Microalga Isochrysis Galbana Research Articles

Early osteological development of the fins in the hatchery-reared red porgy,Pagrus pagrus(L. 1758)

Summary The present study was undertaken to establish the normal, healthy features of morphological structures at various developmental stages as achieved under well-defined environmental culture conditions (temperature between 16 and 21°C, salinity 36 ppt, pH around 7.6, and oxygen saturation over 95%) common in aquaculture of the species. The pectoral fin supports began to develop at 2.90 mm total length (TL), followed by those of dorsal fins at 5.5 mm TL, caudal fins at 5.6 mm TL, pelvic fins at 5.9 mm TL and anal fins at 6.0 mm TL. The pelvic fins appeared fully at 7.4 mm TL. Development of dorsal lepidotrichia was first observed at 6.9 mm TL, attaining their final number at 7.6 mm TL. The dorsal spines first appeared at 6.5 mm TL and were complete at 7.4 mm TL. The anal lepidotrichia appeared during the development phase from 6.8 to 8.6 mm TL. At 5.6 mm TL, the upward flexion of the urostyle was initiated. The caudal lepidotrichia formed within the primordial fin at 5.6 mm TL and reached the final count at 7.4 mm TL. The caudal dermatotrichia first appeared at 7.3 mm TL and all forms were observed by 15.5 mm TL. The development pattern of fin supports found in Pagrus pagrus is quite similar to that described for other Sparid species.

Toxicity of Benzalkonium Chloride on Monoalgal Cultures and Natural Assemblages of Marine Phytoplankton

The current widespread use of benzalkonium chloride (BAC) in different cleaning and disinfecting products led us to investigate its potential toxic effect on phytoplankton. To this aim, different physiological variables were monitored to detect toxicity of four ecologically relevant concentrations of BAC (15–200 μg l−1) on batch cultures of the microalgae Isochrysis galbana and Chaetoceros gracilis, and on a coastal phytoplankton assemblage. Fluorescence variables measured by fast repetition rate fluorometry, specifically variable fluorescence (Fv), were the most suitable to be used as endpoint among all the variables recorded (biomass, growth rate, size structure, and species composition). Calculated effective concentrations from Fv data provided evidences of higher sensitivity in the natural assemblage at short exposure times (natural assemblage—EC50 [24 h] = 36.4 μg l−1 vs. monoalgae—EC50 [24 h] > 120 μg l−1). Despite these differences, standard monoalgal laboratory toxicity tests provided comparable estimates of safe concentrations for microalgae in the environment. Assessed EC10 fall within the range of BAC concentrations reported in the literature for different effluents.

Study on biochemical quality of marine microalga Isochrysis galbana Parke through stoichiometry

Study on biochemical quality of marine microalga Isochrysis galbana Parke through stoichiometry

High cell density culture of marine microalga Isochrysis galbana Parke through stoichiometry

High cell density culture of marine microalga Isochrysis galbana Parke through stoichiometry

Effects of iron electrovalence and species on growth of Haematococcus pluvialis and astaxanthin production

The aim of this article is to increase contents of lipid and saccharide of marine microalga Isochrysis galbana Parke. According to stoichiometry, the composition of C, N and P element, the contents of lipid and saccharide in dry cells of I. galbana Parke during stationary phase were screened. By comparison with fundamental medium (Liu, 2007), concentration of NO3–N was lower than 1mmol/L at end time of log phase and at start time of stationary phase, the contents of both lipid and saccharide reached approximately 55% in dry cells of I galbana Parke.

Crescimento populacional de rotíferos Brachionus plicatilis Müller, 1786, alimentados com microalgas e dieta formulada

The present study evaluated the population growth of the Brachionus plicatilis fed with microalgae and formulated diet in two experiments. In experiment 1, each experimental unit was stored with 50 rotifers mL-1, using the microalga Isochrysis galbana in the cellular densities of 50x104 cells mL-1 and 500x104cells mL-1, and formulated diet Culture Selco® Plus (CSP). There were no significant differences in the rotifers daily densities, however the highest final density occurred with rotifers fed with microalga in the density of 50x104 cells mL-1 (268 rotifers mL-1). In experiment 2, the experimental units were stored with 200 rotifers mL-1 and the feeding was based in the microalgae I. galbana and Nannochloris sp., both with the cellular density of 50x104 cells mL-1 and formulated diet. In this experiment, the highest final density (402 rotifers mL-1) was observed when the rotifers were fed with formulated diet. However, there were significant difference (p < 0.05) in the daily population growth of the rotifers. B. plicatilis reach the highest population density and showed  multiple eggs when fed with formulated diet (CSP).

