Assessment of Nutrients Recovery Capacity and Biomass Growth of Four Microalgae Species in Anaerobic Digestion Effluent

Four microalgae species were evaluated for their bioremediation capacity of anaerobic digestion effluent (ADE) rich in ammonium nitrogen, derived from a biogas plant. Chlorella vulgaris, Chlorella sorokiniana, Desmodesmus communis and Stichococcus sp. were examined for their nutrient assimilation efficiency, biomass production and composition through their cultivation in 3.7% v/v ADE; their performance was compared with standard cultivation media which consisted in different nitrogen sources, i.e., BG-11NO3 and BG-11ΝΗ4 where N-NO3 was replaced by N-NH4. The results justified ammonium as the most preferable source of nitrogen for microalgae growth. Although Stichococcus sp. outperformed the other 3 species in N-NH4 removal efficiency both in BG-11NH4 and in 3.7% ADE (reaching up to 90.79% and 69.69% respectively), it exhibited a moderate biomass production when it was cultivated in diluted ADE corresponding to 0.59 g/L, compared to 0.89 g/L recorded by C. vulgaris and 0.7 g/L by C. sorokiniana and D. communis. Phosphorus contained in the effluent and in the control media was successfully consumed by all of the species, although its removal rate was found to be affected by the type of nitrogen source used and the particular microalgae species. The use of ADE as cultivation medium resulted in a significant increase in carbohydrates content in all investigated species.

Water Use, Leaf Cooling and Carbon Assimilation Efficiency of Heat Resistant Common Beans Evaluated in Western Amazonia

In our study, we analyzed 30years of climatological data revealing the bean production risks for Western Amazonia. Climatological profiling showed high daytime and nighttime temperatures combined with high relative humidity and low vapor pressure deficit. Our understanding of the target environment allows us to select trait combinations for reaching higher yields in Amazonian acid soils. Our research was conducted using 64 bean lines with different genetic backgrounds. In high temperatures, we identified three water use efficiency typologies in beans based on detailed data analysis on gasometric exchange. Profligate water spenders and not water conservative accessions showed leaf cooling, and effective photosynthate partitioning to seeds, and these attributes were found to be related to higher photosynthetic efficiency. Thus, water spenders and not savers were recognized as heat resistant in acid soil conditions in Western Amazonia. Genotypes such as BFS 10, SEN 52, SER 323, different SEFs (SEF 73, SEF 10, SEF 40, SEF 70), SCR 56, SMR 173, and SMN 99 presented less negative effects of heat stress on yield. These genotypes could be suitable as parental lines for improving dry seed production. The improved knowledge on water-use efficiency typologies can be used for bean crop improvement efforts as well as further studies aimed at a better understanding of the intrinsic mechanisms of heat resistance in legumes.

Seasonal Dynamics of Photochemical Performance of PS II of Terrestrial Mosses from Different Elevations

Mosses are critical components of tropical forest ecosystems and have multiple essential ecological functions. The drying and rehydrating and often hot environments in tropical regions present some of the greatest challenges for their photosynthetic activities. There is limited knowledge available on the physiological responses to the changing environments such as temperature and water pattern changes for terrestrial mosses. We examined the seasonal dynamics of photochemical performance of PS II through the measuring of chlorophyll fluorescence of 12 terrestrial mosses in situ from five different elevations by Photosynthesis Yield Analyzer MINI-PAM-II, along with the seasonal changes of climatic factors (air temperature, dew point, relative humidity and rainfall), which were collected by local weather stations and self-deployed mini weather stations. The results showed a great seasonality during observing periods, which, mainly the changes of rainfall and relative humidity pattern, presented significant impacts on the photochemical performance of PS II of terrestrial mosses. All these tested moss species developed a suitable regulated and non-regulated strategy to avoid the detrimental effect of abiotic stresses. We found that only Hypnum plumaeforme, Pterobryopsis crassicaulis and Pogonatum inflexum were well adapted to the changes of habitat temperature and water patterns, even though they still experienced a lower CO2 assimilation efficiency in the drier months. The other nine species were susceptible to seasonality, especially during the months of lower rainfall and relative humidity when moss species were under physiologically reduced PS II efficiency. Anomobryum julaceum, Pogonatum neesii, Sematophyllum subhumile, Pseudotaxiphyllum pohliaecarpum and Leucobryum boninense, and especially Brachythecium buchananii, were sensitive to the changes of water patterns, which enable them as ideal ecological indicators of photosynthetic acclimation to stressed environments as a result of climate change.

