Depth Fluctuations Research Articles

A tide prediction and tide height control system for laboratory mesocosms.

Experimental mesocosm studies of rocky shore and estuarine intertidal systems may benefit from the application of natural tide cycles to better replicate variation in immersion time, water depth, and attendant fluctuations in abiotic and edaphic conditions. Here we describe a stand-alone microcontroller tide prediction open-source software program, coupled with a mechanical tidal elevation control system, which allows continuous adjustment of aquarium water depths in synchrony with local tide cycles. We used this system to monitor the growth of Spartina foliosa marsh cordgrass and scale insect herbivores at three simulated shore elevations in laboratory mesocosms. Plant growth decreased with increasing shore elevation, while scale insect population growth on the plants was not strongly affected by immersion time. This system shows promise for a range of laboratory mesocosm studies where natural tide cycling could impact organism performance or behavior, while the tide prediction system could additionally be utilized in field experiments where treatments need to be applied at certain stages of the tide cycle.

Regional features of present winter snow accumulation variability in the North Eurasia from data of observations, reanalysis and satellites

The paper presents data on winter snow accumulation on the Russian territory obtained from different sources: ground measurements of snow depth on meteorological stations, water snow equivalent calculated from data of route surveys, reanalysis, and satellite observations. Three large regions were isolated which are distinguished by characters of the snow depth fluctuations and their long-term tendencies. Comparison of the trends calculated from data of reanalysis and satellite measurements demonstrated essential disagreement of them with data of in situ observations.

Integration of irrigation district personnel with canal automation projects

Canal companies are adapting automation equipment to assist in the management of their canal systems and provide water to users at a near constant flow rate. Many of these canal companies have been motivated out of need to meet the water demands of their customers while limiting flow rate and depth fluctuations. Several canal automation schemes have been successful, while a few systems have had problems. After studying 179 canal automation projects, key points have been identified that contribute to the success of the automation systems. The most important factor is that the automation system has the support of the board of directors and the management personal. Other factors include a supportive automation company, use of simple, understandable sensors, and reliable equipment.

Statistical simulation of pattern formation by ion-beam sputtering

Purpose – The purpose of this paper is to investigate the influence of ion-flow parameters on surface topography and making numerical simulation at the times when the process of surface erosion becomes strongly nonlinear. Design/methodology/approach – The base of the mathematical model of target ion-sputtering is nonlinear evolutionary equation in which the erosion velocity dependence on ion flux is evaluated by means of a Monte Carlo method. The difference between this equation and the one of continuum theory is that the ion flux is not smooth function. Instead, it is a set of separate incident ions. Findings – Some simulations with using independent random points of arrival for the incident ions leads to results uncorrelated with the continuum model at early times. The ripples are not quite developed or observed. This phenomenon is explained by random fluctuations of the target sputtering depth. Sufficiently big values of the random fluctuations destroy the ripple structure on target surface. The simulation with using equally distributed sequence (Holton sequence) of points of arrival for the incident ions leads to results well correlated with the continuum model. Originality/value – The discrete model which goes into the equation of continuum theory within the appropriate asymptotic limit has been proposed. The discretization parameters influence on surface morphology formation has been studied. This paper may be interesting to researchers making the theoretical and numerical analysis of pattern formation on plane target surfaces undergoing ion-beam sputtering.

Evaluating the impacts of crop rotations on groundwater storage and recharge in an agricultural watershed

