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Enhancing microalgal growth and bioactive compound production is becoming a duty for improving photosynthetic microorganisms. In this study, the growth, carotenoid, and fatty acid profiles of Conticribra weissflogii were studied under four different silicate concentrations and silicate-deficient conditions in an f/2 medium with continuous aeration, light intensity (30 ± 2 µmol m−2 s−1), salinity (25 ± 2‰), pH (8), and temperature (25 ± 2 °C). At the end of the experiment, we observed that a silicate concentration of 120 mg L−1 produced the maximum biomass dry weight (0.86 g L−1), carotenoid content (1.63 µg mL−1), and fucoxanthin content (1.23 mg g−1) in C. weissflogii. The eicosapentaenoic acid (EPA) (11,354.37 µg g−1), docosahexaenoic acid (DHA) (2516.16 µg g−1), gamma-linolenic acid (C18:3n6) (533.51 µg g−1), and arachidonic acid (C20:4n6) (1261.83 µg g−1) contents were significantly higher at Si 120 mg L−1. The results further showed the maximum fatty acid content in C. weissflogii at Si 120 mg L−1. However, the silicate-deficient conditions (Si 0 mg L−1) resulted in higher levels of saturated fatty acids (38,038.62 µg g−1). This study presents a practical approach for the large-scale optimization of biomass, carotenoid, fucoxanthin, and fatty acid production in C. weissflogii for commercial purposes. [ABSTRACT FROM AUTHOR]

The production of fucoxanthin and fatty acids in Conticribra weissflogii has been examined, but there is still a lack of understanding regarding the impact of trace elements, including iron, on their co-production. To address this knowledge gap, this study investigated the effects of FeCl3·6H2O on the growth, fucoxanthin, and fatty acids of C. weissflogii. The findings revealed that the highest cell density (1.9 × 106 cells mL−1), cell dry weight (0.89 ± 0.15 g L−1), and total fatty acid concentration (83,318.13 µg g−1) were achieved at an iron concentration of 15.75 mg L−1, while the maximum carotenoid and fucoxanthin contents were obtained at an iron concentration of 3.15 mg L−1. The study demonstrated that the content of the active substance in C. weissflogii could be increased by adjusting the iron concentration, providing new information as to the more efficient co-production of fucoxanthin and fatty acids and offering experimental support for large-scale production. [ABSTRACT FROM AUTHOR]

To enhance the nutrient removal efficiency of Oocystis borgei for mariculture wastewater (MW), the effects and processes of three phytohormones on nitrogen and phosphorus removal from synthetic mariculture wastewater (SMW) by O. borgei under sequential batch operation were compared. The findings revealed that the supplementation with 10−6 M 3-indoleacetic acid (IAA), gibberellic acid (GA3), and zeatin (ZT) resulted in the most effective elimination, while there was no appreciable difference among them. The nitrogen and phosphorus indices of the effluent dramatically reduced (p < 0.01) upon the supplementation of phytohormones, and the removal effects were ranked as NO3−-N > PO43−-P > NH4+-N > NO2−-N. The removal rates for NH4+-N and PO43−-P were 0.72–0.74 mg·L−1·d−1 and 1.26–1.30 mg·L−1·d−1, respectively. According to physiological studies, phytohormones enhanced the levels of photosynthetic pigments and chlorophyll fluorescence parameters (Fv/Fm and φPSII), thereby improving photosynthetic activity. Additionally, they stimulated Nitrate Reductase (NR) and Glutamine Synthetase (GS) activities to promote nitrogen metabolism and increased Superoxide Dismutase (SOD), Catalase (CAT), and carotenoid contents to mitigate oxidative stress damage caused by abiotic stress. These activities contribute to the proliferation of O. borgei, which in turn resulted in an increase in the assimilation of nitrogen and phosphorus from SMW. In conclusion, phytohormone supplementation significantly increased nutrient removal from SMW by O. borgei in a sequential batch reactor, which has potential application in MW treatment. [ABSTRACT FROM AUTHOR]

This study evaluated the possibility of using Oocystis borgei to prevent and control harmful algae blooms. Firstly, Microcystis aeruginosa and O. borgei were co-cultured to assess the competition for nutrients between them. Different physiological and biochemical parameters, such as growth, cell membrane permeability and esterase activities were determined in exudate culture experiment to investigate allelopathic effects of O. borgei culture and mixed cultures (O. borgei and M. aeruginosa) at different growth phase on harmful microalgae (M. aeruginosa). Results showed that O. borgei could significantly inhibited M. aeruginosa when volume ratios were 4:1 and 1:1 (M. aeruginosa: O. borgei) in co-culture experiment. Further, it was found that the membrane system of M. aeruginosa was disintegrated by the culture filtrate of O. borgei at exponential phase. In addition, esterase activities and photorespiration were significantly inhibited. In conclusion, O. borgei exhibited different allelopathic effects at different growth phase. Its exponential phase showed a significant inhibitory effect, while no inhibitory effect was observed at the decline phase. [ABSTRACT FROM AUTHOR]

