Outdoor Ponds Research Articles

Effects of Dietary Nucleotide Supplementation on Performance, Profitability, and Disease Resistance of Litopenaeus vannamei Cultured in Indonesia under Intensive Outdoor Pond Conditions.

Simple SummaryIn Indonesia, there is an increasing tendency to use vegetable protein sources as a replacement for fish meal in diets for Pacific white shrimp (PWS), Litopenaeus vannamei. This; however, involves a negative impact on shrimp health given the high content of anti-nutritional factors in such protein sources. As dietary nucleotides modulate the immune response, they might be able to counteract this effect by enhancing PWS immunity and improving their performance and resistance to diseases. In this study, we evaluated the effects of nucleotide supplementation in PWS receiving diets in which fish meal had been partially replaced with soybean meal. Our data show that dietary nucleotide supplementation leads to improved growth performance and profitability, as well as to higher resistance to Vibrio harveyi. These positive results indicate that dietary nucleotides could constitute a useful tool in the production of shrimp cultured under intensive open-pond systems.This study evaluated the effects of dietary nucleotide supplementation in Pacific white shrimp, Litopenaeus vannamei, cultured in Indonesia. A total of 22,500 shrimp receiving diets in which fish meal (FM) had been partially replaced with vegetable protein sources were classified into five study groups (4500 shrimp/group) and received different diets for 110 days: 10FM (control group; 10% FM), 6FM (6% FM—low FM and no nucleotide supplementation), 10FMN (10% FM; 0.1% nucleotides), 8FMN (8% FM; 0.1% nucleotides) and 6FMN (6% FM; 0.1% nucleotides). Growth performance, body composition, total hemocyte count (THC), lysozyme activity, and hepatopancreas histopathology were assessed. Organoleptic evaluation and profitability assessments were also performed. In addition, shrimp resistance to a Vibrio harveyi challenge was studied in shrimps after having received the diets for 30 days. Results showed that reducing FM had a negative impact on growth performance and hepatopancreas morphology. Adding nucleotides resulted in better performance and profitability, a healthier histomorphological appearance of the hepatopancreas, and significantly higher survival rates upon challenge with V. harveyi, while it did not negatively affect organoleptic parameters. In conclusion, nucleotide supplementation could be useful for optimizing performance, profitability, and disease resistance in shrimp cultured under intensive outdoor pond conditions.

Temperature regulation schemes for improving biomass productivity and nutrient removal rate in outdoor raceway ponds

This study investigated the possibility of enhancing the biomass productivity and nutrient removal of microalgae grown in raceway ponds through temperature regulation. Scenedesmus sp. grown in anaerobically digested abattoir effluent (ADAE) was cultivated outdoor in eight raceway ponds. Seven ponds were subjected to different temperature regulation schemes (from 15 °C to 25 °C) and varying control windows (from 24 h to daytime-only). From the results of this study, an approximate 60 % increase in biomass productivity was observed for ponds operated at a minimum temperature of 15 °C coupled with a 24 h (T15P24) and 12.5 h (T15P12.5) control period in relation to the uncontrolled temperature pond (UTP). Generally, Scenedesmus ponds operated at 15 °C used 60 % less energy for heating, were more efficient in nutrient removal, and showed significantly higher biomass productivities with respect to the uncontrolled/higher temperature regulated ponds. In other words, significant productivity improvements were observed for the systems with lower energy demands.

Assessment of Eicosapentaenoic Acid (EPA) Production from Filamentous Microalga Tribonema aequale: From Laboratory to Pilot-Scale Study.

