Fatty acid composition of 12 microalgae for possible use in aquaculture feed

Twelve algal strains representing the classes Cyanophyceae, Prymnesiophyceae, Bacillariophyceae, Rhodophyceae, Cryptophyceae, Chlorophyceae, Xantophyceae and Eustigmatophyceae were selected mainly from the culture collection of the Norwegian Institute for Water Research (NIVA). The algae were grown as continuous cultures in a 1.8 l. reactor, internally illuminated with an 11 W fluorescent tube. The retention time was adjusted in the range 2–4 days to fit the growth rate of the algae. The growth responses and fatty acid composition were analysed. The maximum production rate was obtained with Pseudokirchneriella subcapitata (0.63 g 1⁻¹ day⁻¹) and the lowest with Porphyridium cruentum 0.13 g 1⁻¹ day⁻¹. Arachidonic acid (AA) and eicosapentaenoic acid (EPA) were the dominating polyunsaturated fatty acids (PUFAs) in P. cruentum, while only EPA accumulated in Phaeodactylum tricornutum. Docosahexaenoic acid (DHA) was the major PUFA in Isochrysis galbana, while Pavlova sp. had both EPA and DHA. This is the first report on the fatty acid profiles of Nannochloropsis oceanica, Chroococcus sp., Synechococcus sp. and Tribonema sp.     

Decreasing trophic efficiency in cool-water aquaculture ponds: size-selective predation removes large prey

Maximizing young-of-year (YOY) fish production in an aquaculture setting depends on matching predatory demand with prey availability. With a size-selective YOY fish species (saugeye: Sander vitreus Mitchell females × S. canadense Griffith & Smith males) supplied with natural zooplankton prey ( Bosmina sp. Baird), selective removal of larger individuals may decrease prey fecundity. However, increased nutrient fertilization may also ameliorate the top-down effects of fish predation. We tested these interactions in outdoor earthen production ponds (ca. 4000 m²; n =12) by measuring Bosmina sp. size at first reproduction (SFR), maximum size (MAX) and neonate size (NEO) in ponds that varied in YOY saugeye densities (18–50 saugeye m⁻³) and also differed in phosphorus maintenance levels (either 20 or 30 μg PO₄-P L⁻¹). We found that SFR decreased by 8% [from 0.298 mm±0.007 (mean±1 SE) to 0.275 mm±0.005], MAX decreased by 11% (from 0.367 mm±0.009 to 0.328 mm±0.009) and NEO decreased by 5% (0.198 mm±0.004 to 0.189 mm±0.003) over the range of saugeye densities, and that SFR increased by 4% (from 0.279 mm±0.004 to 0.290 mm±0.003) and MAX increased by 3% (from 0.336 mm±0.004 to 0.347±0.004) with increased fertilization. Further, prey offspring lengths strongly related to mother lengths and lengths differed from early to late in the production season. These results indicate that multiple factors affect prey sizes and emphasize that the removal of large prey individuals by size-selective YOY predators may decrease trophic efficiency, ultimately decreasing fish production.     

An indoor solution for mass production of the marine rotifer Brachionus plicatilis Müller fed on the marine microalga Tetraselmis suecica butcher

Mass production of the rotifer Brachionus plicatilis Müller is carried out in a set of 50-liter polyethylene bags in which first the microalga Tetraselmis suecica Butcher is cultured and then the rotifer is grown till most of the algae are grazed.This novel procedure based on a monoxenic production technique, has been conceived with a number of aims in view among which the following should be mentioned: shortest time elapsing between the start and the end of the culture (1 week); minimal care of the cultures; light energy saving for indoor invertebrate mass production systems; unified culture vessel for growing algae and rotifers; accuracy and timing of planned rotifer production. Each bag maintained in the best reported conditions gives over 400 rotifers per ml as final production. Rotifer mass production in plastic bags is better achieved when operated in conjunction with a system of continuous monoxenic cultures of microalgae and of rotifers which provide the inocula.     

