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This study provides the first description of the larval development of the commercially exploited barnacle Megabalanus azoricus. It describes the changes in larval size and shape as well as the general morphology and duration of each larval stage. Embryos were obtained from gravid specimens collected at Sao Miguel Island and reared through six naupliar stages to the cypris stage in laboratory conditions. The planktotrophic nauplii reached the cypris stage after 14 days of hatching in individual cultures at 20 °C under natural illumination and fed with phytoplankton (Chaetoceros gracilis, Isochrysis sp., and Tetraselmis sp.). The nauplius of M. azoricus has a normal size compared with nauplii of other congeneric species, ranging between the 261 μm (nauplius I) and 912 μm (nauplius VI). This work provides the first description of larvae of the genus Megabalanus for the Portuguese oceanic islands and provides comparisons with congeneric species in other parts of the world.

The importance of the dinoflagellate Symbiodinium sp. was studied in the early life stages of the gastropod Strombus gigas. This dinoflagellate was not found in the eggs or the gelatinous mass surrounding the eggs of the mollusk; therefore, Symbiodinium is not inherited directly. To determine whether the planktonic veligers can acquire these algae from the environment, they were exposed to freshly isolated Symbiodinium from adult S. gigas (homologous). The optimal stage for Symbiodinium inoculation was found at 48 h post-hatching. Survival and growth rates of veligers and juveniles were higher when inoculated with freshly isolated Symbiodinium in conjunction with daily feeding of Isochrysis spp. Veligers inoculated with Symbiodinium freshly isolated from three host species elicited distinct responses: (1) veligers did not take up Symbiodinium isolated from the hydrozoan Millepora alcicornis suggesting that there is discrimination on contact prior to ingestion, (2) veligers did take up Symbiodinium isolated from the anemone Bartholomea annulata, but the algae did not persist in the host tissue suggesting that selection against this type took place after ingestion or that the algae did not divide in the host, and (3) veligers did take up Symbiodinium isolated from Pterogorgia anceps where it persisted and was associated with metamorphosis of the larvae. In contrast, the Symbiodinium freshly isolated from S. gigas were not associated with metamorphosis and required an inducer such as the red alga Laurencia poitei. These data present a significant advancement for the establishment of a new approach in the aquaculture of this important but declining Caribbean species.

In this study, the potential of 10 algae species for biodiesel production were evaluated by determining their fatty acid profiles, biodiesel properties besides growth rate, biomass concentration and lipid productivity. Among seven strains with high growth and lipid accumulation properties, excluding Kirchneriella lunaris and Lyngbya kuetzingii, five species Selenastrum capricornutum, Chlorella vulgaris, Scenedesmus obliqnus, Phaeodactylum tricornutum and Isochrysis sphacrica were finally selected for biodiesel production due to their possessing higher lipid productivity and favorable biodiesel properties. The best strain was P. tricornutum, with lipid content of 61.43 ± 0.95%, lipid productivity of 26.75 mgL(-1) d(-1), the favorable fatty acid profiles of C16-C18 (74.50%), C14:0 (11.68%) and C16:1 (22.34%) as well as suitable biodiesel properties of higher cetane number (55.10), lower iodine number (99.2 gI₂/100g) and relatively low cloud point (4.47 °C).

This study was designed to measure responses of four-year-old black-lip pearl oysters (Pinctada margaritifera) to different temperatures and food concentrations and to identify the energy requirements of each sex. Oysters were fed a monospecific microalgal diet of Isochrysis affinis galbana (T-iso). Measurements of oxygen consumption and ingestion rates were carried out at 24 degrees C and 27 degrees C and at two algal (T-iso) concentrations: 5000 and 30 000 cell ml(-1). Glycogen content in adductor muscle, absorption efficiency and scope for growth were also estimated. Females and males responded differently to environmental factors, with food level being the most influential parameter. Oxygen consumption and absorption efficiency were significantly higher in females than in males, but males had significantly higher glycogen content than females. At high food concentration, glycogen content, ingestion rate, oxygen consumption, and scope for growth were significantly higher than at the low food concentration. Only absorption efficiency was significantly higher at the low food concentration. Oxygen consumption was significantly higher at 27 degrees C than at 24 degrees C. These results indicate that females and males have different bioenergetic functioning and that energy demands for reproduction are higher in females.

International audience; 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.).

The overall objective of this research project was to determine if land-based culture of eastern oysters (Crassostrea virginica) is a feasible option using recirculating aquaculture systems with synthetically derived seawater. A twelve week growout study was conducted in a closed-loop recirculating system with zero discharge using synthetically derived seawater. Two species of marine microalgae (Chaetoceros spp. and Isochrysis spp.) were cultured as oyster feed. Oysters were batch fed daily and amounts of algae cells offered to oysters were monitored. Overall, oyster survival remained greater than 99% and growth was steady and averaged 1.3, 1.1, and 0.33 mm per week for length, width, and thickness, respectively. Mean weight increased an average of 0.39 g per week. The means to maintaining suitable water quality was nitrification and supplementation of calcium to maintain ambient levels representative of their natural environments. Data collected is also useful for those who wish to study oysters in controlled environments or for genetic and/or breeding programs.

Nutrition is a major factor governing early development of sea urchins. The morphological development and survival of Tripneustes gratilla larvae, from field-collected urchins, was investigated from two separate feeding trials under different feeding regimes. Microalgae Isochrysis sp., Pavlova lutheri and Chaetoceros muelleri were tested as feed in May 2010 and Tetraselmis suecica, Skeletonema pseudocostatum and C. muelleri were tested in September 2010. Morphometric measurements of post-oral arm (PO), total width, total length, stomach length and mid-body line (MBL) were recorded every second day. In May, larvae fed Pavlova died after 23 days and did not reach competence. Larvae grew significantly better on Chaetoceros and Isochrysis, reaching competence on day 16 and 18 respectively, and had survival rates of 5.12% and 13.8% respectively. In the September trial, larvae fed Tetraselmis died by day 9, whereas larvae fed Skeletonema and Chaetoceros reached competence by day 22. Survival rates for Skeletone...

Four strains of marine microalgae commonly used as live feeds in hatcheries (Isochrysis sp. T.ISO, Tetraselmis suecica, Phaeodactylum tricornutum, Nannochloropsis sp.) were grown in a novel solid-state photobioreactor, the twin-layer system. Microalgae were immobilized by self adhesion to vertically oriented twin-layer modules which consisted of two different types of ultrathin layers, a macroporous source layer (glass fiber nonwoven) through which the culture medium was transported by gravity flow, and a microporous substrate layer (plain printing paper) which carried the algae on both surfaces of the source layer. This simple open cultivation system effectively separated the immobilized microalgae from the bulk of the growth medium and permitted prolonged cultivation of microalgae with average biomass yields of 10–15 g dry weight m−2 growth area after 14–25 days of cultivation. Algal biomass was harvested as fresh weight (with 72–84 % water content) without the need to pre-concentrate algae. No aeration or external CO2 supply was necessary, and due to the microporous substrate layer, no eukaryotic contaminations were observed during the experiment. All experiments were conducted in Germany under greenhouse conditions with natural sunlight. Small-scale growth experiments performed under the same conditions revealed that growth over most of the experimental period (24 days) was linear in all tested algae with growth rates (dry weight per square meter growth area) determined to be 0.6 g m−2 day−1 (Isochrysis), 0.8 g m−2 day−1 (Nannochloropsis), 1.5 g m−2 day−1 (Tetraselmis), and 1.8 g m−2 day−1 (Phaeodactylum). Due to its cost-effective construction and with further optimisation of design and productivity at technical scales, the twin-layer system may provide an attractive alternative to methods traditionally used to cultivate live microalgae.