Effect of the test media and toxicity of LAS on the growth of Isochrysis galbana

In this paper, the toxicity of linear alkylbenzene sulfonate (LAS) was evaluated in the marine microalga Isochrysis galbana using data of growth inhibition toxicity tests at 96-h exposure time. Toxicity was examined in standard conditions and by means of the modification of two variables of the test media: (1) the dilution water and (2) the content of nutrients in the test medium. For this purpose, a total of 10 toxicity test were designed: five dilution waters, four natural marine waters and one synthetic seawater; each in two different nutritive conditions, saturated nutrient concentration (SC) by the addition of modified f/2 nutritive medium, and natural nutrient concentration (NC), i.e., without the addition of f/2. At threshold toxicity levels, the dilution waters used in the test and the nutrient concentrations did not affect the toxicity of LAS. At IC50 concentrations, the toxicity of LAS is influenced by both variables: under SC conditions, the toxic effect of LAS diminishes, obtaining in all the tests IC50 > 10 mg/L LAS. Under NC conditions, IC50 concentrations ranging between 3.15 and 9.26 mg/L LAS have been obtained.

Development of a Toxicity Identification Evaluation Protocol Using Chlorophyll-a Fluorescence in a Marine Microalga

Growth inhibition bioassays with the microalga Nitzschia closterium have recently been applied in marine Toxicity Identification Evaluation (TIE) testing. However, the 48-h test duration can result in substantial loss of toxicants over time, which might lead to an underestimation of the sample toxicity. Although shorter-term microalgal bioassays can minimize such losses, there are few bioassays available and none are adapted for marine TIE testing. The acute (5-min) chlorophyll-a fluorescence bioassay is one alternative; however, this bioassay was developed for detecting herbicides in freshwater aquatic systems and its suitability for marine TIE testing was not known. In this study, a chlorophyll-a fluorescence bioassay using the marine microalga Isochrysis galbana was able to detect contaminants other than herbicides at environmentally relevant concentrations and tolerated the physical and chemical manipulations needed for a Phase I TIE. Phase I TIE procedures were successfully developed using this chlorophyll-a fluorescence bioassay and used to identify all classes of contaminants present in a synthetic mixture of known chemical composition. In addition, TIEs with both the acute fluorescence bioassay and the standard growth inhibition bioassay identified the same classes of toxicants in a sample of an unknown complex effluent. Even though the acute chlorophyll-a fluorescence end point was less sensitive than the chronic cell division end point, TIEs with the chlorophyll-a fluorescence bioassay provided a rapid and attractive alternative to longer-duration bioassays.

Does the presence of microalgae influence fish larvae prey capture?

The green water technique has been widely shown to improve fish larvae growth, survival and feed ingestion. Therefore, fish larvae (Sparus aurata L. and Solea senegalensis Kaup) feeding behaviour was studied through gut content analysis, when using different species of microalgae, as the ‘green water’ technique. Six treatments were used: Stain – food green stain; Tetra – microalgae Tetraselmis chuii; Iso – microalgae Isochrysis galbana; Tetra Sup –T. chuii supernatant (obtained from centrifugation); Phyto – a microalgae paste, Nannochloropsis oculata, (Phytobloom®); and C water – clear water, as control. At 9, 16 and 23 days after hatching (DAH) for S. aurata, and 4, 9 and 14 DAH for S. senegalensis, 40 unfed fish larvae were transferred to 3 L experimental tanks, filled with the different ‘green water’ technique. Fish larvae were sampled 2 h after being fed with live prey, anaesthetized and fixed in buffered formaldehyde for posterior gut content determination. Feeding was evaluated by the feeding rate, percentage of larvae with prey items in the digestive tract and feeding intensity, number of prey in each larva digestive tract. Fish larvae feeding ability was influenced by the interaction between light conditions and substances provided by the presence of microalgae during fish larvae development. Sparus aurata was more dependent on microalgae addition than S. senegalensis larvae, which may be related to the type of prey, larval behaviour, ontogeny and physiology. The presence of microalgae influenced the selection of larger prey (Artemia over rotifers) by S. aurata aged 23 DAH.