A continuous culture apparatus for the mass production of algae

A multi-stage, continuous culture apparatus has been designed and tested for the production of algae for larval molluscs and crustacea. A single-line system produced a maximum of 2.4 × 10¹¹ cells/day, or 5 g ash-free dry weight of Monochrysis lutheri. Multiple-line systems are recommended for hatcheries. The flow rate affected algal cell density, yield, biomass, protein level, and residual nitrate.Maximal cell yield occurred at 10 I flow per day, a dilution rate of 63% of the volume of the first growth carboy, or 30% of the volume of the total system. The system is also adaptable to growth of larger planktonic algae or mixed cultures of algae and protozoa and/or rotifers.     

Effect of Salinity Change on Biomass and Biochemical Composition of Nannochloropsis oculata

Salinity fluctuation is an important factor affecting outdoor microalgae culture. This investigation examined the effect of salinity change (Tr‐1:35–15 g/L, Tr‐2:35–25 g/L, Tr‐3:35–35 g/L, Tr‐4:35–45 g/L, and Tr‐5:35–55 g/L) on growth and the biochemical composition of Nannochloropsis oculata, a candidate for biodiesel production in indoor photo‐bioreactors. Results showed that the algae increased in absorbency and dry biomass as salinity decreased. When the salinity increased, the specific growth rate (SGR) of the algae decreased significantly. The salinity stress also affected the pigments of the algae, the chlorophyll‐a, and carotenoid contents of the algae which decreased with the increase of salinity from 45 to 55 g/L. The fatty acid methyl esters (FAME) content (% of dry biomass) increased with the increase of salinity (e.g., Tr‐4 and Tr‐5). The algae was rich in C16:0 (palmitic acid), C16:1n‐7 (palmitoleic acid), and C20:5n‐3 (eicosapentaenoic acid), and C16:0 content increased with decreasing salinity from 35 to 15 g/L, but C16:1n‐7 content was high in all the treatments ranging from 25.25 ± 1.42% in Tr‐1 to 27.05 ± 1.13% in Tr‐5.     

Improved techniques for rearing mud crab Scylla paramamosain (Estampador 1949) larvae

A series of rearing trials in small 1 L cones and large tanks of 30–100 L were carried out to develop optimal rearing techniques for mud crab (Scylla paramamosain) larvae. Using water exchange (discontinuous partial water renewal or continuous treatment through biofiltration) and micro‐algae (Chlorella or Chaetoceros) supplementation (daily supplementation at 0.1–0.2 million cells mL⁻¹ or maintenance at 1–2 millions cells mL⁻¹), six different types of rearing systems were tried. The combination of a green‐water batch system for early stages and a recirculating system with micro‐algae supplementation for later stages resulted in the best overall performance of the crab larvae. No clear effects of crab stocking density (50–200 larvae L⁻¹) and rotifer (30–60 rotifers mL⁻¹) and Artemia density (10–20 L⁻¹) were observed. A stocking density of 100–150 zoea 1 (Z1) L⁻¹, combined with rotifer of 30–45 mL⁻¹ for early stages and Artemia feeding at 10–15 nauplii mL⁻¹ for Z3–Z5 seemed to produce the best performance of S. paramamosain larvae. Optimal rations for crab larvae should, however, be adjusted depending on the species, larval stage, larval status, prey size, rearing system and techniques. A practical feeding schedule could be to increase live food density from 30 to 45 rotifers mL⁻¹ from Z1 to Z2 and increase the number of Artemia nauplii mL⁻¹ from 10 to 15 from Z3 to Z5. Bacterial disease remains one of the key factors underlying the high mortality in the zoea stages. Further research to develop safe prophylactic treatments is therefore warranted. Combined with proper live food enrichment techniques, application of these findings has sustained a survival rate from Z1 to crab 1–2 stages in large rearing tanks of 10–15% (maximum 30%).     

