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An increase in available nitrogen loading in intertidal ecosystems causes eutrophication and macroalgae blooms. Denitrification and anaerobic ammonium oxidation (anammox) lead to the removal of bioavailable nitrogen, but few studies have examined this in intertidal sediments. The sediment anammox and denitrification rates in September 2015 and November 2016 were measured using a 15N tracer technique at two sites, with and without macroalgae, in the hypereutrophic Yatsu tidal flat, eastern Japan. At both sites, the rate of N2 production via anammox was consistently low compared with that via denitrification, accounting for

Remobilization of radiocesium from anoxic sediments can be an important mechanism responsible for long-term contaminations of lakes. However, it is unclear whether such remobilization occurs in shallow lakes, where concentrations of dissolved oxygen in the hypolimnion (bottom DO) change temporally in response to meteorological conditions, and whether remobilized radiocesium influences the activity in fish. We examined the seasonal dynamics of the activities of dissolved 137Cs and 137Cs in fish (pond smelt and crucian carp) from Lake Kasumigaura, a shallow, hypereutrophic lake, five years after the Fukushima Daiichi Nuclear Power Plant accident. The activities of both dissolved 137Cs and 137Cs in fish declined during that time, but the declines showed a clear seasonal pattern that included a summer peak of 137Cs activity. The activity of dissolved 137Cs increased when the bottom DO concentration decreased, and a nonlinear causality test revealed significant causal forcing of dissolved 137Cs activity by bottom DO. The fact that NH4-N concentrations in bottom waters were higher in the summer suggested that remobilization of 137Cs from sediments could result from highly selective ion-exchange with NH4-N. Despite the shallow depth of Lake Kasumigaura, winds had little influence bottom DO concentrations or dissolved 137Cs activities. The fact that seasonal means of 137Cs activities in pond smelt and crucian carp were positively correlated with the seasonal means of dissolved 137Cs activities suggested that remobilized 137Cs may have influenced the seasonal dynamics of radiocesium in fish through food-chain transfer, but higher feeding rates in warm water could may have also contributed to the seasonal dynamics of 137Cs activity in fish. Our findings suggest that in shallow lakes, intermittent but repeated hypoxic events may enhance remobilization of radiocesium from sediments, and remobilized radiocesium may contributed to long-term retention of radiocesium in aquatic organisms.

To provide new insights into microbial functions in the Kushiro Wetland, Japan, we measured vertical profiles of fluorescein diacetate hydrolysis (total microbial activity), β-glucosidase and xylosidase (organic matter decomposition), acid phosphatase (phosphate production) and potential denitrifying (denitrification) activities as microbial enzyme activities in soil to depths of approximately 1.5 m from two sites with different vegetation in November 2008 (winter) and August 2009 (summer). Active organic matter decomposition, phosphate production and denitrification were evident in shallow litter and peat layers, and total microbial activity was high. Almost no differences in decomposition and total microbial activity were observed between seasons, whereas phosphate production and denitrification were higher in summer. All activities were low in mid-depth volcanic-ash and clay layers because of low carbon, nitrogen and phosphorus levels. Surprisingly, the total microbial activity and decomposition in deep clay & peat and peat layers were the same as or higher than in shallow layers. However, denitrification was limited, probably because dissolved organic matter containing humic-like substances was unsuitable as a substrate. Moreover, total soil phosphorus levels, acid phosphatase activity and multiple linear regression analysis revealed that the soil in the Kushiro Wetland is likely P limited.

Understanding soil chemical properties is necessary to characterize the basic properties of ecosystems. In mangrove ecosystems, soil iron, phosphorus, methane and nitrogen have been well studied under field conditions. However, it is difficult to understand fundamental relationships between mangrove root functions and soil chemical properties, because of the multiple factors present in field data. The aim of this study was to clarify what will happen to soil chemical properties after mangrove plant colonize. To examine the effect of mangrove roots on these soil properties, three representative mangrove species (Avicennia marina, Rhizophora stylosa and Bruguiera gymnorrhiza) were cultivated in a greenhouse and selected soil chemical properties were monitored in comparison with those in unplanted soil. We detected oxidative effects in all three species, including deposition of iron oxide on root surfaces, lowered methane concentrations and increased oxidized inorganic nitrogen concentrations in the soil pore-water, suggesting that radial oxygen loss from mangrove roots had affected these soil chemical properties. Besides the oxidative effects, enhanced Fe2+ concentrations in the soil pore-water were present in A. marina, and enhanced phosphorus concentrations in the soil pore-water were present in all three species, suggesting that mangrove roots provide Fe- and phosphate-solubilizing substrates. The most remarkable change was in soil nitrogen enrichment. During the experimental period, amounts of nitrogen in the mangrove soils increased four times more than in uncolonized soil. Six months from the start of cultivation, bacterial nitrogen fixation (nitrogenase activity) was significantly higher in soil colonized by mangrove plants than in uncolonized soil, suggesting that mangrove roots stimulated bacterial nitrogen fixation. Among these properties, Phosphate mobilization and soil nitrogen enrichment are likely to be particularly important for the growth of mangrove plants, because phosphate and nitrogen are generally limited in mangrove ecosystems. This self-supporting ability of mangroves observed in this study could be one key to the high productivity of mangrove ecosystems.