The algae, Oscillatoria, is commonly found in prawn ponds and can lead to reduced productivity. We examined metabolites of the bacteria Brevibacillus laterosporus for algicidal qualities. To determine the possible algicidal mechanisms of these bioactive metabolites, different amounts of sterile filtrate of bacterial suspensions were added to cultures containing Oscillatoria. The dry weight, the concentrations of chlorophyll-a (chl-a), phycobiliprotein (PC, phycocyanin; APC, allophycocyanin; PE, phycoerythrin), and MDA (malondialdehyde) and the activities of SOD (superoxide dismutase), POD (peroxidase), and CAT (catalase) of algae were measured during the algicidal application. The results showed that lower concentrations of the sterile filtrate (addition ≤ 4 mL) accelerated the growth rate of Oscillatoria, but significant inhibition and lysis were observed with higher concentrations (addition ≥ 8 mL). In two trials (the additions were 8 mL and 10 mL, respectively), the algal dry weights were reduced by 26.02% and 45.30%, and the chl-a concentrations were decreased by 46.88% and 63.73%, respectively, after seven days. During the algicidal treatment, the concentrations of PC, APC, PE, and MDA and the activities of SOD, POD, and CAT were significantly increased in the early cultivation and declined quickly at later stages. Finally, the algae-lysing mechanism of the bioactive metabolites of the bacteria Brevibacillus laterosporus on Oscillatoria had been proposed. [ABSTRACT FROM AUTHOR]

The algae, Oscillatoria, is commonly found in prawn ponds and can lead to reduced productivity. We examined metabolites of the bacteria Brevibacillus laterosporus for algicidal qualities. To determine the possible algicidal mechanisms of these bioactive metabolites, different amounts of sterile filtrate of bacterial suspensions were added to cultures containing Oscillatoria. The dry weight, the concentrations of chlorophyll-a (chl-a), phycobiliprotein (PC, phycocyanin; APC, allophycocyanin; PE, phycoerythrin), and MDA (malondialdehyde) and the activities of SOD (superoxide dismutase), POD (peroxidase), and CAT (catalase) of algae were measured during the algicidal application. The results showed that lower concentrations of the sterile filtrate (addition ≤ 4 mL) accelerated the growth rate of Oscillatoria, but significant inhibition and lysis were observed with higher concentrations (addition ≥ 8 mL). In two trials (the additions were 8 mL and 10 mL, respectively), the algal dry weights were reduced by 26.02% and 45.30%, and the chl-a concentrations were decreased by 46.88% and 63.73%, respectively, after seven days. During the algicidal treatment, the concentrations of PC, APC, PE, and MDA and the activities of SOD, POD, and CAT were significantly increased in the early cultivation and declined quickly at later stages. Finally, the algae-lysing mechanism of the bioactive metabolites of the bacteria Brevibacillus laterosporus on Oscillatoria had been proposed.

Pseudodiaptomus dubia is a calanoid copepod that is distributed widely in the estuarine-coastal waters of Asia and is a dominant copepod in the shrimp grow-out ponds in southern China. A laboratory culture experiment was conducted to evaluate the influences of water temperature on larval development, survival, and reproduction. Results indicate that within a temperature range from 15 to 35 C degrees, larval development increases as the temperature increases. The water temperature for optimal larval survival rate ranges from 20 to 35 C degrees. Longevity and egg hatching time decrease as the temperature increases from 20 to 35 C degrees. Total fecundity and reproduction frequency increase as the water temperature increases, with the maximum at 30 C degrees. Fecundity and reproduction frequency decrease when the temperature exceeds 30 C degrees. Intrinsic growth rate [r(m)] ranges from 0.168 to 0.195 at 25 to 30 C degrees; net reproduction rate [R(0)] and finite growth rate (lambda) are 163 to 264 and 1.183 to 1.215, respectively, when the temperature is greater than 20 and 35 C degrees; population doubling time (t) varies from 3.556 to 4.128 days at temperatures less than 20 and 35 C degrees. Population generation time (T) is negatively correlated with temperature, with the optimal population growth rate at 25 to 30 C degrees.

Calanoid copepods are key components of the marine food web and the food sources of many larval fishes and planktivores, and grazers of phytoplankton. Understanding the ranges of major environmental variables suitable for their growth is essential to maintain the balance between trophic links and resources protection. In this study, the effects of temperature, salinity, pH, and light intensity on the filtering and grazing rates of a herbivorous copepod (Schmackeria dubia) were conducted in several control experiments. Our results indicated that experimental animals grazed normally at water temperatures between 15 and 35 degrees C. The filtering and grazing rates increased by onefold at water temperatures from 15 to 25 degrees C, with a peak at around 30 degrees C. S. dubia fed normally at salinity ranging from 20 to 30 ppt, with significantly low filtering and grazing rates at salinity below 15 ppt and above 35 ppt. The filtering and grazing rates increased as pH increased, peaked at approximately 8.5, and then decreased substantially. Light intensity also displayed an important impact on the filtering and grazing rates. Filtering and grazing rates were high when light intensity was greater than 20 and less than 200 micromol m(-2) s(-1). S. dubia nearly stopped feeding at low light intensity (less than 20 micromol m(-2) s(-1)).