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Field observations of the population dynamics and measurements of photophysiology in Lake Biwa were conducted by size class (< vs. > 30 μm) from early summer to autumn to investigate the relationships between susceptibility to light stress and cell size. Also, a nutrient bioassay was conducted to clarify whether the growth rate and photosystem II (PSII) photochemistry of small and large phytoplankton are limited by nutrient availability. Large phytoplankton, which have lower intracellular Chl-a concentrations, had higher maximum PSII photochemical efficiency (Fv/Fm) but lower non-photochemical quenching (NPQNSV) than small phytoplankton under both dark and increased light conditions. The nutrient bioassay revealed that the PSII photochemistry of small phytoplankton was restricted by N and P deficiency at the pelagic site even at the end of the stratification period, while that of large phytoplankton was not. These results suggest that large phytoplankton have lower susceptibility to PSII photodamage than small phytoplankton due to lower intracellular Chl-a concentrations. The size dependency of susceptibility to PSII photoinactivation may play a key role in large algal blooms in oligotrophic water.

Sediment oxygen demand (SOD) measurement currently requires a long preparation time and bulky experimental equipment, which represent major obstacles to conducting SOD measurements. We developed a new SOD measurement method that can be easily conducted in a shorter time than the existing laboratory method. The undisturbed sediment core was transferred into the custom-made small glass vial (inner diameter 12.8 mm, length 125 mm). The SOD sample was incubated in the dark with or without stirring the overlying water inside the vial. The change in DO concentration was measured using a non-contact fluorescent oxygen sensor, and then the SOD was calculated. For comparison and verification of the new method, SOD was also measured using a large undisturbed sediment core (inner diameter 11 cm, length 50 cm). The SOD measurements using the new method were positively correlated with the SOD measurements using the large undisturbed sediment core, suggesting that the new method is a feasible alternative to the conventional method. In the new method, many SOD measurements can be taken from a single sediment core sample. This makes it possible to reduce the uncertainty associated with the highly heterogeneous structure of the sediments, and thus the new method has great advantages in obtaining reliable SOD data. A novel high-throughput method for SOD was developed that shortens sample preparation time and improves convenience of measurement. The new method is expected to contribute substantially to the accumulation of SOD monitoring data and to make great progress in elucidating the dynamics of dissolved oxygen in lakes.

The most widely used method for measuring bacterial production is tritium-labeled leucine (3H-Leu). Although this method provides methodological simplicity and high sensitivity, the employment of radioactive isotopes is often restricted by regulations, particularly in field settings. In this study, we developed a non-radioactive method for measuring bacterial productivity based on the protein synthesis rate, using deuterium-labeled leucine ((CD3)2CDCD2CD(NH2)COOH; D10-Leu); the proposed method was then compared and verified with the3H-Leu method. The procedures of the proposed method are (1) incorporation of D10-Leu by bacteria, (2) acid hydrolysis (HCl) to amino acids and (3) quantification of D10-Leu (m/z142.10) by liquid chromatography mass spectrometry (LC-MS/MS). In the LC-MS/MS analysis, we detected a larger amount of D9-Leu (m/z141.10) and D8-Leu (m/z140.10) than that of D10-Leu, suggesting that incorporated D10-Leu was rapidly metabolized such as in deamination and aminotransferase reactions. The incorporation rates of D10-Leu, D10-Leu + D9-Leu (D10+D9-Leu) and D10-Leu + D9-Leu + D8-Leu (D10+D9+D8-Leu) were significantly positively correlated to that of3H-Leu, confirming the validity of the proposed method. Since D7-Leu (m/z139.10) could not be detected, the amount of exogenous leucine incorporated into protein can be accurately estimated through D10+D9+D8-Leu measurement. The new compound-based quantification method using stable isotope-labeled leucine can be a powerful tool to estimate pure protein synthesis rate for measuring bacterial production.

This study analyses the impact of using foldable containers in terms of cost savings of truck drayage operations, of both loaded and empty containers, in the hinterland of a seaport. We model a vehicle routing problem to optimise empty container relocation. A simulated annealing algorithm is developed to solve the problem. Numerical experiments are carried out in realistic empty container relocation scenarios. We find that, under certain conditions, foldable containers can offer higher truck productivity compared with standard containers, hence resulting in substantial cost savings. This paper provides managerial insights into how foldable containers can help reduce the costs of hinterland transport.

