Simulated Natural Environment Research Articles

Laboratory study of gravel‐bed cluster formation and disintegration

AbstractIncreased knowledge of clusters is essential for the understanding of sediment transport behavior and the monitoring and protection of aquatic life. A physical study using graded river gravels is conducted in a laboratory environment. Using photogrammetry and painted gravels, a cluster identification tool (CIT) is developed based on image subtraction between subsequent frames, allowing identification of any stable areas and groups of particles on the bed. This is combined with digital particle tracking (DPT) to present a novel approach for monitoring the formation and disintegration of clusters. Clusters from graded gravels are formed successfully during the experimental stage, allowing investigation into the complex dynamic behavior of cluster formation and disintegration in a simulated natural environment. Various anchor stone arrangements are used in the experiments. However, only about one fifth of the potential anchor stones on the bed surface enable cluster formation. In general, clusters classified as “typical” and “heap” are most common. Inspection of temporal cluster coverage of the test‐bed surface shows that the proportion of clusters present on the surface tends to grow with time. Maximum cluster surface coverage of between 5% and 34% is observed. In addition, particles entering and departing from clusters are monitored. Most commonly, particles enter from directly upstream of the cluster, however >20% of particles approach from a direction >20 deg from the streamwise direction. Approximately 35% of all particles directly upstream of a cluster bypass the cluster.

Phytoremediation of Cu, Cr and Pb Mixtures by Lemna minor

The present study reports the capacity of the aquatic macrophyte Lemna minor to remediate combinations of Cu(II), Pb(II) and Cr(III) from a simulated natural environment. The effect of these metal mixtures on the growth of L. minor was also investigated using growth rate and biomass inhibition calculations. L. minor was successful in removing Cr and Pb from the water, and it remained an effective remediation agent when both metals were present in the environment. However, a relatively low absorption capacity was observed for Cu, increasing concentrations of which were associated with significant decreases in growth rate. No statistically significant difference was found between the 24 h and 7 days absorption rates of Cu, Pb and Cr, suggesting that, at the concentrations tested, equilibrium occurs within 24 h of metal exposure.

Intelligent Control System for Intertidal Benthos Research Based on Internet of Things

A simulation system for intertidal zone environment that can be remotely monitored is proposed. The system is divided into the two parts of remote control center and environment simulator, which are interconnected through wireless network technology. The remote control center performs remote monitoring through upper machine software, while the environment simulator can simulate natural environments such as ocean tides, water temperature and light illumination in different types of intertidal zones. Users can change and access the environmental parameters and data of the environment simulator by making instructions at the remote control center. A stable system is realized in accordance with the design requirements, and actual tests show that main features of the simulated natural environment in intertidal zones are very close to actual environment.

Protective silane treatment for patinated bronze exposed to simulated natural environments

The protective efficiency of 3-mercapto-propyl-trimethoxy-silane (PropS-SH) was evaluated towards bare and aged bronze. The wet & dry (stagnant rain) and dropping (runoff) techniques were used both for producing pre-patinated surfaces representative of real artefacts and for performing accelerated tests to verify PropS-SH protection efficiency. The surface corrosion products and the metal release were analyzed through spectroscopic techniques. The role of alloying metals in the corrosion/inhibition process was assessed through electrochemical analyses performed on bare and prefilmed alloying elements. The results showed good protective efficiency of the silane coating on bare and pre-patinated samples, both in stagnant and runoff conditions.

Comparison of insecticidal paint and deltamethrin against Triatoma infestans (Hemiptera: Reduviidae) feeding and mortality in simulated natural conditions.

The vector of Chagas disease, Triatoma infestans, is largely controlled by the household application of pyrethroid insecticides. Because effective, large-scale insecticide application is costly and necessitates numerous trained personnel, alternative control techniques are badly needed. We compared the residual effect of organophosphate-based insecticidal paint (Inesfly 5A IGR™ (I5A)) to standard deltamethrin, and a negative control, against T. infestans in a simulated natural environment. We evaluated mortality, knockdown, and ability to take a blood meal among 5(th) instar nymphs. I5A paint caused significantly greater mortality at time points up to nine months compared to deltamethrin (Fisher's Exact Test, p < 0.01 in all instances). A year following application, mortality among nymphs in the I5A was similar to those in the deltamethrin (χ2 = 0.76, df=1, p < 0.76). At months 0 and 1 after application, fewer nymphs exposed to deltamethrin took a blood meal compared to insects exposed to paint (Fisher's Exact Tests, p < 0.01 and p < 0.01, respectively). Insecticidal paint may provide an easily-applied means of protection against vectors of Chagas disease.