Effect of Temperature on Growth and Biochemical Composition (Sterols, α-tocopherol, Carotenoids, Fatty Acid Profiles) of the Microalga, Isochrysis galbana

The microalga Isochrysis galbana Parke was grown in 100-l polyethylene bags filled with steril- ized seawater enriched with Wallerstein and Miquel nutrient medium (3:1) at two temperatures (18°C and 26°C), 2.5% salinity, and continuous illumination. Samples of microalgae were exam- ined during the exponential growth, stationary growth, and decay phases (days 18, 35, and 58, respectively). Stigmasterol constituted the main sterol group in all phases in both treatments, except during the exponential growth phase at 18°C. The highest concentration of α-tocopherol was 5.22 mg/100 g DW, reached in the decay phase of algae raised in 18°C. Likewise, the high- est total carotenoid (4.14 mg/g DW) and chlorophyll (2.87 mg/g DW) levels were obtained in algae raised in 18°C, during the exponential phase; the main pigments were chlorophyll a, c1, c2, and fucoxanthin. At 18°C, polyunsaturated fatty acids (PUFA) were the predominant fatty acid group, reaching 37.93% of the total fatty acids in the stationary phase. At 26oC, saturated fatty acids (SAF) were the predominant group of fatty acids. The present study suggests that the nutritional value (gross biochemical composition and fatty acid profile) of I. galbana Parke is, to a large extent, determined by the temperature at which it is grown and the harvest time.

Nonylphenol algal bioaccumulation and its effect through the trophic chain

Nonylphenol is a metabolic intermediate from the microbial transformation of detergents used worldwide. While nonylphenol shows some acute toxicity, it is also able to mimic important hormones resulting in the disruption of several processes by interfering with the signals that control the overall physiology of the organism. The effect of the pollutant nonylphenol (NP) through the trophic chain was studied. Microalgae Isochrysis galbana was able to bioconcentrate NP 6940 times, where 77% of initial NP (100microgl(-1)) is accumulated intracellularly after 1-h incubation. Crustacean Artemia fransiscana showed 25% higher growth when fed with NP-rich algae. However, Artemia metabolized almost all NP ingested and only traces of NP could be found in the organism, eliminating future NP effects. Zebrafish (Brachydanio rerio) were affected by the presence of 171microgg(-1) of NP in the diet, showing higher levels of the hormone vitellogenin and lower levels of cytochrome P450 activity. These results showed that organisms placed in the first level of trophic chain are able to significantly bioconcentrate the pollutant and endocrine disruptor NP. These grassed organisms affect the growth of crustacean. Moreover, the organisms placed on the top of some trophic chains, such as fish, could be affected by the presence of NP in their food, in both the hormone levels and metabolic enzymes. This work shows that the environmental presence of NP should be considered as a risk for the organisms living in an ecosystem.

