Effects of stocking density on the survival, growth, size variation and condition index of juvenile rabbitfish Siganus rivulatus

Spinefoot rabbitfish, Siganus rivulatus, is an economically important species of herbivorous fish that is relatively easy to rear and thus considered to be suitable for aquaculture. Juveniles are generally reared in nursery systems before being stocked into growout cages or ponds. We report here our evaluation of the effects of stocking density on the survival, growth, feed efficiency and condition index of S. rivulatus juveniles in nursery tanks. The experiment was conducted in a recirculating system of twelve 52-l aquaria connected to a biological filter and a sand filter. Juvenile fish (average weight 6.5 g) were stocked into aquaria at four stocking densities (10, 20, 30, and 40 fish/aquarium) with three replicate aquaria per treatment. Diet was provided at 3% body weight daily divided into two feedings. Fish were weighed weekly for 8 weeks and the diet increased accordingly. Survival was greater than 95% in all treatments, with no significant differences observed among treatments. There were also no differences in specific growth rate (SGR 2.12–2.27) of the fish among treatments. Growth rate was linear during the 8 weeks in all treatments, and harvested biomass increased proportionally to stocking density (198, 401, 600 and 785 g per increasing stocking density, respectively). Feed efficiency (FE 0.67–0.71) of the fish did not vary significantly among treatments. The coefficient of variation was high (35–41%) among the harvested fish, but it also did not differ significantly among treatments. The final condition indices of the fish in all treatments were similar to each other but significantly greater than the initial values (P < 0.05). The results suggest that there is no apparent effect of stocking density at the levels tested on the survival and growth of juvenile rabbitfish.     

The relationship between water intake rates,paddy ponding depth,and farmers’ water management techniques

Japanese farmers manage their irrigation water based on their past experiences and preferences, considering such factors as weather and available water (hereafter defined as empirical water management). They elaborately control the intake and drainage rates of their own paddy fields to maintain optimal ponding depths. But these well-managed systems will drastically change because of the decreasing number of farmers. Therefore, it is necessary to clarify if the optimal ponding depth will be maintained within the limits of traditionally-allowed water intake rate from the main river. The first objective of this study was the quantification of actual water use in the paddy fields, resulting from the farmers water management on the basis of their experience. The significance of the present water intake rate under empirical water management was studied for a paddy field command area of about 230 ha. Water intake rates and the water requirements of the whole area were investigated by measuring the flow rate at 17 points of irrigation and drainage canals. Characteristics of the farmers empirical water management were investigated by measuring the hourly changes in inflow and outflow rates for a sub-area using an automatic measurement system, and an inferential method of determining water management patterns for the paddy fields was proposed. The newly-proposed inferential method was introduced in the tank model, which expresses the characteristics of water management in the command area. The Shuffled Complex Evolution Algorithm (SCE-UA) method was used for optimizing the model parameters. It was proven that the model accuracy improved when the farmers empirical water management was taken into account. The optimal amount of water to be applied to the command area was quantified by the simulation. The second objective was to predict the effect of the decreasing number of farmers on future water use conditions. The simulated result indicates the difficulty of maintaining optimal ponding depth for the whole command area when the farmers empirical water management is not maintained. In other words, results indicated that efficient water use requires an automatic water management system or a new pipeline system to replace the farmers present empirical water management.     

Regulation of mycorrhiza development in durum wheat by P fertilization: Effect on plant nitrogen metabolism

The aim of this work was to study the effect of arbuscular mycorrhizal fungus Glomus mosseae on growth and nitrogen (N) metabolism of durum wheat (Tritcum durum) under various P soil contents. The analyses were extended to macro and micronutrient tissue concentrations, nitrate reductase and glutamine synthetase activities, as well as protein, aminoacids, pyridine dinucleotides and adenine nucleotides. Arbuscular mycorrhiza increased wheat growth in soil in which P availability was low and nitrate was the dominant N form. The root colonization occurred at the highest level in plants grown in limiting soil P and was inversely related to soil P content. The micorrhizal wheat plants contained also the highest concentrations of macro (P, K, Ca, N) and micronutrients (Fe, Zn, Mn) as well as free amino acids, protein, NAD, NADP, AMP, ADP, ATP in roots and leaves. In particular, the micronutrient tissue concentrations (Zn, Mn) supported that mycorrhiza actively modulated their uptake limiting interferences and optimizing growth better than the plant roots, like a very efficient “rootstock”. Control plants grown at the highest soil P did not reach the same concentration as the mycorrhizal plants. Nitrate reductase activities in the roots of mycorrhizal plants were higher than in the control ones, while glutamine synthetase activities were highest in the leaves. Protein and amino acids concentrations, as well as AMP, ADP, ATP, NAD(P), and NAD(P)H were also higher than in the control. Among the free amino acids in the roots, the high levels of glutamine, asparagine, arginine, support the view that ammonium was transferred through the arbuscules to the root cells where it was re‐assimilated in the cortical cells, forming high N : C ratio‐amino acids. They were transferred to the leaves where all the other N compounds could be largely synthesized using the carbon skeletons supplied by photosynthesis.     