It has long been explored to use EPA-rich unicellular microalgae as a fish oil alternative for production of the high-value omega-3 fatty acid eicosapentaenoic acid (EPA, 20:5, n-3). However, none of the efforts have ever reached commercial success. This study reported a filamentous yellow-green microalga Tribonema aequale that possesses the ability to grow rapidly and synthesize significant amounts of EPA. A series of studies were conducted in a glass column photobioreactor under laboratory culture conditions and in pilot-scale open raceway ponds outdoors. The emphasis was placed on the specific nutrient requirements and the key operational parameters in raceway ponds such as culture depth and mixing regimes. When optimized, T. aequale cells contained 2.9% of EPA (w/w) and reached a very high biomass concentration of 9.8 g L−1 in the glass column photobioreactor. The cellular EPA content was increased further to 3.5% and the areal biomass and EPA productivities of 16.2 g m−2 d−1 and 542.5 mg m−2 d−1, respectively, were obtained from the outdoor pilot-scale open raceway ponds, which were the record high figures reported thus far from microalgae-based EPA production. It was also observed that T. aequale was highly resistant to microbial contamination and easy for harvesting and dewatering, which provide two additional competitive advantages of this filamentous microalga over the unicellular counterparts for potential commercial production of EPA and other derived co-products.

Genetic parameters and genotype by environment interaction for growth traits of razor clam Sinonovacula constricta, from outdoor pond and semi-natural environment

The razor clam, Sinonovacula constricta, is a commercially important bivalve. To date, there have been very limited quantitative genetic studies of this species, especially in different aquaculture environments. This study is the first report of genotype by environment (G × E) interactions for growth traits of razor clams from outdoor pond (OP) and semi-natural environments (SNE). Over a 2-month period, the data for shell length (SL), shell height (SH), shell width (SW), and body weight (BW) of razor clams were recorded for 1 month, and marked as Data 1 and Data 2. Phenotypic data of 1627 individual clams from 17 full-sib families were used for the analysis. The overall heritabilities (h2) for all growth traits were from low to moderate, ranging from 0.127 to 0.230. The h2 of SNE was higher than that of OP (0.243–0.423 vs. 0.101–0.285). Heritabilities for growth traits indicated that these traits could be effectively selected in both aquaculture environments. Overall, both phenotypic (rp) and genetic (rg) characteristics showed high positive correlations among the growth traits. However, the rg and rp were highly variable in OP, ranging from 0.435 to 0.973 and from 0.597 to 0.874, respectively. The rg of SL, SH, SW, and BW between the two aquaculture environments for Data 1 were 0.867, 0.682, 0.651, and 0.844, respectively. The rg ranged from 0.274 to 0.619 for Date 2. These results indicated significant G × E interactions among families at different sites. This study therefore provided optimal guidelines to select breeding programs for razor clams reared in different aquaculture environments.

A novel approach to build algal consortia for sustainable biomass production

In the last decade, microalgae have reemerged as a feedstock for biofuels and a diverse suite of bioproducts. Yet, considerable challenges must be overcome before algal biofuels and bioproducts become technoeconomically viable. At present, single algal strains selected for particular phenotypic traits, such as maximum specific growth rate or lipid content, are commonly scaled for cultivation in open, outdoor raceway ponds. Although this monoculture approach may maximize the production of end products, monocultures are particularly susceptible to crashes associated with environmental variability. An approach that has been proposed to generate more productive and stable microalgal crops is the use of eco-engineered communities, or consortia. However, attempts to construct productive consortia have not been consistently successful. We argue that failures stem from the lack of an eco-engineering approach to design species combinations. Here, we used an in silico method to build consortia before testing their performance against monocultures in the laboratory. Focusing on consortia of Nannochloropsis and Microchloropsis, we measured growth of strains along gradients of light and temperature, as well as in response to a salinity shift. With these data, we used a functional dispersion approach to generate over 8000 consortia combinations. We then tested the 50 most functionally diverse consortia in a laboratory experiment and found that consortia overwhelmingly outperformed monocultures. A positive net biodiversity effect and overyielding was found in the majority of consortia combinations. To our knowledge, this is the first application of an in silico approach to design functionally diverse consortia before laboratory and field testing. Our results highlight the importance of employing a functional diversity approach for consortia design.

Elimination of Pendimethalin in Integrated Rice and Procambarus clarkii Breeding Models and Dietary Risk Assessments.

