Nutrient and phytoplankton dynamics of the Hunter River estuary

Observational studies and nutrient amendment experiments were conducted to better understand the nutrient and phytoplankton dynamics of the Hunter River estuary. Eutrophic conditions above ANZECC guidelines for estuaries dominate the Hunter River estuary. The upper Hunter estuary, upstream of its confluence with the Williams River, had the highest concentrations of nutrients and chlorophyll a. The major source of nutrients appears to be riverine discharge. Discharge from WWTP in the upper Hunter potentially contributes an important secondary source of phosphorus. Processes such as bank erosion and resuspension may also be important in explaining variation in nutrient concentrations. Light and turbidity were the main factors limiting phytoplankton growth in the upper estuary. The nutrient amendment experiments showed that when light limitation was alleviated, phytoplankton were either nitrogen limited or remained unlimited by nutrients (suggesting nutrients were in surplus for growth). The expression of nitrogen limitation is likely due to low N:P in the estuary. Organic nitrogen dominates the nitrogen pool within the Hunter estuary. The bioavailability of organic nitrogen in the estuary is unknown which may explain the lack of relationship between phytoplankton and nitrogen concentrations within the estuary. Diatoms and green algae dominated phytoplankton. There were occasions when toxic cyanobacteria was in high abundance in the upper estuary, however a longer data set of phytoplankton assemblage is needed to more adequately assess the risk of toxic cyanobacteria. Comparison of data from the monthly, twice-weekly, and hourly sampling intervals demonstrated the five-year monthly sampling data appeared to mostly capture the variability of nutrient and chlorophyll a concentrations in relation to their main explanatory factors (discharge and light). There were some examples of chlorophyll a and nitrogen concentrations that fell outside of predicted ranges. Overall the results suggest any increase in nitrogen loads to the estuary may lead to increased phytoplankton growth. Improved light climate may also lead to increased phytoplankton growth. Reducing inputs of both nitrogen and phosphorus to the upper Hunter estuary should be a priority action to increase ecosystem health.

Effects of soil nutrient amendments on growth and grain yield performances of quality protein maize grown under water deficit stress in Ibadan, Nigeria

<p class="042abstractstekst">Drought and poor soil fertility are major limitations to crop production, globally. To investigate the impacts of water deficit stress (WS) and soil nutrient amendment (SA) on growth and yield performances of maize. A two years factorial field study was carried out, using a quality protein maize (QPM) (ILE-1-OB) and a non QPM–drought tolerant check (TZPBSR-W) varieties in Ibadan. Treatments include; six fertilizer application rates; 50 and 100 (kg N ha^-1) ofNPK-20-10-10, 10.7 kg N ha^-1of Tithonia Poultry Compost (TPC), 50 N + 10.7TPC and 100 N + 10.7TPC (kg N ha^-1), three WS; the control (FW), WS at vegetative stage (STR1), and WS at reproductive stage (STR2). Leaf area (LA) and grain yield (GY) were measured using standard procedures. From the results, across WS, LA ranged from STR1 (458.90 ± 12.4) to FW (598.81 ± 13.1 cm²), GY varied from STR2 (2.94 ± 0.2 t ha^-1) to FW (6.59 ± 0.2 t ha^-1), across fertilizers, LA varied from 0 N (397.65 cm²) to 100N + 10.7TPC (622.71 cm²) and 50 N + 10.7TPC (611.03 cm²), respectively. The GY varied from 0 N (2.37 t ha^-1) to 100 N + 10.7TPC (5.82 t ha^-1) and 50N + 10.7TPC (5.26 t ha^-1).<strong> </strong>Drought stress reduced growth and GY performances of QPM, while SA with 50 kg N ha^-1 of inorganic fertilizer and 10.7 kg N ha^-1 of<em> </em>TPC enhanced growth and grain yield of maize under WS.</p>

Network structure of resource use and niche overlap within the endophytic microbiome

Endophytes often have dramatic effects on their host plants. Characterizing the relationships among members of these communities has focused on identifying the effects of single microbes on their host, but has generally overlooked interactions among the myriad microbes in natural communities as well as potential higher-order interactions. Network analyses offer a powerful means for characterizing patterns of interaction among microbial members of the phytobiome that may be crucial to mediating its assembly and function. We sampled twelve endophytic communities, comparing patterns of niche overlap between coexisting bacteria and fungi to evaluate the effect of nutrient supplementation on local and global competitive network structure. We found that, despite differences in the degree distribution, there were few significant differences in the global network structure of niche-overlap networks following persistent nutrient amendment. Likewise, we found idiosyncratic and weak evidence for higher-order interactions regardless of nutrient treatment. This work provides a first-time characterization of niche-overlap network structure in endophytic communities and serves as a framework for higher-resolution analyses of microbial interaction networks as a consequence and a cause of ecological variation in microbiome function.