We measured fluxes of carbon dioxide (CO(2)), methane (CH(4)), and nitrous oxide (N(2)O) simultaneously in two typical fringing zones, sandy shore and salt marsh, of coastal lagoon, Lake Nakaumi, Japan, in mid-summer 2003. Our aim was to quantify net the greenhouse gases (GHGs) fluxes and examine key factors, which control variation of the GHGs fluxes in the two sites. Net CO(2) and CH(4) fluxes were markedly different between the two sites; magnitudes and variations of the both fluxes in sandy shore were lower than those of salt marsh. Meanwhile, magnitude and variation of net N(2)O flux in the two sites were similar. In sandy shore, temporal and spatial variation of the three GHGs fluxes were highly controlled by water level fluctuation derived from astronomic tide. In salt marsh, spatial variation of the three GHGs fluxes were correlated with aboveground biomass, and temporal variation of CO(2) and CH(4) fluxes were correlated with soil temperature. The sum of global warming potential, which was roughly estimated using the observed GHGs fluxes, was ca. 174-fold higher in salt marsh than in sandy shore.

Speciation of Al, including inorganic monomeric Al (Ali, the sum of aquo, hydroxy and inorganically complexed forms), organic monomeric Al (Alo, the organically complexed form), and colloidal mineral Al (Alc, the fine particulate form that passes through a 0.4-μm pore size membrane filter), was investigated in stream waters (pH 6–8) of 4 watersheds in Japan. Total dissolved Al (Alt, the sum of Alc, Ali and Alo) ranged from 0.03 to 3.31 μM, and Alc was a minor component ( 1 μM). In spite of the variation in the range of reactive Al (Alr, the sum of Ali and Alo) in the 4 watersheds (Miomote, 0.03–3.27 μM; Tsukuba, 0.06–0.71 μM; Dorokawa, 0.05–0.71 μM; Tama, 0.03–0.38 μM), the entire data set for Alr could be expressed as a function of the ratio of dissolved organic C (DOC) and Ca: [Alr (μM)] = 0.13 [DOC/Ca (mol/mol)] + 0.11 (r = 0.86, P NO 3 - + SO 4 2 - in stream waters, a high level of Ca (instead of Al) is serving as a major counterion for NO 3 - + SO 4 2 - . However, an additional loading of acidic deposition may result in shortage of Ca and mobilization of Al as a counterion for NO 3 - + SO 4 2 - , and continuous observation of the speciation of Al in Japanese stream waters may reveal future change in the conditions for mobilization of Al from “low Ca and high DOC” to “low Ca and high NO 3 - + SO 4 2 - ”.

Estimation of the isotopic turnover rate in the tissues of organisms allows us to estimate the temporal relationship between the isotope ratio of an organism and its prey, and to analyze seasonal variations of food webs and migratory patterns of animals. We analyzed the isotopic turnover rate in the tissue of lacustrine sockeye salmon, Oncorhynchus nerka, of three age classes in a laboratory food alteration experiment to clarify the isotopic turnover rate. The contribution of growth to isotopic turnover was higher in young and fast-growing lacustrine sockeye salmon than in older and slow-growing fish. Maturation masks the relationship between the contributions of growth and metabolism to isotopic change. Our estimate of the isotopic time lag of lacustrine sockeye salmon can be used to research trophic relationships of anadromous sockeye salmon.

干潟生態系の有機物分解機能を底泥の酵素活性から評価する事を目的として,日本国内5地域(北海道東部,東京湾,伊勢湾,有明海,八重山諸島),13箇所の干潟において夏季干潮時に底泥を採取し,セルロース分解酵素(セルラーゼ,CEL)及びキチン分解酵素(β-アセチルグルコサミニダーゼ,AGA)活性を,それぞれカルボキシルメチルセルロースとp-ニトロフェニル-b-D-グルコサミドを基質として測定した。その結果,CEL活性は2-30nmolg-1h-1,AGA活性は10-140nmolg-1h-1の範囲で干潟問で大きな差が認められた。これらの酵素活性の間には高い相関が見られた。また、これらの酵素活性と底泥の有機物量,シルト粘土含量の間には概ね正の相関が認められ,泥質で有機物含量の高い干潟で酵素活性は高く,分解機能も高いことが示唆された。また,甲殻類の多い干潟ではAGA活性が相対的に高い傾向が見られた。これらの結果から,干潟底泥の酵素活性は干潟の理化学性,生物特性によって大きく変動し,分解機能の指標の一つになると考えられた。

