Globosa Scherffel Research Articles

Visible-Light-Activated Carbon Dot Photocatalyst for ROS-Mediated Inhibition of Algae Growth.

The growing occurrence of detrimental algal blooms resulting from industrial and agricultural activities emphasizes the urgency of implementing efficient removal strategies. In this study, we have successfully synthesized stable and biocompatible carbon dots (R-CDs) capable of generating reactive oxygen species (ROS) upon exposure to natural light irradiation. Phaeocystis globosa Scherffel (PGS) was selected as a representative model for conducting anti-algal experiments. Remarkably, in the presence of R-CDs, the complete eradication of harmful algae within a simulated light exposure period of 27 h was achieved. Furthermore, fluorescence lifetime imaging microscopy (FLIM) was first employed to study the physiological processes involved in the oxidative stress induced by PGS when subjected to ROS attack. The findings of this study demonstrate the potential of R-CDs as a highly promising anti-algal agent. This elucidation of the mechanism contributes to a comprehensive understanding of the efficacy and effectiveness of such agents in combating algal growth, further inspiring the development of other anti-algal agents.

Effects of temperature, salinity, and irradiance on the growth of harmful algal bloom species Phaeocystis globosa Scherffel (Prymnesiophyceae) isolated from the South China Sea

Blooms of Phaeocystis globosa have been frequently reported in Chinese coastal waters, causing serious damage to marine ecosystems. To better understand the ecological characteristics of P. globosa in Chinese coastal waters that facilitate its rapid expansion, the effects of temperature, salinity and irradiance on the growth of P. globosa from the South China Sea were examined in the laboratory. The saturating irradiance for the growth of P. globosa (Is) was 60 μmol/(m2∙s), which was lower than those of other harmful algal species (70–114 μmol/(m2∙s)). A moderate growth rate of 0.22/d was observed at 2 μmol/(m2∙s) (the minimum irradiance in the experiment), and photo-inhibition did not occur at 230 μmol/(m2∙s) (the maximum irradiance in the experiment). Exposed to 42 different combinations of temperatures (10–31°C) and salinities (10–40) under saturating irradiance, P. globosa exhibited its maximum specific growth rate of 0.80/d at the combinations of 24°C and 35, and 27°C and 40. The optimum growth rates (>0.80/d) were observed at temperatures ranging from 24 to 27°C and salinities from 35 to 40. While P. globosa was able to grow well at temperatures from 20°C to 31°C and salinities from 20 to 40, it could not grow at temperatures lower than 15°C or salinities lower than 15. Factorial analysis revealed that temperature and salinity has similar influences on the growth of this species. This strain of P. globosa not only prefers higher temperatures and higher salinity, but also possesses a flexible nutrient competing strategy, adapted to lower irradiance. Therefore, the P. globosa population from South China Sea should belong to a new ecotype. There is also a potentially high risk of blooms developing in this area throughout the year.

Characterization of Phaeocystis globosa (Prymnesiophyceae), the blooming species in the Southern North Sea

Despite significant research dedicated to the marine genus Phaeocystis, which forms large blooms in the coastal waters of the Southern North Sea, some aspects of the taxonomy and biology of this species still suffer from a sketchy knowledge. It is currently admitted that P. globosa is the species that blooms in the Southern North Sea. This has however, never been confirmed by SSU rDNA sequencing which constitutes nowadays, together with the morphology of the haploid flagellate, a reliable taxonomic criterion to distinguish between Phaeocystis species. Also, although the fine morphology of the haploid scaly flagellate is well known, there is a lack of comparable and harmonized description of the other cell types, i.e. colonial cells and diploid flagellates, previously identified within the Phaeocystis life cycle.In this study, we used SSU rDNA sequencing, light and electron scanning microscopy and flow cytometry to identify and characterize three cell types produced in controlled and reproducible manner from two strains of Phaeocystis isolated from the Belgian coastal zone. Our morphometry and sequencing data confirm unambiguously that P. globosa is the species that blooms in the Southern North Sea, but suggest in addition that both strains are representative of the original P. globosa Scherffel. Our study compares, for the first time since the species description, the fine morphometry and ploidy features of diploid colonial cells, diploid and haploid flagellates originating from same strains, providing therefore unambiguous identification criteria for distinguishing them from each other. The diploid stage, colonial or flagellated cell, is thus characterized by a naked surface, has a size range nearly twice that of the haploid flagellate and do not produce the chitinous filaments specific of the haploid stage. Colonial cells lack flagella and haptonema but possess on their apical side two appendages, which elongate to form the flagella of the diploid flagellate.

