Antifouling activities of marine bacteria associated with sponge (Sigmadocia sp.)

The present study aimed at assessing the antifouling activity of bacteria associated with marine sponges. A total of eight bacterial strains were isolated from the surface of sponge Sigmadocia sp., of them, SS02, SS05 and SS06 showed inhibitory activity against biofilm-forming bacteria. The extracts of these 3 strains considerably affected the extracellular polymeric substance producing ability and adhesion of biofilm-forming bacterial strains. In addition to disc diffusion assay, microalgal settlement assay was carried out with the extracts mixed with polyurethane wood polish and coated onto stainless steel coupons. The extract of strain SS05 showed strong microalgal settlement inhibitory activity. Strain SS05 was identified as Bacillus cereus based on its 16S rRNA gene. Metabolites of the bacterial strains associated with marine invertebrates promise to be developed into environment-friendly antifouling agents.     

Updating Mining Resources with Uncertain Data

Mathematical Geosciences - In mining operations, the time delay between grade estimations and decision-making based on those estimations can be substantial. This may lead to the scheduling of...     

Grain‐size variability within a mega‐scale point‐bar system,False River,Louisiana

Point bars formed by meandering river systems are an important class of sedimentary deposit and are of significant economic interest as hydrocarbon reservoirs. Standard point‐bar models of how the internal sedimentology varies are based on the structure of small‐scale systems with little information about the largest complexes and how these might differ. Here a very large point bar (>25·0 m thick and 7·5 × 13·0 km across) on the Mississippi River (USA) was examined. The lithology and grain‐size characteristics at different parts of the point bar were determined by using a combination of coring and electrical conductivity logging. The data confirm that there is a general fining up‐section along most parts of the point bar, with a well‐defined transition from massive medium‐grained sands below about 9 to 11 m depth up into interbedded silts and fine–medium sand sediment (inclined heterolithic strata). There is also a poorly defined increase in sorting quality at the transition level. Massive medium sands are especially common in the region of the channel bend apex and regions upstream of that point. Downstream of the meander apex, there is much less evidence for fining up‐section. Finer sediment accumulated more readily after the establishment of a compound bar in the later stages of construction, at the terminal apex and in the bar tail. This work implies that the best reservoir sands are likely to be located in the centre of the point bar, deposited in a simple bar system. Reservoir quality decreases towards the bar edge. The early‐stage channel plug is largely composed of coarsening‐upward cycles of silt to clay and is dominated by clay and clayey silt material with poor reservoir characteristics.     

Conserving agricultural heritage systems through tourism: Exploration of two mountainous communities in China

Community plays an important role in the preservation of agricultural heritage system （AHS）. Recently, many AHS have been valorized as interesting resources for rural tourism. The expectations are that tourism development （TD） can be supportive for the conservation of AHS while creating benefits for local communities. In this study, two mountainous pilot villages （Longxian and Xiaohuang） in a global conservation project for traditional agricutural systems - Globally Important Agricultural Heritage Systems （GIAHS） were selected to identify the relationship between AHS conservation and TD. The study undertook in-depth interviews, and questionnaires of village residents and informal discussions with local villagers. A t-test and a linear regression model were implemented to explore the comparative dimensions of the two communities with different geographical location, economic situation, and stage of TD. The research found some similarities and differences in the two mountainous communities during AHS conservation and TD. Firstly, AHS are preservaed well in both villages unconsiously, while the residents in Xiaohuang value more highly the heritage elements than the respondents in Longxian, and the villagers in Xiaohuang are more worried about their heritage system; Secondly, both villages expect lots of benefits from TD and they clearly perceive more positive than negative impact from tourism and thus approve TD, while the hugedifferent perception on transportation and accessibility in the two villages reflects the bottleneck of TD in Xiaohuang village. At the same time, the respondents from Xiaohuang perceive more positive and fewer negative impact from tourism than the respondents from Longxian. Thirdly, the respondents in the two villages all show positive attitudes towards participation in tourism mostly motivated by the high income expectation. The main factors to determine the community perception in two villages were also analyzed based on the data process. A location-based coneeputal framework of AHS conservation in partnership with TD at community scale is proposed at the end of the paper. The dynamics of tourism development, that could enhance a better understanding of the complex relationship between conservation objectives and tourism development are discussed.     

