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The sea urchin is a very important aquatic economic organism in many countries and has high food value. However, it has recently been heavily fished, and it would be of great importance to the sustainable development of coral reefs to develop large-scale aquaculture of sea urchins. Sea urchins are prone to death during larval development. Therefore, in this study, three kinds of microalgae were used as the initial food for sea urchins to evaluate whether different kinds of microalgae can improve their survival and growth rates. Chaetoceros muelleri (C), Isochrysis galbana tml (I), and Dunaliella salina (D) were fed to A. crassipina at concentrations of 5000, 10,000, 20,000, and 30,000 cell mL−1. A fasted group was used as control (N). The final body length, final body width, final stomach length, rudiment length, survival rate and morphology were measured to evaluate development and growth. The results showed that feeding with C. muelleri resulted in better growth and survival. After 9 days of feeding with C(20,000 cells mL−1), the rudiment length reached 203.33 ± 12.47 µm. The onset of metamorphosis was observed 12 days post-feeding. The survival rate after feeding C was also significantly higher than that after feeding I and D. In summary, when sea urchins are breeding, it is recommended to choose C(20,000 cells mL−1) or C(30,000 cells mL−1) as the initial feed for larvae to increase the growth and survival of sea urchin seedlings.

The microalgae Nannochloropsis oculata and Tahiti clone Isochrysis galbana (t-ISO) were collected from the Mariculture laboratory, Research Centre for Oceanography, BRIN. Both samples were cultivated and harvested by using a centrifuge. The microalgae biomass obtained was analyzed to determine the fatty acids content. The samples were then extracted, followed by an evaporation process using a rotary evaporator. The microalgae extracts were then tested for its antioxidant activity and antibacterial activity. The results showed that the total fatty acid content of N. oculata (89.82%) was slightly higher than t-ISO (84.97%). The antioxidant activity test showed that t-ISO had slightly higher antioxidant activity than N. oculata (2.4 and 3.33 mg/mL, respectively). As for the results of the antibacterial activity test against the four test bacteria, N. oculata had a slightly lower inhibitory power than t-ISO

Isochrysis galbana is a species of marine microalgae that is principally used to feed the larvae and early juveniles of bivalve mollusks (e.g., ark shells, clams, mussels, oysters and scallops). The artificial hatchery stages of most of these larvae are primarily occur during high-temperature seasons, when the water temperature in the breeding pool frequently exceeds 30 °C and even reaches 35 °C, which may change the lipid composition of I. galbana , thus affecting its nutritional value. In this experiment, we investigated changes in the lipid composition of I. galbana Parke at high temperature using ultra-performance liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometry. The results showed that the sulfoquinovosyldiacylglycerol (SQDG), monogalactosyldiacylglycerol (MGDG), diacylglycerylcarboxyhydroxymethylcholine (DGCC) and digalactosyldiacylglycerol (DGDG) contents increased during growth at 20 and 35 °C. Conversely, the lyso-SQDG, lyso-MGDG, lyso-DGDG, lyso-DGCC and triacylglycerol (TAG) contents clearly decreased. Moreover, higher SQDG, MGDG, DGDG and DGCC contents and lower lyso-lipid and TAG contents were observed in I. galbana Parke grown at 35 versus 20 °C. In addition, the content of docosahexaenoic acid (DHA) improved at 20 and 35 °C during growth, and DHA accumulated to greater levels at 35 °C than at 20 °C at the same time points. These results revealed an increase in DHA content as the temperature rose, which indicated that the nutritional value of I. galbana Parke during logarithmic phase improved in the same cultured time with an increasing temperature.

We determined the effects of various light spectra (white, green, blue, and red) on the growth rate, biochemical composition, and fatty acid content of Tisochrysis lutea (Haptophyta, Isochrysidales) maintained in batch cultures. The growth rate peaked with white and blue light, and the lowest rate was observed with green and red light. The chlorophyll a content differed significantly between light spectra and growth phases—higher values were recorded with blue and red light in both growth phases. The proximal composition varied significantly with growth phases and light spectrum. In the exponential growth phase, protein content was significantly greater with blue light and in the stationary phase with green light. The level of carbohydrates in the exponential growth phase was significantly higher for white light, but unchanged in the stationary growth phase between light spectra. The lipid percentages were similar in the exponential phase but differed significantly in the stationary growth phase. The lipid percentages peaked in the stationary growth phase with red and green light. The highest eicosapentaenoic acid (EPA) levels were seen in white light in the exponential growth phase and under green light in the stationary growth phase. Docosahexaenoic acid (DHA) levels were greatest in the exponential growth phase with red light and in the stationary growth phase with green light. Blue light increased the DHA content in both growth phases. We conclude that T. lutea alters its metabolic pathways and experience shifts in growth rate, proximate composition, and fatty acid content, depending on the type of light used.

