Species Of Marine Microalgae Research Articles

A study of the resistance of mass marine algae to heavy metals

The threshold and lethal concentrations of the heavy metals Hg, Cd, Pb, and Cu were evaluated for mass species of marine microalgae. Algae with high specific surface were found to be the most sensitive to the effects of toxic metals. Among the resilient species that survived a wide range of doses of toxic metal, ranging from low threshold to high lethal levels, were those possessing flexible structures and the ability to grow after toxic stress. Resistant species could survive at high threshold and high lethal metal concentrations. The ratio of sensitive and resistant microalgae can be used for monitoring the quality of marine water.

The effect of light stress on the release of volatile iodocarbons by three species of marine microalgae

We investigated the influence of high light stress on iodocarbon release by three species of marine phytoplankton from different algal classes: the prymnesiophyte Emiliania huxleyi, the prasinophyte Tetraselmis sp., and the diatom Thalassiosira pseudonana. Despite a pronounced decrease in the fluorescence‐based maximum quantum yield for photosystem II (Fv/Fm), increased iodocarbon release relative to lower light controls was not observed in any of the experiments performed. These findings do not support the hypothesis that upper‐ocean iodocarbon concentrations are influenced by light‐induced algal stress.

Effects of various algal diets and starvation on larval growth and survival of Meretrix meretrix

Effects of food availability on larval growth and survival of Meretrix meretrix were studied in two experiments by feeding the larvae with different algae diets and by starving the larvae for different periods of time. Newly hatched larvae of M. meretrix were fed with five different marine microalgae species, singly and in various mixtures. Best growth was with Isochrysis galbana as a single species diet. Nutritional value of the other single species diets was in the order of Dunaliella sp. > Phaeodactylum tricornutum > Platymonas subcordiformis > Pavlova viridis. Of the mixtures tested, 50% I. galbana / 50% Dunaliella sp., 50% I. galbana / 50% P. tricornutum, and 50% I. galbana / 50% P. subcordiformis, supported growth and metamorphosis equivalent to those of the I. galbana control. At 25 °C, larvae of M. meretrix were deprived of food for various days to study the growth compensation from the outset of development. The results showed that M. meretrix larvae could survive long feeding delays, and even reach metamorphosis without food added, although starvation had significant effects on growth. These results suggested that M. meretrix larvae had the capacity to survive ‘starvation’ using alternative sources of energy. It also showed that growth, survival and metamorphosis of M. meretrix were affected by many factors besides food quality and quantity.

An evaluation of the accumulation of intracellular inorganic nitrogen pools by marine microalgae in batch cultures

Methods of extraction, changes in concentrations with growth, and effects of culture conditions on intracellular inorganic nitrogen pools (IIN - ammonia, nitrite, and nitrate) were studied in nine species of marine microalgae in batch cultures. The microalgae were analysed to compare three methods of extraction of IIN, one of them developed in this study. The extraction of IIN occurs efficient by with all three methods for four out of the nine species tested. However, for five species significant differences were found among the methods, the best results being obtained with the new method. Microalgae accumulate inorganic forms of nitrogen in different proportions. The species show higher concentrations of either ammonia or nitrate, and always lower concentrations of nitrite. Microalgae of smaller cellular volumes tend to attain higher values of IIN per cubic micrometer (the converse in large-volume species), with some exceptions (Amphidinium carterae and Nannochloropsis oculata). The use of aeration in the cultures determines a decrease in the concentrations of IIN, favours nitrogen assimilation, and generates an increase in growth rates and C:N ratio. High concentrations of IIN are characteristic of the exponential growth phase, but in some cases their occurrence may result from carbon deficiency.