The effect of three different nutrient depletions (nitrogen, sulphur and magnesium) on the growth and pigment accumulation of the haptophyte Isochrysis aff. galbana (clone T-ISO) has been studied. Pigments were quantified based on RP-UHPLC-PDA-MSn analysis. All nutrient depletions led to reduced maximal biomass concentrations. Besides, all nutrient-depleted cultures accumulated 3-hydroxyechinenone. To our knowledge, this is the first time that 3-hydroxyechinenone has been found in I. aff. galbana T-ISO. Most 3-hydroxyechinenone, as well as the most echinenone and diatoxanthin, were found in the nitrogen-limited culture in which a more severe limitation resulted in higher cellular contents. Similar to accumulation of diatoxanthin, accumulation of 3-hydroxyechinenone and echinenone may be part of a global (stress) response mechanism to oversaturating light conditions.

The need to replace petroleum fuels with alternatives from renewable and more environmentally sustainable sources is of growing importance. Biomass-derived biofuels have gained considerable attention in this regard, however first generation biofuels from edible crops like corn ethanol or soybean biodiesel have generally fallen out of favor. There is thus great interest in the development of methods for the production of liquid fuels from domestic and superior non-edible sources. Here we describe a detailed procedure for the production of a purified biodiesel from the marine microalgae Isochrysis. Additionally, a unique suite of lipids known as polyunsaturated long-chain alkenones are isolated in parallel as potentially valuable coproducts to offset the cost of biodiesel production. Multi-kilogram quantities of Isochrysis are purchased from two commercial sources, one as a wet paste (80% water) that is first dried prior to processing, and the other a dry milled powder (95% dry). Lipids are extracted with hexanes in a Soxhlet apparatus to produce an algal oil ("hexane algal oil") containing both traditional fats (i.e., triglycerides, 46-60% w/w) and alkenones (16-25% w/w). Saponification of the triglycerides in the algal oil allows for separation of the resulting free fatty acids (FFAs) from alkenone-containing neutral lipids. FFAs are then converted to biodiesel (i.e., fatty acid methyl esters, FAMEs) by acid-catalyzed esterification while alkenones are isolated and purified from the neutral lipids by crystallization. We demonstrate that biodiesel from both commercial Isochrysis biomasses have similar but not identical FAME profiles, characterized by elevated polyunsaturated fatty acid contents (approximately 40% w/w). Yields of biodiesel were consistently higher when starting from the Isochrysis wet paste (12% w/w vs. 7% w/w), which can be traced to lower amounts of hexane algal oil obtained from the powdered Isochrysis product.

The need to replace petroleum fuels with alternatives from renewable and more environmentally sustainable sources is of growing importance. Biomass-derived biofuels have gained considerable attention in this regard, however first generation biofuels from edible crops like corn ethanol or soybean biodiesel have generally fallen out of favor. There is thus great interest in the development of methods for the production of liquid fuels from domestic and superior non-edible sources. Here we describe a detailed procedure for the production of a purified biodiesel from the marine microalgae Isochrysis. Additionally, a unique suite of lipids known as polyunsaturated long-chain alkenones are isolated in parallel as potentially valuable coproducts to offset the cost of biodiesel production. Multi-kilogram quantities of Isochrysis are purchased from two commercial sources, one as a wet paste (80% water) that is first dried prior to processing, and the other a dry milled powder (95% dry). Lipids are extracted with hexanes in a Soxhlet apparatus to produce an algal oil ("hexane algal oil") containing both traditional fats (i.e., triglycerides, 46-60% w/w) and alkenones (16-25% w/w). Saponification of the triglycerides in the algal oil allows for separation of the resulting free fatty acids (FFAs) from alkenone-containing neutral lipids. FFAs are then converted to biodiesel (i.e., fatty acid methyl esters, FAMEs) by acid-catalyzed esterification while alkenones are isolated and purified from the neutral lipids by crystallization. We demonstrate that biodiesel from both commercial Isochrysis biomasses have similar but not identical FAME profiles, characterized by elevated polyunsaturated fatty acid contents (approximately 40% w/w). Yields of biodiesel were consistently higher when starting from the Isochrysis wet paste (12% w/w vs. 7% w/w), which can be traced to lower amounts of hexane algal oil obtained from the powdered Isochrysis product.

© 2016. Two microalgal species, Isochrysis galbana and Nannochloropsis oculata, were supplemented to the diet of laying hens, in either non-disrupted or disrupted (by high pressure homogenization) form, to examine the effect of the presence of a cell wall on the omega-3 long chain polyunsaturated fatty acid (n. -. 3 LC-PUFA) enrichment in the egg yolk. Only supplementation of Nannochloropsis led to significant differences in enrichment by supplementation of the two forms, with the highest enrichment obtained with the HPH-disrupted form. This confirms the presence of a rigid cell wall for this species, which reduces the bioaccessibility of the n. -. 3 PUFA. The needed conversion reaction from EPA to DHA on the other hand did not seem to effect the enrichment, since the same n. -. 3 LC-PUFA enrichment was obtained with the supplementation of the DHA source Isochrysis and the EPA source Nannochloropsis, the last in HPH-disrupted form.Next to the microalgal species, fish oil was also supplemented to the diet of the laying hens. Fish oil resulted in a higher enrichment in comparison with the microalgal species, either non-disrupted or HPH-disrupted. This might suggest a difference in bioaccessibility of the n. -. 3 PUFA when added as oil or biomass. publisher: Elsevier articletitle: The cell wall of autotrophic microalgae influences the enrichment of long chain omega-3 fatty acids in the egg journaltitle: Algal Research articlelink: http://dx.doi.org/10.1016/j.algal.2016.03.015 content_type: article copyright: © 2016 Published by Elsevier B.V. ispartof: Algal Research vol:16 pages:209-215 status: published

Filter-feeding bivalves play an important ecological role in aquatic systems through benthic–pelagic coupling. However, the mechanisms by which invasive mussels influence the food uptake by local consumers are little known. We tested the interactive effects of the invasive mussel Arcuatula senhousia and the native clam Ruditapes decussatus on the uptake of 13C-enriched microalgae, Isochrysis sp., by two polychaetes, the surface deposit feeder Cirriformia tentaculata and the sub-surface deposit feeder Phylo foetida. Polychaetes were exposed to two different densities of A. senhousia and R. decussatus used alone or together. In each treatment, the 13C-concentration throughout the sediment horizon (0–0.5, 0.5–2.5 and 2.5–5 cm) was also quantified. Results showed that, irrespective of bivalve densities, the 13C-uptake by C. tentaculata was lower in the presence of the two bivalves together than in the presence of one bivalve species (either A. senhousia or R. decussatus). This was consistent with decreased 13C-concentrations in the 0–0.5 cm sediment layer in the treatment with the two bivalves together. Contrary to C. tentaculata, no changes were observed among treatments in the 13C-uptake by P. foetida. This possibly reflected a limited 13C-enrichment of the lower sediment layers. Our main findings are: (1) A. senhousia reduces the 13C-uptake by R. decussatus, and (2) A. senhousia reduces the availability of phytoplankton-derived C for deposit feeders by impairing the feeding, incorporation and bio-deposition of R. decussatus. We conclude that the interaction of A. senhousia with native bivalves needs to be taken into consideration in future food web studies.