The Mississippi River Valley Alluvial Aquifer, which underlies the Big Sunflower River Watershed (BSRW), is the most heavily used aquifer in Mississippi. Because the aquifer is primarily used for irrigating crops such as corn, cotton, soybean, and rice, the water levels have been declining rapidly over the past few decades. The objectives of this study are to analyze the relationship and interactions between evapotranspiration and groundwater recharge rates in the BSRW, and model the effects of various crop rotation practices on groundwater storage and recharge.The model performed well during the calibration period (R2=0.53–0.68 and NSE=0.49–0.66) and validation period (R2=0.55–0.75 and NSE=0.49–0.72) for daily streamflow, which was achieved by the SUFI-2 auto-calibration algorithm in the SWAT-CUP package. The model also performed well in simulating seasonal water table depth fluctuations during calibration (R2=0.76 and NSE=0.71) and validation (R2=0.86 and NSE=0.79). This study demonstrated a seasonal relationship between evapotranspiration and groundwater storage and recharge in the BSRW SWAT model. In general, groundwater storage decreased during the summer months while ET rates were high, and increased during the winter and spring months when ET rates were low. The crop rotation scenarios that include rice planting resulted in the lowest groundwater storage (down to −10.7%) compared to the baseline crop scenario, which is due to the high irrigation rates of the rice crop. However, the rice crop rotations resulted in the highest increases of groundwater recharge rates (up to +60.1%), likely because of the response to the deficiency of groundwater needed for irrigation as well as the limited water uptake by the rice crop. The crop rotations with corn and cotton resulted in the largest increases in groundwater storage (up to +27.2%), which is the result of the low irrigation rates as well as the short time period for irrigation applications. The results of this study are expected to aid farmers and watershed managers to conserve groundwater resources, but still maintain crop production.

Geochemistry and depositional history of the Union Springs Member, Marcellus Formation in central Pennsylvania

Debate continues over paleoenvironmental conditions that prevail during deposition of organic-carbon (C)-rich marine source rocks in foreland basins and epicontinental seas. The focus of disagreement centers largely on paleowater depth and the prevalence of anoxia/euxinia. The issues of paleodepth and water column conditions are important for prediction of lateral variations in source quality within a basin because the viability of a hydrocarbon play depends on a thorough understanding of the distribution of source rock quality and depositional environments. We used inorganic geochemical data from the Middle Devonian Marcellus Shale in the Appalachian Basin to illustrate interpretive strategies that provided constraints on conditions during deposition. Source evaluation typically relies on the analysis and interpretation of organic geochemical indicators, potentially also providing evidence of the degree of thermal maturity and conditions of the preservation of the organic matter. The Marcellus Formation is thermally mature, making the evaluation of the organic-carbon fraction for geologic interpretation inadequate. Because most labile organic matter has largely been destroyed in the Marcellus Formation, analysis of inorganic elements may be used as an alternative interpretative technique. Several inorganic elements have been correlated to varying depositional settings, allowing for their use as proxies for understanding the paleodepositional environments of formations. A high-resolution geochemical data set has been constructed for the Union Springs Member along a transect of cores from proximal to distal in the Appalachian Basin in central Pennsylvania using major, minor, and trace elemental data. Our results suggested that during deposition, the sediment-water interface, and a portion of the water column, was anoxic to euxinic. As deposition continued, euxinia was periodically interrupted by dysoxia and even oxic conditions, and a greater influx of clastic material occurred. Such variations were likely related to fluctuations in water depth and progradation of deltaic complexes from the eastern margin of the Appalachian Basin.

Interactive effects of wildfire and climate on permafrost degradation in Alaskan lowland forests

AbstractWe examined the effects of fire disturbance on permafrost degradation and thaw settlement across a series of wildfires (from ~1930 to 2010) in the forested areas of collapse‐scar bog complexes in the Tanana Flats lowland of interior Alaska. Field measurements were combined with numerical modeling of soil thermal dynamics to assess the roles of fire severity and climate history in postfire permafrost dynamics. Field‐based calculations of potential thaw settlement following the loss of remaining ice‐rich permafrost averaged 0.6 m. This subsidence would cause the surface elevations of forests to drop on average 0.1 m below the surface water level of adjacent collapse‐scar features. Up to 0.5 m of thaw settlement was documented after recent fires, causing water impoundment and further thawing along forest margins. Substantial heterogeneity in soil properties (organic layer thickness, texture, moisture, and ice content) was attributed to differing site histories, which resulted in distinct soil thermal regimes by soil type. Model simulations showed increasing vulnerability of permafrost to deep thawing and thaw settlement with increased fire severity (i.e., reduced organic layer thickness). However, the thresholds of fire severity that triggered permafrost destabilization varied temporally in response to climate. Simulated permafrost dynamics underscore the importance of multiyear to multidecadal fluctuations in air temperature and snow depth in mediating the effects of fire on permafrost. Our results suggest that permafrost is becoming increasingly vulnerable to substantial thaw and collapse after moderate to high‐severity fire, and the ability of permafrost to recover is diminishing as the climate continues to warm.