UV-B Radiation Suppresses the Growth and Antioxidant Systems of Two Marine Microalgae,Platymonas subcordiformis(Wille) Hazen andNitzschia closterium(Ehrenb.) W. Sm

Abstract: This study investigated whether increased solar UV-B radiation (280–315 nm) could suppress the growth of marine microalgae through effects on their antioxidant systems. Two marine microalgae species, Platymonas subcordiformis (Wille) Hazen and Nitzschia closterium(Ehrenb.) W. Sm, were exposed to a range of UV-B radiation and both showed reductions in their growth rates, and the chlorophyll a (Chl a) and carotenoid (Car) contents when UV-B radiation dose increased. Superoxide anion radical (O2-.) production and the concentration of hydrogen peroxide (H2O2) and malodiadehyde (MDA) also increased with the increasing of UV-B radiation. Antioxidant systems, non-enzymic components (Car and glutathione content) and enzymic components (superoxide dismutase (SOD) and catalase (CAT) activity), decreased as a result of enhanced UV-B radiation. When the exogenous glutathione (GSH) was added, the effects of UV-B radiation on the growth of the two species were alleviated. These results suggest that enhanced UV-B radiation suppressed the antioxidant systems and caused some active oxygen species to accumulate, which in turns retarded the development of the marine microalgae. (Managing editor: Ya-Qin HAN)

Distribution of intracellular nitrogen in marine microalgae: Calculation of new nitrogen-to-protein conversion factors

Nitrogen budgets in microalgae are strongly affected by growth conditions and physiological state of the cultures. As a consequence, protein N (PN) to total N (TN) ratio may be variable in microalgae grown in batch cultures, and this may limit the usefulness of the nitrogen-to-protein conversion factors (N-Prot factors), the most practical way of determining protein content. The accuracy of protein determination by this method depends on the establishment of specific N-Prot factors, and experimental data are needed to fill this gap. Complementing a previous study, the present work was designed to quantify the fluctuations of the main nitrogenous compounds during the growth of 12 species of marine microalgae, as well as to determine N-Prot factors for them. The microalgae were cultured in two experimental conditions: (a) using a N-replete culture medium (initial N concentration, 1.18 mM) and aeration, and (b) with a N-depleted culture medium (initial N concentration, 235 μM) and no aeration. The distribution of intracellular nitrogen was studied by constructing budgets of different nitrogen pools in different growth phases of the cultures. In all species, large variations occurred in the distribution of PN and non-protein N (NPN) in the treatments tested and in different growth phases. Intracellular inorganic nitrogen (NO3 − , NO2 − and NH3 + NH4 + ) was the most important NPN component (0.4 – 30.4% of TN) in all species, followed by nucleic acids (0.3 – 12.2% of TN), and chlorophylls (0.1 – 1.8% of TN). The relative importance of NPN was greater in the exponential phase, decreasing during growth. PN ranged from 59.3 to 96.8% of TN. N-Prot factors are proposed for each of the species studied, based on the ratio of amino acid residues to TN, with values ranging from 2.53 to 5.77. Based on current results and on the previous study, we establish an overall average N-Prot factor for all species, treatments and growth phases of 4.78 ± 0.62 (n = 354). This study confirms that the use of the traditional factor 6.25 is unsuitable for marine microalgae, and the use of the N-Prot factors proposed here is recommended.

Biotransformation of aliphatic and aromatic ketones, including several monoterpenoid ketones and their derivatives by five species of marine microalgae

The biotransformation of a series of aliphatic and aromatic ketones by five cultures of photosynthetic microalgae is reported. The test substrates include the monoterpenoid ketones carvone and menthone and a series of aromatic ketones related to and including acetophenone. All of the test organisms show some degree of specificity and stereoselectivity in the biotransformation of substrates.

Dietary strategies for increasing docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) concentrations in bovine milk: a review.