Pesticide residues in rainwater were investigated for the estimation of pesticide flux into a lake in Ibaraki Prefecture during the 1990 rainy season. The maximum concentration of oxiadiazon in the rainwater was 4.2μg l-1. The maximum concentrations of fenobucarb, fenitrothion and edifenphos in the rainwater were 0.58, 0.53 and 0.36μg l-1, respectively. The annual ratio of fenitrothion redeposition by rainfall was estimated at 1.5% of the total shipping amount in Ibaraki Prefecture. There was no significant difference between redepositions of pesticides by rainfall and shipping amounts in the prefecture (α= 0.05). Pesticide residues in lake water were investigated in Lake Nakanuma, Ibaraki Prefecture, from March to December 1990. The concentrations of molinate, simetryn, iprobenfos, and thiobencarb in irrigation canal water were in the high range (>1.2μg l-1). The concentrations of diazinon, malathion, and fenthion in the water were at a lower level (

Pesticide residues in water and an aquatic plant, Nelumbo nucifera , were investigated near a river mouth in Edosakiiri Bay, Lake Kasumigaura, from April to December, 1986. The maximum concentrations of fenobucarb, diazinon, iprobenfos and simetryn in the water were 1.6, 1.1, 24, and 2.4 μg 1 −1 , respectively. We detected simetryn with peak width at half height for one month, and diazinon with that for two months. The seasonal changes in simetryn concentration in N. nucifera were similar to those in the water. The simetryn residue concentration was highest in the lamina (300 μg kg −1 ) among the various plant organs. The residue and bioconcentration factor 6.0 in June for simetryn were lower than the reported values for aquatic plants.

Residues of 12 pesticides in water and sediment were surveyed in a river system during a rice cultivation period. The highest concentrations of pesticides were 36 μg l−1 for fenobucarb (carbamate insecticide), 11.3 μg l−1 for simetryn (herbicide) and 17.5 μg l−1 for iprobenfos (fungicide). The downstream flux was largest for iprobenfos, which showed a broader peak than the other pesticides. The runoff rates estimated from the ratio of the downstream flux of a pesticide to its retail amount was highest for fenobucarb and lowest for an organochlorine herbicide, chlornitrofen. These rates ranged over two orders according to the difference in the octanol-water partition coefficients or water solubility of the pesticides. Chlornitrofen was persistent in the stream sediment judging from the regression coefficient between concentrations in water and sediment.

To clarify the involvement of the central nervous system in responses of organisms to noise and whole-body vibration, the activity of dopamine (DA) neuron systems was estimated by examining DA turnover rates in various discrete regions of the brains of rats exposed to noise (broad band, 102 dB) or whole-body vibration (20 Hz, 4G) for 90 min. Plasma corticosterone level (COR) was determined simultaneously as an index of stress-induced autonomic-nervous and endocrine functions. Noise and whole-body vibration increased both COR and DA turnover rates (shown by an increase of homovanillic acid (HVA) and/or HVA/DA ratio) in the frontal cortex (FC) and the nucleus accumbens (NAc). Only noise increased the DA turnover rate in the amygdala (AMY). Furthermore, strong positive correlations of the HVA/DA ratios in the FC and the NAc with COR were observed in rats exposed to noise or vibration. These results suggest that the responses of organisms to noise and whole-body vibration may be critically mediated by cerebral DA systems, in particular by the mesocortical DA system, indicating that change of DA in the AMY can be considered a specific response to noise.

Pesticide residues in water and their toxicity to the freshwater shrimp ( Paratya compressa improvisa ) were studied in a river mouth in Takahamairi Bay, Lake Kasumigaura, from April to July in 1987. Concentrations of fenthion, diazinon and fenobucarb in water of the littoral zone were lower than that in the pelagic zone. The maximum concentrations of fenthion, diazinon, iprobenfos and simetryn in water were 1.9, 0.8, 6.5, and 1.1 μg 1 −1 , respectively. The 4-day mortality of the freshwater shrimp increased in lake water at Takahamairi Bay, reaching 50% at maximum in May. The mortality was probably due to residual insectside fenthion.