A cross-continental comparison of stream invertebrate community assembly to assess convergence in forested headwater streams

We studied two forested, headwater streams to compare patterns of invertebrate community structure and consequences for ecosystem functioning in two temperate locations, Galicia (NW Spain) and Vancouver (SW Canada). The two sites were selected due to the similar dominance of congeneric invertebrate species, as well as similarity in their hydromorphological and physico-chemical characteristics. Field experiments tested for similarities and dissimilarities in the invertebrate community assembly in leaf packs in streams. Our results indicated that alder leaves always decomposed faster than eucalyptus leaves, from threefold higher in Galicia to tenfold in Vancouver. At the species level, the biogeographic factor was the main source of variation on invertebrate assemblages (84.9 %), but this percentage quickly decreased at higher levels of taxonomic resolution, i.e. family. Moreover, there was a strong leaf species influence in both sites. There were more invertebrates colonizing leaves (per unit mass) in Vancouver than in Galicia (fourfold on average), though alder leaves seemed to be always the preferred resource (5.5-fold higher density on average). Regardless, a similar trophic structure was found between sites and leaf species. Brillia spp. and Corynoneura spp., a shredder and a collector-gatherer, respectively, seemed to be the most important species and showed similar colonization patterns in both sites with potential to strongly influence the leaf processing and nutrient cycling in these ecosystems. Even though our results are limited to the similarity found between only two sites, results from other studies, where the same species have been found coexisting during leaf pack processing, reinforces our results that common rules and mechanisms determine patterns of key ecological processes on a biogeographical scale.     

Minimum/maximum autocorrelation factors applied to grade estimation

There are many situations in the mining industry where grade estimation of multiple correlated variables is required. The resulting model is expected to reproduce the data correlation, but there is no guarantee that the correlation observed among data will be reproduced by the model if the variables are independently estimated by kriging, and the correlation is not explicitly taken into account. The best geostatistical approach to address this estimation problem is to use co-kriging, which requires both cross and direct covariance modeling of all variables. However, the co-kriging method is labor-intensive when the problem involves more than three attributes. An alternative is to decorrelate the variables and estimate each one independently, using, for instance, the minimum/maximum autocorrelation factors (MAF) approach. This method involves the application of a linear transformation to the correlated variables, transforming the original data into a space where they are uncorrelated. The resulting transformed data can be individually estimated using kriging, avoiding the use of the linear model of coregionalization. Once the kriging has been performed, the MAF estimates are back-transformed to the original data space, re-establishing their correlation.The methodology is illustrated in a case study where there are two variables with correlation coefficient, ρ = ?0.98. The MAF transformation was applied in combination with ordinary kriging (herein denoted as KMAF). Co-kriging was performed to provide a benchmark for comparing the results obtained through KMAF. The results obtained by co-kriging and KMAF showed less than 1 % average deviation between the two block models.     

Seismic behavior of an inverted T-shape flexible retaining wall via dynamic centrifuge tests

In the design procedure for a retaining wall, the pseudo-static method has been widely used and dynamic earth pressure is calculated by the Mononobe–Okabe method, which is an extension of Coulomb’s earth pressure theory computed by force equilibrium. However, there is no clear empirical basis for treating the seismic force as a static force, and recent experimental research has shown that the Mononobe–Okabe method is quite conservative, and there exists a discrepancy between the assumed conditions and real seismic behavior during an earthquake. Two dynamic centrifuge tests were designed and conducted to reexamine the Mononobe–Okabe method and to evaluate the seismic lateral earth pressure on an inverted T-shape flexible retaining wall with a dry medium sand backfill. Results from two sets of dynamic centrifuge experiments show that inertial force has a significant impact on the seismic behavior on the flexible retaining wall. The dynamic earth pressure at the time of maximum moment during the earthquake was not synchronized and almost zero. The relationship between the back-calculated dynamic earth pressure coefficient at the time of maximum dynamic wall moment and the peak ground acceleration obtained from the wall base peak ground acceleration indicates that the seismic earth pressure on flexible cantilever retaining walls can be neglected at accelerations below 0.4 g. These results suggest that a wall designed with a static factor of safety should be able to resist seismic loads up to 0.3–0.4 g.     