Turbulence, Temperature, and Turbidity: The Ecomechanics of Predator-Prey Interactions in Fishes

Successful feeding and escape behaviors in fishes emerge from precise integration of locomotion and feeding movements. Fishes inhabit a wide range of habitats, including still ponds, turbulent rivers, and wave-pounded shorelines, and these habitats vary in several physical variables that can strongly impact both predator and prey. Temperature, the conditions of ambient flow, and light regimes all have the potential to affect predator-prey encounters, yet the integration of these factors into our understanding of fish biomechanics is presently limited. We explore existing knowledge of kinematics, muscle function, hydrodynamics, and evolutionary morphology in order to generate a framework for understanding the ecomechanics of predator-prey encounters in fishes. We expect that, in the absence of behavioral compensation, a decrease in temperature below the optimum value will reduce the muscle power available both to predator and prey, thus compromising locomotor performance, suction-feeding mechanics of predators, and the escape responses of prey. Ambient flow, particularly turbulent flow, will also challenge predator and prey, perhaps resulting in faster attacks by predators to minimize mechanical instability, and a reduced responsiveness of prey to predator-generated flow. Reductions in visibility, caused by depth, turbidity, or diel fluctuations in light, will decrease distances at which either predator or prey detect each other, and generally place a greater emphasis on the role of mechanoreception both for predator and prey. We expect attack distances to be shortened when visibility is low. Ultimately, the variation in abiotic features of a fish's environment will affect locomotion and feeding performance of predators, and the ability of the prey to escape. The nature of these effects and how they impact predator-prey encounters stands as a major challenge for future students of the biomechanics of fish during feeding. Just as fishes show adaptations for capturing specific types of prey, we anticipate they are also adapted to the physical features of their preferred habitat and show a myriad of behavioral mechanisms for dealing with abiotic factors during predator-prey encounters.

Live-Bed Scour at Bridge Piers in a Lightweight Polystyrene Bed

AbstractExperiments on scour at bridge piers were carried out in a sediment recirculating flume with a bed of polystyrene particles. The focus of the research reported in this paper was given to live-bed experiments. All experiments were run until equilibrium conditions with flow velocities u ranging from 0.8–8.5 times the critical velocity for the incipient motion of sediment particles uc. Maximum scour depth was continuously measured with an endoscopic camera from inside the pier, which was constructed by a plexiglass cylinder. Bed load transport with dunes was identified as the main transport mode for 1<u/uc<4. For ratios of u/uc≥4 entrainment into suspension without development of bedforms dominated. Results show that scour rapidly reach equilibrium in the bed of polystyrene pellets. In the clear-water experiments equilibrium scour depth remained constant in time. In the bed load region the fluctuation of scour depth corresponded to the dune migration through the scour hole, while in the suspended loa...

Ichnofabrics of shallow-marine mudstone, the result of changing environmental conditions: an example from the Middle Jurassic ore-bearing clay from southern Poland

Analysis of the trace fossil association and ichnofabrics from a Middle Jurassic shallow-marine mudstone, referred to as the Ore-Bearing Częstochowa Clay Formation, is used to reconstruct the seafloor conditions and identify the factors responsible for their changes. The trace fossil association contains Chondrites, Trichichnus, Palaeophycus, Planolites, Protovirgularia, ?Rosselia, Schaubcylindrichnus, Taenidium, cf. Tasselia, Thalassinoides, and five types of pyritized burrow. The association represents the distal expression of Cruziana ichnofacies, temporarily changing to a more proximal development. The ichnofacies suggests that the depositional site was located in the lower offshore to offshore-transition zone, periodically passing to the distal lower shoreface. Eight subtypes of the ichnofacies are recognized, reflecting variations in seafloor oxygenation, sedimentation rate, and benthic food content. The sequence of ichnofabrics 1a–1b–2a–2b reflects increasing oxygenation; ichnofabrics 4a, 4b, and 5 record high sedimentation rates, whereas ichnofabric 3 reflects sediment starvation. Vertical changes of ichnofabrics reflect major fluctuations in basin depth and distance from the shoreline, which partly correlate with previously recognized transgressive–regressive cycles. However, they do not record minor variations of the shoreline position.