Effect of light on toxicity of nanosilver to Tetrahymena pyriformis

More and more silver nanoparticles (AgNPs) have been released into the aquatic environment due to their widespread use, which may result in harmful effects on aquatic organisms. Environmental risk assessments of AgNPs on aquatic organisms in the natural environment (including light, sound, etc.) are indispensable. The aim of the present study was to elucidate the influence of light on the toxicity of AgNPs to Tetrahymena pyriformis. Silver nanoparticles, which were synthesized by reduction of silver nitrate with sodium borohydride, ranged in size from 5 to 20 nm with most particles approximately 10 nm. The authors performed AgNPs toxicity assays under a simulated natural environment with sunlight. The results indicated that the toxicity of AgNPs is higher than silver ion in the environment without light, but under the light condition, the toxicity of AgNPs decreased greatly. After 24 h of incubation with AgNPs, the inhibition ratio was 69.2 ± 7% in the dark and 35.5 ± 2% in the light, and the degree of inhibition was reduced by 33.7%. However, the effect of light on Ag(+) could be negligible. Further investigation indicated that the light irradiation could induce the growth of AgNPs and sequentially form bulk agglomeration. This decreased the surface area and the number of bare Ag atoms, resulting in a slower release rate and less Ag(+) ions released from AgNPs. At the same time, bulk agglomeration induced the deposition of part of the AgNPs to the aquatic bottom, which decreased the amount of AgNPs existing in water. All these phenomena led to the weakened toxicity of AgNPs in a light irradiation environment.

Fecal Reproductive Steroid Profiles for Monitoring Reproductive Patterns in Female Formosan Black Bears (Ursus Thibetanus Formosanus)

Fecal sexual estradiol (E2) and progesterone (P4) analyses were conducted on three adult female Formosan black bears in order to establish non-invasive enzyme-linked immunosorbent assays (ELISA) for describing the endocrine profile in a simulated natural breeding environment. Moreover, we investigated whether the Formosan black bear living in subtropical habitats in Taiwan is a seasonal breeder with delayed embryo implantation, ovulation pattern, and maternal perinatal fasting. Our results indicate that mating behavior occurred both before and after the fecal E2 peak of March–June. Fecal P4 concentrations initially increased after mating, then decreased to lower levels, and finally increased again, which is indicative of a delayed embryo-implantation. Fecal P4 levels decreased postpartum. Peaks of fecal P4 levels were also observed in unmated female bears housed with male bears without coitus: their annual fecal P4 levels were higher from winter to spring, similar to the pregnant female bear. Interestingly, only pregnant female bears displayed a physiological state of fasting before and after parturition. These results suggest that Formosan black bears' breeding is seasonal and takes place from spring to early summer. Delayed implantation, maternal perinatal fasting and induced ovulation from male stimulation independent of coital stimulation alone are typical for the species.

Separating Effects of Gene Flow and Natural Selection along an Environmental Gradient

Genetic differentiation along environmental clines is often observed as a result of interplay between gene flow and natural selection. In order to understand the relative roles of these processes in shaping this differentiation, we designed a study in which we used two approaches that have not previously been combined, the QST–FST comparison and crossbreeding. We examined (1) interpopulation phenotypic and genetic (AFLP) variation, and (2) performance of interpopulation hybrids in a common annual Senecio glaucus. Fitness of interpopulation hybrids (F1 and F2) was tested under simulated population natural conditions in terms of aridity and analyzed for a relationship with (1) spatial distance and (2) environmental differences (amount of annual rainfall). While phenotypic variation corresponded to the clinal changes in aridity along population locations, viz. narrower and longer leaves, longer leaf outgrowths and advanced flowering in more arid environments, the FST < 0.1 calculated from AFLP data suggested intensive interpopulation gene flow, with little if any contribution of genetic drift. Performance of hybrids in simulated natural environments revealed heterosis in F1, but a hybrid breakdown in F2 generation. These effects were related to both the spatial distance between hybrid parents and their population rainfall differences. The detected clinal phenotypic variation and outbreeding depression in F2 strongly support presence of aridity-induced clinal natural selection, which is matched by the observed QST ≫ FST. From this we conclude that QST–FST comparison can detect effect of diversifying selection when patterns of phenotypic variation across sampled locations can be reliably predicted from environmental variation.