Abstract A review was made of the literature concerning the metabolism of fatty acids in the dairy cow, and the potential of increasing the content of the essential fatty acids eicosapentaenoic acid (EPA; C20:5) and docosahexaenoic acid (DHA; C22:6) in cows' milk. EPA and DHA are two n-3 polyunsaturated fatty acids, which can be synthesised from a-linolenic acid (LNA, C18:3). Both EPA and DHA have anti-thrombotic and anti-carcinogenic effects. The UK Department of Health has recommended that the daily human intake of total n-3 PUFA should be 0.2 g/d, which is approximately double the current average intake. The richest source of dietary EPA and DHA is marine products, but the consumption of fish in the UK is declining. Milk fat consumption constitutes 30% of total fat consumption in the UK diet, and so enhancing the concentration of EPA and DHA in milk fat could be an effective means of increasing the consumption of these fatty acids in the UK. Grass and linseed are rich sources of LNA for dairy cows, while fish oil or marine algae are the richest sources of EPA and DHA. However, a large proportion of these fatty acids ( ca 0.9) are hydrogenated to more saturated fatty acids by the microorganisms in the rumen. The proportion of absorbed n-3 PUFA is therefore only about 7 g/kg ingested n-3 PUFA. Absorbed EPA and DHA are transported around the body as phospholipids, associated with the high-density lipoprotein fraction of the plasma. This fraction is not a good substrate for lipoprotein lipase, which is the enzyme in the mammary gland that removes fatty acids from the circulation for incorporation into milk fat. The uptake by the mammary gland of absorbed EPA and DHA is therefore extremely low. The concentration of EPA and DHA in milk fat therefore remains low even when the diet is enriched with these fatty acids. It is possible that the EPA and DHA present in the milk arise from de novo synthesis of these acids from LNA in the mammary gland. However, while EPA is synthesised from LNA, there appears to be a block on the subsequent synthesis of DHA from EPA. EPA and DHA are not stored in adipose tissue triacylglycerols, and they are not used for oxidative metabolism. There is therefore little competition for circulating EPA and DHA between the mammary gland and adipose tissue, or between secretion and oxidation. There is some potential storage of these acids in the phospholipids of muscle tissue and adipose tissue. Grass is a rich source of LNA, and the LNA content of milk can be enhanced by increasing the herbage content of the diet. This potentially provides more precursors of EPA and DHA. However, increasing the proportion of forage in the diet also tends to increase the extent of rumen biohydrogenation of PUFA as this process is encouraged by higher rumen pH and reduced propionate production. Including either fish oil or some species of marine microalgae in the diet increases the EPA and DHA content of milk. However, these oils can adversely affect rumen function, so that total dry matter intake and milk fat content are reduced. Feeding fish oils to ruminant animals may also not be a sustainable practice in the longer-term. Protecting marine oils from rumen biohydrogenation should prevent the adverse effects on rumen function. However, the evaluation of a protected marine microalgae product suggested that the protection was far from complete, and a reliable means of treating algae to protect it from rumen metabolism still awaits development. Further enhancement of the EPA and DHA content of cows' milk requires more research. Issues, which need to be addressed, are the development of a suitable oil supplement, and a reliable means of protecting it from rumen biohydrogenation. A means of transporting the absorbed EPA and DHA in the circulation so that it is readily taken up by the mammary gland for incorporation into the milk fat also needs to be developed. Changes in the marketing of milk that has been improved in this way would also be required to meet the increased cost of producing this nutritionally enhanced milk.

Dietary strategies for increasing docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) concentrations in bovine milk: a review.

