Seasonal variations of water column nutrients in the inner area of Ariake Bay, Japan: the role of muddy sediments

To investigate seasonal variations of nutrient distribution in the mudflat–shallow water system, we conducted field surveys once a month from August 2007 to July 2008 in the inner area of Ariake Bay (IAB), Japan. The NH₄ ⁺–N concentration of the water column increased in autumn because of the high NH₄ ⁺ release from the sediments, ranging from 850 to 3,001 μmol?m^?2?day^?1. The NO₃ ^?–N concentration was maximal in January, which was thought to be caused by NO₃ ^? release from the oxic sediments and by NO₃ ^? regeneration due to water column nitrification. The PO₄ ^3?–P concentration of the water column was high in summer–autumn due to the high PO₄ ^3? release from the reduced sediments, ranging from 22 to 164 μmol?m^?2?day^?1. We estimated the total amounts of DIN and PO₄ ^3?–P release (R _DIN and $ {R_{{\mathrm{P}{{\mathrm{O}}_4}}}} $ , respectively) from the muddy sediment area of the IAB. In summer–autumn, R _DIN and $ {R_{{\mathrm{P}{{\mathrm{O}}_4}}}} $ corresponded to about 47.7 % of DIN input and about 116.6 % of PO₄ ^3?–P input from the river, respectively. Thus, we concluded that the muddy sediments were an important source of nutrients for the water column of the IAB during summer–autumn. In addition, we found that phosphorus necessary for the growth of Porphyra (Porphyra yezoensis, Rhodophyceae) would be insufficient in the water column when phosphorus during the Porphyra aquaculture period is supplied only from the river. Therefore, the phosphorus release from the muddy sediments was thought to play an important role in the sustainable production of Porphyra in Ariake Bay.     

The generative power of metaphor: long‐term action research on disaster recovery in a small Japanese village

Disaster recovery is a dynamic process of creating, maintaining, and changing the meaningful context of survivors. It is completed when they redevelop their self‐reliance and resume managing their social relations with a sense of community. This study employed action research to examine how researchers and survivors collaborated to change disaster recovery through the generative power of metaphor in a small village in Japan that experienced the Niigata–Chuetsu earthquake on 23 October 2004. It outlines long‐term collaborative practices as survivors undertook new activities owing to the power of the metaphor of ‘school’. Once ‘school’ was adopted as the metaphor for where survivors learnt new skills and passed on traditional knowledge, they created new metaphors and performed new activities independently, which is critical for recovery as it demonstrates self‐reliance. The paper assesses the reasons why generative metaphors worked effectively in this case and highlights some academic and practical implications for disaster recovery.     

Growth and reproductive cycles of the marine fouling ascidians Ciona intestinalis,Styela plicata,Botrylloides violaceus,and Leptoclinum mitsukurii at Aburatsubo-Moroiso Inlet (central Japan)

Experimental cultivations of post-metamorphosis juveniles were repeated in different seasons for Ciona intestinalis (L.) and Styela plicata (Lesueur) (simple ascidians) as well as for Leptolinum mitsukurii (Oka) and Botrylloides violaceus Oka (compound ascidians) at Aburatsubo-Moroiso Inlet near Misaki Biological Station (Japan). Growth in body length of simple ascidians was exponential during juvenile development up to near sexual maturity. C. intestinalis grew to sexual maturity in 1 month in summer and in 2 months in winter; S. plicata, in 2 months in summer and in nearly 5 months in winter. The doubling time decreased approximately twofold in the two simple ascidians with a 10C° increase in environmental temperature. Growth of colonies in compound ascidians was exponential after maturation of the first functional zooids. Sexual reproduction of L. mitsukurii and B. violaceus was continuous throughout the year, forming many generations in a year. Doubling time of colony growth in the two compound ascidians decreased approximately threefold with a 10C° increase in temperature.     