Uncultured microorganisms as a source of secondary metabolites

The vast majority of microbial species are 'uncultured' and do not grow under laboratory conditions. This has led to the development of a number of methods to culture these organisms in a simulated natural environment. Approaches include placing cells in chambers that allow diffusion of compounds from the natural environment, traps enclosed with porous membranes that specifically capture organisms forming hyphae--actinobacteria and microfungi, and growth in the presence of cultivable helper species. Repeated cultivation in situ produces domesticated variants that can grow on regular media in vitro, and can be scaled up for secondary metabolite production. The co-culture approach has led to the identification of the first class of growth factors for uncultured bacteria, iron-chelating siderophores. It appears that many uncultured organisms from diverse taxonomical groups have lost the ability to produce siderophores, and depend on neighboring species for growth. The new cultivation approaches allow for the exploitation of the secondary metabolite potential of the previously inaccessible microorganisms.

Increased intrinsic growth rate is advantageous even under ecologically stressful conditions in coho salmon (Oncorhynchus kisutch)

Growth rate is an ecologically important trait, affecting the energy acquisition from, and provisioning to, the surrounding community. One of many costs suggested to counteract the evolution of increased intrinsic growth rate is an associated reduction in tolerance to conditions of nutrient stress. Here we test this concept with individuals possessing experimentally increased intrinsic growth rates (growth hormone transgenic coho salmon, Oncorhynchus kisutch) relative to wild genotypes. Using a series of three experiments, survival and growth of both genotypes were assessed on a physiological and behavioral level while varying food abundance, social interactions, and predation risk. Only in complete absence of exogenous food in newly emerged fry did the high intrinsic growth rate appear costly with a shorter average survival time compared to wild-type (Exp. 1). In experiment 2, genotypes with elevated intrinsic growth showed equal or higher survival and growth than wild-type genotypes In a third experiment, adding very limited amounts of food and allowing for social interactions in a simulated natural environment benefited transgenic individuals relative to wild-types, but at similar magnitudes in both the absence and presence of predators. Populations with transgenic individuals present did not crash under these competitive conditions as previously reported when studied in simple environments where hiding and attack escape were not possible. Our data suggest that transgenic fish have a greater scope for growth under most conditions, but are not obligated to use this capability. Physiological (e.g. appetite and conversion efficiency) and behavioral traits (e.g. competitive ability and risk-taking) found previously to correlate positively with intrinsic growth rate in the transgenic strain likely aided in their survival and growth, even under food limited conditions. Hence, at least in coho salmon, intrinsic growth rate does not appear to strongly affect survival under nutrient stress.

Variations in perceptions of danger, fear and preference in a simulated natural environment

Although natural environments can help promote health, they also contain a number of dangers. This study attempted to examine how variations in the physical structure of a simulated natural environment influenced perceptions of both overall and specific types of danger, fear and preference before exploring the relationships between these variables. Three simulated walks through a natural environment differing in levels of prospect-refuge were created for the study. Respondents were randomly assigned to one of the conditions and asked to imagine taking the walk for real. In support of the typology, the results found that the walks with higher levels of prospect-refuge (higher visibility, fewer hiding places and more accessibility) were perceived as less dangerous and fearful and more preferred than walks with lower levels of prospect-refuge. However despite levels of prospect-refuge appearing to impact on the perceived likelihood of encountering a physical danger or becoming lost, they were not found to impact on the perception of encountering a social danger.

Assessment of Prerelease Diet Regimes on Growth of Juvenile Atlantic Sturgeon

AbstractTo determine whether the growth rates of juvenile Atlantic sturgeon Acipenser oxyrinchus would be improved if the fish were weaned to natural food before being released into a simulated natural environment, 60 sturgeon from the 2006 and 2007 year‐classes (ages 2 and 1, respectively) were subjected to two prerelease diet regimes (n = 30 per treatment, 120 total). Each year‐class was divided into two groups, a control group that was fed a commercial diet for 10 d until stocking into a 0.2‐ha earthen pond in June 2008 and a treatment group that was weaned to natural food over a 10‐d period before stocking. Final sampling (84 d poststocking) showed that year‐class had an effect on the specific growth rate (% weight gain/d) but that treatment did not. The survival rates were 77% and 80% among the controls from the 2007 and 2006 year‐classes and 87% and 90% among the treatment fish. This study shows that weaning to natural food before release into a natural environment does not significantly affect the specific growth or survival rates of Atlantic sturgeon.