Phaeocystis globosa Scherffel, a harmful microalga, and its production of dimethylsulfoniopropionate

The production of dimethylsulfoniopropionate (DMSP) and its cleavage products (DMS) are well studied in phytoplankton worldwide. However, less is known about their sources, distributions, and impacts in the coast of China. We examined the production of DMSP and DMS in Phaeocystis globosa Scherffel and other benthic macroalgae from the South China coast in relation to environmental conditions. P. globosa was a harmful marine microalgal species and its bloom took place in the eutrophic waters along the South China Sea frequently. It also produced high content of DMSP at different growth stages, with the highest concentration usually observed in the stationary period. Moreover, the production of DMSP in P. globosa was significantly affected by salinity and temperature with the highest contents associated with high salinity (e.g. 40) and low temperature (e.g. 20°C). In field benthic macroalgae, there was also a marked difference in the DMSP of various species or different samples of the same species. Chlorophyll a contents were also determined for each macroalgal species. The highest chlorophyll a (238.7 ng/g fresh weight) was recorded in Chlorophyta Ulva lactuca at Guishan Island (Zhuhai), while the lowest value (1.5 ng/g fresh weight) was found in Rhodophyta Gracilaria tenuistipitata in Zhanjiang. Further correlation analysis indicated that there was no significant relationship between the content of DMSP and chl-a in macroalgae samples (P > 0.05). All the results suggested that the production of DMSP in marine algae was not only species- and stage-related, but also greatly affected by various environmental factors.

Buoyancy Regulation in Phaeocystis globosa Scherffel Colonies

Buoyancy of Phaeocystis globosa Scherffel (Prymnesiophyceae) colonies was investigated by measuring the vertical distribution of colonies in quiescent water where convection had been removed. Over 60% of the colonies exhibited negative buoyancy regardless of light condition or growth phase. Positively and neutrally buoyant colonies lost their buoyancy in the dark, but regained buoyancy upon return to the light. Colonies with closer cell packing; i.e., more cells per unit colonial surface area, had greater capability to remain buoyant. Our results suggest that colony buoyancy was not uniform within a P. globosa population, and that biological regulation of colony buoyancy required light energy.

Negative effects of Phaeocystis globosa on microalgae

The potential allelopathic effects of the microalga, Phaeocystis globosa Scherffel, on three harmful bloom algae, Prorocentrum donghaiense Lu, Chattonella marina (Subrahmanyan) Hara et Chihara and Chattonella ovata Hara et Chihara were studied. The growth of C. marina and C. ovata was markedly reduced when the organisms were co-cultured with P. globosa or cultured in cell-free spent medium. Haemolytic extracts from P. globosa cells in the senescence phase had a similar inhibitory effect on the three harmful bloom algae. However, P. globosa had less influence on the brine shrimp, Artemia salina. These results indicate that P. globosa may have an allelopathic effect on microalgae, which would explain the superior competitive abilities of P. globosa. Because the addition of the haemolytic toxins from P. globosa had similar effects on algae as spent media, these compounds may be involved in the allelopathic action of P. globosa.

Subtle biological responses to increased CO2 concentrations by Phaeocystis globosa Scherffel, a harmful algal bloom species

Recent investigations into the role of carbon dioxide on phytoplankton growth and composition have clearly shown differential effects among species and assemblages, suggesting that increases in oceanic CO2 may play a critical role in structuring lower trophic levels of marine systems in the future. Furthermore, alarming increases in the occurrence of harmful algal blooms (HABs) in coastal waters have been observed, and while not uniform among systems, appear in some manner to be linked to human impacts (eutrophication) on coastal systems. Models of HABs are in their infancy and do not at present include sophisticated biological effects or their environmental controls. Here we show that subtle biological responses occur in the HAB species Phaeocystis globosa Scherffel as a result of CO2 enrichment induced by gentle bubbling. The alga, which has a polymorphic life history involving the formation of both colonies and solitary cells, exhibited altered growth rates of colonial and solitary forms at [CO2] of 750 ppm, as well as increased colony formation. In addition, substantial modifications of elemental and photosynthetic constituents of the cells (C cell−1, N cell−1, potential quantum yield, chl a cell−1) occurred under elevated CO2 concentrations compared to those found at present CO2 levels. In contrast, other individual and population variables (e.g., colony diameter, total chlorophyll concentration, carbon/nitrogen ratio) were unaffected by increased CO2. Our results suggest that predictions of the future impacts of Phaeocystis blooms on coastal ecosystems and local biogeochemistry need to carefully examine the subtle biological responses of this alga in addition to community and ecosystem effects.