EFFECT OF MICROALGAL CONCENTRATION AND WATER TEMPERATURE ON THE PHYSIOLOGY OF THE CARIBBEAN SCALLOPS NODIPECTEN NODOSUS

Argopecten nucleus and Nodipecten nodosus are two Caribbean scallops occurring in Colombia, which have recently been selected for artificial culture based on their high commercial value. As part of an effort to develop culture technology for these species, we studied the effects of food concentration and temperature on feeding rates (filtration, ingestion, and absorption), oxygen consumption, ammonium excretion and scope for growth in adults of the two scallop species. We tested the effects of four concentrations of the microalga Isochrysis galbana (10, 20, 40 and 60 cells μL−1) at three water temperatures (20, 25 and 28°C), at a constant salinity of 36‰. The results showed that increases in food concentration induced increases in feeding rate, oxygen consumption and growth potential, but at values of 60 cells μL−1 these variables decreased, indicating saturation of the digestive tract. The excretion rate increased at low food concentrations, particularly at the middle (25°C) and/or at the highest temperature tested (28°C). This suggested utilization of endogenous proteins as a supplementary energy source under these conditions. The increase in temperature had no significant effect on the feeding variables or on the scope for growth of A. nucleus, but raised the N. nodosus ones. All the physiological rates for the two species were similar except for oxygen consumption, which was greater in N. nodosus than in A. nucleus. Using values obtained for the algae concentrations, which produced the greatest growth potential, the optimal value for I. galbana for both the scallops was 40 cells μL−1, whereas the optimal temperature for N. nodosus was 25°C. There was no single optimal temperature for A. nucleus, which functioned equally well at between 20°C and 28°C.

Use of biomass of the marine microalga Isochrysis galbana in the nutrition of goldfish (Carassius auratus) larvae as source of protein and vitamins

The effect of the replacement of fish protein hidrolizate and vitamin premix by freeze-dried biomass of the marine microalga Isochrysis galbana in the feed for goldfish (Carassius auratus) larvae was tested. Larvae (3.4±0.7 mg) were fed with three experimental microparticulated diets that differ from each other in the percentage of replacement of fish protein hidrolizate (25% or 100%) or vitamin premix by I. galbana biomass. The control diet and the diet containing microalgae biomass as a substitute of 25% of fish protein hidrolizate (MP25) presented the highest survival, being almost 100%, with no significant differences between them. Survival in diets in which 100% of fish protein hidrolizate (MP100) or vitamin premix (MV) had been substituted by microalgal biomass was 78% and 66% respectively. Growth, measured as weight, was lower than with the control diet in all treatments in which microalgal biomass was included, with lowest results being obtained with the MP100 diet. Differences between treatments and control were lower when growth was measured as length. The harvesting and processing microalgae biomass is crucial to maintain the nutritive value and could be the cause for the obtained results.

Comparative growth and survival of juvenile hard clams,Mercenaria mercenaria, fed commercially available diets

Hobbyist and researchers often use commercially available phytoplankton concentrates to maintain filter feeding organisms held in their ornamental or experimental tanks. This study investigated the nutritional value of 10 products available commercially for juvenile hard clams, Mercenaria mercenaria. Growth and mortality rates in clams fed these products were compared with those found in clams fed fresh cultures of the microalgae Isochrysis galbana, which is considered an industry standard for supporting growth of juvenile bivalves. Our results show a clear difference in feed nutritional value between non-living and living commercial diets, and among commercial diets advertised as containing live algae. Overall, results showed that juvenile hard clams fed fresh cultures of I. galbana displayed the best growth and lowest mortality rates, followed by those fed the commercial diet DT's Live Marine Phytoplankton. Growth and mortality rates in unfed controls were similar to those found in clams fed commercial non-living algae mixes or diets advertised as containing live algae (Phyto-Feast Live product). Results also showed that the nutritional value of fresh algae (I. galbana) cultures is lost rapidly when cultures are maintained at 4°C, suggesting that algae present in some commercial diets may lose their nutritional value during processing or refrigerated storage. The commercial blend, DT's Live Marine Phytoplankton, seems to represent a good substitute to lab grown algae for clams held in ornamental or experimental aquariums. Zoo Biol 0:1–13, 2006. © 2006 Wiley-Liss, Inc.

