expanding marine animal aquaculture industry.
Abstract: Algal aquaculture worldwide is estimated to be a $5-6 billion U.S. per year industry. The largest portion of this industry is represented by macroalgal production for human food in Asia, with increasing activity in South America and Africa. The technical foundation for a shift in the last half century from wild harvest to farming of seaweeds lies in scientific research elucidating life histories and growth characteristics of seaweeds with economic interest. In several notable cases, scientific breakthroughs enabling seaweed-aquaculture advances were not motivated by aquaculture needs but rather by fundamental biological or ecological questions. After scientific breakthroughs, development of practical cultivation methods has been accomplished by both scientific and commercial-cultivation interests. Microalgal aquaculture is much smaller in economic impact than seaweed cultivation but is the subject of much research. Microalgae are cultured for direct human consumption and for extractable chemicals, but current use and development of cultured microalgae is increasingly related to their use as feeds in marine animal aquaculture. The history of microalgal culture has followed two main paths, one focused on engineering of culture systems to respond to physical and physiological needs for growing microalgae and the other directed toward understanding the nutritional needs of animals-chiefly invertebrates such as mollusks and crustaceans-that feed upon microalgae. The challenge being addressed in current research on microalgae in aquaculture food chains is to combine engineering and nutritional principles so that effective and economical production of microalgal feed cultures can be accomplished to support an expanding marine animal aquaculture industry.

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TL;DR: The accumulation of DNA damage (thymine dimers and 6‐4 photoproducts) induced by ultraviolet‐B radiation was studied in Palmaria palmata under different light and temperature conditions, using specific monoclonal antibodies and subsequent chemiluminescent detection.
Abstract: The accumulation of DNA damage (thymine dimers and 6-4 photoproducts) induced by ultraviolet-B radiation was studied in Palmaria palmata (L.) O. Kuntze under different light and temperature conditions, using specific monoclonal antibodies and subsequent chemiluminescent detection. Both types of damage were repaired much faster under ultraviolet-A radiation (WAR) plus photosynthetically active radiation (PAR) than in darkness, which indicates photoreactivating activity, At 12 degrees C, all thymine dimers were repaired after 2 h irradiation with WAR plus PAR, whereas 6-4 photoproducts were almost completely repaired after 4 h, After 19 h of darkness, almost complete repair of 6-4 photoproducts was found, and 67% of the thymine dimers were repaired, In a second set of experiments, repair of DNA damage under UVAR plus PAR was compared at three different temperatures (0, 12, and 25 degrees C), Again, thymine dimers were repaired faster than 6-4 photoproducts at all three temperatures. At 0 degrees C, significant repair of thymine dimers was found but not of 6-4 photoproducts. Significant repair of both thymine dimers and 6-4 photoproducts occurred at 12 and 25 degrees C, Optimal repair efficiency was found at 25 degrees C for thymine dimers but at 12 degrees C for 6-4 photoproducts, which suggests that the two photorepair processes have different temperature characteristics.

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TL;DR: Phylogenetic trees produced from SSU‐only analyses differed somewhat in particulars of branching within lineages 2 and 4 but overall were congruent with the LSU‐only and combined LSU–SSU results.
Abstract: Sequence data are presented for approximately 85% of the nuclear large subunit (LSU) rDNA gene for one member of the Bangiophyceae and 47 members of the Florideophyceae, the latter representing all but one of the currently recognized florideophyte orders. Distance, parsimony, and maximum likelihood analyses of these data were used to generate phylogenetic trees, and bootstrap resampling was implemented to infer robustness for distance and parsimony results. LSU phylogenies were congruent with published nuclear small subunit (SSU) rDNA results in that four higher level florideophyte lineages were resolved: lineage 1, containing the order Hildenbrandiales; lineage 2, recovered only under distance analysis, composed of the orders Acrochaetiales, Balliales, Batrachospermales, Corallinales, Nemaliales, Palmariales, and Rhodogorgonales; lineage 3, containing the Ahnfeltiales; and lineage 4, composed of the orders Bonnemaisoniales, Ceramiales, Gelidiales, Gigartinales, Gracilariales, Halymeniales, Plocamiales, and Rhodymeniales. Analyses were also performed on a combined LSU-SSU data set and an SSU-only data set to account for differences in taxon sampling relative to published studies using this latter gene. Combined LSU-SSU analyses resulted in phylogenetic trees of similar topology and support to those obtained from LSU-only analyses. Phylogenetic trees produced from SSU-only analyses differed somewhat in particulars of branching within lineages 2 and 4 but overall were congruent with the LSU-only and combined LSU-SSU results. We close with a discussion of the phylogenetic potential that the LSU has displayed thus far for resolving relationships within the Florideophyceae.