Aphanizomenon flos-aquae,A Toxic Blue-Green Alga in Commercial Channel Catfish,Ictalurus punctatus,Ponds:

During the summers of 1990 and 1991 in the Lowcountry region of South Carolina, high mortality rates (50-90%) of channel catfish, Ictalurus punctatus, in production ponds were attributed to the toxic form of the blue-green alga (Cyanobacterium) Aphanizomenon flos-aquae. Toxicity varied with algal strain and/or stage in life history, and a simple bioassay was developed to account for the differential toxicity of algae within ponds. The bioassay required an intraperitoneal injection of a sonicated, 30X concentrate of algal cells that are injected into 8- to 20-g fish. Injection with 0.05 ml of concentrate from the toxic strains caused hyperactivity and paralysis in fish within 10 minutes and mortality within an hour. The endotoxin from A. flos-aquae (aphantoxin) was neutralized with the equivalent of 1.7 mg/L potassium permanganate beyond demand. In production ponds, an application of copper sulfate followed with potassium permanganate had variable success. Muddying the ponds had only limited success but appeared promising. Water and soil chemistry in this geographic area probably influenced the frequency of toxic A. flos-aquae blooms.     

缺氧和有毒微囊藻胁迫下三角帆蚌鳃和主要消化器官以及晶杆体的扫描电镜观察

为了阐明缺氧和有毒铜绿做囊藻对三角帆蚌鳃和主要消化器官的毒理效应和组织病理,实验利用扫描电镜研究了暴露于缺氧和有毒铜绿做囊藻下三角帆蚌的鳃、胃、肠以及晶杆体等器官组织病理学变化。结果显示,从第7天开始缺氧和有毒藻类复合胁迫组三角帆蚌的鳃丝及柱状细胞出现大量坏死和脱落,胃肠腔面纤毛脱落、上史细胞破裂坏死,晶杆体在第5天已经完全消失;第7天单独缺氧组和单独有毒藻类组的鳃和消化道出现少量的病变,单独缺氧组晶杆体在第7天完全消失,单独有毒藻类组晶杆体则一直存在。胁迫消失后,3个实验暴露组的晶杆体都未恢复正常对照组水平,因此缺氧和有毒铜绿做囊藻对三角帆蚌鳃和消化系统产生不可恢复性损伤,双重胁迫组影响最为严重,缺氧胁迫组相对有毒铜绿做囊藻胁迫组影响更为显著。本研究为三角帆蚌在缺氧和有毒藻类胁迫下的生理适应机制提供了组织病理学上的参考,并为其作为富营养化水体治理工具种的可行性提供了理论依据。     

Testing the yield of a pilot‐scale bubble column photobioreactor for cultivation of the microalga Rhodomonas salina as feed for intensive calanoid copepod cultures

A dual column photobioreactor (PBR) (2 × 47 L) with mixed CO₂/air bubbling was tested for cultivation of the microalga Rhodomonas salina as food for live feed copepods. In the continuous growth phase, the cell density was relatively stable at 2.40 ± 0.13 × 10⁶ cells/ml at an average dilution rate of 0.46 ± 0.02 per day throughout the 30‐day experiment. The produced algae had a high content of both total fatty acids (TFA) and free amino acids (FAA). Especially, the harvested algae contained a high proportion of poly‐unsaturated fatty acids that made up 80% of the TFA and of essential amino acids (35% of all FAA), implicating desirable components as feed for copepods. The current PBR was sufficient to feed a culture of the calanoid copepod Acartia tonsa at a density of 2,500 adult/L in ca. 500 L culture with a daily yield of approximately 17 × 10⁶ eggs. To be able to sustain the integrated copepods production, the suggested volume of the algae cultures should be ca. 20% of the copepod culture volume.     

Chemical cues promote settlement in larvae of the green-lipped mussel, Perna canaliculus

The large (70,000 tonnes) mussel aquaculture industry for the endemic New Zealand green-lipped mussel, Perna canaliculus Gmelin, currently relies almost entirely (80%) on wild caught seed that is often harvested attached to great quantities of floating algae. Natural vagaries in catches of wild mussel seed frequently result in shortages of mussel seed that, at times, have severely affected commercial aquaculture production. Both field and laboratory experiments were used to establish that chemical cues derived from algae significantly increase settlement of mussel larvae on artificial substrates. This is the first time an algal chemical cue has been implicated in the settlement behavior of P. canaliculus larvae. These results have potential commercial implications for improving mussel seed supply through inducing higher or more reliable levels of mussel settlement for aquaculture seed collection.     