The surf Spisula solida and the striped venus Chamelea gallina clams support important fisheries in Europe. These fisheries have been affected by inter-annual fluctuations in stock abundance and recruitment failures. Aquaculture could contribute to address these problems through the production of larvae or juveniles for stock-enhancement programmes. In the present study, the prerequisites to produce these species in hatchery were established. Of the different methods used to obtain gametes (thermal stimulation, scarification and flow through), C. gallina spawned in the flow through only. By its turn, the best method for obtaining gametes for S. solida was stripping. Higher survivals of D-larvae were found at 15 and 17 degrees C. The greatest larval survival and growth rates were obtained from larvae fed Isochrysis aff. galbana (T-iso). First C. gallina and S. solida pediveliger larvae were found at day 8 and day 26 respectively. The presence of metamorphosed larvae found even in the unfed treatment for C. gallina and for S. solida is an advantage for aquaculture production. After metamorphosis, the S. solida juveniles' survival was quite low, whereas there was no mortality for C. gallina juveniles reared without substrate regardless the diet provided. Juveniles fed the binary diet (Chaetoceros calcitrans - C. cal + T.iso) and the monodiet T-iso showed relatively higher growth in shell length and weight than C. cal. The hatchery production of these two species was possible, however the results of this study showed that C. gallina can be more attractive for aquaculture than S. solida.

The effect of egg density on embryonic development and larval quality as well as the lipid and fatty acid contents (eicosapentaenoic acid, EPA; docosahexaenoic acid, DHA) of cultured microalgae fed to Perna perna larvae was studied under controlled conditions to provide information needed for development of an experimental hatchery. Embryonic development followed the common sequence exhibited by other bivalves. d-larva stage was attained 40–44 h post-fertilisation at 21 ± 1 °C. The umbo-stage was reached in 11 days, and pediveliger larvae were observed 26 days post-fertilisation. Low egg density (range 20–100 eggs cm−2) produced high proportions of normal d-larvae. Larval development showed two growth phases: 1st—the mixotrophic stage and 2nd—the exotrophic stage where the composition of diets had significant effects on larval growth with higher rates in larvae fed with the mixed microalgae (Isochrysis galbana + Chaetoceros calcitrans, I. galbana + Phaeodactylum tricornutum and I. galbana + Skeletonema costatum) in comparison with the monospecific diet (I. galbana). Fatty acid analysis showed that larval growth and survival were strongly influenced by proportions of dietary DHA and EPA. These results indicate that DHA and EPA are the key factors in determining larval performance, considerably more than the total amount of other fatty acids.

This study compared the efficacy of four products that are commonly used in hatchery for nutritional enhancement of rotifer Brachionus plicatilis as the starter food for yellowtail kingfish Seriola lalandi larvae. This experiment consisted of one fresh algae and three enrichment products: (1) Fresh algae were a mixture of Nannochloropsis and Isochrysis at 2:1 on a cell concentration basis; (2) S.presso, (Selco S.presso ® , INVE Aquaculture); (3) Algamac 3050 ® (Aquafauna, USA); (4) Nutrokol ® (NutraKol, Australia). Survival rates of the fish fed rotifers enriched with fresh microalgae (40.69%) and S.presso (31.21%) were higher than those fed Algamac 3050 (10.31%). On 3 day post hatch (DPH), fish feeding incidence in the fresh algae treatment was significantly higher than that in other treatments. On 6 DPH, fish showed the lowest feeding incidence in the Algamac 3050 treatment. The methods of enrichment did not affect total lipid levels in either rotifer or fish larvae, but Algamac 3050 enrichment achieved the highest DHA/EPA ratio and lowest EPA/ARA ratio in both rotifers and fish larvae. This study indicates that fresh algae can be replaced by S.presso, but Algamac 3050 is not as good as other formula for rotifer enrichment in rearing yellowtail kingfish larvae in this system.

Microalga, Isochrysis galbana, biomass was entrapped into alginate gel by liquid curing method in the presence of Ca(II) ions. The biosorption of chromium(III) by the entrapped live algal biomass was studied in a batch system. The effect of initial cadmium concentration, pH, temperature and liquid and solid ratio on Cr(III) removal was investigated. The maximum experimental biosorption capacities for entrapped live algal biomass were found to be 335.27 mg Cr(III) g−1 of dry algal biomass. The kinetics of chromium biosorption was slow; approximately 75 % of biosorption took place in 2 h. The percent adsorption increased with increase in pH; pH 5 of the solution was found to favor adsorption very strongly. The equilibrium biosorption data were evaluated by Langmuir and Freundlich isotherm models, and was best described by Langmuir and Freundlich isotherms. The biosorbent was characterized and evaluated, the functional groups –OH, –COOH and C=O were involved in the biosorption process. Since binding capacity was relatively high for immobilized live algal biomass, those algal forms are to be considered as suitable biosorbent for the removal of chromium in wastewater treatment.

Even though the microalgal species of Isochrysis and Pavlova are widely used as live food in bivalve hatcheries, they are difficult to culture in mass during the summer season. Therefore, the present study was conducted to determine the optimum species or strains of Isochrysis and Pavlova to produce good growth and high contents of fatty acids at temperatures over . Four species of Isochrysis (I. galbana KMMCC12, I. galbana KMMCC214, I. aff. galbana, and Isochrysis sp.) and four of Pavlova (P. lutheri, P. gyrans, P. viridis, and Pavlova sp.) were cultured at , , and , and then analyzed for specific growth rate and fatty acid composition. Microalgae were cultured in f/2 medium at 23 psu and continuous light of photons . For the I. galbana, growth rates were highest at and decreased at to the level observed at . I. galbana (KMMCC12) and Isochrysis sp. cultured at and , respectively, exhibited the highest growth rates of all Isochrysis species. In terms of fatty acids, I. galbana (KMMCC12) contained higher contents of PUFA and n-3 HUFA at than did Isochrysis sp. For species of Pavlova, growth rates of P. gyrans and P. viridis at and , respectively, were higher than those of the other Pavlova species. In particular, P. viridis grew as well at as it did at . However, P. lutheri and Pavlova sp. did not grow at . In terms of fatty acids, P. viridis cultured at also exhibited higher contents of PUFA and n-3 HUFA, as compared to P. gyrans. Based on these results, we suggest that I. galbana (KMMCC12) and P. viridis are suitable species for mass culture during the high temperature season.