Carbon dioxide exchange in a tropical wet grassland

Wet grasslands in the Brazilian Cerrado occupy around 1 % of the Cerrado extension, acting as ecotones connecting well-drained savanna vegetation and gallery forest. Wet grasslands help maintain biodiversity and water balance, and are an important component of the carbon (C) balance, storing an average of 241 MgC h−1 in the top 60 cm soils. However, in addition to increased climactic variability, Brazilian wet grasslands are under pressure from domestic water use and agricultural irrigation. Here, we present 2 years of carbon balance data from a Brazilian wet grassland, which was exposed to below average seasonal and annual precipitation during the first year and excess precipitation during the second year. We used the eddy covariance approach to measure net ecosystem carbon exchange (NEE) and ecosystem respiration (R e). Results indicated that the wet grassland was a carbon sink during both years, taking up similar amounts each year (−86.5 gC m−2 year−1 in 2005 and −81.3 gC m−2 year−1 in 2006). However, seasonal NEE was variable and driven by fluctuations in the water table depth (P < 0.05), shifting the balance from a carbon sink to a carbon source from 1 month to the next by as much as 50 gC m−2 when water table dropped below 20 cm depth. The gross ecosystem carbon uptake (GEE) decreased with water table depth, while Re increased due to the exposure of old organic carbon to microbial decomposition. Results indicated that a prolonged drought, which is probable under future projected climatic variability, could lead the ecosystem to be a carbon source and highlight the importance of management strategy in preserving soil water in these ecosystems.

Biostratinomic analysis of Lycoptera beds from the Early Cretaceous Yixian Formation, western Liaoning, China

AbstractLittle is known about the palaeoenvironments of the Early Cretaceous lakes of western Liaoning. Uncertainties exist especially about the water depth, water temperatures and annual temperature fluctuations. Here, we analyse the preservation of the most abundant fish of the lakes, the teleost Lycoptera, articulated skeletons of which occur in large concentrations suggestive of mass mortality. Taphonomic features such as degree of disarticulation, orientation patterns and displacement of skeletal elements reveal distinct preservational patterns. They suggest that the water temperature was low during winter and exhibited pronounced seasonal fluctuations. The depth of the lakes was not deep. Possible causes of the fish mortality are discussed, of which anoxia is favoured. This leads to a more refined palaeoenvironmental model for these palaeolakes, which harbour one of the most important Mesozoic Lagerstätten.

A multi-parametric spatial modeling of vulnerability due to arsenic pollution in Murshidabad district of West Bengal, India

Arsenic pollution in groundwater is the most serious geo-environmental problem posing a threat to the health of millions of people in the densely populated area of interfluvial region of Bhagirathi-Hugli and the Jalangi-Ichamati Rivers. The present paper focuses on arsenic vulnerability assessment at the mouza level (smallest revenue unit) in Beldanga II block of Murshidabad district of West Bengal in India. A number of indicators (e.g., arsenic concentration in groundwater, population density, well depth, and seasonal fluctuation of water level) have been incorporated, and weighted linear combination method was adopted into this model to develop a composite vulnerability index. The results reveal that about 15 and 10 % of the total mouzas are respectively high and extreme vulnerable, found in the eastern part of block, where 34 % people are potentially vulnerable due to arsenic pollution. This study reveals a multi-parametric spatial model for micro level arsenic vulnerability assessment, may be further improved if more relevant parameters are incorporated into this model, and it can facilitate as a basis for directing policy interventions.