Enzymatic hydrolysis of phospholipids from Isochrysis galbana for docosahexaenoic acid enrichment

This paper describes the use of lipases for the production of a lipid fraction rich in docosahexaenoic acid (DHA) using phospholipids from the microalga Isochrysis galbana as raw material. Fatty acid compositions of total lipids and lipid classes of I. galbana were studied. DHA accounted for 13.5% of total fatty acids. However, the DHA content of the phospholipid fraction was 50% and 75% of total DHA was carried by phospholipids, mainly at the sn-2 position. These phospholipids contained neither eicosapentaenoic acid nor arachidonic acid. Selective phospholipid hydrolysis using 12 lipase preparations has been studied in order to produce lipid fractions enriched in DHA. Five lipases showed discrimination between DHA and other fatty acids. A lipid fraction containing 80% of DHA was obtained with two lipases. Even though both preparations were equivalent in terms of DHA enrichment (1.5–1.6), lipase from Rhizopus oryzae gave better results as far as DHA recovery (85%) is concerned. Lipase from Mucor javanicus gave a slightly lower recovery yield (71%) for the same reaction time (3 h).

Histological study of the gonadal development of <i>Ruditapes decussates</i> (L.) (Mollusca: Bivalvia) and its relationship with available food

This article describes the effects of food availability on the sexual maturation of Ruditapes decussates through histological examination of the gonadal tissue. Three food rations were tested: High (H: 1 mg. organic matter. g live weight –1 .day -1 of the microalgae Isochrysis galbana clone T-ISO), intermediate (I: 0.5 mg OM g live weight -1 day -1 ) and nutritionally restricted (R: 0.25 mg OM g live weight -1 day -1 ). The tests were carried out at a constant temperature of 18°C for a period of 70 days for diets H and I, and 120 days for diet R. The results showed that in R. decussatus the energy from ingestion was mainly channelled to reproductive processes, especially when food was restricted. The clams matured sexually under all the conditions tested, both with a somatic growth and with a loss of body mass. The available food was directly related to the rate of the gonadal development and with the total quantity of gonad generated. Equally, food restrictions limited gonadal recovery after spawning episodes. Food quantity also affected the dry weight of soft tissues (DW), which increased with the highest ration (H) and decreased notably with the lowest ration (R). Decreases in DW when food was scarce appeared to be more related to loss of reserve tissue rather than to variations in the quantity of reproductive tissue.

The role of lipids in the gonadal development of the clam Ruditapes decussatus (L.)

The evolution of phospholipids, free fatty acids, triacylglycerols, sterols and sterol and wax esters was studied throughout the process of sexual maturation in Ruditapes decussatus. The clams were fed with three daily food rations of the microalga Isochrysis galbana: R1: 2.5%, R2: 5.0% and R3: 10.0% (percentages correspond to the organic weight of food supplied as a proportion of the live weight of clams). The content of total lipids in the soft tissue increased with sexual maturation. During this process, the females always accumulated a greater quantity of lipids than the males, with triacylglycerols, phospholipids and sterol and wax esters being the components, which mostly determined the sexual differentiation. The size of the differences between sexes was influenced by the quantity of food available. Phospholipids constituted the largest lipid fraction in R. decussatus, representing 57–83% of total lipids. The total quantity of phospholipids was significantly greater in females than in males, although the percentage with respect to total lipids was greater in the males, which showed a low proportion of triacylglycerols. The females always presented a greater total quantity of triacylglycerols than the males, and a greater percentage with respect to total lipids (between 9.98% and 18.8%, as a function of the food ration). The triacylglycerols were absent in the males throughout sexual maturation, when the food quantity was moderate (R1). When the food was more abundant (R2 and R3), the sexually mature males temporarily accumulated triacylglycerols (between 0% and 3.18% of total lipids), although they disappeared in the final phase of sexual maturation. The sterol and wax esters followed the same process as the triacylglycerols, although they were present in lesser proportion (between 4.07% and 6.46% of total lipids in females and between 0% and 5.75% in males), and also disappeared in the final phase of sexual maturation.

Expression of the Isochrysis C18-delta9 polyunsaturated fatty acid specific elongase component alters Arabidopsis glycerolipid profiles.