Fucoxanthin, a main marine carotenoid, in five species of fucoxanthin-containing microalgae, was quantified by high-performance liquid chromatography. Among the studied species, Isochrysis aff. galbana contained the highest amount of fucoxanthin (18.23 mg/g dried sample). This microalga showed good fucoxanthin extraction efficiency under the tested solvents (methanol, ethanol, acetone, and ethyl acetate), with the exception of n-hexane. In addition, most fucoxanthin (∼95%) could be extracted by a single extraction in ethanol within 5 min, and only 15% degradation of fucoxanthin was detected during ethanol extraction for 24 h. The two-phase solvent system of n-hexaneethanol-water with a volume ratio of 10:9:1 was determined to be the best system for the separation of fucoxanthin and lipids from extracts of I. aff. galbana. Under these conditions, fucoxanthin was fractionated in the hydroalcohol phase apart from the hexane phase containing lipids. These results imply that I. aff. galbana can be a commercial source for the spontaneous production of valuable fucoxanthins and lipids.

The goal of this study was to investigate the time response of two major carbon (C) reserves, respectively neutral lipids (NL) and total carbohydrate (TC), in the Haptophyte Isochrysis sp. growing in nitrogen (N)-sufficient or N-starved conditions and under light:dark (L:D) cycles. Experiments were carried out in a cyclostat culture system that allowed the following of the dynamics of the main cell compounds at both hourly and daily time scales. Under N-sufficient conditions, the L:D cycles cause the population to be synchronized, with most of the cells dividing at the beginning of the dark period. The C-specific growth rate was maximal around midday and negative during the dark period due to respiration processes. NL and TC both accumulated during the day and consumed during the night. We showed that NL and TC are highly dynamic compounds, as more than three quarters of NL and TC accumulated during the light period were consumed during the dark period. In contrast to NL, phospholipid and glycolipid to C ratios remained quite stable during the light/dark cycles. The major effect of N starvation on the NL and TC dynamics was to uncouple their diel variations from the L:D cycle, in two different ways depending on their respective role during short-term acclimation. Whereas the TC per cell ratio increased rapidly to reach a stable value in response to N starvation, NL per cell continued to oscillate, but with a pattern out of phase with the L:D cycle.

Microalgae concentrates (paste) can be used as an alternative feed to replace live microalgae for aquaculture due to its nutritional value and convenience. However, the clumping of cells and negative buoyancy of algae concentrate can affect bivalve culture as bivalves only capture particles in suspension and ingest a certain size range of particles. This study investigated the effect of shaking and blending treatments on the preparation of food suspensions prepared from algae concentrates (Isochrysis and Pavlova). The results indicated that the higher the shaking time (5, 10, and 15 times) or blending time (10, 30, and 60 seconds), the smaller was the diameter of the resulting algae particles. Moreover, the greater the volume of algae concentrate used in preparation, the larger the diameter of algae particles produced. Shaking may be the best option because it is cheaper and simpler. However, all the treatments provided a suitable particle size range for ingestion by bivalves.

This study tested the diet enrichment with fatty acid EPA and DHA during the broodstock conditioning of scallops Nodipecten nodosus in hatchery. For this, before the conditioning the animals were induced to spawning and then were placed in tanks for maturation of 30 days, and subjected to five treatments: (1) Cm100%, (2) Cm + DHA, (3) T-Iso100%, (4) T-Iso + EPA e (5) Mix (mix of the microalgae Isochrysis sp., Chaetoceros muelleri and Skeletonema sp. , in the rate 50:25:25, respectively). After the conditioning, the animals were induced to spawning. The sexual stage by histology, spawning, larviculture and settlement was evaluated. The treatment T-Iso + EPA in broodstock showed 100% of the animals mature, stage 2B (advanced pre-spawning), higher yield in larvae D, pediveliger and spat. These results indicate that broodstock feeding with T-Iso + EPA provides a positive effect on the maturation, as well as a higher larvae and spat survival in hatchery.

We investigated the photoresponses of diadinoxanthin (DD) and diatoxanthin (DT) using Isochrysis gal- bana cultures that had been acclimated to four different levels of photon flux density (PFD). DD can play a role as a photosynthetic light-harvesting pigment, whereas DT can play a role as a photoprotective pigment. The PFD ranged from limited light conditions (LL) to saturated light conditions (SL) for growth. The photoresponses of these pig- ments during light-dark transitions at each acclimation PFD were consistent. The photoresponses of these xantho- phyll pigments, as normalized to either cell density or chlorophyll a (Chl a) concentration, to light-dark transitions varied with acclimation PFD. The stoichiometric variations between the DD or DT : Chl a ratio observed at the two higher acclimation PFDs suggested that these xanthophyll dynamics are controlled by xanthophyll cycling processes in addition to de novo processes and interconversion between DD and fucoxnathin under SL conditions. Significant linear relationships were observed between the levels of DD and/or DT normalized to either the cell density or Chl a concentration. Based on the cellular pigment content and the xanthophyll : Chl a ratio, the slopes of the linear rela- tionships normalized to either the cell density or Chl a concentration were significantly related to the acclimation PFD linearly and sigmoidally, respectively. Similarly, the acclimation PFD at the interaction of the sigmoidal change and the transition point from the LL to SL condition suggests that these xanthophyll pigment dynamics can be char- acterized by acclimation to the light conditions. An examination of the slope may provide information leading to a better understanding of photoacclimation in the algal photosynthetic apparatus.

Algal allelopathy is an ecological or physiological phenomenon that has focused attention on the interactions among algae and the production of algal toxins.A species of marine bloom-forming microalga: Amphidinium carterae was selected in the present study to estimate its potentially allelopathic effects on other species of microalgae.The cell-free filtrates of A.carterae in two growth phases: exponential grwoth phase(abbreviated as growth phase Ⅰ) and stationary growth phase(abbreviated as growth phase Ⅱ) were prepared,and its inhibitory effects on growth of other species of marine microalgae were studied under stable environmental conditions(temperature,light and illuminating periodicity,etc.).The cell-free culture filtrates were prepared firstly when A.carterae were cultured phaseⅠand phaseⅡ,which was about the the growth 7th and 17th respectively,and enriched with f/2 medium.The above prepared culture filtrates were used to culture 4 species of marine microalgae: Skeletonema costatum、Prorocentrum micans、Scrippsiella trochoidea and Isochrysis golbana.Moreover,the crude extractions in the cell-free filtrate of A.carterae of growth phaseⅡ were extracted by GC/MS,and the major components were analyzed.Results showed that: in the enriched cell-free filtrates,S.costatum were obviously inhibited in either filtrates of phase I(F=15.18475,P=0.002980.05) or phase Ⅱ(F=6.24559,P=0.031490.05) as compared to that in the control which in f/2 enriched medium,but the cell numbers of S.trochoidea were only about 79.3% and 68.9% in filtrates prepared from phaseⅠand phaseⅡ as compared to the control by the end of experiment.As to P.micans,its growth was obviously suppressed(F=4.84438,P=0.049250.05) in the filtrate prepared from phaseⅡduring the last 3 days.Little inhibition was observed in I.golbana in either filtrates prepared from either phases(P0.05).Cell-free filtrate cultures experiment of A.carterae is one of the basic approaches on allelopathy research.Results in the present study suggested that A.carterae secreted or released some substances into the culture medium,which inhibited the co-cultured S.costatum and P.micans,and these inhibitory effects could not caused by light,nutrients or cell contact to gain a competitive advantage.Many algae could release allelochemicals into the environment which may alter phytoplankton growth to enhance its predominance.Besides,growth of these two species was more inhibited in enriched cell-free filtrate prespred from growth phaseⅡ than that from phaseⅠ.It also proved that the allelochemical effects on algae were species-specific because growth of S.costatum and P.micans was inhibited,but exerted little effects on S.trochoidea and I.golbana.Another experiment was performed to further prove the allelopathic effect of A.carterae.The crude extractions from cell-free filtrates of A.carterae at different concentrations were added into S.costatum and P.micans culture media,found that cells dissolved in higher concentration after many hours.It is noted that the crude extractions had the function of dissolving some algal cells.Then the crude extractions were analyzed by GC/MS.Four components in the crude exactions were suspected to have the allelopathic effects,they were Butylated Hydroxytoluene,Butyl citrate,Benzene,1-Chlorodifluoromethoxy-4-nitro-,and Benzyl butyl phthalate,among with Butylated Hydroxytoluene(BHT) was reported with oxidative characteristic and was used as an antioxidant additive.Results in the present study brought light on the hypothesis that A.carterae could realese allelochemical(s);however,deep research should carry out to explain the possible inhibiting mechanism.