Fine sediment on leaves: shredder removal of sediment does not enhance fungal colonisation

Inorganic fine sediments are easily carried into streams and rivers from disturbed land. These sediments can affect the stream biota, including detritivorous invertebrates (shredders) and impair ecosystem functions, such as leaf litter decomposition. We hypothesized that fine sediment (kaolin) deposited on leaves would reduce or suppress fungal development, reducing decomposition rates of leaves. Moreover, we predicted that shredders would act as ecosystem engineers by perturbing sediment deposition, reducing its impact on decomposition and fungi. We used a fully crossed experimental design of sediment addition (control, 400?mg?L^?1) and shredders (none, Gammarus, Potamophylax) in laboratory aquaria. Leaf mass loss, suspended solids, microbial respiration, fungal biomass and spore production were measured. Sediment addition had no significant effects on the leaf mass remaining nor on shredders?? consumption rates. However, sediment slightly reduced fungal assemblage richness and the sporulation rate of three fungal species. The presence of shredders substantially increased the resuspension of fine sediments (>300%), resulting in higher suspended loads. However, the action of shredders did not have a significant effect on fungal biomass nor on leaf mass loss. Even if shredders did not enhance fungal colonisation, they affected the settlement of fine sediment, serving as allogenic engineers. Our study suggests that concentrations of fine sediment of 400?mg?L^?1 with short exposure times (192?h) can have some effect on leaf decomposition.     

Export of fine particulate organic carbon from redwood‐dominated catchments

Recently, researchers have recognized the significant role of small mountainous river systems in the transport of carbon from terrestrial environments to the ocean, and the scale of such studies have ranged from channel bed units to continents. In temperate zones, these mountain river systems commonly drain catchments that are largely forested. However, the magnitude of carbon export from rivers draining old‐growth redwood forests has not been evaluated to date. Old‐growth redwood stands support some of the largest quantities of biomass in the world, up to 350 000 Mg of stem biomass km^‐2 and soil organic carbon can reach 46 800 Mg km^‐2. In north coastal California, suspended sediment samples were collected at three gaging stations for two to four years on streams draining old‐growth redwood forests. Carbon content, determined through loss‐on‐ignition tests, was strongly correlated with turbidity, and continuous turbidity records from the gaging stations were used to estimate annual carbon exports of 1 · 6 to 4 · 2 Mg km^‐2 yr^‐1. These values, representing 13 to 33% of the suspended sediment load, are some of the highest percentages reported in the global literature. The fraction of organic carbon as part of the suspended sediment load decreased with discharge, but reached an asymptote of 5 to 10% at flows 10 to 20 times the mean annual flows. Although larger rivers in this region exhibit high sediment yields (up to 3600 Mg km^‐2 yr^‐1), mainly attributed to high rates of uplift, mass movement, and timber harvest, the small pristine streams in this study have sediment yields of only 8 to 100 Mg km^‐2 yr^‐1. Because the current extent of old‐growth redwood stands is less than 5% of its pre‐European‐settlement distribution, the present organic carbon signature in suspended sediment loads in this region is likely different from that in the early 20th century. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.     

Geochemical and Sr–Nd isotopic constraints on the petrogenesis of the Goesan monzodiorite pluton in the central Okcheon belt,Korea

The Permian–Triassic high pressure metamorphism and potassic magmatism in central Korea attest to the extension of the Dabie‐Sulu collision belt in central‐eastern China towards the Korean Peninsula and possibly the Japanese Islands. We present major and trace element and Sr–Nd isotope data for a ca. 230 Ma monzodiorite pluton emplaced in the Goesan area, central Okcheon belt, Korea. This pluton shows geochemical features comparable with those of the coeval monzonite–syenite–gabbro–mangerite suite documented recently in the Gyeonggi massif. The metaluminous and alkali–calcic signatures of the Goesan intrusives correspond to the Caledonian‐type post‐orogenic granitoids. The K₂O/Na₂O ratios of all analyzed samples are greater than 1, and are not correlative with their SiO₂ contents. The enrichment of both large‐ion‐lithophile elements and highly compatible elements in the Goesan pluton is probably indicative of metasomatized mantle origin. The elemental fractionation in the source region must have occurred in the distant past, possibly the Paleoproterozoic, to generate significantly negative ε_Nd(t) values (< –16). Chondrite‐normalized rare earth element patterns as well as Rb/Sr and Ba/Rb ranges suggest that the source consists of amphibole‐bearing rocks. Progressive decreases in negative Eu anomaly and Ba, Sr, Ni, Cr and V contents with increasing SiO₂ contents reflect an important role of plagioclase, biotite and hornblende for the fractionation process. Zr is undersaturated in the potassic, metaluminous melt. The initial Sr–Nd isotopic compositions of the samples are correlated with their SiO₂ contents, substantiating a role of crustal assimilation during the magmatic differentiation. The Sr–Nd elemental and isotopic modeling suggests that the Goesan pluton was initially slightly heterogeneous in its isotopic composition, and underwent concurrent assimilation and fractional crystallization. The occurrence of the Goesan pluton provides further evidence corroborating the amalgamation of allochthonous terranes within the Okcheon belt during the Permian–Triassic collisional orogeny.