Atmospheric NO2 and CO concentration in Lima,Peru

The atmospheric concentration of NO2 in Lima, Peru was measured through 1 year using passive samplers. The concentration was stable and evident seasonal change was not observed. Also, the distribution of NO2 concentration in entire Lima was monitored twice in different seasons. The average NO2 concentrations at 33 and 27 sites of these monitoring were 17.1 and 15.3 ppb, respectively. NO2 distribution was high in the downtown area and decreased gradually with distance from there. The wind that almost always blew from the ocean had a great influence on it. High NO2 level and the change of CO concentration suggest that the residential area in the northeast side forms a topological channel among hills to blow out the pollutants from the downtown area.     

Determination of dissolved oxygen limitation in aerobic biofilm reactors

The concentration of dissolved oxygen (DO) strongly influences the performance of aerobic biofilm reactors because organic oxidation is limited by the availability of oxygen. However, it is not necessary to maintain a high DO level in the reactors in order to overcome this limitation. Excessive aeration wastes energy. Therefore, the determination of the onset of DO limitation against organic substrate removal in aerobic biofilm reactors is important for their effective operation. This study is aimed at developing an expression to determine the onset of DO limitation and hence to control the aeration system. The expression developed is as follows: , where S_b and C_b are the bulk concentrations of organic substrate and DO, respectively; D_ws and D_wc are the diffusion coefficients of organic substrate and oxygen in the reactors respectively; and R_b is an overall ratio of oxygen consumption to organic substrate removal in the reactors. The latter is the key parameter in the equation, and is determined by the characteristics of the substrate, biofilm, and reactor. In order to measure the value of R_b, the authors have developed a micro-biofilm reactor. The value of R_b was determined to be 0.13 (mg O₂ mg⁻¹ COD_cr) for glucose removal with this reactor. The equation has, subsequently, been verified with data from batch and continuous experiments.     

Effects of Nitrogen Supply on the Sensitivity to O3 of Growth and Photosynthesis of Japanese Beech (Fagus crenata) Seedlings

To obtain basic information for evaluating critical levels of O₃ under different nitrogen loads for protecting Japanese beech forests, two-year-old seedlings of Fagus crenata Blume were grown in potted andisol supplied with N as NH₄NO₃ solution at 0, 20 or 50 kg ha⁻¹ year⁻¹ and exposed to charcoal-filtered air or O₃ at 1.0, 1.5 and 2.0 times the ambient concentration from 16 April to 22 September 2004. The O₃ induced significant reductions in the whole-plant dry mass, net photosynthetic rate at 380 μmol mol⁻¹ CO₂ (A ₃₈₀), carboxylation efficiency (CE) and concentrations of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and total soluble protein (TSP) in the leaves. The concentrations of Rubisco and TSP were negatively correlated with the concentration of leaf acidic amino acid, suggesting that O₃ enhanced the degradation of protein such as Rubisco. The N supply to the soil did not significantly change the whole-plant dry mass and A ₃₈₀, whereas it significantly increased the CE and concentrations of Rubisco and total amino acid. No significant interactive effects of O₃ and N supply to the soil were detected on the growth, photosynthetic parameters and concentrations of protein and amino acid in the leaves. In conclusion, N supply to the soil at ≤50 kg ha⁻¹ year⁻¹ does not significantly change the sensitivity to O₃ of growth and net photosynthesis of Fagus crenata seedlings.     

Effect of Poly(dioxolane) as Compatibilizer in Poly(ɛ-caprolactone)/Tapioca Starch Blends

The influence of poly(dioxolane) (PDXL), a poly(ethylene oxide-alt-methylene oxide), as compatibilizer on poly(ɛ-caprolactone) (PCL)/tapioca starch (TS) blends was studied. In order to facilitate blending; PCL, PDXL and TS must be blended together directly; so that PDXL is partially adhered at the TS surface as shown by scanning electron microscopy. The molecular weight effect of PDXL on the PCL/TS blends showed that mechanical properties of PCL/TS/PDXL blends from low molecular weight (M _n=10,000) and high molecular weight (M _n=200,000) PDXL were rather dependent on TS content. The enzymatic degradability of PCL/TS/PDXL blends using α-amylase increased as the TS content increased but was independent on the dispersion of tapioca starch in the PCL matrix.