Abstract A review was made of the literature concerning the metabolism of fatty acids in the dairy cow, and the potential of increasing the content of the essential fatty acids eicosapentaenoic acid (EPA; C20:5) and docosahexaenoic acid (DHA; C22:6) in cows' milk. EPA and DHA are two n-3 polyunsaturated fatty acids, which can be synthesised from a-linolenic acid (LNA, C18:3). Both EPA and DHA have anti-thrombotic and anti-carcinogenic effects. The UK Department of Health has recommended that the daily human intake of total n-3 PUFA should be 0.2 g/d, which is approximately double the current average intake. The richest source of dietary EPA and DHA is marine products, but the consumption of fish in the UK is declining. Milk fat consumption constitutes 30% of total fat consumption in the UK diet, and so enhancing the concentration of EPA and DHA in milk fat could be an effective means of increasing the consumption of these fatty acids in the UK. Grass and linseed are rich sources of LNA for dairy cows, while fish oil or marine algae are the richest sources of EPA and DHA. However, a large proportion of these fatty acids ( ca 0.9) are hydrogenated to more saturated fatty acids by the microorganisms in the rumen. The proportion of absorbed n-3 PUFA is therefore only about 7 g/kg ingested n-3 PUFA. Absorbed EPA and DHA are transported around the body as phospholipids, associated with the high-density lipoprotein fraction of the plasma. This fraction is not a good substrate for lipoprotein lipase, which is the enzyme in the mammary gland that removes fatty acids from the circulation for incorporation into milk fat. The uptake by the mammary gland of absorbed EPA and DHA is therefore extremely low. The concentration of EPA and DHA in milk fat therefore remains low even when the diet is enriched with these fatty acids. It is possible that the EPA and DHA present in the milk arise from de novo synthesis of these acids from LNA in the mammary gland. However, while EPA is synthesised from LNA, there appears to be a block on the subsequent synthesis of DHA from EPA. EPA and DHA are not stored in adipose tissue triacylglycerols, and they are not used for oxidative metabolism. There is therefore little competition for circulating EPA and DHA between the mammary gland and adipose tissue, or between secretion and oxidation. There is some potential storage of these acids in the phospholipids of muscle tissue and adipose tissue. Grass is a rich source of LNA, and the LNA content of milk can be enhanced by increasing the herbage content of the diet. This potentially provides more precursors of EPA and DHA. However, increasing the proportion of forage in the diet also tends to increase the extent of rumen biohydrogenation of PUFA as this process is encouraged by higher rumen pH and reduced propionate production. Including either fish oil or some species of marine microalgae in the diet increases the EPA and DHA content of milk. However, these oils can adversely affect rumen function, so that total dry matter intake and milk fat content are reduced. Feeding fish oils to ruminant animals may also not be a sustainable practice in the longer-term. Protecting marine oils from rumen biohydrogenation should prevent the adverse effects on rumen function. However, the evaluation of a protected marine microalgae product suggested that the protection was far from complete, and a reliable means of treating algae to protect it from rumen metabolism still awaits development. Further enhancement of the EPA and DHA content of cows' milk requires more research. Issues, which need to be addressed, are the development of a suitable oil supplement, and a reliable means of protecting it from rumen biohydrogenation. A means of transporting the absorbed EPA and DHA in the circulation so that it is readily taken up by the mammary gland for incorporation into the milk fat also needs to be developed. Changes in the marketing of milk that has been improved in this way would also be required to meet the increased cost of producing this nutritionally enhanced milk.

Long chain polyunsaturated fatty acid production and partitioning to triacylglycerols in four microalgae

This work shows that different species of marine microalgae produce and partition EPA and DHA into triacylglycerols to different extents and at different times in the growth cycle. Such information is valuable for the discovery of genes associated with these events.

Effects of different nitrogen sources on the growth and biochemical profile of 10 marine microalgae in batch culture: an evaluation for aquaculture

Growth responses and biochemical composition were investigated in 10 species of marine microalgae of potential use in aquaculture. The algae were grown in Walne's medium and supplied with nitrate, ammonium or urea as a nitrogen (N) source at a high concentration (1.18 mM). Growth was monitored by daily cell counts, and samples for biochemical analysis were taken near the end of the exponential growth phase, when N nutrient and phosphate still remained in the medium. Two species, Hillea sp. and Prorocentrum minimum, failed to grow with ammonium-N because of the toxic effect of ammonia in high concentration. Hillea sp. and Nannochloropsis oculata on urea-N, and Isochrysis galbana, Phaeodactylum tricornutum and Synechococcus subsalsus on ammonium-N, showed significantly lower final yield than with the other N sources. Greater percentages of protein and chlorophyll (dry matter) occurred in the treatment (N source) that produced higher final cell yield. Treatments producing lower final yields tended to give a larger relative content of carbohydrate and lipid in the cells, and in some cases greater cellular volumes. Seven species tended to produce lower percentages of polyunsaturated fatty acids (PAs) with urea-N. Hillea sp., a microalga not yet used in aquaculture, seems to be a promising food-species because of its fast growth rate with nitrate-N and its large relative content of protein and lipids, and because it produces all essential FAs. Differences in chemical profiles resulted from the use of different nitrogen sources in most cases, but few general trends were identified, even within the same taxonomic group (diatoms, green algae).

Influence of organic solvents on the growth of marine microalgae.