Nutrient limitations to bacterial and fungal growth during cellulose decomposition in tropical forest soils

Nutrients constrain the soil carbon cycle in tropical forests, but we lack knowledge on how these constraints vary within the soil microbial community. Here, we used in situ fertilization in a montane tropical forest and in two lowland tropical forests on contrasting soil types to test the principal hypothesis that there are different nutrient constraints to different groups of microorganisms during the decomposition of cellulose. We also tested the hypotheses that decomposers shift from nitrogen to phosphorus constraints from montane to lowland forests, respectively, and are further constrained by potassium and sodium deficiency in the western Amazon. Cellulose and nutrients (nitrogen, phosphorus, potassium, sodium, and combined) were added to soils in situ, and microbial growth on cellulose (phospholipid fatty acids and ergosterol) and respiration were measured. Microbial growth on cellulose after single nutrient additions was highest following nitrogen addition for fungi, suggesting nitrogen as the primary limiting nutrient for cellulose decomposition. This was observed at all sites, with no clear shift in nutrient constraints to decomposition between lowland and montane sites. We also observed positive respiration and fungal growth responses to sodium and potassium addition at one of the lowland sites. However, when phosphorus was added, and especially when added in combination with other nutrients, bacterial growth was highest, suggesting that bacteria out-compete fungi for nitrogen where phosphorus is abundant. In summary, nitrogen constrains fungal growth and cellulose decomposition in both lowland and montane tropical forest soils, but additional nutrients may also be of critical importance in determining the balance between fungal and bacterial decomposition of cellulose.     

Environmental effects on soil NO concentrations and root N uptake in beech and spruce forests

This study aimed to investigate the shifts in net nitrogen (N) uptake and N compounds of fine roots over the vegetation period (i.e., spring, summer, autumn) and correlate this with NO concentration in the soil. Soil NO concentration was measured using gas lysimeters for collection and a chemiluminescence analyzer for quantification. Net N uptake by the roots was determined using the ¹⁵N enrichment technique. N pools were quantified using spectrophotometric techniques. Soil NO concentrations at beech and spruce forest sites were highest in spring (June), and lowest in winter (December). Total N of the roots was similar during the seasons and between the two years under study despite considerable variation of different N compounds. Net N uptake generally increased with higher N supply. Correlation analysis revealed a positive relationship between soil NO concentration and net N uptake only for spruce trees. This relationship seemed to be modulated by environmental factors and tree species.     

Biochar improves sediment microbial fuel cell performance in low conductivity freshwater sediment

Purpose

The low conductivity of sediments for mass and electron transport is the most severe limiting factor in sediment microbial fuel cells (SMFCs), so that sediment ameliorations yielded more remarkable effects than electrode improvements. The objective of this research was to enhance the electricity generation of SMFCs with amendments of biochar to freshwater sediments for conductivity enhancement.

Materials and methods

Laboratory-scale SMFCs were constructed and biochars were produced from coconut shells at different temperatures. Variations in the power output, electrode potential, internal resistance, total organic carbon (TOC) content, and microbial communities were measured.

Results and discussion

Amending with biochar reduced the charge transfer resistances of SMFCs and enriched the Firmicutes (mainly Fusibacter sp.) in the sediment, which improved the SMFC power generation by two- to tenfold and enhanced the TOC removal rate by 1.7- to fourfold relative to those without the amendment.

Conclusions

The results suggested that biochar amendment is a promising strategy to enhance SMFC power production, and the electrical conductivity of biochar should be considered important when interpreting the impact biochar has on the electrical performance of soil or freshwater sediment MFCs.

