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By mimicking the info-chemicals emitted by grazers, the common anionic surfactant sodium dodecyl sulfate (SDS) can induce colony formation in the green algal genus Scenedesmus at environmentally relevant concentrations. The morphogenetic effects can hinder the feeding efficiency of grazers, reducing energy flow along the pelagic food chain from Scenedesmus to consumers. Despite this potential ecological risk, few studies exist on whether the SDS-triggered induction of colonies is common in other species of the family Scenedesmaceae. Here, we investigated the effects of SDS on the growth and morphology of three species of Scenedesmaceae (Desmodesmus subspicatus, Scenedesmus acutus, and Tetradesmus dimorphus) and on the clearance rates of Daphnia galeata grazing on the SDS-induced colonies. SDS triggered colony formation in all algal species at concentrations nonlethal to them; however, the induction levels of colony formation were generally lower than for those in the Daphnia culture medium. We also found that the SDS-induced colonial algae reduced D. galeata clearance rates. Our results highlight the potential effect of SDS on the Daphnia–Scenedesmaceae system by evoking the morphological response of Scenedesmaceae at concentrations below those that exert toxicity. Such disruptive effects of pollutants on predator–prey interactions should be considered within the framework of ecological risk assessments.

Neonicotinoid insecticides, the most widely used category of insecticides for 20 years and candidate risk of neurodevelopment, have been detected in human urine and in hair. If the former reflecting dietary contamination over short periods and the latter total exposure over longer periods is not known. We quantified and compared the concentrations in spot urine by LC-MS/MS and in hair by UHPLC-MS/MS.In the first study, samples from an international group of scientists in Italy in 2016 (M/F=12/7),detection rate in urine and in hair was 0% vs 85.0% for imidacloprid; 0% vs 52.5% for thiacloprid; 0% vs 45.0% for acetamiprid; 0% vs 25.0% for thiamethoxam; and 0% vs 17.5% for clothianidin.In the second study, samples from 99 volunteers in three islands of the Philippines in 2017,detection rate in urine and in hair was 48.5% vs 60.6% for imidacloprid; 1.0% vs 8.1% for thiacloprid; 10.1% vs 13.1% for acetamiprid; 31.3% vs 30.3% for thiamethoxam; and 14.1% vs 45.5% for clothianidin. In the Philippine, concentrations were negatively correlated between urine and hair for thiamethoxam (r = -0.70, p = 0.016), but not for clothianidin or imidacloprid. Both analyses of urine and hair are complementary to assess human neonicotinoid exposure.

To evaluate whether microbial stoichiometries of biomass and enzyme activity could vary in response to changes in nutrient availability in an arable soil during the crop growth period, temporal variation in nutrient availability, soil enzyme activities associated with carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) acquisition, and microbial biomass C, N, and P were measured in an Allophanic Andosol amended with chemical fertilizer and cow manure. The ratio of l -asparaginase to β- d -glucosidase activities had a significant negative correlation with potentially mineralizable N. In addition, the ratio of arylsulfatase to β- d -glucosidase activities showed a significant negative correlation with available S. Thus, it seems plausible that microorganisms in the soil would allocate their resources to synthesis of N - and S-acquiring enzymes in response to variation in the nutrient availability caused by fertilization and over time. Also, the ratio of microbial biomass C/P had a significant negative correlation with available P, suggesting that this stoichiometry could reflect P availability in the soil. These results imply that microbial biomass and ecoenzymatic stoichiometries are useful for evaluating nutrient availability in soils.

Neonicotinoid insecticides that have been on the market since 1992 have been used globally including in Japan. Because they are sprayed over forests and agricultural areas, inadvertent toxicity in nontarget insects (especially honey bees) and humans is a matter of public concern. However, information on exposure levels and potential health impacts of neonicotinoids in children living around sprayed areas is scarce. Thus, we determined neonicotinoid exposure levels in children living in communities where thiacloprid was used to control pine wilt disease. A total of 46 children (23 males and 23 females) were recruited for the present study, and informed written consent was obtained from their guardians. Urine specimens were collected before, during, and after insecticide spraying events; and atmospheric particulate matter was also collected. Concentrations of thiacloprid and 6 other neonicotinoid compounds were determined in urine samples and in atmospheric particulate matter specimens using liquid chromatography-electrospray ionization-tandem mass spectrometry. In urine specimens, thiacloprid concentrations were

Methane ( $$\mathrm {CH}_{4}$$ ) is known to be emitted from lakes to the atmosphere via processes such as diffusion and ebullition (i.e., bubble emission). We developed a practical method for partitioning eddy-covariance $$\mathrm {CH}_{4}$$ fluxes from a shallow lake into diffusive and ebullitive fluxes using a wavelet analysis based on local scalar similarity between the $$\mathrm {CH}_{4}$$ concentration and other reference scalars, such as the air temperature or water vapour concentration, in the wavelet time-scale domain, with the hypothesis that similar and dissimilar fluctuation components are related to diffusive and ebullitive $$\mathrm {CH}_{4}$$ fluxes, respectively. Our method is applied to approximately two weeks of data obtained at a shallow mid-latitude lake. The partitioned diffusive flux has a physically sound relationship with wind speed, supporting the validity of the method. The ratio of the diffusive flux to the total flux is typically 0.11 with flow from an area of steady bubble emission, but otherwise 0.36. Further validation is required using a larger dataset and data from other lakes. The proposed method can be easily applied to historical data because it requires only 10-Hz data of $$\mathrm {CH}_{4}$$ concentration and other reference scalars, along with an empirical parameter.