Detection of Phaeocystis globosa using sandwich hybridization integrated with nuclease protection assay (NPA-SH)

Phaeocystis globosa Scherffel is one of the common harmful algae species in coastal waters of the southeastern China. In this study, sandwich hybridization integrated with nuclease protection assay (NPA-SH) was used to qualitatively and quantitatively detect P. globosa. Results showed that this method had good applicability and validity in analyzing the samples from laboratory cultures and from fields. The linear regression equation for P. globosa was obtained, and the lowest detection number of cells was 1.8 x 10(4) cells. Statistics showed that there was no distinct difference between the results of detecting the microalgae by NPA-SH and traditional microscopy. This technique has good reliability, accuracy, and can give a remarkably high sample processing rate. Sandwich hybridization integrated with nuclease protection assay will provide an efficient alternative to microscopic method for monitoring and investigating the bloom of P. globosa.

A Phaeocystis globosa bloom associated with upwelling in the subtropical South Atlantic Bight

We observed an unusual, subtropical bloom of Phaeocystis globosa Scherffel during a strong upwelling event and confirmed its identity using morphological, physiological and genetic traits. This low-latitude bloom of P. globosa colonies occurred on the South Atlantic Bight continental shelf during the summer of 2003. Maximum chlorophyll a concentration measured during this subsurface bloom was 11.37 μg L at 31 m depth. Divers reported abundant flocculent material below the steep thermocline, and this material was identified as Phaeocystis sp. using microscopy. Using morphological and physiological traits as well as the sequence of the 18S small subunit ribosomal RNA gene (GenBank Accession # EF100712), this phytoplankton was identified as P globosa. Interactions of physical and biological conditions may restrict low-latitude P globosa blooms to strong upwelling events.

Characterization of the Hemolytic Properties of an Extract from Phaeocystis globosa Scherffel

Abstract: Phaeocystis globosa Scherffel, an organism that causes harmful algal blooms, is a genus of the family Prymnesiophyta (or Haptophyta) with eurythermal and euryhaline characteristics. P. globosa has been confirmed to produce hemolytic substances, which are a mixture of liposaccharides. In the present study, the hemolytic properties of extract of P. globosa are analyzed further. The effects of temperature, pH, different divalent cations, and membrane lipids on extract-induced hemolysis are discussed, as is the possible hemolytic mechanism. The results of the present study showed that the hemolytic activity of the extract was approximately 127.1 hemolytic units (HU)/L. The hemolytic reaction became fastest and a 50% decrease in absorbance was induced at 30 min at 37 °C, and at pH 7.0; Hg2+ was the strongest inhibitor of the hemolysis compared with the other divalent cations and many membrane lipids, except for phosphatidic acid, inhibited the hemolytic activity to different degrees. These results suggest that the toxin may make pores in the surface of red blood cells and that Hg2+ either combines with the hemolysin or closes the pores, hence inhibiting its further hemolytic reaction. The toxin probably has no specific membrane receptor in the red blood cell membrane. (Managing editor: Ya-QinHAN)

Development and grazing of Temora longicornis (Copepoda, Calanoida) nauplii during nutrient limited Phaeocystis globosa blooms in mesocosms

The rates of development and food intake of the copepod Temora longicornis (Muller) were studied using artificial blooms of Phaeocystis globosa Scherffel under different conditions of nutrient limitation. Mesocosms with 800 l of natural seawater were manipulated by inoculation with cultured P. globosa and by addition of nitrogen and/or phosphorus, to obtain N- or P-limited blooms of P. globosa. During development and ageing of these blooms, water from the mesocosms was used as medium for incubation of nauplii of T. longicornis. Only moderate rates of naupliar development as well as high rates of mortality were observed, irrespective of major differences of nutrient conditions and density of P. globosa. Grazing by the nauplii on P. globosa seemed to be low, suggesting a low food quality of this alga at all physiological conditions studied. The results of this study indicate a low capability of T. longicornis nauplii for control of nuisance algal blooms caused by P. globosa.