Far-Red Chlorophyll Fluorescence Radiance Tracks Photosynthetic Carbon Assimilation Efficiency of Dark Reactions

Solar-induced chlorophyll fluorescence (SIF) observations from space have shown close relationships with terrestrial photosynthesis rates. SIF originates from the light reactions of photosynthesis, whereas carbon fixation takes place during the dark reactions of photosynthesis. Questions remain regarding whether SIF is able to track changes in the efficiency of the dark reactions in photosynthesis. Using concurrent measurements of leaf-scale gas exchange, pulse amplitude-modulated (PAM) fluorescence, and fluorescence spectral radiances, we found that both far-red fluorescence radiances and PAM fluorescence yields responded rapidly to changes in photosynthetic carbon assimilation due to changes in environmental factors or induced stomatal closure under constant light conditions. Uncertainties in outgoing and incoming irradiance mismatch for SIF measurements may very likely obscure the contributions of the dark reactions, thereby causing the inconsistent findings previously reported, which were no change in far-red SIF and PAM fluorescence yields after clear reductions in the photosynthetic carbon assimilation efficiency of dark reactions. Our results confirm that high-quality SIF measurements have the potential to provide insights into the dark reactions of photosynthesis. This study is particularly relevant for better interpreting satellite SIF observations that are obtained under roughly constant overpass times and relatively stable light intensities.

Research and application of parameter estimation method in hydrological model based on dual ensemble Kalman filter

Although field measurements and using long hydrological datasets provide a reliable method for parameters' calibration, changes in the underlying basin surface and lack of hydrometeorological data may affect parameter accuracy in streamflow simulation. The ensemble Kalman filter (EnKF) can be used as a real-time parameter correction method to solve this problem. In this study, five representative Xin'anjiang model parameters are selected to study the effects of the initial parameter ensemble distribution and the specific function form of the parameter on EnKF parameter estimation process for both single and multiple parameters. Results indicate: (1) the method of parameter calibration to determine the initial distribution mean can improve the assimilation efficiency; (2) there is mutual interference among the parameters during multiple parameters' estimation which invalidates some conclusions of single-parameter estimation. We applied and evaluated the EnKF method in Jinjiang River Basin, China. Compared to traditional approaches, our method showed a better performance in both basins with long hydrometeorological dataset (an increase of Kling–Gupta efficiency (KGE) from 0.810 to 0.887 and a decrease of bias from −1.08% to −0.74%); and in basins with a lack of hydrometeorological data (an increase of KGE from 0.536 to 0.849 and a decrease of bias from −15.55% to −11.42%).

Grazing intensity changed the activities of nitrogen assimilation related enzymes in desert Steppe Plants

Background Nitrogen, as a limiting factor for net primary productivity in grassland ecosystems, is an important link in material cycles in grassland ecosystems. However, the nitrogen assimilation efficiency and mechanisms of grassland plants under grazing disturbance are still unclear. This study investigated Stipa breviflora desert steppe which had been grazed for 17 years and sampled the root system and leaf of the constructive species Stipa breviflora during the peak growing season under no grazing, light grazing, moderate grazing and heavy grazing treatments. The activities of enzymes related to nitrogen assimilation in roots and leaves were measured. Results Compared with no grazing, light grazing and moderate grazing significantly increased the activities of nitrate reductase (NR), glutamine synthetase (GS), glutamic oxaloacetic transaminase (GOT) and glutamic pyruvate transaminase (GPT) in leaves, and GS, GOT and GPT in roots of Stipa breviflora, while heavy grazing significantly decreased the activities of GS in leaves and NR in roots of Stipa breviflora. NR, GOT and GPT activities in leaves and roots of Stipa breviflora were positively correlated with nitrogen content, soluble protein, free amino acid and nitrate content. Conclusions Grazing disturbance changed the activities of nitrogen assimilation related enzymes of grassland plants, and emphasized that light grazing and moderate grazing were beneficial for nitrogen assimilation by grassland plants. Therefore, establishing appropriate stocking rates is of great significance for material flows in this grassland ecosystem and for the stability and sustainable utilization of grassland resources.

Physiological and Molecular Analysis Reveals the Differences of Photosynthesis between Colored and Green Leaf Poplars

Leaf coloration changes evoke different photosynthetic responses among different poplar cultivars. The aim of this study is to investigate the photosynthetic difference between a red leaf cultivar (ZHP) and a green leaf (L2025) cultivar of Populus deltoides. In this study, ‘ZHP’ exhibited wide ranges and huge potential for absorption and utilization of light energy and CO2 concentration which were similar to those in ‘L2025’ and even showed a stronger absorption for weak light. However, with the increasing light intensity and CO2 concentration, the photosynthetic capacity in both ‘L2025’ and ‘ZHP’ was gradually restricted, and the net photosynthetic rate (Pn) in ‘ZHP’ was significantly lower than that in ‘L2025’ under high light or high CO2 conditions, which was mainly attributed to stomatal regulation and different photosynthetic efficiency (including the light energy utilization efficiency and photosynthetic CO2 assimilation efficiency) in these two poplars. Moreover, the higher anthocyanin content in ‘ZHP’ than that in ‘L2025’ was considered to be closely related to the decreased photosynthetic efficiency in ‘ZHP’. According to the results from the JIP-test, the capture efficiency of the reaction center for light energy in ‘L2025’ was significantly higher than that in ‘ZHP’. Interestingly, the higher levels of light quantum caused relatively higher accumulation of QA- in ‘L2025’, which blocked the electron transport and weakened the photosystem II (PSII) performance as compared with ‘ZHP’; however, the decreased capture of light quantum also could not promote the utilization of light energy, which was the key to the low photosynthetic efficiency in ‘ZHP’. The differential expressions of a series of photosynthesis-related genes further promoted these specific photosynthetic processes between ‘L2025’ and ‘ZHP’.