Temporal and spatial variations in methane (CH4) emissions from the littoral zone of a shallow mid-latitude lake, Lake Suwa, were examined using the eddy covariance technique. The observation data were supplemented with dissolved CH4 measurement and incubation experiments of lake sediment and water. This lake had areas with steady bubble CH4 emissions, shaping the spatial variation in CH4 flux with strong spot emissions. In the other areas, CH4 was emitted via diffusion and episodic ebullition. CH4 emissions from this area had a clear seasonal variation, reflecting temperature variations, with a maximum monthly mean emission of 0.39 µ mol m − 2 s − 1 in August. The higher emission in summer was due to higher CH4 production in the sediment and the resulting higher dissolved CH4 concentration in the surface water. The steady bubble CH4 emission was seasonally controlled by the total hydrostatic pressure, with higher emission under lower pressure, suggesting regulation of the amount of bubbles emitted from the lake bottom by pressure. Isotope analysis revealed that this CH4 was produced biologically. This natural gas seepage was estimated to emit 1.9 Mg of CH4 annually. Compared with other eddy covariance studies over inland waters, CH4 emissions from Lake Suwa may be large for the latitude. This may be related to eutrophication, which enhances CH4 production.

The mineralization of organic phosphorus (P) in soil is mainly driven by extracellular phosphatases secreted by soil microbes. Previous studies have suggested that microbial phosphatase production is regulated by soil nutrient stoichiometry and, thus, promoted by carbon and nitrogen (CN) amendment. However, the mechanism leading to increased phosphatase activity after nutrient amendment to soil is unclear, and it is not known how long the effect of the nutrient amendment lasts. To address these questions, we performed a 24-day time-series analysis of full-factorial soil microcosms with CN amendment. Phosphatase activity as well as that expressed per unit of β- d -glucosidase activity, increased sharply and significantly in response to the CN amendment. This suggests that the microbial community shifted their resource allocation after the nutrient amendment and preferentially produced phosphatases rather than β- d -glucosidase. This shifted resource allocation pattern was maintained throughout the 24-day incubation period, and copiotrophic microbes dominated soils that received CN amendment. These results indicate that the effect of the CN amendment on soil microbial resource allocation lasted for >24 days. Together, our results highlight the importance of high-resolution time-series observations that complement long-term studies for which frequent observation is often difficult.

Soil microbes are drivers of global ecosystem functionality and are continuously subjected to external perturbations. It is fundamental for ecologists and environmental scientists to understand and further predict the microbes’ responses to these perturbations. A major and ubiquitous perturbation is the addition of chemical nutrients, including fertilizers and animal urine, to soil. Recent biogeographical studies suggest that soil nutrient stoichiometry (i.e., nutritional balance) determines microbial community structure and its functions with regard to material circulation. Given this information, here, we show that soil nutrient stoichiometry, or the bioavailable C:P ratio, determines the impact of nutrient addition on the soil’s microbial communities. We sampled two soils with similar carbon and nitrogen concentrations but with a 20-fold difference in phosphorus bioavailability. Soil microcosms with carbon and nitrogen amendments were constructed for both the soils. The phosphorus-depleted soil received prolonged effect from carbon and nitrogen amendments: the phosphatase activity gradually increased over a 24-day incubation period and the microbial community structure did not present recovery to its initial state. In contrast, in the other soil, both phosphatase activity and microbial community structure gradually returned to those of the control samples. Phosphorus depletion mitigated carbon and nitrogen intake; therefore, the effects of carbon and nitrogen amendment lasted longer. Our results demonstrate that nutritional stoichiometry is a strong predictor of microbial community dynamics in response to trophic perturbation, particularly when considering the length of time the trait of perturbation persists in the soil.

The impact of eutrophication on aquatic ecosystems remains an important topic in aquatic ecology; however, recent successes in water quality restoration in highly eutrophicated water bodies present new research potential regarding re-oligotrophication. Successfully reducing nutrient loading from sewage treatment through restoration activities, induces large changes in phytoplankton composition and biomass, particularly replacement of cyanobacterial dominance. In Lake Suwa, a shallow eutrophic lake in central Japan, recovery has occurred due to water quality restoration efforts since the 1970s. The improvement of lake trophic state from hypertrophic to mesotrophic is accompanied by various changes, such as rapid decreases in biomass of phytoplankton, benthic invertebrates and planktivorous pond smelt, and increases in biomass of aquatic vegetation, mainly floating leaved plants. During re-oligotrophication, zooplankton are important because they are major secondary producers in lake ecosystems. In Lake Suwa, the Research and Education Center for Inland Water Environment, Shinshu University has collected bi-weekly zooplankton samples and analyzed species composition since 1996, when the lake was in a hypertrophic state with serious Microcystis blooms. Lake Suwa is one representative lake for re-oligotrophication in a shallow eutrophic system, and our zooplankton dataset can be used to understand the changes in ecosystem structure and function.