Viability of a Freshwater Mussel (Elliptio complanata) as a Biomechanical Filter for Aquaculture Ponds I: Clearance Rate of Chlorophyll-α

The production and livelihood of aquaculture facilities depend on increased growth of species being harvested. Only 15%-25% of nitrogen and phosphorus are retained in farmed fish even when all feed is consumed. In both marine and freshwater aquaculture systems, bivalves have proven to be an inexpensive method for controlling algal growth through suspension feeding. With 25% of the native U.S. freshwater mussel species under federal protection, their use in aquaculture ponds could lead to further propagation and restoration of natural populations. Elliptio complanata is an important species in Delaware rivers and connected estuaries; a recent two-year study by the United States Geological Survey found that 98% of mussels found in the Delaware River were Elliptio complanata. The objective of this study was to calculate the clearance rate of E. complanata in a laboratory study. This would help us determine if mussels can serve as an addition to chemical and mechanical filtration regiments and thrive in an aquaculture setting. Using feeding chambers we investigated the effect of E. complanata on algae grown from an aquaculture pond and on a cultured alga over a four-hour period. Temperature, dissolved oxygen, and pH were monitored, and samples were than analyzed for total chlorophyll-α. The average of both the single cell using Chlorella vulgaris and mixed assemblage treatments chlorophyll-α clearance rate was 0.187 liters per hour per mussel. Prior to this experiment, these mussels were held for a period for two months in the holding system in the laboratory. The resulting low clearance rate as compared to the previous studies in the field is possibly due to the stress from holding these mussels. However, our study demonstrated that mussels have the potential to be used in an aquaculture setting and/or recreational ponds to help reduce algae populations that can occur as a result of eutrophication.     

Copulation behaviour of Neptunea arthritica: baseline considerations on broodstocks as the first step for seed production technology development

Copulation trials under three different scenarios were performed aiming to study the copulation behaviour of Neptunea arthritica and determine whether broodstock maintenance is required for artificial seed production. Neptunea arthritica showed polygamy, copulating at least three times with different partners. From all males and females used in this study, 43% of them copulated at least once. Female whelks showed rejection behaviour, which generated significant difference in copulation time between rejected (13.7±10.7 min) and non‐rejected (49.7±44.7 min) males. The effect of body size on copula duration appeared to be superficial, while its effect on accumulative copulas played an important role as an indicator of copulation capacity because whelks varied in size. After first copula, males showed a contrasting tendency to mate copulated females over non‐copulated females (χ²=6.23, d.f.=1, P=0.01). Broodstock maintenance as the first step in seed production is possible but considering low mating percentage and female rejection, it would be not economically reasonable due to the considerable number of whelks required and related logistical factors.     

Tank culture of larval sunshine bass, Morone chrysops (Rafinesque)×M. saxatilis (Walbaum), at three feeding levels

Sunshine bass, a hybrid of female white bass Morone chrysops (Rafinesque) and male striped bass M. saxatilis (Walbaum), fingerling production occurs almost exclusively in ponds. To increase production and maintain year‐round production in temperate climates, indoor tank culture is required. While tank production of fingerlings has been demonstrated, little is known about feeding requirements. Sunshine bass larvae, stocked at 75 L^?1 in 100 L of brackish water, were fed sequentially with rotifers Brachionus plicatilis cultured with a Nannochloropis algae paste and enriched with highly unsaturated fatty acids, decapsulated Artemia nauplii, and a microencapsulated commercial diet. The larvae in one treatment (three replicates) were initially fed rotifers at a daily rate of 20 mL^?1, then nauplii at an initial rate of 2 mL^?1, and then the commercial diet at 1 g. Larvae in two other treatments received two and three times as much food daily. The highest feeding rate resulted in a survival (52.9%) that was significantly higher than the survival rate (22.4%) of larvae fed the least. The total biomass produced was the highest in the treatment receiving the most food. The lowest feeding rate produced the least fish, but they were the heaviest. The intermediate feeding rate produced the shortest fish (11.3 mm).     