Fast repetition rate fluorometer (FRRf) is a beneficial method for measuring photosystem II (PSII) photophysiology and primary productivity. Although FRRf can measure PSII absorption cross-section (σPSII), maximum photochemical efficiency (Fv/Fm), effective photochemical efficiency (Fq'/Fm'), and non-photochemical quenching (NPQNSV) for various eukaryotic algae and cyanobacteria, almost all FRRf studies to date have focused on phytoplankton. Here, the protocol describes how to measure PSII photophysiology of an epizoic alga Colacium sp. Ehrenberg 1834 (Euglenophyta), in its attached stage (attached to zooplankton), using cuvette-type FRRf. First, we estimated the effects of substrate zooplankton (Scapholeberis mucronata O.F. Müller 1776, Cladocera, Daphniidae) on baseline fluorescence and σPSII, Fv/Fm, Fq'/Fm', and NPQNSV of planktonic Colacium sp. To validate this methodology, we recorded photophysiology measurements of attached Colacium sp. on S. mucronata and compared these results with its planktonic stage. Representative results showed how the protocol could determine the effects of calcium (Ca) and manganese (Mn) on Colacium sp. photophysiology and identify the various effects of Mn enrichment between attached and planktonic stages. Finally, we discuss the adaptability of this protocol to other periphytic algae.

Fast repetition rate fluorometer (FRRf) is a beneficial method for measuring photosystem II (PSII) photophysiology and primary productivity. Although FRRf can measure PSII absorption cross-section (σPSII), maximum photochemical efficiency (Fv/Fm), effective photochemical efficiency (Fq'/Fm'), and non-photochemical quenching (NPQNSV) for various eukaryotic algae and cyanobacteria, almost all FRRf studies to date have focused on phytoplankton. Here, the protocol describes how to measure PSII photophysiology of an epizoic alga Colacium sp. Ehrenberg 1834 (Euglenophyta), in its attached stage (attached to zooplankton), using cuvette-type FRRf. First, we estimated the effects of substrate zooplankton (Scapholeberis mucronata O.F. Muller 1776, Cladocera, Daphniidae) on baseline fluorescence and σPSII, Fv/Fm, Fq'/Fm', and NPQNSV of planktonic Colacium sp. To validate this methodology, we recorded photophysiology measurements of attached Colacium sp. on S. mucronata and compared these results with its planktonic stage. Representative results showed how the protocol could determine the effects of calcium (Ca) and manganese (Mn) on Colacium sp. photophysiology and identify the various effects of Mn enrichment between attached and planktonic stages. Finally, we discuss the adaptability of this protocol to other periphytic algae.

Combinable containers can either be used as a standard 20 ft or in combined state as a 40 ft container by altering the dimensional to match the cargo size. This paper examines the viability of combinable containers for saving the container related costs. We present a model of a minimum cost multi-commodity network flow problem that can be used to simultaneously determine the fleet sizes of standard and combinable containers and their empty container allocation/repositioning. Based on numerical experiments, we discovered that mixed use of both types of containers can save a significant portion of container related cost.

In Lake Biwa, the largest lake in Japan, external pollutant loads have decreased since the 1980s, leading to improved water quality, such as reduction in biochemical oxygen demand (BOD) and PO43− concentrations. We examined long-term variation of bacterial production (BP) under these environmental changes from 2016–2017 in the north basin of Lake Biwa. BP was estimated by measuring the incorporation of stable isotope 15N-labeled deoxyadenosine (15N-dA) from June 2016 and December 2017 and compared with measurements from 1986 and 1997–1998. In 1986, BP was measured by following 3H-labeled thymidine (3H-TdR) incorporation and in 1997–1998 by tracking bacterial abundance in incubations and calculating specific growth rates (μ). To allow direct comparison of 15N-dA and 3H-TdR incorporation rates, we determined a conversion factor. To estimate μ in 2016–2017, we determined a factor for converting 15N-dA incorporation to cell number increase. In 2016–2017, the 15N-dA incorporation rate ranged from 0.13 to 30.7 pmol l−1 h−1 and μ ranged from 0.016 to 0.70 day−1. BP values from 3H-TdR incorporation rates in 1986 and μ in 1997–1998 were 4.6 and 2.1 times BP values in 2016–2017, respectively, confirming the decrease in BP over the past 3 decades in Lake Biwa. Water quality data showed only low decrease rates for BOD and total phosphorus concentration from the 1980s, whereas the rate of decrease for PO43− concentrations was equivalent to that of BP. BP and decomposition of organic matter are known to be strongly P-limited in Lake Biwa. Our results suggest that the decrease in BP can be explained by a reduction in readily bioavailable PO43−. Organic phosphorus can also be an important P-source for BP under conditions with very low PO43− concentrations (nM), and changes in the bioavailability of organic phosphorus might have also regulated BP dynamics.