A Comparative Study on the use of Soil - Organic and Inorganic Biostimulants in the Remediation of Oily Waste

Remediation of oily waste using soil-organic (goat dung, poultry dropping) and inorganic (NPK fertilizer) nutrients was assessed for twelve weeks using culture-dependent microbiological technique and chemical procedures. The results indicate increased counts of Hydrocarbon-utilizing bacteria, fungi and actinomycetes with remediation time for both nutrient types. Bacteria in the remediated waste were members of the genera Bacillus, Pseudomonas, Acinetobacter, Alcaligenes and Serratia, fungi: Penicillium, Aspergillus and Cladosporium, and actinomycetes: Rhodococcus, Nocardia and Streptomyces for all soil-nutrient amendment techniques. pH of the NPK fertilizer ranged between 6.7 ± 0.03 and 7.3±0.06 whereas the goat dung and poultry dropping amendments was 6.5± 0.02 and 7.1 ±0.05. Dehydrogenase activity increased for the biostimulant treatment cells with remediation time. Total Petroleum Hydrocarbon reduction was 99.3 and 99.6% in organic and 99.8% for inorganic amendments. Polycyclic Aromatic Hydrocarbons of the remediated waste for both techniques revealed values below detectable limits (< 0.01) at the end of remediation period. Remediation with soil-goat dung and soil-poultry dropping amendments compared favorably with soil-NPK fertilizer technique because microbial activities were enhanced to produce eco-friendly waste. The use of soil-organic amendments is therefore a low-cost alternative biostimulant for the management of oily waste in the petroleum industry.

Improving Farmers’ Revenue in Crop Rotation Systems with Plot Adjacency Constraints in Organic Farms with Nutrient Amendments

The search for sustainable agriculture is leading many economies to turn to crop rotation systems and to abandon monoculture systems which generally require increased use of pesticides and synthetic fertilizers. But the optimization of crop rotation remains a challenge, especially when considering organic farming. This work tackles the optimization of crop rotation in traditional organic farms with plot adjacency constraints and nutrient amendments. In the present configuration, each farmer owns a certain quantity of rudimentary equipment and a number of workers, all considered as resources. Farms are subdivided into plots and each plot allows only one crop at a given period. At a given interval of time, each plot receives a certain quantity of nutrient. The generated rotations are of fixed durations for all plots and the objective is to maximize farmers’ income. A linear programming approach is used to determine the solution of the proposed farming model. Three levels of constraints are combined in the linear program to generate realistic rotations: (i) biophysical constraints including crop succession and plot adjacency; (ii) structural constraints including budget and resources; (iii) organizational constraints such as nutrient amendment and market demand. To evaluate the performance of the model, scenarios based on real-world data has been defined and solved using free solvers. The solutions obtained indicate that all the constrains are satisfied. In addition, farmers’ revenue is improved, reaching a stationary position when the quantity of available resources is equal or greater than the quantity of required resources. Finally, Cbc solver is faster than GLPK solver; and it provides solutions on larger instances where GLPK does not.

Nutrients cause consolidation of soil carbon flux to small proportion of bacterial community

Nutrient amendment diminished bacterial functional diversity, consolidating carbon flow through fewer bacterial taxa. Here, we show strong differences in the bacterial taxa responsible for respiration from four ecosystems, indicating the potential for taxon-specific control over soil carbon cycling. Trends in functional diversity, defined as the richness of bacteria contributing to carbon flux and their equitability of carbon use, paralleled trends in taxonomic diversity although functional diversity was lower overall. Among genera common to all ecosystems, Bradyrhizobium, the Acidobacteria genus RB41, and Streptomyces together composed 45–57% of carbon flow through bacterial productivity and respiration. Bacteria that utilized the most carbon amendment (glucose) were also those that utilized the most native soil carbon, suggesting that the behavior of key soil taxa may influence carbon balance. Mapping carbon flow through different microbial taxa as demonstrated here is crucial in developing taxon-sensitive soil carbon models that may reduce the uncertainty in climate change projections.

Biodegradation of Natural Rubber: Microcosm Study

In the present work, natural rubber (NR) biodegradation, by means of a microbial consortium, naturally selected in a tyre dump soil, has been evaluated. To this purpose, prepared soil microcosms were incubated for 236 days, at room temperature, and natural light/dark cycles. The effect of primary C-source and fresh soil addition, soil aeration, and humidity maintenance has been monitored by means of microbiological and respirometric analysis, dry weight loss determinations, and SEM micrographs. During the incubation, in biodegradation microcosms (BD), containing NR samples, the produced CO2 was significantly higher than that of biotic controls (BC). Furthermore, after 236 days, a NR dry weight loss of 15.6%, in BD microcosms, was registered, about four-fold higher than that registered in BC control (3.7%). Obtained results confirmed that the naturally selected microbial consortium was able to use NR as the only C-source and to biodegrade it. The positive effect of soil mixing evidenced that the biodegradation process was mainly carried out by aerobic biomass, especially filamentous fungi, as confirmed by microbial counts and SEM observations. Results obtained in the microcosm study provided useful information in terms of soil aeration and nutrient amendment in view of a future biodegradation process scale-up.

Ideal Feedstock and Fermentation Process Improvements for the Production of Lignocellulolytic Enzymes

The usage of lignocellulosic biomass in energy production for biofuels and other value-added products can extensively decrease the carbon footprint of current and future energy sectors. However, the infrastructure in the processing of lignocellulosic biomass is not well-established as compared to the fossil fuel industry. One of the bottlenecks is the production of the lignocellulolytic enzymes. These enzymes are produced by different fungal and bacterial species for degradation of the lignocellulosic biomass into its reactive fibers, which can then be converted to biofuel. The selection of an ideal feedstock for the lignocellulolytic enzyme production is one of the most studied aspects of lignocellulolytic enzyme production. Similarly, the fermentation enhancement strategies for different fermentation variables and modes are also the focuses of researchers. The implementation of fermentation enhancement strategies such as optimization of culture parameters (pH, temperature, agitation, incubation time, etc.) and the media nutrient amendment can increase the lignocellulolytic enzyme production significantly. Therefore, this review paper summarized these strategies and feedstock characteristics required for hydrolytic enzyme production with a special focus on the characteristics of an ideal feedstock to be utilized for the production of such enzymes on industrial scales.