Arthropod prey vary among orders in their nutrient and exoskeleton content

Insectivores gain macronutrients and elements from consuming arthropod prey, but must also deal with indigestible components (i.e., exoskeleton) of prey. For example, avian chicks (e.g. northern bobwhites; Colinus virginianus) have limited gut space, and ingesting prey with relatively higher proportions of indigestible components may impact assimilation efficiency, growth, and survival. The ability of insectivores to choose higher quality prey would depend on prey taxa varying consistently in nutritional content. We tested if there were consistent differences among taxonomic orders of arthropod prey in their macronutrient (protein and lipid), elemental (C and N), and exoskeleton content. We used northern bobwhite chicks as our focal insectivore and focused on their potential prey as a case study. We also tested the influence of indigestible exoskeleton on the measurement of macronutrient content and the ability of elemental content to predict macronutrients. We found large and consistent variation in macronutrient and elemental content within and between arthropod orders. Some orders had consistently high protein content and low exoskeleton content (i.e., Araneae) and are likely higher quality prey for insectivores. Abundant orders common in the diets of insectivores, like Hymenoptera and Coleoptera, had high exoskeleton content and low protein content. We also found support for the ability of elements to predict macronutrients, and found that metabolizable (i.e. exoskeleton removed) elemental content better predicted macronutrient content. A better understanding of arthropod nutrient content is critical for elucidating the role of spatial and temporal variation in prey communities in shaping the growth and survival of insectivores.

Photosynthetic Parameters Show Specific Responses to Essential Mineral Deficiencies

In response to decreases in the assimilation efficiency of CO2, plants oxidize the reaction center chlorophyll (P700) of photosystem I (PSI) to suppress reactive oxygen species (ROS) production. In hydro-cultured sunflower leaves experiencing essential mineral deficiencies, we analyzed the following parameters that characterize PSI and PSII: (1) the reduction-oxidation states of P700 [Y(I), Y(NA), and Y(ND)]; (2) the relative electron flux in PSII [Y(II)]; (3) the reduction state of the primary electron acceptor in PSII, QA (1 − qL); and (4) the non-photochemical quenching of chlorophyll fluorescence (NPQ). Deficiency treatments for the minerals N, P, Mn, Mg, S, and Zn decreased Y(II) with an increase in the oxidized P700 [Y(ND)], while deficiencies for the minerals K, Fe, Ca, B, and Mo decreased Y(II) without an increase in Y(ND). During the induction of photosynthesis, the above parameters showed specific responses to each mineral. That is, we could diagnose the mineral deficiency and identify which mineral affected the photosynthesis parameters.

Nutrient Incorporation in First Feeding Seahorses Evidenced by Stable Carbon Isotopes

Nutritional issues are among the most critical factors in the initial survival of juvenile seahorses. Currently, there is a knowledge gap on the relationship between nutrient assimilation and the effects on initial mortalities and growth. In the present study, the stable isotope approach was used to assess the incorporation of two live preys (Artemia and copepods) in juvenile seahorses Hippocampus guttulatus. The changes in stable carbon isotope (δ13C) values were studied through two feeding experiments: feeding on Artemia or copepods (experiment 1), and shifting feeding from copepods to Artemia (experiment 2). In experiment 1, after 24–48 h of feeding, juvenile seahorses exhibited small but progressive changes in δ13C values towards those of the corresponding diet, indicating that the assimilation of the food offered was progressively enhanced from days 2–3. Similarly, in experiment 2, a diet shifting from copepods to Artemia caused an increase in δ13C values, reflecting a switch towards the isotopically enriched new diet (Artemia metanauplii). Differences in the assimilation efficiency of preys offered are discussed based on growth and survival rates. The enhanced growth performances and survivals achieved when the juveniles were fed on copepods could be related to higher efficient assimilation of copepods compared to Artemia. The present study demonstrates that the consumption and further assimilation of preys by juvenile seahorses could be traced using stable carbon isotopes. The research on nutrient assimilation of juvenile seahorses should enhance our knowledge on nutrient processes in developing seahorses for a better understanding of initial ontogeny in the early life stages of the species.