Fast repetition rate fluorometer (FRRf) is a beneficial method for measuring photosystem II (PSII) photophysiology and primary productivity. Although FRRf can measure PSII absorption cross section (σPSII), maximum photochemical efficiency (Fv/Fm), effective photochemical efficiency (Fq′/Fm′), and non-photochemical quenching (NPQNSV) for various eukaryotic algae and cyanobacteria, almost all FRRf studies to date have focused on phytoplankton. Here, we describe how to measure PSII photophysiology of an epizoic alga Colacium sp.Ehrenberg 1834 (Euglenophyta), in its attached stage (attached to zooplankton) using cuvette-type FRRf. First, we estimated the effects of substrate zooplankton (Scapholeberis mucronata O.F. Müller 1776, Cladocera, Daphniidae) on background fluorescence and σPSII, Fv/Fm, Fq′/Fm′, and NPQNSV of planktonic Colacium sp. To validate our methodology, we recorded photophysiology measurements of attached Colacium sp. on S. mucronata and compared these results with its planktonic stage. Representative results showed how the protocol can determine effects of Ca and Mn on Colacium sp. photophysiology and identify the various effects of Mn enrichment between attached and planktonic stages. Finally, we discuss the adaptability of this protocol to other periphytic algae.

To explore the mechanisms in the deposition and release of phosphorus (P) in the sediment of a shallow eutrophic lake using preserved samples, we investigated the vertical and temporal changes in P, manganese (Mn), sulfur (S), iron (Fe), aluminum (Al), calcium (Ca), and magnesium (Mg) in the sediment samples and the phosphate in the sediment pore water samples over a period of 6 years. The upper 15 cm of sediment from Lake Kasumigaura in Japan was collected monthly from 2003 to 2008 from the center of the lake. Sediment cores were divided into seven depth segments and were acid-digested for an elemental analysis via inductively coupled plasma atomic emission spectroscopy. Phosphate concentrations of the sediment pore water were determined using the molybdenum blue method. A multiple regression analysis was conducted by setting the P content as the response variable and Mn, S, Fe, Al, Ca, and Mg as explanatory variables. The results of the multiple regression analysis demonstrated that P co-precipitates with Fe and Al oxides and accumulates on the sediment surface. The vertical distributions of Mn and S suggest that Mn reduction occurs within the 0–1-cm-depth layer of the sediment and that iron sulfide is actively formed in the 6–10-cm-depth layer of the sediment. These findings imply that the layer in which ferric oxides are reduced to ferrous ions is present near the 1–6-cm-depth layer of the sediment. This layer corresponds to the layer in which the maximum phosphate concentration of the sediment pore water often occurred (the 2–6-cm-depth layer). These results indicate that vertical distributions of mineral elements are useful for assessing P dynamics in sediments. The lake sediments record the dynamics of P in the sediment. Our analytical approach using long-term observation data demonstrated that the accumulation and release of P associated with a change in the redox state can be assessed based on the vertical distributions of mineral elements in the lake sediments.

Appropriate management of macrophyte biomass via harvesting is crucial for maintaining eutrophic inland waters. However, information on the effects of macrophyte harvesting on the quality and bottom environment of these waters is limited. For our project on Lake Biwa in Japan, we focused on the pore water quality of the surface sediment as a reliable tool for estimating the effects of macrophyte harvesting. We compared the release of heavy metals and nutrients from the sediment based on the pore water quality of harvesting and non-harvesting sites. Our results suggested that macrophyte harvesting affected the water quality poorly in terms of sediment resuspension, but effectively reduced the amount of macrophyte litter on the lake bottom. Different methods of macrophyte harvesting are discussed, and cutting away only the upper section of macrophytes to avoid sediment resuspension instead of pulling up the macrophytes by the root was found to be the ideal harvesting method. In addition, sustainable harvesting to reduce the macrophyte litter on the lake bottom would be required to conserve the lake environment.

The intensity of the 340/430-nm peak in the three-dimensional excitation-emission matrix spectra of water samples has been used as an index of the concentration of aquatic humic substance (AHS). However, whether this peak corresponds uniquely to AHS has not been definitively verified. Therefore, in this study, our objectives were: (1) to determine whether the 340/430-nm peak in the spectra of lake and river water samples does, in fact, correspond uniquely to AHS; (2) to determine what type of dissolved organic matter (DOM), in terms of hydrophobicity, accounts for the peak; and (3) to determine the advisability of using excitation-emission matrix spectroscopy to rapidly estimate AHS concentrations. We found that the 340/430-nm peak originates not only from the AHS fraction of DOM but also from a portion of the hydrophilic fraction. By analyzing the quantitative relationship between AHS concentration and 340/430-nm peak intensity for DOM samples, we found the intensity can be used to estimate AHS concentration in lake water when the concentration is strongly affected by influent river water or when the ratio of ultraviolet (UV) absorbance to dissolved organic carbon concentration is relatively high.