The biomass, proximal composition and fatty acid profile of Isochrysis sp., Chaetoceros muelleri and their mixture, grown under greenhouse conditions, were evaluated. The nutritional value of both species supplied as the monoalgal (Chaetoceros muelleri: Diet I, and Isochrysis sp. Diet II) and mixed diet (Diet III) for larval Litopenaeus vannamei was also assessed on the basis of the development and biochemical composition of the larvae. The highest protein levels were obtained in Diets I and II (40% and 35%, respectively). No significant differences in larval survival were found among the diets; however, larvae fed on Diet II had the lowest mean larval length.

The effect of algal species on the life history of the euryhaline cladoceran, Daphniopsis australis was investigated under laboratory conditions. Three algal species, Tetraselmis suecica (T), Nannochloropsis oculata (N) and Isochrysis tahitian (I) were used to form three mono-alga species and four multi-algae species (T × N, I × N, I × T and I × T × N) to feed D. australis . The type of algal species significantly affected the life history of D. australis at both individual and population levels. The mono-alga T. suecica enhanced animal longevity and reproductive output but hampered animal body growth. In contrast, the mono-alga N. oculata and I. tahitian resulted in the highest growth rate of D. australis while the multi-algae I × N reduced the age at first reproduction with a possible cause of high carbon contents in the N. oculata and I. tahitian diets. The mono-alga I. tahitian led to the shortest longevity and poorest reproduction output. Egg development was the fastest when animals fed on mono-algal species but was delayed by feeding animals on multi-algal species. The animals fed on the mono-algal species T. suecica showed the highest net reproduction ( Ro ) and the longest generation time ( GT ) while those fed on the mono-algal diet I. tahitian exhibited the lowest Ro and the shortest GT . The intrinsic growth rate was the highest when the animals fed either on the mono-alga T. suecica or on the multi-algae I × N. This study indicates that species composition of algae in the diet can affect development, growth and reproduction of D. australis and thereby influence the population dynamic of cladocerans living in heterogeneous food environments.

This study assessed the nutritional value of four species of microalgae for larval sandfish, Holothuria scabra (Echinodermata: Holothuroidea). Two-day-old larvae were fed either a single diatom (Chaetoceros muelleri, Chaetoceros calcitrans), flagellate (Isochrysis aff. galbana (T-ISO), Pavlova salina), or a ternary microalgal diet (TMD) comprised of 40% C. muelleri, 40% T-ISO, and 20% P. salina for 12 d. On Days 4, 6, and 8 length of larvae fed either C. muelleri, C. calcitrans, or the TMD was significantly greater than in T-ISO and P. salina fed larvae as well as the unfed control larvae. T-ISO fed larvae had a significantly greater length compared to unfed larvae on Days 4, 6, and 8; however, larvae fed P. salina had a significantly greater length compared to unfed larvae on Days 6 and 8 only. Survival of larvae fed either C. muelleri or the TMD was significantly better than the flagellate fed and unfed larvae on Days 4, 8, and 12. There was no significant difference between survival of unfed larvae and larvae fed either T-ISO or P. salina during the 12-d larval culture period. On Day 12, larvae fed either a diatom or the TMD developed in excess of 84% competent doliolariae. Larvae fed C. muelleri had a significantly higher percentage competent doliolariae than larvae from all other treatments except the TMD. Neither larvae fed either T-ISO or P. salina nor unfed larvae developed any competent doliolariae. In conclusion, this study showed C. muelleri to be the most effective of the four microalgae tested as a single microalgal diet for larval H. scabra and, as such, C. muelleri will be used as a reference diet in future studies.

As an alternative biomass for producing biofuel, microalgae have many advantages over land biomass. For example, they are not a food source, they are fast-growing and have a high oil content, and they can reduce CO2. However, the high costs of cultivation and harvesting using existing technology make microalgal-based biofuels uncompetitive with fossil fuels. This study investigates the feasibility of producing high-value microalgal pigments, including chlorophyll and carotenoid for apportioning the high cost of cultivation and harvest. Five microalgae were tested to determine their pigment and lipid production in a feed-batch bioreactor under light conditions of 167 μmol photon/(m2 s) for 12 h daily. Among them, Dunaliella primolecta and Isochrysis aff. galbana achieved the highest chlorophyll yields of 5.3% and 5.6%, respectively, with the optimal carotenoid yields of 2.6% and 2.0%, and lipids yields of 23% and 24%, respectively. The feasibility of simultaneously extracting both lipids and pigments was investigated. Two solvents, methanol and hexane, were used in the extraction of pigments and lipids. The extraction yields of pigments and lipids using methanol and hexane reached 98% and 90%, respectively. Therefore, we expect that the simultaneous production and extraction of high-value pigments accompanied by the lipids can potentially offset the high cultivation and harvesting costs, and may make microalgal biomass economically competitive for biofuel production.

Three Isochrysis galbana strains, one I. galbana “substrain”, and one Nannochloropsis sp. strain were grown in nutrient replete conditions at 15, 20, 25, and 30 °C. The interactive effect of temperature and isolate on growth rate, cell volume, production, dry weight, protein content, carbohydrate content, and total lipid content was examined. Nannochloropsis sp., growth rate had no relation with temperature; all I. galbana isolates increased linearly with temperature, with no significant differences. Cell volume and dry weight decreased linearly with temperature, with significant isolate and species differences. Biovolume-production did not vary significantly with temperature, but significant isolate and species differences occurred. Although significant temperature isolate interactions existed, no consistent trends in the change of protein, carbohydrate, and lipid with temperature occurred. We indicate a need to consider temperature induced affects in application using microalgae isolates, at various taxonomic levels, as some intraspecific differences were as great as interspecific differences.