Ninety-six-hour toxicity tests of five organic solvents (methanol, ethanol, acetone, N,N-dimethylformamide [DMF], and dimethyl sulfoxide [DMSO]) on nine species of marine microalgae (Bacillariophyceae; Skeletonema costatum, and Chaetoceros calcitrans, Prasinophyceae; Tetraselmis tetrathele, Haptophyceae; Isochrysis galbana and Pavlova lutheri, Dinophyceae; Prorocentrum minimum, Raphidophyceae; Heterosigma akashiwo, Euglenophyceae; Eutreptiella sp., Chlorophyceae; Dunaliella tertiolecta) were conducted. For D. tertiolecta, T. tetrathele, I. galbana, and P. lutheri, methanol was the least toxic solvent. For S. costatum, C. calcitrans and Eutreptiella sp., DMSO was the least toxic solvent. For Heterosigma akashiwo, DMF was the least toxic solvent. In general, solvent toxicity was ethanol > methanol or acetone > DMF > DMSO. In relation to sensitivity of the microalgae to solvents, D. tertiolecta and T. tetrathele were lower in sensitivity, and Eutreptiella sp. and H. akashiwo were higher in sensitivity than the other species. The no observed effect concentration (NOEC) of acetone, DMF, and DMSO were higher than for ethanol and methanol. Acetone, DMF, and DMSO were suitable for carrier solvents used in toxicity test of water-insoluble chemicals. Excellent regression between logEC(50) and logNOEC was obtained (logNOEC = 1.09 x logEC(50) - 0.84, R(2) = 0.91). This equation indicated that higher toxicity was higher application factor (EC(50)/NOEC) than lower toxicity. All application factors were higher than 0.1.

Training radial basis function neural networks: effects of training set size and imbalanced training sets

Obtaining training data for constructing artificial neural networks (ANNs) to identify microbiological taxa is not always easy. Often, only small data sets with different numbers of observations per taxon are available. Here, the effect of both size of the training data set and of an imbalanced number of training patterns for different taxa is investigated using radial basis function ANNs to identify up to 60 species of marine microalgae. The best networks trained to discriminate 20, 40 and 60 species respectively gave overall percentage correct identification of 92, 84 and 77%. From 100 to 200 patterns per species was sufficient in networks trained to discriminate 20, 40 or 60 species. For 40 and 60 species data sets an imbalance in the number of training patterns per species always affected training success, the greater the imbalance the greater the effect. However, this could be largely compensated for by adjusting the networks using a posteriori probabilities, estimated as network output values.

Effects of dissolved inorganic carbon availability on growth, nutrient uptake and chlorophyll fluorescence of two species of marine microalgae

Growth of two species of marine microalgae, namely Nannochloropsis gaditana Lubián (Eustigmatophyceae) and Nannochloris maculata Butcher (Chlorophyceae), was investigated in cultures submitted to three different concentrations of dissolved inorganic carbon (DIC). Cultures of N. gaditana grown in the absence of DIC in the medium and aerated with less than 0.0001% (v/v) CO 2 in air (low DIC conditions) showed a reduction in final cell biomass of approximately 56% as compared with the biomass obtained in cultures grown under control conditions (2 mM DIC in the medium and aerated with air-equilibrated levels of CO 2, i.e. 0.03% (v/v) CO 2). Growth was not observed in N. maculata cultured under low DIC conditions. A concentration of 1% (v/v) CO 2 in air (high DIC conditions) did not modify growth of N. gaditana in relation to that in the control-culture but enhaced growth of N. maculata. Nutrient (NO 3 − and PO 4 3−) uptake was also analyzed under the different growth conditions. The uptake of NO 3 − and PO 4 3− by N. maculata was dependent on the inorganic carbon level; thus, whereas no nutrient absorption was observed in the low DIC-culture, growth at the highest inorganic carbon concentration caused an accelaration of the uptake. Capacity to use nitrate was restricted in N. gaditana cells under low DIC conditions, but nutrient uptake was similar in cultures adapted to air levels of CO 2 and to CO 2-enriched air. Chlorophyll fluorescence measurements were used to determine the photochemical efficiency of photosystem II and the non-photochemical quenching. A similar pattern of evolution of the actual quantum yield of photosystem II (φ PSII) was observed in all cultures of N. gaditana over the growth period, without development of non-photochemical quenching. In contrast, changes in φ PSII of N. maculata differed between treatments and were concurrent with carbon and nutrient availabilities. Non-photochemical quenching rose in this alga when carbon or phosphate limitation constrained proton dissipation from the lumen. Results are discussed in relation to the particular carbon uptake mechanism of each alga.