This study investigated elimination of the herbicide pendimethalin using an integrated rice and Procambarus clarkii breeding model of indoor and outdoor (pond culture) exposure tests. The pendimethalin levels in 484 samples from the primary rice and P. clarkii integrated breeding areas in Hubei province were monitored, and dietary risk assessments of pendimethalin were calculated. Pendimethalin was quantified using high-performance liquid chromatography tandem mass spectrometry, and detection levels were linear in the range of 1.0 to 10.0 μg/L, and peak areas were positively correlated with concentration, with a correlation coefficient of 0.9996. Recoveries ranged from 86.9 to 103.5%, and the limit of quantitation was 2.5 × 10−4 μg/L in water, and 1 × 10−2 μg/kg in tissues, sediments, and waterweeds. The dissipation rate of pendimethalin in tissues and water followed first-order kinetics, with half-lives of 0.51–5.64 d. In 484 samples taken from aquaculture farms, pendimethalin was detected in 8.67% of the samples at levels in the range of 1.95 to 8.26 μg/kg in Hubei province from 2018 to 2020. The maximum residue limit of pendimethalin in P. clarkii has not been established in China, but our dietary risk assessments indicated that consumption of P. clarkii from integrated rice farms was acceptable.

Biodiversity and disease risk in an algal biofuel system: An experimental test in outdoor ponds using a before-after-control-impact (BACI) design.

For outdoor cultivation of algal feedstocks to become a commercially viable and sustainable option for biofuel production, algal cultivation must maintain high yields and temporal stability in environmentally variable outdoor ponds. One of the main challenges is mitigating disease outbreaks that leads to culture crashes. Drawing on predictions from the ‘dilution effect’ hypothesis, in which increased biodiversity is thought to reduce disease risk in a community, a teste of whether algal polycultures would reduce disease risk and improve feedstock production efficiencies compared to monocultures was performed. While the positive benefits of biodiversity on disease risk have been demonstrated in various systems, to the best of our knowledge this is the first test in an algal biofuel system. Here, the results a before-after-control-impact (BACI) experimental design to compare mean monoculture (control) and polyculture (impact) yield, stability, and productivity before and after fungal infection when grown in 400-L outdoor raceway ponds are presented. It has been found that polycultures did not experience a reduction in disease risk compared to monocultures or differ in production efficiencies throughout the course of the 43-day experiment. These results show that polyculture feedstocks can maintain similar levels of productivity, stability, and disease resistance to that of a monoculture. Determining whether these results are generalizable or represent one case study requires additional outdoor experiments using a larger variety of host and pathogen species.

PHYTOPLANKTON COMMUNITY PROFILE IN INDOOR AND OUTDOOR WHITE LEG SHRIMP (Litopenaeus vannamei) INTENSIVE CULTURE

Water quality can change according to the availability, abundance, and composition of phytoplankton in these waters. The fertility of a waters can be reviewed by observing the phytoplankton community in it. The purpose of this study was to determine the effect of using different types of ponds, namely indoor and outdoor, on the diversity and abundance of phytoplankton and water quality. This research was carried out in six different ponds consisting of three indoor pools and three outdoor pools for 56 . Samples of phytoplankton in indoor and outdoor ponds were taken as many as 4 points each. The abundance of phytoplankton in indoor ponds ranged from 880-9482 ind/L while at outdoor ponds ranged from 506-3344 ind/L., which generally consist of 5 phyla, i.e. Bacillariophyta, Charophyta, Chlorophyta, Cyanobacteria, and Glaucophyta. The highest abundance of phytoplankton was found in the indoor pondl (A2) of 5979.60±3353.59 ind/L , while the lowest was in the outdoor pool (B3) of 1350.80±628.75 ind/L . Comparison of the abundance of phytoplankton in indoor and outdoor ponds showed significantly different results. Water quality measurements showed that the indoor was better than the outdoor ponds

Eco‐friendly method for rearing sea cucumber ( Apostichopus japonicus ) larvae

Seed production plays an important role in aquaculture. The sea cucumber Apostichopus japonicus is an important marine aquaculture species in many Asian countries. By 2020, the annual total seed production of A. japonicus reached 551 billion individuals in China. However, the traditional method of culturing A. japonicus larvae is cost intensive and causes environmental pollution. In this study, we developed an eco-friendly method for rearing sea cucumber larvae. We designed a cage system to provide a suitable living environment for larvae in open-air outdoor ponds, and then, we identified 0.2 larvae per ml as the optimal stocking density for larval rearing. We also found that substrates made of oyster and scallop shells were optimal for larval settlement. A. japonicus larvae showed good survival, growth, development and settlement when cultured using this low-cost and non-polluting method. Our results can be applied to support sustainable development of the sea cucumber industry.