Anaerobic digestion effluent (ADE) from aquatic macrophytes (Egeria densa, Elodea nuttallii, Ceratophyllum demersum and Potamogeton maackianus) contains insufficient available magnesium ions (Mg2+) to achieve maximum algal yield and nutrient removal, although Mg concentrations are not scarce at 6–10 mg L−1. Unavailable Mg2+ may be bound into complexes with dissolved organic matter (DOM). We determined the effects of ADE exposure to ultraviolet C (UVC), and degradation of DOM, on Mg availability for growth of Chlorella sorokiniana. Molecular sizes of DOM binding Mg2+ were identified with high-performance size-exclusion chromatography. The results demonstrated that 3 h exposure to UVC can decompose DOM, and release sufficient amounts of available Mg2+, i.e. 0.09 mg from 1 mg of dissolved organic carbon, thus enhancing algal yield and nutrient removal. Almost 50 % of Mg in the ADE was bound by DOM with a molecular size of 400–1170 Da as organic complexes, and the remaining Mg was bound by DOM of

We tested the hypothesis that mineralization of molybdenum unreactive phosphorus (MUP) in pore water is the major pathway for the changes in the concentration of molybdenum-reactive P (MRP) in pore water and inorganic P in sediment particles. The concentration of inorganic P in the sediment particles increased from December to April in Lake Kasumigaura, whereas concentrations of organic P in the sediment particles and MUP in pore water decreased. These results suggest that MUP mineralization plays a key role as the source of MRP, whereas desorption of inorganic P from the sediment particles into the pore water is a minor process. One-dimensional numerical simulation of sediment particles and the pore water supported the hypothesis. Diffusive flux of MUP was small in pore water, even in near-surface layers, so mineralization was the dominant process for changing the MUP concentration in the pore water. For MRP, diffusion was the dominant process in the surface layer, whereas adsorption onto the sediment was the dominant process in deeper layers. Researchers usually ignore organic P in the sediment, but organic P in sediment particles and the pore water is a key source of inorganic P in the sediment particles and pore water; our results suggest that in Lake Kasumigaura, organic P in the sediment is an important source, even at depths more than 1 cm below the sediment surface. In contrast, the large molecular size of MUP in pore water hampers diffusion of MUP from the sediment into the overlying water.

Bacterial production has been often estimated from DNA synthesis rates by using tritium-labeled thymidine. Some bacteria species cannot incorporate extracellular thymidine into their DNA, suggesting their biomass production might be overlooked when using the conventional method. In the present study, to evaluate appropriateness of deoxyribonucleosides for evaluating bacterial production of natural bacterial communities from the viewpoint of DNA synthesis, incorporation rates of four deoxyribonucleosides (thymidine, deoxyadenosine, deoxyguanosine and deoxycytidine) labeled by nitrogen stable isotope (15N) into bacterial DNA were examined in both ocean (Sagami Bay) and freshwater (Lake Kasumigaura) ecosystems in July 2015 and January 2016. In most stations in Sagami Bay and Lake Kasumigaura, we found that incorporation rates of deoxyguanosine were the highest among those of the four deoxyribonucleosides, and the incorporation rate of deoxyguanosine was approximately 2.5 times higher than that of thymidine. Whereas, incorporation rates of deoxyadenosine and deoxycytidine were 0.9 and 0.2 times higher than that of thymidine. These results clearly suggest that the numbers of bacterial species which can incorporate exogenous deoxyguanosine into their DNA are relatively greater as compared to the other deoxyribonucleosides, and measurement of bacterial production using deoxyguanosine more likely reflects larger numbers of bacterial species productions.

To investigate differences in culturable freshwater bacterioplankton between summer and winter, we examined specific bacterioplankton in the low temperature surface water of two shallow, hypereutrophic, temperate lakes in Japan over two winters, and compared our results with the previously published data. We used the size-exclusion assay method (SEAM), a cultivation-based approach that simply and effectively isolates typical freshwater bacterioplankton. The specific clusters detected in the winter samples were the Rhodoferax sp. BAL47 cluster (LimA and LimC), a predominant and ubiquitous freshwater lineage, and the LiUU-5-340 cluster. To confirm tolerance to low water temperature of winter-specific groups, we also compared growth rates at 5°C among several pure strains of typical freshwater bacterioplankton clusters belonging to the Rhodoferax sp. BAL47, Polynucleobacter necessarius, GKS98, LiUU-5-340, and IRD18C08 of the class Betaproteobacteria, and the Luna-1 and Luna-2 of the class Actinobacteria. Specific detectability of freshwater bacterioplankton clusters/subclusters by SEAM in the winter sample substantially correlated with the low temperature-specific growth characteristics of each isolate. Response to water temperature is a key control factor in freshwater bacterioplankton assemblage composition. These results provide important insights into the specific response to water temperature of several ubiquitous culturable freshwater bacterioplankton clusters inhabiting a temperate climate zone.