Active transport of CO2 by three species of marine microalgae

The occurrence of an active CO2 transport system and of carbonic anhydrase (CA) has been investigated by mass spectrometry in the marine, unicellular rhodophyte Porphyridium cruentum (S.F. Gray) Naegeli and two marine chlorophytes Nannochloris atomus Butcher and Nannochloris maculata Butcher. Illumination of darkened cells incubated with 100 μM H13CO3− caused a rapid initial drop, followed by a slower decline in the extracellular CO2 concentration. Addition of bovine CA to the medium raised the CO2 concentration by restoring the HCO3−–CO2 equilibrium, indicating that cells were taking up CO2 and were maintaining the CO2 concentration in the medium below its equilibrium value during photosynthesis. Darkening the cell suspensions caused a rapid increase in the extracellular CO2 concentration in all three species, indicating that the cells had accumulated an internal pool of unfixed inorganic carbon. CA activity was detected by monitoring the rate of exchange of 18O from 13C18O2 into water. Exchange of 18O was rapid in darkened cell suspensions, but was not inhibited by 500 μM acetazolamide, a membrane‐impermeable inhibitor of CA, indicating that external CA activity was not present in any of these species. In all three species, the rate of exchange was completely inhibited by 500 μM ethoxyzolamide, a membrane‐permeable CA‐inhibitor, showing that an intracellular CA was present. These results demonstrate that the three species are capable of CO2 uptake by active transport for use as a carbon source for photosynthesis.

Biotransformation of aromatic aldehydes by five species of marine microalgae

The biotransformation of a series of aromatic aldehydes such as benzaldehyde, salicy aldehyde, methoxybenzaldehydes and mono- and dichlorobenzaldehydes by five cultures of photosynthetic microalgae are reported. The microalgae, Chlorella minutissima, Nannochloris atomus, Dunaliella parva, Porphyridium purpureum and Isochrysis galbana, reduced most of the aldehydes to the corresponding primary alcohols. Substituted aromatic aldehydes were reduced with varying selectivity depending on the nature and position of the substituent.

Effects of shear on two microalgae species. Contribution of pumps and valves in tangential flow filtration systems

The circulation of microorganisms in tangential flow filtration systems induces perturbations and then the damage of brittle cells. This work is focused on the shearing of two marine microalgae species (Skeletonema costatum and Haslea ostrearia), both largely cultivated in western France (Région des Pays de la Loire). We have studied the effects of the circulation of these cells in pumps and valves. For the pumps, it is shown that shear stress is due to the type of pump, but that mechanical shear can have different effects even if the pumps and the number or frequency of loops are the same. Hence other intrinsic parameters of the pump must be taken into account: rotating velocity (omega), capacity (Cyl = output flow/rotating velocity) or internal leakage (K = inner volume/capacity). In throttling valves, the aim is to correlate the effect of shear to a parameter related to the inner geometry of the valve and to operating conditions. An overall parameter is then evaluated: the pressure drop coefficient Kv which integrates both the type of valve (ball valve or globe valve type) and its opening degree. Kv is derived from the relationship DeltaH = Kvu2/2g. The modelling of the shear effects is now conceivable: basic descriptive data used so far (type of pump, geometry or opening degree of the valve, etc.) being completed and partially substituted by quantitative parameters (rotating velocity, capacity, or internal leakage for the pumps, Kv coefficient for the valves).

Distribution of aliphatic, nonhydrolyzable biopolymers in marine microalgae

The recent discovery of several marine microalgal species which biosynthesize nonhydrolyzable, aliphatic biomacromolecules, termed algaenans, has provided new insights about the nature and origin of the organic matter preserved in marine sediments. This paper reports the examination of 12 new species of marine microalgae from five different classes; the results are discussed together with previous observations on marine algaenans. None of the diatoms and prymnesiophytes and only one of the dinoflagellates examined in the present study produced algaenan, whereas all the eustigmatophytes biosynthesize a very specific algaenan composed of polyether-linked long-chain alkyl units. Many of the chlorophytes investigated, as with their freshwater counterparts, also produce algaenan. The location of the algaenan in the algal cells and the resistance of these materials to chemical and bacterial attack are discussed with respect to their role as a potential sink of organic carbon in aquatic environments.