Comparison of planktonic bacterial communities indoor and outdoor of aquaculture greenhouses.

Greenhouses are widely used in agriculture systems to shield crops from unfavourable weather to achieve a year-round food supply. In recent years, aquaculture ponds have been placed in greenhouses in many regions. The impacts of the greenhouses on planktonic bacterial communities should be uncovered. In this study, two polyolefin film greenhouses accommodating aquaculture ponds were established and planktonic bacterial communities were compared from samples taken in aquaculture ponds inside and outside the greenhouses, using Illumina 16S rRNA sequencing. The results showed there were significant variations in bacterial community structure between indoor and outdoor samples. Obvious differences were also found between two greenhouses, whereas the differences in indoor samples were weaker than outdoor samples. Significantly higher temperature (in summer), pH and permanganate index were found in the outdoor pond samples. Results of redundancy analysis showed that Proteobacteria and Bacteroidota were positively related to the dissolved oxygen, total nitrogen and total phosphorus, and Actinobacteriota were positively related to pH, temperature and permanganate index, whereas Cyanobacteria were positively related to the salinity, conductivity, total dissolved solids and ammonia nitrogen. The results of this study revealed that greenhouses significantly influenced planktonic bacterial communities in aquaculture ponds. This study isexpected to provide a scientific basis for aquaculture in greenhouses.

Effects of LED lighting on Nannochloropsis oceanica grown in outdoor raceway ponds

Growth in most microalgal mass cultivation systems is light-limited, particularly in raceway ponds (RWP) where the light path is higher. Artificial lighting can be a promising solution to diminishing dark zones and enhance microalgal productivity. Therefore, our goal was to prevent the cell shift from photosynthesis to a respiration-only stage by resorting to LED illumination. Nannochloropsis oceanica cultures were accordingly grown outdoors in a preliminary small-scaleexperiment, followed by pilot-scale trials. In the former, three 3.0-m2 RWP were set up under three distinct conditions: 1) without LEDs (control); 2) LEDs turned on during the night; and 3) LEDs turned on for 24 h. In the pilot-scale trial, one of two 28.9-m2 pilot-scale RWPs was coupled to the best LED setup – determined in the small-scale preliminary experiment – using the same light intensity (normal mode) and half of the intensity (economy mode), with the second RWP serving as a control. In the preliminary experiment, the use of LEDs for 24 h was deemed as not helpful during daytime, before the culture reached ≈0.5 g DW L−1 – when dark zones appeared during the day due to sunlight attenuation in the 0.1 m-deep cultures. Overall, use of LEDs increased biomass growth chiefly by increasing nighttime productivities – materialized in higher chlorophyll, protein, and carbohydrate productivities in LED-lit cultures. A higher impact of LED lighting was observed under lower sunlight irradiances. A preliminary economic analysis indicates that use of LEDs in RWPs outdoors should be considered for high-value metabolites only.

Piggery wastewater treatment with algae-bacteria consortia: Pilot-scale validation and techno-economic evaluation at farm level

The efficiency of an outdoor pilot-scale raceway pond treating the wastewaters generated by a large-scale piggery farm in Northern Italy was evaluated. The biomass productivity over 208 days of experimentation was 10.7 ± 6.5 g TSS·m−2·d−1, and ammoniacal nitrogen, orthophosphate, and COD average removal efficiencies were 90%, 90%, and 59%, respectively. Results were used to perform a comprehensive techno-economic analysis for integrating algae-based processes in farms of different sizes (100–10000 pigs). The amount of N disposed of on agricultural land could be reduced from 91% to 21%, increasing the fraction returned to the atmosphere from 2.4% to 63%, and the fraction in the biomass from 6.2% to 16%. For intensive farming, the release of 110 t N·ha−1·y−1 contained in the digestate could be avoided by including algae-bacteria processes. The biomass production cost was as low as 1.9 €·kg−1, while the cost for nitrogen removal was 4.3 €·kg N−1.