The Silurian of south-western margin of the East European Platform (Ukraine, Moldova and Romania): lithofacies and palaeoenvironments

Silurian strata, stretching along the western margin of the East European Platform from the Baltic to the Black Sea, represent a potential target for both conventional and unconventional hydrocarbon exploration. Distribution of the black shale facies, prospective for shale gas, and the reef facies, prospective for oil, has been studied in respect of palaeoenvironments. The Silurian sequence has been investigated in the territory of Ukraine (Volyn-Podillyan Plate, Dobrogean Foredeep) and correlated with the data on Moldova and Romania (Moldovian Platform). The occurrence of Silurian strata, their thickness, and petrographic and lithological characteristics allowed reconstructing the distribution of open-shelf, reef and lagoonal facies. The reef facies migrated during the Wenlock–Middle Pridoli, shifting towards the open sea and back towards the shore, and therefore has been termed a migrating reef facies. Correspondingly, the boundary between the open-shelf and reef facies was shifting. The facies distribution was controlled by the transgressive-regressive cycles, which caused the fluctuations of the shelf water depth in different time intervals of the Silurian. The shelf water depth of about 100 m, where the top of the oxygen-minimum layer impinged on the sea bottom, was the boundary between the open-shelf facies, represented by organic-rich sediments, and the reef buildups.

A232 下向き閉塞分岐配管に生じる流動現象に関する研究 : 侵入深さの変動メカニズム(OS2 保全・設備診断技術(5))

Hot water in a main pipe flows into a branch pipe and forms a thermally stratified layer with cold water at a bent section. Fluctuation of the thermally stratified layer may initiates thermal fatigue crack in the branch pipe. It has been reported that the fluctuation of penetration depth induced by the main flow in the branch pipe with a closed end was caused by generation of a large swirl flow at L = 4D_b. Experiments with the rectangular and reduced branch pipes were conducted to suppress the fluctuation of penetration depth induced by the main flow. It was shown that the fluctuation of penetration depth in the rectangular pipe was suppressed, because the large swirl flow at L = 4D_b was not formed. It was also shown that the rectangular and reduced branch pipes were available to decrease the penetration depth by the main flow in the branch pipe.

Seasonal variation in groundwater depth does not explain structure and diversity of tropical savannas

AbstractIt has recently been proposed that seasonal fluctuations in groundwater depth drive spatial patterns of tree density and diversity in Neotropical savannas. Here I consider three major problems in the analysis that led to this conclusion, providing examples that demonstrate that groundwater levels do not constrain the establishment of woody communities and, therefore, cannot be used to explain patterns of tree density and diversity in savannas.

A new empirical procedure for estimating intra-annual heat storage changes in lakes and reservoirs: Review and analysis of 22 lakes

Evaporation is an important component of the water and energy balance of lakes and reservoirs. The energy balance combination method for estimating evaporation requires the heat storage changes (Qt) to be known. The lack of data on water temperature profiles and water depth fluctuations hinders routine computations of Qt. Following successful estimation of the soil heat flux density of land surfaces (G) and heat storage change of urban areas and wetlands from net all wave radiation (Rn), we investigated in this paper whether a similar generic Qt(Rn) empirical relationship can be developed for lakes and reservoirs. A comprehensive literature survey was conducted and experimental datasets for 22 lakes with different characteristics were collected. A linear Qt(Rn) model with a hysteresis function to describe seasonal warming and cooling effects was developed (Qt=a∗Rn+b+c∗dRn/dt) that fits the 22 independently gathered datasets satisfactory (R2 of 0.83 and RMSE of 22Wm−2) for bi-weekly and monthly time scales. Predictive models for the coefficients a, b and c were also developed, using Rn and water surface temperature measurements that can be retrieved from routine earth observation measurements. The average R2 between measured and modeled Qt was 0.84 and the RMSE was 37Wm−2 if predictive models were used for the assessment of lake specific Qt(Rn) functions. Two independent satellite-derived products were explored: the ARC-Lake (ATSR Reprocessing for Climate) product for water surface temperature using the ATSR (Along Track Scanning Radiometer) series data, and the CM SAF (Satellite Application Facility on Climate Monitoring) product for solar radiation Rs based on the AVHRR (Advanced Very High Resolution Radiometer) data. The proposed procedure using purely satellite-derived data as inputs resulted in comparably good Qt estimates as those using in-situ measurements. The new Qt hysteresis model can thus be applied together with satellite measurements for supporting the computation of evaporation from open water bodies based on energy balance equations.