The recalcitrant landfill leachate was anaerobically digested at various mixing ratios with labile synthetic wastewater to evaluate the degradation properties of recalcitrant wastewater. The proportion of leachate to the digestion system was increased in three equal steps, starting from 0% to 100%, and later decreased back to 0% with the same steps. The chemical oxygen demand (COD) for organic carbon and other components were calculated by analyzing the COD and dissolved organic carbon (DOC), and the removal efficiencies of COD carbon and COD others were evaluated separately. The degradation properties of COD carbon and COD others shifted owing to changing of substrate degradability, and the removal efficiencies of COD carbon and COD others were improved after supplying 100% recalcitrant wastewater. The UV absorptive property and total organic carbon (TOC) of each molecular size using high performance liquid chromatography (HPLC)-size exclusion chromatography (SEC) with UVA and TOC detectors were also investigated, and the degradability of different molecular sizes was determined. Although the SEC system detected extracellular polymeric substances (EPS), which are produced by microbes in stressful environments, during early stages of the experiment, EPS were not detected after feeding 100% recalcitrant wastewater. These results suggest that the microbes had acclimatized to the recalcitrant wastewater degradation. The high removal rates of both COD carbon and COD others were sustained when the proportion of labile wastewater in the substrate was 33%, indicating that the effective removal of recalcitrant COD might be controlled by changing the substrate's degradability.

Molecular size and dissolved organic carbon (DOC) distributions of dissolved organic matter (DOM) in seawater were determined qualitatively and quantitatively by high-performance size exclusion chromatography (HPSEC). To estimate the relationship between molecular size distribution and the DOC concentration of seawater DOM, seawater was desalinated with an electric dialyzer. The recent technological advancements of desalination make us possible to recover a high percentage of seawater DOM. Surface coastal seawater samples were collected from three locations in Japan: Tokyo Bay, Kashima Port, and Cape Inubo. Samples were evaluated by a chromatography system coupled with ultraviolet (UV) absorbance, fluorescence, and non-dispersive infrared total organic carbon detectors in series. Two peaks, 1 (1.24 × 105−1.54 × 105 Da) and 2 (9.48 × 102−1.81 × 103 Da), were detected in all sample chromatograms. Peak 1 showed little fluorescence and UV absorption in all samples. It has been shown that carbohydrates, one of the main components of seawater DOM, exhibit almost no fluorescence or UV absorption; thus, Peak 1 could mainly consist of carbohydrates which are usually labile DOM. Total DOC concentrations of the Tokyo Bay, Kashima Port, and Cape Inubo were 1.38, 0.92, and 0.80 mg C L−1, respectively. Peak 2 accounted for 75–80% of the total DOC and showed a substantial humic-like fluorescence and UV absorption in all samples. These results indicate that the photochemical characteristics of seawater DOM significantly differ depending on its molecular size. Thus, analysis of molecular size with our HPSEC provides a new approach for quantitative and qualitative characterization of seawater DOM.

Deoxygenation of sorbitol was carried out over a Pt-modified Ir-ReOx/SiO2 catalyst in biphasic solvent system (n-decane + H2O) without external hydrogen. Good yield of gasoline-ranged products was obtained including C5–C6 alkanes and C2–C6 mono-functionalized compounds such as ketones, alcohols, cyclic ethers and carboxylic acids. The Pt(3 wt%)-Ir-ReOx/SiO2 catalyst showed the best performance in the production of gasoline-ranged products. The maximum yield of gasoline-ranged products was 42%. The distribution of the products can be tuned by the addition of HZSM-5. The main products were C5–C6 alkanes with addition of HZSM-5 while the main products were C2–C6 mono-functionalized compounds without addition of HZSM-5. Characterizations such as TPR, XRD, TEM, XANES, EXAFS, CO adsorption were performed. The results demonstrated that the Pt-Ir-ReOx/SiO2 catalyst showed the structure of Pt-Ir alloy particles partially covered with ReOx species. The number of surface Pt atoms in Pt(3)-Ir-ReOx/SiO2 was larger than that of Pt/SiO2 or Pt-ReOx/SiO2 because of the small size of Pt-Ir alloy particles. The large number of surface Pt atoms and the synergetic effect of Pt, Ir and ReOx species make the catalyst efficiently generate hydrogen by aqueous phase reforming of sorbitol, and the generated hydrogen is consumed in the hydrogenolysis C O bonds.