Small scale photobioreactor, outdoor open pond cultivation of Chlorella sp. and harvesting at log and stationary growth phase towards lipids and methyl ester production

Microalgae are the promising feedstock for biodiesel production than other first and second-generation feedstocks. Generating huge biomass sustainably per unit volume per day is vital to the continuous utilization of algal feedstock for sustainable biodiesel production. But, cultivation and harvesting of microalgae are the significant cost drivers and the commonly used cultivation systems for microalgae are outdoor pond and photobioreactor. In this study, small scale photobioreactor, outdoor open pond and Erlenmeyer flask based cultivation of Chlorella sp. and harvesting at log phase and stationary phase for biomass, lipids towards FAME (fatty acid methyl ester) production was investigated. Photobioreactor grown Chlorella sp. showed higher growth in terms of biomass yield, biomass productivity and chlorophyll content. In the case of lipid content, Chlorella sp. unveiled a similar percentage of lipid about 20% (log phase) and 24% (stationary phase) irrespective of the cultivation systems tested. Non-polar lipid percentage 46% in log phase, while in stationary phase, Chlorella sp. showed higher levels of non-polar lipids at about 66% in photobioreactor and open pond systems. A similar pattern of fatty acids was seen from cultures grown in all three cultivation systems and among identified fatty acids, γ-linolenic acid is prevalent in the range between 14 and 15% followed by palmitic acid in the range between 11 and 13%.

Loss of gut microbial diversity in the cultured, agastric fish, Mexican pike silverside (Chirostoma estor: Atherinopsidae).

Teleost fish are the most diverse group of extant vertebrates and have varied digestive anatomical structures and strategies, suggesting they also possess an array of different host-microbiota interactions. Differences in fish gut microbiota have been shown to affect host development, the process of gut colonization, and the outcomes of gene-environment or immune system-microbiota interactions. There is generally a lack of studies on the digestive mechanisms and microbiota of agastric short-intestine fish however, meaning that we do not understand how changes in gut microbial diversity might influence the health of these types of fish. To help fill these gaps in knowledge, we decided to study the Mexican pike silverside (Chirostoma estor) which has a simplified alimentary canal (agastric, short-intestine, 0.7 gut relative length) to observe the diversity and metabolic potential of its intestinal microbiota. We characterized gut microbial populations using high-throughput sequencing of the V3 region in bacterial 16S rRNA genes while searching for population shifts resulting associated with fish development in different environments and cultivation methods. Microbiota samples were taken from the digesta, anterior and posterior intestine (the three different intestinal components) of fish that grew wild in a lake, that were cultivated in indoor tanks, or that were raised in outdoor ponds. Gut microbial diversity was significantly higher in wild fish than in cultivated fish, suggesting a loss of diversity when fish are raised in controlled environments. The most abundant phyla observed in these experiments were Firmicutes and Proteobacteria, particularly of the genera Mycoplasma, Staphylococcus, Spiroplasma, and Aeromonas. Of the 14,161 OTUs observed in this experiment, 133 were found in all groups, and 17 of these, belonging to Acinetobacter, Aeromonas, Pseudomonas, and Spiroplasma genera, were found in all samples suggesting the existence of a core C. estor microbiome. Functional metagenomic prediction of bacterial ecological functions using PICRUSt2 suggested that different intestinal components select for functionally distinct microbial populations with variation in pathways related to the metabolism of amino acids, vitamins, cofactors, and energy. Our results provide, for the first time, information on the bacterial populations present in an agastric, short-gut teleost with commercial potential and show that controlled cultivation of this fish reduces the diversity of its intestinal microbiota.

Machine learning-informed and synthetic biology-enabled semi-continuous algal cultivation to unleash renewable fuel productivity

Algal biofuel is regarded as one of the ultimate solutions for renewable energy, but its commercialization is hindered by growth limitations caused by mutual shading and high harvest costs. We overcome these challenges by advancing machine learning to inform the design of a semi-continuous algal cultivation (SAC) to sustain optimal cell growth and minimize mutual shading. An aggregation-based sedimentation (ABS) strategy is then designed to achieve low-cost biomass harvesting and economical SAC. The ABS is achieved by engineering a fast-growing strain, Synechococcus elongatus UTEX 2973, to produce limonene, which increases cyanobacterial cell surface hydrophobicity and enables efficient cell aggregation and sedimentation. SAC unleashes cyanobacterial growth potential with 0.1 g/L/hour biomass productivity and 0.2 mg/L/hour limonene productivity over a sustained period in photobioreactors. Scaling-up the SAC with an outdoor pond system achieves a biomass yield of 43.3 g/m2/day, bringing the minimum biomass selling price down to approximately $281 per ton.

