Quantifying the ecosystem service of non-native weed seed predation provided by invertebrates and vertebrates in upland wheat fields converted from paddy fields

The extent of post-dispersal weed seed predation in upland wheat fields converted from paddy fields was quantified in Shizuoka Prefecture, central Japan. We investigated the temporal variability in seed predation of Italian ryegrass (Lolium multiflorum Lam.), a non-native winter annual weed in Japan, during summer after the seed shed in both the field interior areas and boundary strips, and estimated the total seed loss due to predation during the summer. Furthermore, the contribution of invertebrates and vertebrates to seed predation was estimated by using exclosures. The total seed loss due to predation during four months (from late June to late October) in the field interior areas and boundary strips was estimated to be 35–43% (the maximum proportion of seed predation per two weeks = 27%) and 42% (25%), respectively. The seed predators in the field interior areas were vertebrates (rodents or birds) and invertebrates (crickets and ground beetles). In contrast, seed predators in the boundary strips were mainly invertebrates (crickets and ground beetles). The results of this study suggest that predators make a substantial contribution in the depletion of post-dispersal seeds of Italian ryegrass in converted paddy fields.     

CIELAB color variables as indicators of compost stability

The composting process of different organic wastes both in laboratory and on a large-scale was characterized using CIELAB color variables to evaluate compost stability for the better application in agriculture. The time courses of the CIELAB variables of composting materials were determined directly from the bottom of a glass petri dish filled with dried and ground samples using a Minolta Color Reader (CR-13) calibrated with clean empty petri dishes placed on a white tile. To compare the proposed method with conventional methods, the same materials were also evaluated using commonly used compost stability evaluation indices. Most of the CIELAB variables of a compost made from a mixture of green tea waste and rice bran reached a plateau after 84 days of composting and showed strong relationships with the commonly used compost stability evaluation indices. The time needed for CIELAB variables, especially the L*and b* values, to stabilize at large-scale composting plants of cattle litter, farmyard manure, kitchen garbage and bark compost, were more or less similar to the times of maturation evaluated by the respective compost producers. The CIELAB color variable offers a new, simple, rapid and inexpensive means of evaluating compost stability and its quality prior to agricultural use.     

Effects of biosurfactants on assays of PCB congeners in transgenic arabidopsis plants carrying a recombinant guinea pig AhR-mediated GUS reporter gene expression system

The transgenic Arabidopsis plants carrying a recombinant guinea pig (g) aryl hydrocarbon receptor (AhR)-mediated β-glucuronidase (GUS) reporter gene expression system were generated for assays of polychlorinated biphenyl (PCB) congeners. The selected transgenic Arabidopsis plant XgD2V11-6 exhibited a correlation between uptake of PCB126 and PCB126-induced GUS activity. Also, the plants showed induced GUS activity towards the supplemental indole 3-acetic acid (IAA). Thus, the GUS assay may reflect induction by both endogenous and exogenous AhR ligands. When biosurfactants, MEL-B, produced in the culture of yeast isolated from plants were used for assays of PCB congeners in the transgenic Arabidopsis plants, they showed marked PCB126 dose-dependent and toxic equivalency factor (TEF) dependent GUS activities. The effects of biosurfactants were clearer when the plants were cultivated on soils containing PCB congeners for 7 days as compared with on soils for 3 days as well as in the medium for 3 days. Threfore, it was estimated that biosurfactants form micellae with PCB congeners, which are easily uptaken by the plants in a mode of passive diffusion, transport into the aerial parts and then induce GUS activity.     

Spatial distribution and vertical profile of polybrominated diphenyl ethers and hexabromocyclododecanes in sediment core from Tokyo Bay, Japan

Brominated flame retardants (BFRs), hexabromocyclododecanes (HBCDs) and polybrominated diethyl ethers (PBDEs) were detected in three sediment cores and six surface sediments of Tokyo Bay, Japan. HBCDs were detected for the first time in this region with concentrations ranging from 0.056 to 2.3 ng/g dry wt, implying their widespread contamination, even though their concentrations were lower than summation operatorPBDEs (di- to nona-BDEs) and BDE-209. Levels of these compounds were higher near to the highly populated industrial area of the bay implicating industrial and human activities as sources of these compounds. Summation operatorPBDEs increased in the sediment layer up to the mid-1990s and decreased afterwards, whereas BDE-209 showed an increasing trend until now, following the usage of different commercial BDE mixtures. HBCDs first appeared in the mid-1970s and increased until today. The annual surficial flux of HBCDs (0.62-2.4 ng/cm2/yr) is equal to summation operatorPBDEs (0.95-2.6 ng/cm2/yr) but lower than that of BDE-209 (17-58 ng/cm2/yr).     