Filtration rate and ingestion rate of different stages of Paphia malabarica larvae (D-shape, (80 μm), Umbo (120 μm) and veliger (180 μm)) were determined in relation to feeding on various micro algae. The micro algae tested were Nannochloropsis salina, Isochrysis aff. galbana, Dicrateria inornata, Tetraselmis gracilis and Chaetoceros calcitrans at 5 or 10 × 103 cells mL−1. Both filtration and ingestion rate of micro algae tested were increased with increasing larval size; however, at all larval stages, C. calcitrans resulted in lower filtration and ingestion rate. Of the algal diets tested, P. malabarica larvae showed greatest filtration rate and ingestion rate with N. salina. Maximum filtration rate for N. salina was 15.7, 26.3 and 33.9 μL h−1 and highest ingest rate was 15, 92 and 177 cells larva−1 h−1 in D shape larvae, umbo and pediveliger, respectively. Filtration rate and ingestion rate of N. salina were always higher than those other algal species tested because of its small cell size (2 μm).

This paper deals with the application of electrolysis technology for the selective control of marine algal species. The sensitivity of different marine algal species to electrolysis may be different due to their size and structural differences. Electrolysis experiments were conducted using four algal species, namely Chlorella spp., Chaetoceros spp., Isochrysis spp. and Tetraselmis spp. Batch and continuous runs were conducted from 0-7 minutes and 0-80 minutes, respectively. Drastic depletion of algal cell number was not observed during batch electrolysis. However, fluorescein diacetate and propidium iodide staining showed significant algal mortality. Different sensitivities were also observed for similar electrolysis conditions. Continuous electrolysis data revealed almost no survival for Chlorella spp. at 80 minute electrolysis time while survival for Isochrysis spp. was around 60% at similar conditions. Results indicated that the green algae Chlorella spp. is the most sensitive while the brown algae Isochrysis spp. is the most resistant among the four species studied. More importantly, this confirmed that the beneficial marine algae Isochrysis spp. can be allowed to dominate by selectively limiting the growth of three other algal species tested in this work through electrolysis treatment. DOI: 10.4038/sljas.v11i0.2221 Sri Lanka J. Aquat. Sci. 11 (2006): 27-42

This study analyzed the effect of water quality, different diets, and water temperature regimes in the conditioning and maturation of the Pacific oyster Crassostrea gigas. A recirculating aquaculture system prototype was used in this experiment and 2 different trials were performed. During the first trial, the effects of 3 different diets using different preserved concentrates of microalgae held at 20°C were tested: D1 (fed with Tetraselmis 3600), D2 (fed with Isochrysis 1800), and D3 (fed with a 50:50 mix of Tetraselmis and Isochrysis). During the second trial, 3 different temperatures regimes—T1, 16–24°C; T2, 20°C; and T3, 24°C (fed with preserved concentrates of microalgae at a 50:50 Tetraselmis and Isochrysis food ratio)—were evaluated. For each one of these treatments, 43 organisms were used and every treatment was done in triplicate. Seven samplings were completed in 72 days. During each sampling period, 9 oysters from each treatment were collected, and a gonad sample was obtained for histo...

The diatom Chaetoceros calcitrans forma pumilum is an important dietary component for cultured Greenshell™ mussel larvae, Perna canaliculus. However concerns surrounding potentially deleterious side effects have motivated a series of experimental trials to optimise the safe usage of this alga. Bioassays involved raising veliger larvae in the purpose-built Cawthron Ultra-Density Larval rearing (CUDL) system; an array of 2.5-L tanks were stocked with 2-day-old veligers (200 larvae mL−1) supplied with inflowing water dosed with sufficient microalgae to maintain a fixed concentration of cells, after compensating for ingestion. The nutritional role of C. ‘calcitrans’ was examined by adjusting its cellular fraction in the feed environment. Diets of 0, 5, 66, 95 and 100% C. ‘calcitrans’ were each offered to six replicate rearing tanks, using Isochrysis aff. galbana (T-Iso clone) to maintain a total of 40 cells μL−1 in the larval cultures. The 66% C. ‘calcitrans’ diet was also offered at 3, 20, 60 and 120 cells µL−1 (n = 6). Higher C. ‘calcitrans’ fractions sustained faster growth, with 95% and 100% treatments producing 23-day-old pediveligers of 240 ± 15 μm and 228 ± 5 μm mean shell length, respectively; compared to 212 ± 7 μm in the 66% treatment (40 cells μL−1). However, high C. ‘calcitrans’ treatments were more volatile, had higher mortality and greater predisposition towards population crashes. Similarly, reduced survival was observed in the high feed treatment of 120 cells µL−1, reflected in a final pediveliger yield of 29 ± 6%, compared to 47 ± 3% at 60 cells µL−1 and 36 ± 7% at 40 cells µL−1. The 5% C. ‘calcitrans’ and 20 cells µL−1 treatments showed signs of nutrient limitation, while larvae fed 0% C. ‘calcitrans’ or a total of 3 cells µL−1 starved, failing to reach metamorphosis. A standard diet consisting of 66% C. ‘calcitrans’ and 34% I. aff. galbana maintained at 40 cells μL−1 was used to test the hypothesis that culture age increased deleterious side effects associated with feeding C. ‘calcitrans’. The final stage of batch culture, using 20-L nylon carboys inoculated with 1010 C. ‘calcitrans’ cells was allowed to age for 2, 3, 4, 5 or 6 days before being fed to larvae. After 21 days eating 2-day-old C. ‘calcitrans’ larvae reached a mean shell length of 236 μm, were eating 35,000 cells larva−1 day−1, and had a survival rate of 59 ± 3%; in contrast, larvae eating 6-day-old cells only reached 214 µm, eating 17,000 cells larva−1 day−1, with an overall survival of 46 ± 7%. While C. ‘calcitrans’ is valuable in the larval culture of P. canaliculus and many other bivalves, appropriate feeding protocols are needed when using this diatom.

To determine variability of marine microalgal lipids during cell growth and respiration, and within intracellular structures, we conducted two series of experiments: (1) batch culturing Isochrysis sp., Gymnodinium sp., Platymonas subcordiforus , Heterosigma akashiwo Hada, and Skeletonema costatum with lipid analysis for cell samples collected in exponential growth and stationary phase respectively; and (2) batch culturing Isochrysis sp. and Gymnodinium sp. from exponential growth to stationary phase and followed by dark incubation with progressive lipid analysis. Moreover, membrane and intracellular storage fatty acids were separated using Si-gel chromatography from representative samples of each species in the second experiment (respectively in exponential growth, stationary phase, and dark respiration). Results from the first experiment showed that no matter how differently microalgae grew, their lipid yields were 4–38 × higher in stationary phase than in exponential growth phase. Progressive lipid analysis in the second experiment indicated that total fatty acid (FA) yields in two microalgal cultures continuously increased throughout exponential and stationary phases but total neutral lipid (NL) yields slowed or stopped to increases in stationary phase. During dark incubations, total FA yields decreased steadily in both Isochrysis (with constant cell density) and Gymnodinium (with declining cell density) cultures but total NL yields decreased only in Gymnodinium culture. Lipid compositions and proportions of membrane vs. intracellular fatty acids varied differently with growth phases and respiration in two cultures. This study suggests that the effect of cell growth phase on cellular lipid yield and composition is species-dependent and is likely related to the capacity of cells to synthesize membrane vs. intracellular storage lipids.