Conditions for the Production of Carotenoids by Thraustochytrium sp. ATCC 26185 and Aurantiochytrium sp. ATCC PRA-276

There is an intensive search for alternative sources of bioactive molecules, including carotenoids, due to their potent antioxidant activities. Some aquatic microorganisms, such as thraustochytrids, have the ability to synthesize large amounts of carotenoids. The objective of this investigation was to study the effect of growth conditions (carbon: total nitrogen ratio and cultivation system) on the production of carotenoids by Thraustochytrium sp. and Aurantiochytrium sp. For Thraustochytrium sp. culture, carotenoid production was lowered by increasing the initial glucose concentration or continuous supply of glucose and nitrogen. For Aurantiochytrium sp. culture, restraining nitrogen supply or especially using a continuous supply of glucose and total nitrogen decreased total carotenoid productivity. The highest total carotenoid production (2.22 mg/L, w/v) was obtained after 192 h of cultivation of Thraustochytrium sp. using initial concentrations of 30 g/L glucose and 2.4 g/L total nitrogen (batch system). The highest production of astaxanthin was achieved in the fed-batch system with a C/N ratio of 6.2 for Thraustochytrium sp. and 40 for Aurantiochytrium sp. Therefore, it was found that the carotenoid profile can be changed by modifying the growth conditions, which can be useful for the food industry and biotechnological applications.     

Collection,Analysis, and Utilization of Biogas from Anaerobic Treatment of Crab Processing Waters

Abstract

Two laboratory-scale, upflow anaerobic reactors were constructed to treat blue crab (Callinectes sapidus) cooking wastewater for determination of the volume and composition of the resulting bio-gas. Both systems (A and B) consisted of two 4-liter (L) upflow anaerobic reactors and one 8-L aerobic reactor in series. The first anaerobic reactor of System A contained 240,12.7 mm foam cubes, while the first anaerobic reactor of System B contained 180 foam pieces (25.4 ×25.4 ×12.7 mm). Biogas production rates for System A ranged from 6.6 L gas/L feed to 10.0 L gas/L feed. Mean values for System B ranged from 7.1 L gas/L feed to 11.9 L gas/L feed. Methane and carbon dioxide comprised 68% and 28%, respectively, of the gas from both systems. Hydrogen sulfide averaged 1.5% and 1.4% for systems A and B, respectively. A pilot-scale biogas collection and utilization system was also constructed and successfully demonstrated. Details of the pilot-scale system design are provided in the paper to help processors better understand how the technology might be applied.     

pH Dependent Growth of Chlorella in a Continuous Culture System 1

Production and growth of a local strain of marine Chlorella sp. was investigated under different pH levels ranging from pH 6.0–8.5 using 200 L capacity algal tubes. The results show that a pH of 6.5 will be most conducive for producing this species in a continuous culture system. The highest production was 136 g/m³/d with a mean of 117 ± 11 g/m³/d at pH 6.5 compared with other pH levels tested. The total fatty acid content was elevated at low pH levels and ω 3 PUFA increased as the pH was lowered from 8.5 to 6.5. The investigations show that algal productivity is considerably higher in the continuous culture system than in any of the other culture systems available.     

Experiments on the operation of a combined aquaculture-algae system

A combined aquaculture-algae system was developed for the purification and reuse of effluent water from intensive fish production in a combination of a high-rate algal pond and extensive fishpond. The integrated system was operated as a closed system, thus the water demand was reduced through the recirculation of the treated water. The pilot-scale experimental system consisted of three different compartments: tanks for intensive fish production, an algal pond where the excess nutrients are removed by algae uptake and a fishpond where the produced algae biomass was consumed by fish. The objective of this study was to describe and evaluate the nutrient transformation efficiency of the combined system through the analysis of the organic carbon, nitrogen and phosphorus budgets.     