A comparison of the restorative effect of a natural environment with that of a simulated natural environment

This study aimed to compare the restorative effects of 30 min relaxation in a natural environment with an indoor simulation of the same natural environment. A repeated-measure design was carried out and 18 participants suffering from stress and/or burnout syndrome were counterbalanced into the two conditions. Both physiological measures and psychological instruments were applied. Further, qualitative descriptions of experiences were obtained. A phenomenological analysis of the qualitative data resulted in six categories for the natural environment: Intensified sensory perception; A feeling of harmony and union with nature; Well-being and quality of life; Renewed energy and awakening; “Here-and-now” thinking; and A sense of tranquillity, while for the simulated natural environment, there were five categories: Restlessness and anxiety; Lack of concentration; A sense of being cut off from nature's sensory input; A longing to be in ‘real’ nature; and Positive emotions. The natural environment yielded a significantly higher rating of degree of altered states of consciousness (ASC) and energy than the simulated natural environment. The results suggest that both environments facilitated stress reduction, with the natural environment additionally bringing increased energy and ASC, thus possibly enhancing and promoting restoration.

Sustained predation effects of hatchery‐reared transgenic coho salmon Oncorhynchus kisutch in semi‐natural environments

Summary 1. The potential risks of accidental or intentional introduction of transgenic organisms to nature are unknown. We have previously shown that, after being reared in the hatchery, growth hormone transgenic coho salmon Oncorhynchus kisutch can exert a stronger predation effect on natural prey under simulated natural conditions compared with hatchery‐reared genetically wild conspecifics. However, when reared in a simulated natural environment, the difference between the two genotypes was greatly reduced. 2. Here, we tested if the difference in predation rate between the two genotypes after being reared in the hatchery diminishes with time spent in a simulated natural environment. Genetically wild coho salmon reared in the hatchery were size matched to younger satiation‐fed (fast‐growing) and same age restricted‐fed (growth rates matched to wild‐type) transgenic fish. These three types of predators were released into simulated natural habitats and their effects on prey survival and growth were monitored over a 2‐month period. 3. Restricted‐fed, but not satiation‐fed, transgenic predators consumed significantly more prey (×2·7) relative to wild predators during the first month, with an increase to 3.8 times during the second period. Prey biomass decreased more in the presence of restricted‐fed predators during the first period, but a faster growth of these prey during the second period compensated for the higher predation rate resulting in no significant difference in prey biomass among predators after 2 months. Transgenic predators grew more in length than wild type, but all three types converged in weight and condition over time. 4. Synthesis and applications. Behavioural phenotypes developed in the hatchery showed little plasticity after release. Hence, development of policy on the use of transgenic organisms must incorporate knowledge of the effect of environmental conditions, experienced by the organism prior to escape or release, on phenotype. The risk posed by culture‐reared organisms may depend on the frequency of escapes, number of individuals escaping and age of escapees. Important to note is that wild‐reared organisms may be biologically different from culture‐reared and thus require separate evaluation. Our results will be important for science policy makers and regulators to consider when deciding whether to allow commercial application of transgenic species in aquaculture.

Dynamics of genetically modified Lactococcus lactis in simulated natural environments and impacts on microbial communities

The survival, impacts on microbiota and gene transfer ability of genetically modified (GM) Lactococcus lactis containing ermAM gene in soil and water environments were investigated. After inoculation of GM L. lactis into environments, its DNA remained longer, and the microbial community was changed. No transfer of chromosomal ermAM was observed.

Crystal ball – 2009

Crystal ball – 2009

A trap for in situ cultivation of filamentous actinobacteria

The approach of growing microorganisms in situ, or in a simulated natural environment is appealing, and different versions of it have been described by several groups. The major difficulties with these approaches are that they are not selective for actinomycetes — a group of gram-positive bacteria well known as a rich source of antibiotics. In order to efficiently access actinomycetes, a trap for specifically capturing and cultivating these microorganisms in situ has been developed, based on the ability of these bacteria to form hyphae and penetrate solid environments. The trap is formed by two semi-permeable membranes (0.2–0.6 μm pore-size bottom membrane and 0.03 μm pore-size top membrane) glued to a plastic washer with sterile agar or gellan gum inside. The trap is placed on top of soil, and filamentous microorganisms selectively penetrate into the device and form colonies. Decreasing the size of the pores of the lower membrane to 0.2 μm restricted penetration of fungi. The trap produced more filamentous actinobacteria, and a higher variety of them, as compared to a conventional Petri dish cultivation from the same soil sample. Importantly, the trap cultivation resulted in the isolation of unusual and rare actinomycetes.