The haptophyte Isochrysis aff. galbana (T-iso) was cultured during 2 consecutive years (from spring to autumn) in outdoor horizontal tubular photobioreactors (PBRs) that had a size compatible with that recommended for hatchery service. Around one-third of the cultures carried out in these PBRs showed immediate growth after inoculation up to a maximum biomass. In all other instances a lag phase or a culture collapse were found. In the cultures that showed productivity, average growth rate, μ (d−1), productivity (g L−1 d−1) and photosynthetic efficiency, PE (%), were 0.39 ± 0.085 d−1, 0.075 ± 0.038 g L−1 d−1 and 2.51 ± 0.85%, respectively. These values were low compared to values for cultures routinely incubated indoors, which were used as inocula for the outdoor cultures, and were studied as a reference. In these 50-L acrylic columns (19.4 cm internal diameter) growth, productivity and PE were 0.91 ± 0.087 d−1, 0.076 ± 0.012 g L−1 d−1 and 13.72 ± 2.23%, respectively. Outdoor productivity of T-iso was limited to average temperatures above 15 °C, while below an average temperature of 21 °C growth rate and productivity were lower than above 21 °C. Above this temperature, solar irradiance and biomass density had a more important effect on growth rate and productivity than temperature. Analysis of our data revealed a critical value of the ratio between incident solar irradiance (MJ m−2 d−1) and cell density (106 cells ml−1) at the moment when the protective black netting was removed from the cultures. Cultures that had a ratio above 1.5 suffered an initial lag phase or collapsed, while cultures that showed direct growth had a value below 1.5. This seemed to be independent of absolute initial cell density. However, we recommend using cell densities higher than the ca. 5 × 106 cells ml−1 used in the present study. In the South of Spain this seems to be especially relevant in spring, when temperatures are relatively low in relation to incident solar irradiance. T-iso seems to be particularly sensitive to the variable conditions outdoors and we suggest that new designs of closed PBRs, specifically developed for outdoor cultivation of T-iso, try to achieve more stable and homogeneous conditions throughout the system and over the daily cycle.

Biomass and lipid productivity, lipid content, and quantitative and qualitative lipid composition are critical parameters in selecting microalgal species for commercial scale-up production. This study compares lipid content and composition, and lipid and biomass productivity during logarithmic, late logarithmic, and stationary phase of Nannochloropsis sp., Isochrysis sp., Tetraselmis sp., and Rhodomonas sp. grown in L1-, f/2-, and K-medium. Of the tested species, Tetraselmis sp. exhibited a lipid productivity of 3.9-4.8 g m(-2) day(-1) in any media type, with comparable lipid productivity by Nannochloropsis sp. and Isochrysis sp. when grown in L1-medium. The dry biomass productivity of Tetraselmis sp. (33.1-45.0 g m(-2) day(-1)) exceeded that of the other species by a factor 2-10. Of the organisms studied, Tetraselmis sp. had the best dry biomass and/or lipid production profile in large-scale cultures. The present study provides a practical benchmark, which allows comparison of microalgal production systems with different footprints, as well as terrestrial systems.

Chromatographic and mass spectrometric analysis of surface sediments from perennially ice-covered Lake Fryxell (McMurdo Dry Valleys, East Antarctica) enabled tentative identification from mass spectral data of previously unreported pentaunsaturated ketones, octatriacontapentaen-2-one (C38:5Me), nonatriacontapentaen-3-one (C39:5Et) and tetradecapentaen-2-one (C40:5Me). In addition, the C37, C38 and C40 alkenones occur as di, tri and tetraunsaturated compounds, whereas the C39 alkenones only include the tetraunsaturated components. Analysis of environmental DNA extracted from the water column of Lake Fryxell produced two 18S rDNA sequences closely related to Isochrysis spp., Chrysotila lamellosa and haptophyte sequences previously recognized in sediment samples collected from a Greenland lake and from Ace Lake, Antarctica. Based on the alkenone distribution, coupled with phylogenetic data, we propose that haptophytes related to Isochrysis and/or C. lamellosa are the source organisms of alkenones in Lake Fryxell. The occurrence of pentaunsatured alkenones may represent a response to the year-round cold water temperature (ca. 1 °C average), likely combined with oxygen supersaturation and growth under light- and nutrient-limited conditions in the upper water column.

The variation of fatty acid (FA) content and composition of the microalgal production (Isochrysis sp., Pavlova lutheri and Chaetoceros muelleri) in a continuous large-scale production system (500-L bags) used in hatcheries were analysed. The variation of the FAs was analysed in replicate bags over time for the different species. Total FA content (pg cell−1) increased significantly (p

A research on the application of MSSIP-2 nutrient in marine phytoplankton culture has been conducted to produce biomass to be used as raw material for biofuel. Marine phytoplankton was cultivated using the nutrient media and the growth rates were studied by measuring the cell solidity at various growth times. Seven phytoplanktons; Isochrysis aff galbana, Spirulina sp., Thalassiosira sp., and Nitzchia sp., Chlorella vulgaris, Chaetoceros calcitrans and Isochrysis tahiti were used in the research. The experimental temperature, salinity, and pH of the media were measured and the specific growth rates of phytoplanktons were determined using the first order rate equation. Results showed that the highest specific growth rate was given by Chlorella vulgaris (0.0322 cells/hour) and the lowest one was by Thalassiosira sp. (0.0277 cells/hour). The highest biomass weight was obtained from Isochrysis aff galbana (0.329 g), whereas the lowest one (0.27 g) was from Nitzchia sp. The carbohydrate content was various, the highest content was 34.07% found in Isochrysis aff galbana and the lowest was 28.16% in Thalassiosira sp.

The biochemical composition of microalgae used as food is essential for aquatic species in commercial production systems, such as rotifers and microcrustaceans. Life table bioassays with the rotifer Brachionus sp. “Alvarado” strain were performed using three microalgae (Nannochloropsis oculata, Dunaliella salina and Isochrysis sp.) as food. Microalgae growth rate, dry weight and biochemical composition (protein, lipid, carbohydrate) and pigments (chlorophyll and carotenoid) were determined. The microalgae showed significant differences in their biochemical composition. N. oculata showed the highest growth rate, while D. salina showed the slowest growth rate, but instead, it displayed a higher content of proteins, lipids, carbohydrates, chlorophyll, and carotenoids per cell. Rotifer life table analysis showed no significant differences among any of the microalgae as food bioassays. However, Isochrysis sp. had a higher effect on the net reproductive rate of the rotifer Brachionus sp. “Alvarado” followed by D. salina, while N. oculata showed a higher effect on life expectancy and generation time. In conclusion, the three microalgae are found to be useful to support rotifer cultures; however, both, D. salina and Isochrysis sp., might improve the rotifer culture due to better growth and reproduction in short time. This information is useful to implement the culture of this tropical strain of Brachionus plicatilis complex in order to obtain high population densities, making rotifers available for several applications such as the establishment of larviculture in hatcheries, bioassays for ecological studies or to assess its sensitivity through toxicity tests.