Predator Group Composition Indirectly Influences Food Web Dynamics through Predator Growth Rates.

AbstractConsiderable theoretical work predicts that intraspecific trait variation can have profound ecological consequences by altering species interactions. Because of their high flexibility, behavioral traits may be especially relevant in mediating how species respond to one another, thus affecting food web dynamics and ecosystem functioning. However, empirical evidence supporting this idea is limited. Here, we generated predator groups where we manipulated the composition of behavioral types within the groups to assess effects on predator growth rates, prey communities, basal resources, and ecosystem functioning in replicated outdoor ponds. Using European perch (Perca fluviatilis), we created three types of predator populations: two where all individuals expressed either bold or shy phenotypes and one that contained a mix of individuals of the two behavioral types. Bold perch grew faster in mixed populations, indicating that predator growth depends on each individual's behavioral type and that of its group members. However, there was no evidence that the behavioral composition of the perch population directly altered the dynamics of lower trophic levels. Instead, final perch biomass, not behavioral composition, had the strongest influence on lower trophic levels. Thus, the central question may not be whether predator behavior matters at all for trophic dynamics but rather when behavioral effects will predominate over effects of other influences, such as predator biomass variation.

Biodiversity risk assessment of genetically modified Chaetoceros gracilis for outdoor cultivation.

A genetically modified (GM) strain of the diatom Chaetoceros gracilis expressing the phosphite dehydrogenase gene (ptxD), which is a useful gene both for the biological containment and the avoidance of microbial contamination, was characterized to estimate the risk against the biodiversity by laboratory experiments. GM strain could grow in the medium containing phosphite as a sole source of phosphorus, while its general characteristics such as growth, salt tolerance, heat and dehydration resistance in the normal phosphate-containing medium were equivalent to those of wild type (WT) strain. The increase in potential toxicity of GM strain against plant, crustacean, fish and mammal was also disproved. The dispersal ability of WT strain cultured in an outdoor raceway pond was investigated for 28 days by detecting the psb31 gene in vessels, settled at variable distances (between 5 and 60 m) from the pond. The diatom was detected only in one vessel placed 5 m apart. To estimate the influence on the environment, WT and GM strains were inoculated into freshwater, seawater and soil. The influence on the microbiome in those samples was assessed by 16S rRNA gene amplicon sequencing, in addition to the analysis of the survivability of those strains in the freshwater and the seawater. The results indicated that the effect to the microbiome and the survivability were comparable between WT and GM strains. All results showed that the introduction of the ptxD gene into the diatom had a low risk on biodiversity.

Aquaphotomics determination of nutrient biomarker for spectrophotometric parameterization of crop growth primary macronutrients using genetic programming

Water quality assessment is currently based on time-consuming and costly laboratory procedures and numerous expensive physicochemical sensors deployment. In response to the trend of device minimization and reduced outlays in sustainable aquaponic water monitoring, the integration of aquaphotomics and computational intelligence is presented in this paper. This study used the combination of temperature, pH, and electrical conductivity sensors in predicting crop growth primary macronutrient concentration (nitrate, phosphate, and potassium (NPK)), thus, limiting the number of deployed sensors. A total of 220 water samples collected from an outdoor artificial aquaponic pond were temperature perturbed from 16 to 36 °C with 2 °C increments to mimic ambient range, which varies water compositional structure. Aquaphotomics was applied on ultraviolet, visible light, and near-infrared spectral regions, 100 to 1 000 nm, to determine NPK compounds. Principal component analysis emphasized nutrient dynamics through selecting the highly correlated water absorption bands resulting in 250 nm, 840 nm, and 765 nm for nitrate, phosphate, and potassium respectively. These activated water bands were used as wavelength protocols to spectrophotometrically measure macronutrient concentrations. Experiments have shown that multigene symbolic regression genetic programming (MSRGP) obtained the optimal performance in parameterizing and predicting nitrate, phosphate, and potassium concentrations based on water physical properties with an accuracy of 87.63%, 88.73%, and 99.91%, respectively. The results have shown the established 4-dimensional nutrient dynamics map reveals that temperature significantly strengthens nitrate and potassium above 30 °C and phosphate below 25 °C with pH and electrical conductivity ranging between 7 and 8 and 0.1 to 0.2 mS cm−1 respectively. This novel approach of developing a physicochemical estimation model predicted macronutrient concentrations in real-time using physical limnological sensors with a 50% reduction of energy consumption. This same approach can be extended to measure secondary macronutrients and micronutrients.