Decrease in the capacity for RuBP carboxylation and regeneration with the progression of cold-induced photoinhibition during winter in evergreen broadleaf tree species in a temperate forest.

We measured the photosynthetic capacity (RuBP carboxylation and electron transport capacity at 25°C) and the maximum photochemical efficiency (Fv/Fm) from autumn to spring in saplings of two evergreen broadleaf tree species and examined the negative effects of photoinhibition on the photosynthetic capacity. Saplings were grown in pots under three simulated natural light environments typical of temperate forests: an open site, deciduous understorey and evergreen understorey. During winter, the photosynthetic capacity and Fv/Fm synchronously decreased in leaves in the sun, but not those in the shade. We found large differences in Fv/Fm and photosynthetic capacity, along with a positive correlation between Fv/Fm and the photosynthetic capacity among leaves in different light environments. In photoinhibited leaves that were transferred to the shade in mid-winter, photosynthetic capacity increased synchronously with the increment of Fv/Fm. The decrease in photosynthetic capacity in photoinhibited leaves and the synchronous recovery of photosynthetic capacity with photoinhibition supported the hypothesis that photoinhibition depressed the photosynthetic capacity during winter. We showed that difference in the degree of photoinhibition was responsible for the different winter photosynthetic capacity among leaves exposed to different light environments.

Reaction of Thiometon and Disulfoton with Reduced Sulfur Species in Simulated Natural Environment

The reactions of thiometon and its ethyl analogue, disulfoton, with reduced sulfur species [e.g., bisulfide (HS-), polysulfide (S(n)2-), thiophenolate (PhS-), and thiosulfate (S2O3(2-))] were examined in well-defined aqueous solutions under anoxic conditions. The role of reduced sulfur species was investigated in the abiotic degradation of thiometon and disulfoton. Experiments at 25 degrees C demonstrated that HS-, S(n)2-, PhS-, and S2O3(2-) promoted the degradation of thiometon to a great extent while only S(n)2- and PhS- showed a small accelerating effect in the degradation of disulfoton. Reactions were monitored at varying concentrations of reduced sulfur species to obtain the second-order rate constants. The reactivity of the reduced sulfur species decreased in the following order: S(n)2- > PhS- > HS- approximately S2O3(2-). Transformation products were confirmed by standards or characterized by gas chromatography mass spectrometry. The results illustrate that multiple pathways occur in the reactions with reduced sulfur species, among which the nucleophilic attack at the alpha-carbon of the alkoxy group was the predominant pathway. Activation parameters of the reaction of thiometon and disulfoton with HS- were also determined from the measured second-order rate constants over a temperature range. DeltaH( not equal) values indicated that the reactivity of thiometon toward HS- was much greater than for disulfoton. Nucleophilic attack at the alkoxy group was more important for thiometon than disulfoton. When the measured second-order rate constants at 25 degrees C are multiplied by [HS-] and Sigma[S(n)2-] reported in saltmarsh porewaters, predicted half-lives show that reduced sulfur species present at environmentally relevant concentrations may present an important sink for thiometon in coastal marine environments.

Method for Assessment of Viability and Morphological Changes of Bacteria in the Early Stage of Colony Formation on a Simulated Natural Environment

A quantitative analysis of changes in the physiological status of bacterial cells is a fundamental type of study in microbiological research. We devised a method for measuring the viability of bacteria in the early stage of colony formation on a simulated natural environment. In this method, a solid medium containing soil extract was used, and the formation of bacterial microcolonies on a membrane filter was determined by use of a laser scanning cytometer combined with live-dead fluorescent dyes. A polychlorinated biphenyl degrader, Comamonas testosteroni TK102, was used in this study. Surprisingly, approximately 20% of the microcolonies had their growth stopped and eventually died. In the presence of biphenyl, the growth arrest was increased to 50%, and filamentous cells were observed in the colonies. Predicted intermediate metabolites of biphenyl were added to the medium to determine the relationship between the change of viability and the production of metabolites, and the addition of 2,3-dihydroxybiphenyl showed low viability. The arrest was not observed to occur on nutrient-rich medium, suggesting that the change in viability might occur in a nutrient-poor natural condition. The results of this study demonstrated that toxic metabolites of xenobiotics might change cell viability in the natural environment.