We observed phosphorus (P) compound groups in sediment in Lake Kasumigaura in winter (February and March) and summer (July and August) to identify how their composition differs between the seasons. The concentration of soluble unreactive P in sediment pore water (SUPpore) was significantly higher in winter than in summer, whereas the concentration of soluble reactive P (SRPpore) was significantly higher in summer than in winter. In summer, when the concentration of SRPpore was high, the concentration of orthophosphate was greatest (~80 %) among the P compound groups. The concentration of orthophosphate diesters had a significant negative correlation with SUPpore concentration and was significantly lower in winter (high SUPpore concentration) than in summer. Such relative abundance of P compound groups in sediment could have resulted from adsorption of orthophosphate in summer and degradation of orthophosphate diesters in winter; these seasonal processes could contribute significantly to the changes in the concentrations of SRPpore and SUPpore, possibly influencing the P concentrations in the water column in Lake Kasumigaura.

This study aimed to clarify the vertical differences in bacterial growth and grazing pressure on bacteria by heterotrophic nanoflagellates (HNF) and to identify the controlling factors of bacterial growth in temperate coastal waters of Sagami Bay, Japan. In addition to environmental factors, the annual monthly variations in bacterial growth rate (BGR) and the relative abundance of bacteria to HNF (BA/HNFA) were investigated in the euphotic and disphotic layers between May 2012 and May 2013. Significant vertical differences in BGR and BA/HNFA were evident between the two layers during the thermal stratification times of May to October 2012 and April to May 2013. BGR indicated significantly stronger limitation of bacterial growth in the euphotic layer compared to the disphotic layer. In contrast, significantly lower BA/HNFA was observed in the euphotic layer, suggesting significantly higher grazing pressure on bacteria by HNF. However, significant differences in BGR and BA/HNFA were not observed between the two layers from November 2012 to Match 2013, when the water column was well-mixed vertically due to the cooling and wind-induced mixing of surface water. This study indicates that bacteria in the euphotic layer grow less actively and are more vulnerable to predatory grazing by HNF relative to the disphotic layer during the stratification period. Further, multiple regression analyses indicate that bacterial growth was most controlled by the concentrations of chlorophyll a and dissolved organic carbon in the euphotic and disphotic layers, respectively.

Understanding the proximate factors and mechanisms driving primary production in manmade reservoirs is crucial because such production can translate into added fish yields that provide people with food and livelihoods. Furthermore, reservoir fish production could potentially compensate for the loss of fish yields due to habitat fragmentation and alterations caused by damming and impoundment. We monitored primary production, identified environmental factors responsible for its variability, and examined the relationship between primary production and fish production in nine large water bodies of the Lower Mekong Basin for 2 years. The estimated primary production ranged from 40 to 302 g C/m2/y and was generally greater in the wet season than in the dry season. Linear mixed-effects modelling identified the concentration of dissolved inorganic carbon as a significant fixed-effect variable regulating primary production, after variability due to random and fixed effects of water body and seasonality, respectively, were taken into account. Fish yields marginally increased with increasing primary production across the water bodies, with the estimated energy transfer efficiency ranging from 0.004 to 0.009. Dissolved inorganic carbon was partly determined by the lithological composition of the water body catchment, suggesting that the geographic locations of proposed dams determine the magnitude of primary production and hence future fish production.

Changes in the characteristics of dissolved organic matter (DOM: the dissolved fraction of natural organic matter) during a series of wastewater treatment plant (WWTP) processes were investigated by using a combination of molecular size analysis and excitation emission matrix (EEM) spectroscopy coupled with parallel factor analysis. The characteristics of DOM were compared following aerobic, anoxic, and anaerobic treatments. Three peaks at about 100,000 Da (high-molecular-size DOM, Peak 1) and about 900–1,100 Da (intermediate-molecular-size DOM, Peak 2; low-molecular-size DOM, Peak 3 as the shoulder of Peak 2) were observed in the distribution of total organic carbon molecular sizes in the influent of the WWTPs. In this study, five fluorescent components (C1 to C5) were identified in the EEM spectra. Molecular size analysis and molecular size fractionation revealed that the C3 (humic-like) and C5 (specific to sewage) fluorophores had intermediate or low molecular sizes. Comparison of the changes of the concentrations of dissolved organic carbon in each reaction tank and investigation of the removal selectivity of each treatment (aerobic, anaerobic, and anoxic) suggested that the heterogenous compounds present in DOM of the influent were homogenized into intermediate-molecular-size DOM with high hydrophobicity and aromaticity, or into C4 fluorophores (DOM-X), during anaerobic or anoxic treatment. DOM-X was able to be transformed or removed by aerobic treatment. The results suggested that introduction of aerobic treatment at the appropriate stage of wastewater treatment or inclusion of physical or chemical treatment should be an effective way to optimize DOM removal.