A cDNA isolated from the prymnesiophyte micro-alga Isochrysis galbana, designated IgASE1, encodes a fatty acid elongating component that is specific for linoleic acid (C18:2n-6) and alpha-linolenic acid (C18:3n-3). Constitutive expression of IgASE1 in Arabidopsis resulted in the accumulation of eicosadienoic acid (EDA; C20:2n-6) and eicosatrienoic acid (ETrA; C20:3n-3) in all tissues examined, with no visible effects on plant morphology. Positional analysis of the various lipid classes indicated that these novel fatty acids were largely excluded from the sn-2 position of chloroplast galactolipids and seed triacylglycerol, whereas they were enriched in the same position in phosphatidylcholine. EDA and ETrA are precursors of arachidonic acid (C20:4n-6), eicosapentaenoic acid (C20:5n-3), and docosahexaenoic acid (C22:6n-3) synthesized via the so-called omega6 Delta8 desaturase and omega3 Delta8 desaturase biosynthetic pathways, respectively. The synthesis of significant quantities of EDA and ETrA in a higher plant is therefore a key step in the production of very long chain polyunsaturated fatty acid in oil-seed species. The results are further discussed in terms of prokaryotic and eukaryotic pathways of lipid synthesis in plants.

Transient initial phase in continuous culture of Isochrysis galbana affinis Tahiti

Starting microalgae continuous culture generally includes a preliminary batch culture to obtain sufficient cell density. It is possible to apply continuous regime from the beginning of the culture (IC mode) rather than to begin by an initial batch (IB mode). It is our purpose to check that both initial modes lead to identical steady-state cell characteristics. The microalga Isochrysis galbana affinis Tahiti was used for this comparative study. With an initial cell density of 5 × 10 5 cell ml –1 and a dilution rate of about 1.0 d –1, both IB and IC modes led to identical cell density once steady-state is reached between 6 and 8 d after inoculation in the two cases. Cell concentration of chlorophyll a and pheopigment a were found to be similar for IB and IC modes at steady-state. Initial culture conditions did not influence saturation irradiance and oxygen consumption rate, which were found to be 650 ± 143 μmol phot m –2 s –1 and 1.54 × 10 –3 ± 10 –5 μmol O 2 ml –1 min –1, respectively. At steady-state, nutrient cell uptakes were ρ N = 83.3 ± 2.0 fmol N cell –1 d –1 for NO 3 – and ρ P = 5.5 ± 0.4 fmol P cell –1 d –1 for H 2PO 4 – and did not exhibit significant differences between IB and IC modes. Under the prevailing experimental conditions, results show that IC mode involved very similar steady-state cell characteristics when compared to IB mode subsequent steady-state. IC mode could be an attractive alternative especially for experimental laboratory studies, as it should lead to higher flexibility in starting continuous cultures.

Iodate reduction by Isochrysis galbana is relatively insensitive to de-activation of nitrate reductase activity—are phytoplankton really responsible for iodate reduction in seawater?

The reduction of iodate to iodide in laboratory cultures of the marine microalga Isochrysis galbana was found to be essentially independent on the presence or absence of nitrate reductase activity. This places serious doubt on the hypothesis that iodate is inadvertently reduced by NR, when it is mistaken for nitrate. NR activity was de-activated by growing the algae with tungsten instead of molybdenum, and supplying ammonium-N. An alternative mechanism is proposed linking iodate to photo-inhibition in phytoplankton. When observed, iodide production was found to be close to linear with time. A preliminary fit of the Michaelis–Menten model to the graph of iodide production versus iodate substrate concentration is promising, yielding V max and K m (with 95% confidence limits) of 62 (±21) nM day −1 and 87 (±80) μM, respectively. Iodide production was only observed when the iodate concentration was higher than that found naturally. This was also found to be the case with cultures of Skelotenema costatum. Further, no significant iodide production was observed from 0.5 μM iodate in cultures of Cyclotella cryptica and Synechococcus sp. At the higher concentrations of iodate and after rationalisation to the prevailing concentrations of chlorophyll a and iodate, iodide production was typically 0.003 nM-I − μg chlorophyll a −1 day −1 μM −1-IO 3 −. At most, these dense cultures were only able to reduce 0.3% of the prevailing iodate, and it is argued that this is too low to explain the 0.2 μM reduction commonly experienced across the temperate continental shelf or within the photic zone of the tropical water column.