     

Comparison of effects of high-pressure processing and heat treatment on immunoactivity of bovine milk immunoglobulin G in enriched soymilk under equivalent microbial inactivation levels

Immunoglobulin-rich foods may provide health benefits to consumers. To extend the refrigerated shelf life of functional foods enriched with bovine immunoglobulin G (IgG), nonthermal alternatives such as high-pressure processing (HPP) may offer advantages to thermal processing for microbial reduction. To evaluate the effects of HPP on the immunoactivity of bovine IgG, a soymilk product enriched with milk protein concentrates, derived from dairy cows that were hyperimmunized with 26 human pathogens, was subjected to HPP or heat treatment. To achieve a 5 log reduction in inoculated Escherichia coli 8739, the HPP or heat treatment requirements were 345 MPa for 4 min at 30 degrees C or for 20 s at 70 degrees C, respectively. To achieve a 5 log reduction in natural flora in the enriched soymilk, the HPP or heat treatments needed were 552 MPa for 4 min at 30 degrees C or for 120 s at 78.2 degrees C, respectively. At equivalent levels for a 5 log reduction in E. coli, HPP and heat treatment caused 25% and no detectable loss in bovine IgG activity, respectively. However, at equivalent levels for a 5 log reduction in natural flora, HPP and heat resulted in 65 and 85% loss of bovine IgG activity, respectively. Results of combined pressure-thermal kinetic studies of bovine milk IgG activity were provided to determine the optimal process conditions to preserve product function.     

Colorimetric evaluation of phenolic content and GC-MS characterization of phenolic composition of alimentary and cosmetic argan oil and press cake

The global phenolic content of argan oil and press cake samples (alimentary and cosmetic) was evaluated using the Folin-Ciocalteu colorimetric method and the phenolic composition of argan oil (alimentary and cosmetic) and press cake (alimentary) samples were analyzed by GC-MS after extraction with 80:20 (v/v) methanol:water and silylation. Identification of chromatographic peaks was made by mass selective detection. Nineteen simple phenols were detected, 16 in press cake, 6 in the alimentary oil, and 7 in the cosmetic oil, among which 15 compounds [3-hydroxypyridine (3-pyridinol), 6-methyl-3-hydroxypyridine, catechol, resorcinol, 4-hydroxybenzyl alcohol, vanillin, 4-hydroxyphenylacetic acid, vanillyl alcohol, 3,4-dihydroxybenzyl alcohol, 4-hydroxy-3-methoxyphenethyl alcohol, methyl 3,4-dihydroxybenzoate, hydroxytyrosol, protocatechuic acid, epicatechin, and catechin] were identified for the first time in such materials.     

A bayesian model for the analysis of lactation curves of dairy goats

This article aims to determine the effect of certain covariates, such as season of kidding, parity, and time of kidding on the characteristics of the lactation curve of Saanen dairy goats. Characteristics investigated are peak milk yield, time of peak milk yield, total milk production, persistency, and the relationship between fat and protein in milk composition, as well as between lactation curves of the same animal in successive years. The analysis is carried out using a hierarchical Bayesian approach, together with Wood’s model, to model lactation. Posterior distributions of quantities of interest are obtained by means of the Markov chain Monte Carlo (MCMC) methods. These clearly illustrate the significant effect of especially parity, but also season and time of kidding on the characteristics of the lactation curve. Total and peak milk yield increase with increasing parity up to about the third or fourth parity, while peak yield is later for first than for later parities. The analysis also enables estimation of lactation characteristics of untested animals, prediction of future characteristics and identification of exceptional animals.     

Effect of bensulfuron-methyl (a sulfonylurea herbicide) on the soil bacterial community of a paddy soil microcosm

The effect of bensulfuron-methyl (BSM) on a soil microbial community in a model paddy microcosm was studied. Total bacterial numbers in the overlying water and surface soil were monitored for 2 months after the application of BSM at the field rate and a ten-fold field rate. Pentachlorophenol (PCP) was used for comparison. Neither chemical affected the total bacterial numbers remarkably, either in the overlying water or in the surface soil. In contrast, the nitrification potential was significantly suppressed by the BSM application. The bacterial community structure, as evaluated by the denaturing gradient gel electrophoresis (DGGE) of PCR amplification products from bacterial 16S rDNA, was unaffected by the BSM treatments over 8 weeks in the surface soil, compared with the control (no pesticide). In contrast, the surface soil exposed to PCP at a ten-fold field rate showed different patterns from the controls at 4 weeks and 8 weeks after application. The DGGE patterns of the overlying water were much more variable than those of the surface soil in any treatments. Cluster analysis showed that the BSM plots were classified within the same group as the control at 1 week after application and that the BSM and PCP plots from 2 weeks onward after application were grouped differently from the control. Of 22 clones excised from the DGGE gels, 20 clones belonged to the Proteobacteria and two belonged to the Verrucomicrobia. It was considered that the impact of BSM on the overall microbial community (total numbers, community structure of soil) was negligible, although BSM had an impact on some specific functions of the soil microbial community (nitrification) and a part of the community (overlying water).