Molecular evidence identifies bloom-forming Phaeocystis (Prymnesiophyta) from coastal waters of southeast China as Phaeocystis globosa

Sequence data from the 18S small subunit ribosomal RNA gene have been used to identify the species of a Phaeocystis (Prymnesiophyta) that caused harmful algae blooms in the coastal waters of southeast China. This Phaeocystis has morphological and physiological features that differ from those previously described for either P. globosa Scherffel or P. pouchetii (Hariot) Lagerheim. However, the sequence comparison of the Phaeocystis 18S rDNA clearly showed that it was remarkably similar to several isolates of P. globosa. Thus, the species isolated from the southeast coast of China is identified as P. globosa rather than P. cf. pouchetii or another species. Our results also demonstrate that phenotypes of different members of the genus Phaeocystis are variable, apparently changing in response to environmental conditions. It is concluded that, on the basis of this phylogenetic analysis, the bloom forming southeast China coast species of Phaeocystis most likely originated from an endemic warm-water, rather than a foreign source.

THE CHITINOUS NATURE OF FILAMENTS EJECTED BY PHAEOCYSTIS (PRYMNESIOPHYCEAE)1

ABSTRACTFilaments ejected by Phaeocystis globosa Scherffel, organized in star‐like structures, were observed and analyzed before and after their discharge from cells. Ultrastructural observations obtained after cryofixation and cryosubstitution led to a model for their storage within the cell and for their ejection from the cell. Electron diffraction analysis on the ejected filaments demonstrated their chitinous composition. This technique indicated without ambiguity that each filament was in fact a whisker‐like α‐chitin crystal, with the axes of the corresponding polymer chains aligned with the filament's axis. X‐ray microanalysis of the mats of filaments indicated that the silica content suggested by earlier workers was an artifact resulting from the filtration procedure.

ISOLATION AND CHARACTERIZATION OF A VIRUS INFECTING PHAEOCYSTIS POUCHETII (PRYMNESIOPHYCEAE)1

ABSTRACTA virus infecting the haptophyte Phaeocystis pouchetii (Hariot) Lagerheim was isolated from Norwegian coastal waters in May 1995 at the end of a bloom of this phytoplankter. The virus was specific for P. pouchetii because it did not lyse 10 strains of P. globosa Scherffel, Phaeocystis sp., and P. antarctica Karsten. It was a double‐stranded DNA virus, and the viral particle was a polyhedron with a diameter of 130–160 nm. The virus had a main polypeptide of about 59 kDa and at least five minor polypeptides between 30 and 50 kDa. The latent period of the virus when propagated in cultures of P. pouchetii was 12–18 h, and the time required for complete lysis of the cultures was about 48 h. The burst size was estimated to be 350–600 viral particles per lysed cell.

Genetic differentiation among three colony-forming species of Phaeocystis: further evidence for the phylogeny of the Prymnesiophyta

Sequence data from the 18S small subunit ribosomal RNA gene have been used to support the species status of three colony-forming species of Phaeocystis Lagerheim (Prymnesiophyta). Two of these correspond to Phaeocystis globosa Scherffel and Phaeocystis pouchetii (Hariot) Lagerheim. The third species originates from antarctic waters and is referred to Phaeocystis antarctica, described by Karsten at the tum of the century. Morphological and physiological data supporting the separation of the three species is compiled from the literature. Phylogenetic trees generated from the sequence data suggest that the warm-water species, Phaeocystis globosa diverged prior to the separation of the two cold-water forms. Tectonic events and climatic changes during the middle to late Cenozoic provide mechanisms by which speciation events could have occurred as both polar oceans were being formed.