Microalgae are considered a sustainable source of high-value products with health benefits. Marine algae-derived omega-3 long-chain polyunsaturated fatty acids (LC-PUFA), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are considered dietary elements with effects on mental health, cognition enhancement, and cardiovascular protection. This study investigated the temperature effect on omega-3 LC-PUFA production in eight species of microalgae from various taxonomic groups, with a focus on achieving an optimal balance between omega-3 accumulation and efficient growth performance. Samples were batch-cultivated at four different temperatures, with constant light, and fatty acid methyl esters (FAME) were analyzed by gas chromatography. Several nutritional indices were calculated to assess the potential value of biomass produced for human consumption. Two promising candidates were identified suitable for batch cultivation and large-scale production: Nannochloropsis oculata for EPA and Isochrysis galbana for DHA production, with optimum productivities obtained between 14 and 20 °C, and nutritional indices falling within the range required for nutritional benefit.

The Isochrysidaceae is a family of non-calcifying organisms within the haptophyte order Isochrysidales. Isochrysis galbana , a species widely used as a food source in aquaculture, is the best-known representative of this family that contains three genera but only six described species. We sequenced partial nuclear small subunit (SSU) and large subunit rDNA and mitochondrial cytochrome oxidase 1 genes of 34 isochrysidacean culture strains (including authentic strains when available) and compared molecular phylogenetic inferences with cytological and ultrastructural observations. The isochrysidaceaen culture strain Isochrysis affinis galbana (Tahiti isolate), widely used in aquaculture and commonly known as T-Iso, is clearly genetically distinct from Isochrysis galbana , despite seemingly being morphologically identical. A strain with a similar ultrastructure to that of Isochrysis galbana except for the lack of body scales had sequences that were more similar to but still distinct from those of Isochrysis galbana. Dicrateria inornata , a species that lacks body scales, is classified within the Isochrysidaceae, but the SSU rDNA sequence of the authentic strain of this species matches that of Imantonia rotunda within another haptophye order, the Prymnesiales. D. inornata and Imantonia rotunda have similar ultrastructure except for the respective absence/presence of scales. These results lead us to propose the erection of one new genus ( Tisochrysis gen. nov.) and two new species ( Tisochrysis lutea sp. nov. and Isochrysis nuda sp. nov.). D. inornata is reclassified within the Prymnesiales, and Imantonia rotunda is transferred to this genus ( Dicrateria rotunda comb. nov.).

Microalgal biomass is a sustainable and valuable source of lipids with omega-3 fatty acids. The efficient extraction of lipids from microalgae requires fast and alternative extraction methods, frequently combined with biomass pre-treatment by different procedures. In this work, Pressurized liquid extraction (PLE) was optimized and compared with traditional lipid extraction methods, Folch and Bligh and Dyer, and with a new Ultrasound Assisted Extraction (UAE) method for lipids from microalgae Isochrysis galbana. To further optimize PLE and UAE, enzymatic pre-treatment of microalga Isochrysis galbana was studied with commercial enzymes Viscozyme and Celluclast. No significant differences were found for lipid yields among different extraction techniques used. However, advanced extraction techniques with or without pre-treatment are a green, fast, and toxic solvent free alternative to traditional techniques. Lipid composition of Isochrysis was determined by HPLC-ELSD and included neutral and polar lipids, showing that each fraction comprised different contents in omega-3 polyunsaturated fatty acids (PUFA). The highest polar lipids content was achieved with UAE (50 °C and 15 min) and PLE (100 °C) techniques. Moreover, the highest omega-3 PUFA (33.2%), eicosapentaenoic acid (EPA) (3.3%) and docosahexaenoic acid (DHA) (12.0%) contents were achieved with the advanced technique UAE, showing the optimized method as a practical alternative to produce valuable lipids for food and nutraceutical applications.