In order to determine the pathogenesis of gastric mucosal lesions induced by whole-body vibration (WBV), the effects of WBV (3.0 G, 10 Hz, 90 min) on gastric mucosal blood flow (GMBF), plasma corticosterone (COR) and catecholamines (CA), and gastric ulcer formation were investigated in relation to the effects of forced water-immersion stress (FWI) upon the same parameters. While WBV increased GMBF during the exposure, FWI decreased it both during and after the stress. No difference in the severity of ulcer formation between the WBV and the FWI groups was seen. Both WBV and FWI increased plasma COR and CA, although the degree of the increase in COR that accompanied WBV was less than that associated with FWI. Truncal vagotomy attenuated the reduction of GMBF and the extent of ulcer formation that occurred with FWI, but promoted a reduction of GMBF with WBV. These findings indicate that ulceration induced by WBV may be caused primarily by its direct and specific mechanical actions and not by indirect, central nervous system effects known to be important in the pathogenesis of ulcerations produced by mental stress.

In order to clarify the involvement of cerebral 3, 4-dihydroxyphenylacetic acid (DOPAC) and vasoactive intestinal polypeptide (VIP) in whole-body vibration stress, DOPAC and VIP-like immunoreactivity (VIP-LI) in various discrete brain regions of rats exposed to whole-body vibration (4G, 20Hz, 90min) were assayed. The results showed that the whole-body vibration increased the DOPAC level in the frontal cortex and nucleus accumbens, but did not induce a concurrent change of VIP-LI in these regions. VIP-LI was significantly increased in the amygdala, and decreased in the hippocampus, accompanied by no significant change of DOPAC. These results show that whole-body vibration affects cerebral VIP neuron systems in addition to its nonspecific action, i. e. the activation of mesofrontal and mesoaccumbens dopamine neuron systems. It is assumed that the amygdalofugal VIP neuronal system is involved in the regulation of hypothalamic and pituitary hormone secretions, and that VIP in the hippocampus plays a part in modulating the blood circulation in the cortex in whole-body vibration stress.

In order to clarify the involvement of substance P (SP) and neurotensin (NT) neurons in the response of organisms to stress, SP-like immunoreactivity (SP-LI) and NT-like immunoreactivity (NT-LI) were determined in various regions of the rat brain following exposure to the whole-body vibration (20 Hz, 4 G, 90 min). SP-LI and NT-LI in the rat brain were measured by means of a sensitive and specific double-antibody solid-phase enzyme immunoassay. SP-LI in the frontal cortex was significantly reduced following whole-body vibration, while that in the nucleus accumbens and amygdala was significantly increased. NT-LI in both the frontal cortex and the hypothalamus of rats exposed to the whole-body vibration was significantly increased. However, striatal SP-LI and NT-LI remained unchanged. The present findings indicate that the SP and NT neuronal systems in various brain areas are involved in the response to stress. The frontal and amygdalofugal SP and hypothalamic NT neuronal systems, in particular, may have an important role in mediating the response of organisms to the whole-body vibration-induced stress.

In the present study it was found that, in vibrating-tool operators with Raynaud's phenomenon, whole blood viscosity was significantly higher than in operators without Raynaud's phenomenon at shear rates from 230 to 11.5 s-1. In addition rats were experimentally exposed to local vibration (60 Hz, 5 g) on their hind limbs for 4 h/d for 30 or 90 d. In the case of 30-d exposure, the small arteries in the exposed site did not change. However, after exposure for 90 d, disruption of the internal elastic lamina was observed in the small arteries. The disruption was followed by focal cell proliferation with regenerative formation of collagen and elastic fibers. The fibro-cellular thickening of the intima was further augmented, and, in addition, a complete stenosis of the small lumen of the small artery was observed. Medial thickness did not show significant differences between the control and exposed groups for either exposure duration. The whole blood viscosity was significantly increased by the 90-d but not by the 30-d exposure. These results suggest that there are some relationships between the increase in whole blood viscosity and the intimal thickening of some small arteries in the exposed site.

In order to clarify the combined effects of whole‐body vibration and noise on dopamine (DA) metabolism within the brain, which is known to regulate the response of the organism to various stimuli, the DA turnover rate in regions of the rat brain was determined. The rats were divided into five groups: (1) control; (2) wholebody vibration (4 G, 20 Hz, 90 min) exposure alone; (3) noise [70 dB(A), 90 min] exposure alone; (4) noise [100 dB(A), 90 min] exposure alone; and (5) combined exposure for 90 min to whole‐body vibration (4 G, 20 Hz) and noise [100 dB(A)]. Changes of plasma corticosterone levels were examined as indices of the pituitary‐adrenal function (PAF). The whole‐body vibration exposure alone caused increases in the DA turnover rate [an increase of homovanillic acid (HVA) or HVA/DA] in the frontal cortex and nucleus accumbens. Noise exposure alone caused metabolic increases in the amygdala. The combined effect of whole‐body vibration and noise on the DA neuron systems suggested that the response o...