Aeration level in HDPE-lined nursery ponds that optimizes yield and production cost of preadult redclaw crayfish, Cherax quadricarinatus

The potential for commercial Australian redclaw crayfish culture is considered very significant. However, information on the effect that different water exchange and aeration levels has on growth, survival, yield and nursery production costs of redclaw is limited. We evaluated the effect of aeration levels in the yield and production cost of preadult redclaw crayfish, Cherax quadricarinatus, during the nursery phase. In a preliminary trial, 4 levels of water exchange: 0%, 2.5%, 5% and 7.5% day−1, were tested in 1.7 m diameter (2.26 m2) tanks, stocking 3.0 ± 0.2 g juveniles at a density of 15 juveniles m−2. After 60 days, the physicochemical water quality parameters were within the recommended intervals for cultivation of the species. Final weight, survival, biomass and FCR’s of pre-adult C. quadricarinatus did not show any significant differences (p > 0.05) among treatments so we conclude that adequate production of C. quadricarinatus during zero-water exchange nursing is feasible. With the previous information, 4 aeration levels (0, 6, 12 and 24 hr day−1) were evaluated in triplicate 100 m2 HDPE-lined outdoor ponds. Juveniles (3.5 ± 0.5 g) were stocked at a density of 15 juveniles’ m−2. After 84 days of cultivation, survival was not significantly different among treatments and varied within 86–87%. The highest final average weight, growth rate and biomass were obtained with 12 h of aeration per day (3.2 ton ha−1), but there were no significant differences from those obtained in ponds with continuous aeration (24 hr day−1). The feed conversion rates were within 0.72 − 0.75. We conclude that it is possible to maximize C. quadricarinatus production in HDPE-lined ponds without water exchange, maintaining aeration at a rate of at least 12 hr day−1. A cost analysis shows that, with this strategy, it is possible to reduce the electricity costs required for water pumping and aeration in 70% and 50%, respectively. With this, a reduction of 11.17% in the production cost of pre-adult C. quadricarinatus during the nursery phase is achieved, compared with the best published reports.

Growth and Biochemical Composition Characteristics of Arthrospira platensis Induced by Simultaneous Nitrogen Deficiency and Seawater-Supplemented Medium in an Outdoor Raceway Pond in Winter.

Arthrospira platensis, a well-known cyanobacterium, is widely applied not only in human and animal nutrition but also in cosmetics for its high amounts of active products. The biochemical composition plays a key role in the application performance of the Arthrospira biomass. The present study aimed to evaluate the growth and biochemical composition characteristics of A. platensis, cultured with a nitrogen-free and seawater-supplemented medium in an outdoor raceway pond in winter. The results showed that the biomass yield could achieve 222.42 g m−2, and the carbohydrate content increased by 247% at the end of the culture period (26 d), compared with that of the starter culture. The daily and annual areal productivities were 3.96 g m−2 d−1 and 14.44 ton ha−1 yr−1 for biomass and 2.88 g m−2 d−1 and 10.53 ton ha−1 yr−1 for carbohydrates, respectively. On the contrary, a profound reduction was observed in protein, lipid, and pigment contents. Glucose, the main monosaccharide in the A. platensis biomass, increased from 77.81% to 93.75% of total monosaccharides. Based on these results, large-scale production of carbohydrate-rich A. platensis biomass was achieved via a low-cost culture, involving simultaneous nitrogen deficiency and supplementary seawater in winter.