The life cycle of Phaeocystis (Prymnesiophycaea): evidence and hypotheses

The present paper reviews the literature related to the life cycle of the prymnesiophyte Phaeocystis and its controlling factors and proposes novel hypotheses based on unpublished observations in culture and in the field. We chiefly refer to P. globosa Scherffel as most of the observations concern this species. P. globosa exhibits a complex alternation between several types of free-living cells (non-motile, flagellates, microzoopores and possibly macrozoospores) and colonies for which neither forms nor pathways have been completely identified and described. The different types of Phaeocystis cells were reappraised on the basis of existing microscopic descriptions complemented by unpublished flow cytometric investigations. This analysis revealed the existence of at least three different types of free-living cells identified on the basis of a combination of size, motility and ploidy characteristics: non-motile cells, flagellates and microzoospores. Their respective function within Phaeocystis life cycle, and in particular their involvement in colony formation is not completely understood. Observational evidence shows that Phaeocystis colonies are initiated at the early stage of their bloom each by one free-living cell. The mechanisms controlling this cellular transformation are still uncertain due to the lack of information on the overwintering Phaeocystis fomms and on the cell type responsible for colony induction. The existence of haploid microzoospores released from senescent colonies gives however some support to sexuality involvement at some stages of colony formation. Once colonies are formed, at least two mechanisms were identified as responsible of the spreading of colony form: colony multiplication by colonial division or budding and induction of new colony from colonial cells released in the external medium after colony disruption. The latter mechanism was clearly identified, involving at least two successive cell differentiations in the following sequence: motility development, subsequent flagella loss and settlement to a surface, mucus secretion and colony formation, colonial cell division and colony growth. Aggregate formation, cell motility development and subsequent emigration from the colonies, release of non-motile cells after colony lysis on the other hand, were identified as characteristics for termination of Phaeocystis colony development. These pathways were shown to occur similarly in natural environments. In the early stages of the bloom however, many recently-formed colonies were found on the setae of Chaetoceros spp, suggesting this diatom could play a key-rôle in Phaeocystis bloom inception. Analysis of the possible environmental factors regulating the transition between the different phases of the life cycle, suggested that nutrient status and requirement of a substrate for attachment of free-living cells would be essential for initiation of the colonial form. Physical constraints obviously would be important in determining colony shape and fragmentation although autogenic factors cannot be excluded. Some evidence exists that nutrients regulate colony division, while temperature and nutrient stress would stimulate cell emigration from the colonies.

Phaeocystis colonies wintering in the water column?

Phytoplankton net samples collected the year round in the Marsdiep tidal inlet (Dutch Wadden Sea) frequently contained Phaeocytis colonies. In the winter months of 1990 and 1991, before the spring bloom, large colonies were present in low concentrations of a few per m 3. These colonies might provide the inoculum for the spring bloom. Colonies observed in winter are similar to those occurring in spring and summer; they all belong to Phaeocytis globosa Scherffel.

The light and temperature dependence of growth rate and elemental composition of Phaeocystis globosa scherffel and P. Pouchetii (HAR.) Lagerh. in batch cultures

The light and temperature dependence of growth, cellular elemental composition (C, N, P) and chlorophyll content during exponential growth and phosphate starvation of batch cultures of the temperate algal species Phaeocystis globosa were investigated. Temperature-dependent minimum generation time and cell phosphorus content were compared with those of the cold water species P. pouchetii. The variation in growth and cell carbon content was due to the different origin of seawater used for the culture media. Coastal, estuarine seawater enabled shorter doubling times than “offshore” and oceanic-influenced seawater. At nutrient-saturated growth, P. globosa was able to compete with diatoms only if high temperature (14°C) and high irradiances (180 μE·m −2·s −1) predominated. P. pouchetti showed markedly shorter generation times than P. globosa did at temperatures below 10°C. At 6°C, the cell carbon content exceeded the value at 18°C by a factor of 1.7. High C/N atomic ratios of 6.9±0.7 and high C/Chl a ratios of ≥ 54.0 during exponential growth could not entirely be explained by the carbon content of the colony mucus. There was no significant light and temperature dependence of the : N : P ratio during exponential growth. At phosphate starvation (subsistence P quota of cells) this was so only at temperatures higher than 10°C. With their stored phosphorus quota P. globosa and P. pouchetii were capable of only two cell divisions. Hence, because of their limited ability to store phosphorus, the two Phaeocystis species cannot compete with planktonic diatoms for growth. The frequent change in nutrient concentrations (particularly of silicate and phosphate) in coastal and estuarine waters at summer temperatures and light conditions causes a rapid alternation of smaller blooms of P. globosa and diatoms.