Abstract This study assessed the effect of salinity on the development of the mangrove oyster, Crassostrea rhizophorae, during the pediveliger, metamorphosis, and post-larvae stages, with individuals retained on ≥ 345 µm and ≥ 700 µm meshes. The experiment followed a completely randomized design with five salinity treatments (15, 20, 25, 30, and 35) and four replicates, conducted in three phases: (1) pediveliger and metamorphosis (7-day duration); (2) post-larvae retained on a ≥ 345 and < 500 µm mesh (16-day duration); and (3) post-larvae retained on ≥ 700 and < 1,000 µm meshes (21-day duration). Experimental units consisted of a downwelling system using screen-bottomed PVC cylinders. Oysters were fed Isochrysis galbana and Chaetoceros sp., with feed concentrations adjusted for each developmental stage. Yield (percentage of the initial stock retained alive on the final mesh) and survival (total live post-larvae relative to the initial stocked number) were determined by sieving. A salinity of 30 produced the highest yield during the pediveliger and metamorphosis phase (31.94% ± 4.53%), while salinities between 15 and 30 favored survival for post-larvae in the ≥ 345 µm size class. No significant differences in survival or yield were detected during the final post-larval stage. Overall, a salinity of 30 is recommended for the final larval and the post-larval stage for C. rhizophorae. Resumo Este estudo avaliou o efeito da salinidade no desenvolvimento da ostra Crassostrea rhizophorae nas fases de pedivéliger, metamorfose e pós-larvas retidas em malhas ≥ 345 µm e ≥ 700 µm. O experimento foi conduzido em delineamento inteiramente casualizado, com cinco tratamentos (salinidades 15, 20, 25, 30 e 35) e quatro repetições, em três fases: (1) pedivéliger e metamorfose (sete dias), (2) pós-larvas inicialmente retidas em malha ≥ 345 e < 500 µm (16 dias), e (3) pós-larvas inicialmente retidas em malha ≥ 700 e < 1,000 µm (21 dias). Utilizou-se um sistema downwelling com cilindros de PVC e fundo de tela como unidades experimentais. A alimentação consistiu em dieta composta por Isochrysis galbana e Chaetoceros sp., com concentrações ajustadas conforme a fase de desenvolvimento. Os dados de rendimento (taxa de pós-larvas vivas retidas nas malhas finais em cada fase, em relação ao povoamento inicial) e sobrevivência (número total de pós-larvas vivas em relação ao número de animais povoados em cada unidade) foram obtidos por peneiramento. Os dados foram submetidos a análise de variância (ANOVA), Kruskal-Wallis e teste de Tukey. Os resultados indicaram que a salinidade 30 proporcionou maior rendimento na fase pedivéliger e metamorfose (31,94% ± 4,53%), enquanto salinidades entre 15 e 30 favoreceram a sobrevivência na fase de pós-larva ≥ 345 µm. Não foram observadas diferenças significativas na sobrevivência e rendimento das pós-larvas entre os tratamentos na fase final. Conclui-se que a salinidade 30 deve ser usada no final do cultivo larval e na fase de pós-larvas para Crassostrea rhizophorae.

Nanoparticulate titanium dioxide (TiO(2)) is highly photoactive, and its function as a photocatalyst drives much of the application demand for TiO(2). Because TiO(2) generates reactive oxygen species (ROS) when exposed to ultraviolet radiation (UVR), nanoparticulate TiO(2) has been used in antibacterial coatings and wastewater disinfection, and has been investigated as an anti-cancer agent. Oxidative stress mediated by photoactive TiO(2) is the likely mechanism of its toxicity, and experiments demonstrating cytotoxicity of TiO(2) have used exposure to strong artificial sources of ultraviolet radiation (UVR). In vivo tests of TiO(2) toxicity with aquatic organisms have typically shown low toxicity, and results across studies have been variable. No work has demonstrated that photoactivity causes environmental toxicity of TiO(2) under natural levels of UVR. Here we show that relatively low levels of ultraviolet light, consistent with those found in nature, can induce toxicity of TiO(2) nanoparticles to marine phytoplankton, the most important primary producers on Earth. No effect of TiO(2) on phytoplankton was found in treatments where UV light was blocked. Under low intensity UVR, ROS in seawater increased with increasing nano-TiO(2) concentration. These increases may lead to increased overall oxidative stress in seawater contaminated by TiO(2), and cause decreased resiliency of marine ecosystems. Phototoxicity must be considered when evaluating environmental impacts of nanomaterials, many of which are photoactive.

Fucoxanthin is a carotenoid that exerts multiple beneficial effects on human health. However, reports comparing microalgae culture conditions and their effect on growth and fucoxanthin production are still limited . Isochrysis galbana and Phaeodactylum tricornutum cultures in different light (62.0, 25.9, 13.5, or 9.1 μmol photons m -2  s -1 ), mixing conditions (1 vvm aeration or 130 rpm agitation), and media compositions (F/2 and Conway medium) were studied for comparison of cellular growth and fucoxanthin production on F/2 medium. I. galbana showed a better adaptation to tested culture conditions in comparison with P. tricornutum , reaching 2.15 × 10 7  ± 4.07 × 10 6  cells mL -1 and a specific growth rate (μ) of 1.12 ± 0.05 day -1 under aerated conditions and 62.0 μmol photons m -2  s -1 light intensity. Fucoxanthin concentration was about 25 % higher in P. tricornutum cultures under 13.5 μmol photons m -2  s -1 light intensity and aerated conditions, but the highest fucoxanthin total production was higher in I. galbana , where 3.32 mg can be obtained from 1 L batch cultures at the 16th day under these conditions. Moreover, higher cell densities (~32.41 %), fucoxanthin concentration (~42.46 %), and total production (~50.68 %) were observed in I. galbana cultures grown in Conway medium, if compared with cultures grown in F/2 medium. The results show that the best growth conditions did not result in the best fucoxanthin production for either microalgae, implying that there is not a direct relationship between cellular growth and fucoxanthin production. Moreover, the results suggest that I. galbana cultures on Conway medium are strong candidates for fucoxanthin production, where 1.2 to 15 times higher fucoxanthin concentration are observed in comparison to macroalgal sources.