Culturing microalgae using commercial media is expensive. Proliferation of aquaculture is generating high amount of wastewater containing nitrogen and phosphorus and this could be a source of nutrient for cultivating microalgae thereby reducing the production costs. This study compared the growth, productivity, and proximate composition of Chaetoceros calcitrans, Nannochloris maculate, and Tetraselmis chuii cultured in aquaculture wastewater and Conway medium. Results indicated that selected microalgae cultivated in wastewater and Conway medium did not show any significant differences (p > 0.05) in terms of cell density, optical density, and biomass. Further, volumetric and areal productivity showed similar trend for all the three species. But lipid productivity (LP) in N. maculate was significantly higher (p < 0.05) when cultured in wastewater medium compared to the Conway medium. There were no significant differences (p > 0.05) for C. calcitrans and T. chuii in terms of LP when cultivated in the two media. N. maculate and T. chuii had significantly higher (p < 0.05) protein and lipid content compared to C. calcitrans when cultured in wastewater medium. The three species did not show any significant differences (p > 0.05) in terms of carbohydrate content when cultured either in wastewater or Conway medium. The results indicate that aquaculture wastewater can be re-used as a possible source of low-cost nutrient for culturing selected microalgae for live feed utilization in aquaculture.
This study reveals the effect of elevated pCO 2 on Porites cylindrica and Galaxea fascicularis. The corals responded differently under elevated pCO 2 . Zooxanthellae cell density, cell mitotic index, and photosynthesis rate of P. cylindrica decreased drastically under the elevated pCO 2 . At the end of the experiment, P. cylindrica suffered from a declining calcium carbonate precipitation rate. G. fascicularis increased its respiration rate and expelled 71% of its symbiotic zooxanthellae algae under elevated pCO 2 . Photosynthetic pigments in the remaining zooxanthellae algae increased from 1.85 to 11.5 times to sustain its photosynthetic outputs. At the end of the experiment, G. fascicularis managed to increase the rate of its calcium carbonate precipitation. Increase pCO 2 in the atmosphere may affect species diversity of coral reefs.
Exposure to heat‐shock protein (Hsp) stimulating factors induces Hsp accumulation and confers tolerance to lethal ammonia stress on the common carp Cyprinus carpio. This study investigated whether a non‐lethal heat shock bestowed similar protective effects against ammonia and induced thermotolerance, both thought to be rendered by increased amounts of Hsps. The 30‐min lethal temperature (30 min LHT) and 1‐h lethal ammonia concentration (1 h LCT) for this species occurred at 41°C and 14.2 mg/L NH3 respectively. Heating juvenile carp (5 cm) from 28°C to 32, 34 and 38°C, with a subsequent 8‐h recovery period augmented tolerance to lethal heat and ammonia perturbation by two to threefold as compared with animals held at 28°C. Protection occurred in conjunction with Hsp70 accumulation in gills, substantiating the role of this Hsp in enhancing the stress tolerance of common carp.
Terubok (Tenualosa toli) is one of Malaysia commercially important fish which is found mainly in Sarawak. Their numbers of catch have been declining in the past 15 years due to heavy exploitation. Hence, a study was done to determine the mitochondrial genetic diversity of T. toli from Daro and Mukah, Sarawak inferred by partial Cytochrome b gene. DNA extraction was done on 84 T. toli samples. PCR amplification using Cyt-b primers had been carried out and sequence of 469 bp length was obtained from each sample. Next, phylogenetic analysis was performed to study the relationship among the individuals. The genetic diversity of the population was determined through the haplotype and nucleotide diversity. Result of the study showed that the Haplotype Diversity (HD) of T. toli was relatively low for Daro (Hd = 0.232) and Mukah populations (Hd = 0.178). The nucleotide diversity was also low for both populations. Moreover, only nine haplotypes were identified from the 84 individuals. A single haplotype was shared amongst 76 individuals. These findings correlate with previous study that showed the number of the fish caught had declined drastically and might cause a genetic deprivation towards its population. Comparably, maximum likelihood analysis revealed that two T. toli individuals were separated from the main clade, suggesting that these two individuals might come from another Terubok population. Genetic diversity of the mitochondrial DNA Cytochrome b of the T. toli obtained in this study would be useful in the implementation of conservation and fisheries management of this species in Sarawak.
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