Relation between the sedimentary organic record and the climatic oscilations in the Holocene attested by palynofacies and organic geochemical analyses from a pond of altitude in southern Brazil

This paper presents the quantitative and qualitative results obtained from palynofacies and geochemistry analyses carried out on a core covering approximately 8000 years of sedimentation of a pond of altitude located at the mining district of Ametista do Sul, southernmost Brazil. The main objective of this paper is to consider the paleoclimatic and paleoenvironmental significance of these analyses. The hydrological isolation renders this pond climatically sensitive to variations in pluviometric regime and this enabled infer rainfall events during the early Holocene, which was responsible for the beginning of the processes of water accumulation in the gossan and the sedimentation of the pond. Changes in the pattern of moisture over the time become the drier environment, resulting in the intermittent pattern of water depth that currently exists at the site. The fluctuations in water depth are inferred from the frequency of Botryococcus and other algae, which tend to decrease progressively toward the top where the autochthonous elements are replaced by parautochthonous and allochthonous elements. Pseudoschizaea, in turn, appears to act as a biological marker of these transitional intervals. The present results are of great importance for understanding the extent of climate change and its environmental impacts at regional and global levels.

Phytoplankton of the Chaco-Pampean Plain

Fil: Zalocar, Yolanda. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Nordeste. Centro de Ecologia Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecologia Aplicada del Litoral; Argentina

Large dinosaurian tracks from the Upper Cretaceous (Cenomanian–Turonian) portion of the Winton Formation, Lark Quarry, central-western Queensland, Australia: 3D photogrammetric analysis renders the ‘stampede trigger’ scenario unlikely

The largest dinosaurian tracks at Lark Quarry, central-western Queensland, Australia, were re-examined using revised analytical protocols that incorporate three-dimensional (3D) structure. Comparisons were made with archival photographs, replica specimens (c. 1977) and the in situ tracks (2013) to account for changes to the track surface. Damage caused both during and after the excavation of the tracks was evident, and in cases where the archival photographs and 1970's replicas strongly differ from the in situ tracks, it is apparent that restoration has modified the original track morphology.Even after accounting for recent damage and alteration, several of the track morphologies obtained from new 3D evaluation models differ considerably from the track outlines that were published in the original description of the site. Compared with the new set of representations, some of the original outlines seem to represent simpler, stylized versions of the tracks. A number of the original outlines are >20% larger than the in situ tracks, while others appear to incorporate cracks as part of the margin of digit impressions. Overall, the best-preserved tracks show blunt digit impressions, reaffirming the idea that the trackmaker was a large ornithopod and supporting a reassignment to cf. Iguanodontipus. The new analysis also reveals the nature of the displacement rims associated with the tracks, and the overprinting of these rims by other ichnites—initially by tool marks (presumably caused by floating vegetation) and then by other dinosaurian tracks (assignable to Wintonopus latomorum). In the context of these observations, we see no evidence for an interaction between the cf. Iguanodontipus trackmaker and the smaller-bodied W. latomorum trackmakers, as neither can be inferred to have been present at the tracksite at, or even close to the same time. Similarly, there is no evidence to support the idea that the approach of the cf. Iguanodontipus trackmaker in some way triggered the movement of the W. latomorum trackmakers. Rather than a snap-shot of dinosaurian ‘stampede’, this study supports the idea that Lark Quarry most likely represents a complex time-averaged assemblage of multiple dinosaurian ichnites, preserved over an extended period of time (hours to days) and bracketed by discrete phases of trackmaker activity and fluctuations in water depth.