Artificial upwelling to stimulate growth of non‐toxic algae in a habitat for mussel farming

Large‐scale artificial upwelling was tested as a method to enhance the environmental conditions for the growth of non‐toxic algae in a Norwegian fjord (61°0′N, 6°22′E). The experiment was designed to evaluate if nutrient‐rich seawater, brought up from below the mixed zone of a stratified fjord to the euphotic zone by air bubbling, would stimulate the growth of non‐toxic relative to toxic algae. Pumping 44 m³ min^?1 of air at 1 atm through a pipe diffuser submerged at 40 m depth formed a buoyancy flux that lifted 60 m³ s^?1 of deep water to the upper 17 m over a period of 21 days. The supply of silicate, inorganic nitrogen and phosphate to the upper 10 m in the fjord increased, and a significant increase in the biomass of non‐toxic algae was observed. The upwelling gave an increased growth of the non‐toxic dinoflagell ates Ceratium furca and C. tripos. After termination of the experiment, the phytoplankton biomass decreased significantly, whereas a distinct increase occurred in the relative biomass of the potentially toxic Dinophysis spp. The result is considered promising when it comes to creating controlled geographical areas with non‐toxic food for mussel production.     

A dynamic simulation analysis of Japanese abalone (<Emphasis Type="Italic">Haliotis discus hannai</Emphasis>) production in Chile

In this paper the author develops a dynamic simulation model and uses it to analyze the economics of pond cultivation of Japanese abalone in Chile. The analysis is done in continuous time by defining discounted free cash flows on the basis of explicit relationships between several biological, technical, and economic functions. In a culture batch starting with 600,000 seedlings when abalone has an average length of 19 mm, and the optimal harvest time is day 763 from stocking, harvesting at that optimum time implies a per-unit cost of production of approximately CH$320 per abalone. This includes consumption of 443,644 kg algae per generation, providing approximately 1.46 kg algae per abalone, and an electric energy requirement of about 433,200 kWh. Even at the optimum time of harvest, the profits are rather low. This explains why Japanese abalone culture has been substantially reduced in the north of Chile. To obtain abalones with an average weight of 100 g, harvest should be on day 1,460, when operating net present value is negative. In addition, the effect of changes of some key parameters on the results is analyzed via a sensitivity analysis.     

Nutritional Properties of the Marine Rotifer Brachionus plicatilis Fed the Freshwater Microalgae Selenastrum capricornutum

This study examined the effects of storage time on the fatty acid composition of freshwater Selenastrum capricornutum algal paste under 4 C refrigeration, the fatty acid composition of rotifers fed the fresh and stored algal paste, and the toxicological properties of the algal paste. Microalgae were produced in a hydraulically integrated serial turbidostat algal reactor (HIS-TAR), harvested as a paste, refrigerated and analyzed every 2 wk. Fresh Selenastrum capricornutum paste had almost three times greater concentration of unsaturated fatty acids than saturated fatty acids. Over 50% of the unsaturated fatty acids were made up of n-3 and n-6 fatty acids. Total unsaturated, n-3 group and n-6 group fatty acids decreased ( P 0.05) during storage, including the nutritionally important fatty acids (C20:4n6, C20:5n3, C22: 6n3). Rotifers fed 2– and 4-wk-old algal paste had a significantly lower ( P 0.05) total unsaturated fatty acid percentage and significantly greater ( P 0.05) total saturated fatty acids than those fed fresh algae. There were no significant changes in the n-6 group fatty acid level in the 4-wk-old paste feeding study or for the n-3 or n-6 groups in the 2-wk-old paste feeding study as compared to fresh algae. The levels of the three nutritionally important fatty acids (C20:4n6, C20:5n3, C22:6n3) did not differ between rotifers fed fresh and stored algae. Stored algae did not present toxicity to rotifers and Daphnia at the normal feeding concentration. These results indicated that the use of refrigerated freshwater algal paste for production of rotifers results in live feed with adequate nutritional properties for marine larviculture. This could eliminate the costs associated with production of marine algae, which could be replaced with freshwater algae, and may provide an alternative to cryopreservation.