CO 2 occupies over 90% of artificially emitted the Greenhouse Gas (GHG). As related in CO 2 emission from road traffic, we focus on a vehicle routing for marine container transport. There are three container conditions: inbound trip, outbound trip and empty condition. And also there are two situations for vehicles: trailer truck (with full or empty container loaded) and empty truck (as tractor only). In this study, we address the tractor head assignment to trailers (chassis) with full/empty container with considering the precedence constraints for visiting customers, as to minimize CO 2 emissions. As the computational results, there are around 25 % reductions of CO 2 emissions in our proposed MIP model.

This study was conducted to acquire novel insight into differences between bulk (16S rDNA) and metabolically active (16S rRNA) prokaryotic communities in the sediment of a hypereutrophic lake (Japan). In the bulk communities, the class Deltaproteobacteria and the order Methanomicrobiales were dominant among bacteria and methanogens. In the metabolically active communities, the class Alphaproteobacteria and the order Methanomicrobiales and the family Methanosaetaceae were frequently found among bacteria and methanogens. Unlike the bulk communities of prokaryotes, the composition of the metabolically active communities varied remarkably vertically, and their diversities greatly decreased in the lower 20 cm of sediment. The metabolically active prokaryotic community in the sediment core was divided into three sections based on their similarity: 0–6 cm (section 1), 9–18 cm (section 2), and 21–42 cm (section 3). This sectional distribution was consistent with the vertical pattern of the sedimentary stable carbon and nitrogen isotope ratios and oxidation–reduction potential in the porewater. These results suggest that vertical disturbance of the sediment may influence the communities and functions of metabolically active prokaryotes in freshwater lake sediments. Overall, our results indicate that rRNA analysis may be more effective than rDNA analysis for evaluation of relationships between actual microbial processes and material cycling in lake sediments.

There are many problems related to overgrowth of aquatic macrophytes in many lakes and rivers throughout the world; for instance, the harvesting costs in Lake Biwa have been increasing by 200 million Japanese yen a year (equivalent to 1.8 million USD). Historically, aquatic macrophytes were harvested for use as fertilizer in agriculture in Japan, but are no longer in use because chemical fertilizers promote plant growth more effectively and are easier and cheaper to use. Thus, developing effective ways to utilize aquatic macrophytes is important to resolve this issue. In addition, sustainably harvesting macrophytes is also important for aquatic ecosystem management because macrophytes play a key role in aquatic ecosystems as nursery grounds and refuges for other small organisms living in the littoral area. Therefore, management and effective utilization of macrophytes through sustainable harvesting may play an important role in the conservation of lake ecosystems. In this short review, a recycling system using anaerobic digestion (AD) of submerged macrophytes, which were sustainably harvested from lakes, and microalgal mass culturing with AD effluent were introduced as a new technique for the conservation of lake ecosystems.

We herein designed novel PCR primers for universal detection of the pepA gene, which encodes the representative leucine aminopeptidase gene, and investigated the genetic characteristics and diversity of pepA genes in sediments of hypereutrophic Lake Kasumigaura, Japan. Most of the amino acid sequences deduced from the obtained clones (369 out of 370) were related to PepA-like protein sequences in the M17 family of proteins. The developed primers broadly detected pepA-like clones associated with diverse bacterial phyla-Alpha-, Beta-, Gamma-, and Deltaproteobacteria, Acidobacteria, Actinobacteria, Aquificae, Chlamydiae, Chloroflexi, Cyanobacteria, Firmicutes, Nitrospirae, Planctomycetes, and Spirochetes as well as the archaeal phylum Thaumarchaeota, indicating that prokaryotes in aquatic environments possessing leucine aminopeptidase are more diverse than previously reported. Moreover, prokaryotes related to the obtained pepA-like clones appeared to be r- and K-strategists, which was in contrast to our previous findings showing that the neutral metalloprotease gene clones obtained were related to the r-strategist genus Bacillus. Our results suggest that an unprecedented diversity of prokaryotes with a combination of different proteases participate in sedimentary proteolysis.