Sugar compound products of the periphytic diatom <Emphasis Type="Italic">Navicula ramosissima</Emphasis> induce larval settlement in the barnacle, <Emphasis Type="Italic">Amphibalanus amphitrite</Emphasis>

This study investigated the response of cyprids of the barnacle Amphibalanus amphitrite to 23 strains of laboratory cultured periphytic diatoms isolated from microbial biofilms that formed on glass slides immersed in Tachibana bay, Nagasaki, and those from mass-production tanks in the Fisheries Center of Nagasaki City, Japan. In addition, periphytic diatoms were subjected to various treatments, in order to investigate the nature of the chemical cue in periphytic diatoms. Cyprids of A. amphitrite responded differently to the 23 different periphytic diatom strains and settled in high percentages on Cocconeis sp. and Navicula ramosissima strain A. On the other hand, nine strains of diatoms significantly inhibited settlement. The settlement inducing activity of N. ramosissima strain A increased linearly with diatom density, and its activity was enhanced by culturing the diatom under a bacteria-free condition, suggesting that specific diatom species, i.e., N. ramosissima strain A, may play an important role on larval settlement of the barnacle. Subjecting N. ramosissima strain A biofilm to hydrochloric acid (HCl) and ethanol (EtOH) treatments or heating it at 100°C did not inactivate the film, indicating that the settlement cue was a stable surface bound compound that did not decompose from the above treatments. Moreover, of the various lectins, enzymes, and drugs [H₅IO₆ and sodium dodecyl sulfate or (SDS)] used, only Lentil Agglutinin (LCA) treatment of N. ramosissima strain A biofilm resulted in the reduction its settlement inducing activity. A positive correlation was observed between the settlement inducing activity and the amount of LCA conjugated fluorescein isothiocyanate (FITC-LCA) of N. ramosissima strain A. On the other hand, subjecting biofilms of N. ramosissima strain B, an inactive strain, to various types of treatments resulted in the induction of A. amphitrite larval settlement but LCA treatment also reduced the activity of these treated N. ramosissima strain B biofilms. These findings suggest that a cue containing an LCA-binding sugar chain is present in both A and B strains of N. ramosissima but the large amount of mucous substance covering N. ramosissima strain B biofilm probably makes the sugar chain containing active subunit in strain B unavailable to A. amphitrite cyprids. In conclusion, periphytic diatoms such as N. ramosissima play an important role in larval settlement of the barnacle A. amphitrite. The cue in the diatom was an LCA-binding sugar chain(s) compound that may have similarities to the settlement inducing protein complex (SIPC) from adult shell of the barnacle.     

Larval metamorphosis of the mussel <Emphasis Type="Italic">Mytilus galloprovincialis</Emphasis> in response to <Emphasis Type="Italic">Alteromonas</Emphasis> sp. 1: evidence for two chemical cues?

Bacterial isolates from multi-species biofilms were identified by 16S rDNA gene sequences and investigated for their inductive effects as monospecific biofilms on larval metamorphosis of Mytilus galloprovincialis. Alteromonas sp. 1 biofilm was found to have inductive activity, which increased with increasing cell density. The cue(s) of Alteromonas sp. 1 biofilm responsible for inducing larval metamorphosis was further investigated. Treatment of the biofilm with formalin, ethanol, heat or ultraviolet irradiation resulted in a significant reduction in the inductive activity of Alteromonas sp. 1, and the crude extract of surface-bound products of the biofilm showed no activity. These results indicated that if the cue was a surface-bound chemical cue, it was unstable, or susceptible to the treatments or the extraction process. On the other hand, the inductive activity of treated biofilms had a linear regression to the cell survival of bacteria, indicating a metabolically active biofilm was a requirement for larval metamorphosis. Conditioned water of the biofilm did not induce larvae to metamorphose. However, larval crawling behavior in the conditioned water was the same as that in the biofilm prior to larval metamorphosis, and significantly different to larval behavior in seawater. This indicated that a potential or partial waterborne cue existed, but remained inactive when alone. A synergistic effect of the conditioned water with formalin-fixed Alteromonas sp. 1 biofilm resulted in a significant increase in larval metamorphosis. Heat treatment and fractionation of the conditioned water demonstrated that the waterborne cue was heat-stable and <3,000 Da in molecular weight. Platinum-coating, Lentil Lectin and Wheat Germ Agglutinin treatments of the formalin-fixed biofilm significantly reduced its synergistic effect with the conditioned water, suggesting that a surface-bound cue was present on the biofilm and that the cue might be associated with the bacterial exopolysaccharide or glycoprotein. Evidence presented here suggests that two chemical cues derived from bacteria act synergistically on larval metamorphosis of Mytilus galloprovincialis.