Growth of marine copepods is influenced by feed. The purposes of this trial were to observe both growth and fatty acid compositions of harpacticoid copepod nauplii, Tisbe holothuriae by feeding with several microalgal species in laboratory: (A) Isochrysis tahiti; (B) Nannochloropsis oculata; (C) Rhodomonas sp., and (D) Tetraselmis chuii. The trial was carried out for 35 days with randomized complete design and triplicates in each treatment. The results showed that final copepod nauplii densities were not significantly different (P>0.05) in all treatments. However, lipid content of copepod nauplii fed with T. chuii was significantly higher (P

The enzyme-labeled fluorescence (ELF-97®) substrate produces an insoluble, fluorescent yellow-green product at the site of alkaline-phosphatase (AP) activity. Fifteen coastal phytoplankton species were tested to determine if AP activity could be detected in phosphate- depleted media. All species tested, except Synechococcus bacillaris, expressed AP activity. Subsequently, threshold concentrations of soluble reactive phosphate (SRP) at which AP activity could be detected by ELF-97® were deter- mined for Chaetoceros neogracile, Chlorella autotrophica, Isochrysis sp., Prorocentrum minimum ,a ndTetraselmis chui. Microalgal species differed significantly in the SRP con- centration at which AP activity was first detectable (10.1- 16.4 µM), well above concentrations normally considered limiting for phytoplankton. P. minimum began to express AP activity at a higher SRP concentration than the other algal species; this may be attributable to a relatively high DNA/cell ratio in P. minimum, compared to the other phytoplankton. Thus, phytoplankton species may respond to phosphorus deficiency at high SRP concentrations.

The activities of extracellular enzymes that initiate the microbial remineralization of high molecular weight organic matter were investigated in the water column and sandy surface sediments at two sites in the northeastern Gulf of Mexico. Six fluorescently labeled polysaccharides were hydrolyzed rapidly in the water column as well as in permeable sediments. This result contrasts with previous studies carried out in environments dominated by fine-grained muds, in which the spectrum of enzymes active in the water column is quite limited compared to that of the underlying sediments. Extracts of Spirulina, Isochrysis, and Thalassiosira were also used to measure hydrolysis rates in water from one of the sites. Rates of hydrolysis of the three plankton extracts were comparable to those of the purified polysaccharides. The broad spectrum and rapid rates of hydrolysis observed in the water column at both sites in the northeastern Gulf of Mexico may be due to the permeable nature of the sediments. Fluid flux through the sediments is sufficiently high that the entire 1.5 m deep water column could filter though the sediments on timescales of a few days to two weeks. Movement of water through sediments may also transport dissolved enzymes from the sediment into the water column, enhancing the spectrum as well as the rate of water column enzymatic activities. Such interaction between the sediments and water column would permit water column microbial communities to access high molecular weight substrates that might otherwise remain unavailable as substrates.

Arachidonic acid (ARA, 20:4 n − 6) is essential for oysters and has been implicated in reproduction and immune response of different mollusk species, probably by modulating the levels of prostaglandins. We tested the effect of dietary ARA on reproduction, PGE 2 levels, and some immune variables in Crassostrea corteziensis . Oysters were fed Isochrysis affinis galbana , clone Tahiti (T-iso) for three weeks, which has low ARA and high DHA (22:6 n − 3) levels and that was supplemented with 0, 1 and 9% ARA-rich lipid emulsions at 10% of algal dry weight biomass using a once-daily batch system to supply the microalgae. Survival and growth were not affected by the ARA enrichment. More gonadic tissue was found in oysters fed 1% ARA but oysters fed the 9% ARA were in a more advanced stage of maturation. ARA-enrichment did not affect fatty acid concentration in membrane phospholipids, but ARA concentration was higher in triacylglycerols of oysters fed 9% ARA compared to 0% ARA diet. PGE 2 and/or PGF 1 α concentration was higher in oysters fed the 9% ARA diet. Total hemocyte count was not affected by ARA enrichment, but the proportion of granulocytes and the superoxide anion activity (SOA) in relation to total hemocyte count were higher in oysters fed the 1% ARA diet. These results suggest that feeding moderate levels of ARA to oysters can boost immune system response and oocyte production. However, high levels of ARA favor final maturation and advanced stages of vitellogenesis but possibly at the expense of immune response.

Selected rotifer enrichment diets were compared on the basis of growth, survival, and fatty acid content of larval Florida pompano, Trachinotus carolinus L. Two 9-day larval rearing trials were conducted using a recirculating aquaculture system. In Trial 1, two microalgae concentrates (Isochrysis sp., ISO; and Pavlova sp.), a semi-moist paste (Protein Selco Plus, PS+), and a combination of the three diets were compared. In Trial 2, PS+ and three dry enrichment diets (Ori-Green, OG; Protein HUFA, PH; and AlgaMac 3050, AM) were compared. Larvae were fed rotifers 4 times daily at a rate of 2.5 rotifers/ml/feeding at 2–9 days post-hatch (DPH). Although larval growth in both trials was likely influenced by differences in culture density resulting from variable survival, in Trial 1 at 9 DPH standard length (SL) of larvae fed Pavlova-enriched rotifers (4.60 ±0.39 mm, mean ± SD) was greater (P

Previous studies suggest that the coccolithophorid haptophyte Emiliania huxleyi entered the Black Sea ~ 3400 yrs ago and since then a coccolith ooze defined as Unit I has developed. Unit I sediments contain long-chain alkenones derived from E. huxleyi whereas the alkenone distribution of the deeper coccolith-free sapropel (Unit II) is rather unusual. Alkenone-derived past sea surface temperature (SST) estimates suggest a large difference between Unit II and Unit I, which is likely a result of unusual biological precursors of the alkenones in Unit II. Here, we report a high-resolution stratigraphic analysis of ancient haptophyte DNA to establish the Holocene succession of haptophytes as sources of the alkenones in the Black Sea. Haptophytes related to brackish Isochrysis spp. were the initial sources of alkenones, and appeared immediately after the onset of sapropel deposition (~ 7550 yrs before present [a BP]). As salinity increased, Isochrysis-related haptophytes were slowly replaced by a complex suite of E. huxleyi strains as sources of alkenones. Our paleogenetic data showed that E. huxleyi colonized the Black Sea shortly after the onset of sapropel deposition, ~ 4000 yrs earlier than previously recognized based on their preserved coccoliths. E. huxleyi strains were the most likely source of the previously reported abundant and unusual C36 di-unsaturated “Black Sea alkenone”. Strong haptophyte species and strain-specific effects were observed on the level of unsaturation of alkenones which resulted in spurious alkenone-derived SST estimates before 5250 a BP. In contrast, from ~ 5250 a BP onwards a relatively stable haptophyte assemblage dominated by a different suite of E. huxleyi strains yielded robust alkenone-SST values and indicated a gradual cooling from 19 °C to ~ 15 °C at the top of the record (~ 450 a BP).