n-Pentane, pentanols and xylitol can be separately produced from hemicellulose (xylan) over an Ir–ReOx/SiO2 catalyst combined with acids by simply adjusting the reaction conditions. n-Pentane can be produced by using Ir–ReOx/SiO2 combined with HZSM-5 + H2SO4 in a biphasic solvent system (4 ml n-dodecane + 9.5 ml H2O) with a reaction temperature of 463 K for 24 h. Pentanols can be produced by using Ir–ReOx/SiO2 combined with H2SO4 in a biphasic solvent system (20 ml n-dodecane + 9.5 ml H2O) with a reaction temperature of 413 K for 144 h. Xylitol can be produced by using Ir–ReOx/SiO2 combined with H2SO4 in the aqueous phase with a reaction temperature of 413 K for 12 h. The highest yields of n-pentane, pentanols and xylitol could reach 70%, 32% and 79%, respectively. The reuse of the catalyst was feasible when the catalyst was regenerated by calcination at 773 K for 3 h. The calcination step is for removing the humins which were formed at the hydrolysis + hydrogenation step during conversion of xylan. The humins covered the active site of Ir–ReOx/SiO2 and HZSM-5, and they deactivated Ir–ReOx/SiO2 in C–O hydrogenolysis performance in part. The mineral ions (such as Na+ and K+) in xylan decreased the hydrogenolysis activity of Ir–ReOx/SiO2 significantly since the mineral ions can make the number of hydroxorhenium sites (Re–OH) smaller, which is the active site of Ir–ReOx/SiO2 for C–O hydrogenolysis, by ion exchange. The appropriate amount of H2SO4 addition is very crucial for the production of target products in high yield. The addition of H2SO4 not only neutralized the residual alkali of xylan after being isolated from lignocellulose to make the reaction solution acidic, but also improved the C–O hydrogenolysis activity of Ir–ReOx/SiO2 through increasing the number of hydroxorhenium sites by competitive adsorption on the Re site with mineral ions.

After the passage of typhoon Malou in 2010, daily field samplings were conducted at both inshore (Sta. A) and offshore (Sta. M) stations in Sagami Bay, Japan, to evaluate responses of bacteria and phytoplankton to variations of physical-chemical environments induced by typhoon passage. Malou passage caused an abrupt decline of salinity and a large increase in the amount of nutrients at both stations. The relationships between salinity and nutrient concentrations suggested that major nutrient sources were terrestrial runoff at Sta. M and sediment resuspension in addition to terrestrial runoff at Sta. A. Bacterial production (BP) at Sta. A showed 114 ± 21 mg C m −3 d −1 one day after Malou passage, while primary production (PP) was 76 ± 8 mg C m −3 d −1 , suggesting the dominance of BP (BP/PP ratio = 1.5). PP exceeded BP two days after Malou passage, and then reached a maximum of 554 ± 32 mg C m −3 d −1 five days later (BP/PP ratio = 0.10). PP was always dominant at Sta. M throughout the study period (BP/PP ratio = 0.13 ± 0.05). The ratio of BP to bacterial abundance (BP/BA ratio) at Sta. M showed a positive correlation with PP, suggesting that bacterial productivity depended on autochthonous substrates derived from phytoplankton. The BP/BA ratio at Sta. A showed no relationship with PP, suggesting that bacterial productivity was enhanced not only by PP, but also loading of allochthonous substrates. BP/BA ratios at both stations increased exponentially with the increase of PO 4 and NH 4 concentrations; these concentrations are likely coming from sediment pore waters. The results suggest that sediment resuspension induced by typhoon passage enhanced bacterial productivity abruptly just after the passage at an inshore station. The bacterial response could be regulated by difference in relative contribution of nutrient sources after the passage of typhoon.

This study proposed a non-radioactive quantitative measurement of bacterial production using stable isotope nitrogen-15-labeled deoxyadenosine ([15N5]-2′-deoxyadenosine; 15N-dA) by liquid chromatography mass spectrometry (LC–MS). The method of preparing 5N-dA described in this study included incubation of seawater or lake water with 15N-dA for 5–24 h, filtration onto a membrane filter, DNA extraction, enzymatic hydrolysis of DNA to nucleosides and quantification of 15N-dA by LC–MS. In the DNA extraction, the silica beads method was examined first, but a large amount of salts and enzymatic inhibitors used in the method caused failure of subsequent procedures, such as enzymatic hydrolysis and LC–MS analysis. On the other hand, the magnetic beads method showed much better results for the extraction. The incorporation rate of 15N-dA was significantly positively correlated to that of tritium-labeled thymidine (3H-TdR) in samples of coastal seawaters and lake waters. The average 15N-dA: 3H-TdR incorporation ratio for the seawater sample was 0.55 with 2.5 and 97.5 % confidence intervals of 0.51 and 0.58, respectively; the average ratio for the lake water sample was 0.28 with 2.5 and 97.5 % confidence intervals of 0.23 and 0.34, respectively. The results suggest that the 15N-dA method can be applied to the measurement of bacterial production in aquatic ecosystems, and that this method can accurately predict the DNA synthesis rates measured by the conventional method.