Occurrence of UVA- and UVB-absorbing compounds in 152 species (206 strains) of marine microalgae

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 189:35-51 (1999) - doi:10.3354/meps189035 Occurrence of UVA- and UVB-absorbing compounds in 152 species (206 strains) of marine microalgae S. W. Jeffrey1,*, H. S. MacTavish1,2,3, W. C. Dunlap4, M. Vesk2, K. Groenewoud1,2 1CSIRO Division of Marine Research, GPO Box 1538, Hobart, Tasmania 7001, Australia 2Electron Microscope Unit, Sydney University, New South Wales 2006, Australia 3Department of Agricultural Science, University of Tasmania, Tasmania 7001, Australia 4Australian Institute of Marine Science, PMB 3, Townsville, Queensland, 4810, Australia *E-mail: s.w.jeffrey@marine.csiro.au ABSTRACT: Marine microalgae (152 species, 206 strains) from 12 classes were examined for the presence of UVA- and UVB-absorbing compounds. Cultures were grown under white fluorescent light without supplementary UVA or UVB radiation and were extracted after harvest in tetrahydrofuran:methanol (20:80, v/v). Ratios of UV absorbance (280 to 390 nm) to chlorophyll a (chl a) (665 nm) obtained by spectrophotometry ranged from 0.18 to 6.75. Three groups of species were distinguished: those with low UV:chl a ratios (0.18 to 0.9, diatoms, green algae, cyanophytes, euglenophytes, eustigmatophytes, rhodophytes, some dinoflagellates, some prymnesiophytes), those with intermediate ratios (0.9 to 1.4, chrysophytes, some prasinophytes, some prymnesiophytes) and those with very high ratios (1.4 to 6.75, surface bloom-forming dinoflagellates, cryptomonads, prymnesiophytes and raphidophytes). UV-absorbing pigments varied across species of the same algal class and strains of the same species. HPLC analysis of extracts of 5 species (1 diatom, 2 bloom-forming raphidophytes and 2 bloom-forming dinoflagellates) showed suites of mycosporine-like amino acids in 4 of them, which included mycosporine-glycine, asterina-330, shinorine, porphyra-334 and palythine. The dinoflagellate Gymnodinium catenatum also contained major quantities of unknown UV-absorbing compounds. KEY WORDS: Ultraviolet radiation · Microalgae · Dinoflagellates · Cryptomonads · Prymnesiophytes · Raphidophytes · Mycosporine-like amino acids · Bloom-forming species · Gymnodinium catenatum Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 189. Publication date: November 26, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.

Comparative study of dissolved inorganic carbon utilization and photosynthetic responses inNannochloris(Chlorophyceae) andNannochloropsis(Eustigmatophyceae) species

Four species of marine microalgae with similar morphology and life cycle, namely Nannochloris atomus Butcher, Nannochloris maculata Butcher, Nannochloropsis gaditana Lubian, and Nannochloropsis oculata (Droop) Hibberd, have been examined with respect to their affinity for different sources of dissolved inorganic carbon. External carbonic anhydrase activity was not found in any of these species, but the cell affinity for dissolved inorganic carbon (DIC) in Nannochloris species was affected by the inhibitor acetazolamide at a concentration of 400 µM. Measurement of photosynthetic rates and CO2compensation points at different pH values showed that the Nannochloris species had a greater capacity for CO2rather than HCO3-utilization. In contrast, the observed rates of photosynthetic oxygen evolution in Nannochloropsis species were greater than could be accounted for by the theoretical rate of CO2supply from the spontaneous dehydration of bicarbonate in the external medium. This indicates that these algae were able to transport bicarbonate across the plasmalemma. Furthermore, the K0.5(DIC) value at acidic pH showed that Nannochloropsis oculata could also use CO2as an exogenous carbon source for photosynthesis. Although the species of marine phytoplankton used in this study possess similar morphological characteristics and life cycle, there exist many differences in the mode of inorganic carbon utilization between these microalgae.Key words: Nannochloris, Nannochloropsis, inorganic carbon utilization, bicarbonate transport, CO2compensation point, photosynthesis.