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TL;DR: The effect of a 12:12‐h light:dark (LD) cycle on the phasing of several cell parameters was explored in a variety of marine picophytoplanktonic strains and results should help to interpret diel variations in oceanic optical properties in regions where picoplankton dominates.
Abstract: The effect of a 12:12-h light:dark (LD) cycle on the phasing of several cell parameters was explored in a variety of marine picophytoplanktonic strains. These included the photosynthetic prokaryotes Prochlorococcus (strains MED 4, PCC 9511, and SS 120) and Synechococcus (strains ALMO 03, ROS 04, WH 7803, and WH 8103) and five picoeukaryotes ( Bathycoccus prasinos Eikrem et Throndsen, Bolidomonas pacifica Guillou et Chretiennot-Dinet, Micromonas pusilla Manton et Parke, Pelagomonas calceolata Andersen et Saunders, and Pycnococcus provasolii Guillard et al.). Flow cytometric analysis was used to determine the relationship between cell light scatter, pigment fluorescence, DNA (when possible), and the LD cycle in these organisms. As expected, growth and division were tightly coupled to the LD cycle for all of these strains. For both Prochlorococcus and picoeukaryotes, chl and intracellular carbon increased throughout the light period as estimated by chl fluorescence and light scatter, respectively. In response to cell division, these parameters decreased regularly during the early part of the dark period, a decrease that either continued throughout the dark period or stopped for the second half of the dark period. For Synechococcus , the decrease of chl and scatter occurred earlier (in the middle of the light period), and for some strains these cellular parameters remained constant throughout the dark period. The timing of division was very similar for all picoeukaryotes and occurred just before the subjective dusk, whereas it was more variable between the different Prochlorococcus and Synechococcus strains. The burst of division for Prochlorococcus SS 120 and PCC 9511 was recorded at the subjective dusk, whereas the MED 4 strain divided later at night. Synechococcus ALMO 03, ROS 04, and WH 7803, which have a low phycourobilin to phycoerythrobilin (PUB:PEB) ratio, divided earlier, and their division was restricted to the light period. In contrast, the high PUB:PEB Synechococcus strain WH 8103 divided preferentially at night. There was a weak linear relationship between the FALS max :FALS min ratio and growth rate calculated from cell counts ( r � 0.83, n � 11, P � 0.05). Because of the significance of picoplanktonic populations in marine systems, these results should help to interpret diel variations in oceanic optical properties in regions where picoplankton dominates.

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TL;DR: In this paper, the current state of phaeophycean phylogeny was assessed by using the EMBL/GenBank database, and three new alignments designed to maximize taxon sampling while minimizing information loss due to partial sequences were developed.
Abstract: To better assess the current state of phaeophycean phylogeny, we compiled all currently available rbcL, 18S, and 26S rDNA sequences from the EMBL/GenBank database and added 21 new rbcL sequences of our own We then developed three new alignments designed to maximize taxon sampling while minimizing information loss due to partial sequences Phylogenetic analyses were performed on separate and combined data sets (with and without taxa from the sister classes Tribophyceae and Phaeo-thamniophyceae as outgroups) using a variety of assumption sets, tree-drawing algorithms (parsimony, neighbor joining, and likelihood), and resampling methods (bootstrap, decay, jackknife) Partition homogeneity testing (PHT) by codon position within rbcL showed that all positions could be used despite mild third position saturation PHT by gene and domain within rDNA showed that the 26S D1 and D2 regions do not enhance phylogenetic signal even when combined with the 18S The rbcL and rDNA (excluding the 26S DI and D2) could be combined under PHT The topology of the combined tree was the same as that of the rbcL tree alone, but bootstrap support was consistently higher in the combined analysis, applied to more branches, and enabled the establishment of sister group relationships among six orders Although the taxon sampling for the combination tree was lower (n = 22) than for individual gene analyses (n = 58 for rbcL and n = 59 for rDNA), results show that the Laminariales (previously reported) and Sphacelariales (new) are both paraphyletic Choristocarpus tenellus (Kutzing) Zanardini is the most basal phaeophyte and the Dictyotales the most basal order In contrast, the Laminariales sensu stricto (ss) and Ectocarpales sensu lato (sl) are the most derived For phylogenetic studies in the Phaeophyceae, rbcL has more resolving power than rDNA, though the reason for this is unclear based on the fact that both genes are highly conserved

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TL;DR: UVBR‐mediated DNA damage, as measured by cyclobutane pyrimidine dimer (CPD) abundance, was detected in all plankton size fractions, and highest levels were found in the smallest size fraction, mainly consisting of heterotrophic bacteria.
Abstract: During a survey from January to March 1998, the occurrence of W-B radiation (UVBR)-induced DNA damage in Antarctic marine phytoplankton and bacterioplankton was investigated, Sampling was done in Ryder Bay, off the British base Rothera Station, 67 degreesS, 68 degreesW (British Antarctic Survey). Samples were taken regularly during the survey period at fixed depths, after which DNA damage was measured in various plankton size fractions: (> 10, 2-10, and 0,2-2 mum). Incident solar radiation was measured using spectroradiometry, whereas attenuation of biologically effective UVBR was studied using a DNA dosimeter, A diatom bloom was found in the bay during the research period, judging from microscopic observations and HPLC analyses of taxon-specific pigments, The high phytoplankton biomass likely caused strong attenuation of DNA effective UVBR (Kbd-eff). Kbd-eff values ranged from 0.83 .m(-1) at the peak of the bloom to 0.47 .m(-1) at the end of the season. UVBR-mediated DNA damage, as measured by cyclobutane pyrimidine dimer (CPD) abundance, was detected in all plankton Size fractions, Highest levels were found in the smallest size fraction, mainly consisting of heterotrophic bacteria. Clear CPD depth profiles were found during mid-summer (January, beginning of February) with surface levels exceeding 100 CPDs per million nucleotides in the bacterioplankton fraction. At that time, melting of the continuously present shelf ice caused strong salinity gradients in the upper meters, thereby stimulating water column stabilization. At the end of February and beginning of March, this phenomenon was less pronounced or absent, At that time, DNA damage was homogeneously distributed over the first 10 m, ranging between 20 and 30 CPDs per million nucleotides for the smallest size fraction,