Varying Water Depth Research Articles

Gray Wolf Optimization for Scheduling Irrigation Water

Although various optimization algorithms have been developed for operational purposes, the development of new optimization algorithms is still an open problem due to the complex system of irrigation canals that must be addressed. Recently, a new algorithm named gray wolf optimization (GWO) has been introduced and applied in different contexts. It mimics the social hierarchy and hunting behavior of gray wolves in nature. In this research, GWO was formulated, developed, and linked to irrigation canal system simulation (ICSS) to schedule water delivery. A fitness (optimization) function was defined according to the standard water delivery performance indicators. Normal and water shortage operational scenarios in the E1R1 Dez canal in Iran were tested and evaluated. The results revealed that GWO is a powerful optimization method and avoids local optimal points when normal conditions exist. However, it has relatively poor performance in water shortage conditions in which there is not enough water. Water depth variations remain inside acceptable margins. Its results were comparable to fuzzy state, action, reward, state, action (SARSA) learning (FSL) in the same canal, showing a value of maximum absolute error (MAE) and integral absolute error (IAE) of 10.7% and 9.2%, respectively, and it can distribute water between turnouts adequately, efficiently, equitably, and dependably in normal conditions.

Analysis Of Wave Height To Ship Motion With Displacement Of 7,597 Tons By Finite Element Method

Seakeeping is the ship's ability to stay afloat on the waves. The ship's maneuverability is greatly influenced by external factors related to the state of the sea and the waters in which the ship sails. Calculating seakeeping with various variations of depth, current, and wave height is needed for ship safety when sailing in the calculation of seakeeping using linear strip theory to calculate the response of heaving and pitching movements while roll damping theory for rolling movements. In this study, the ship's motion is calculated using the Finite element method software Hydrodynamic Diffraction and Hydrodynamic Time Response. For variations in wave height and water depth, referring to the conditions of Indonesian waters, from the reference, variations in wave height of 3 m, and 5 m (based on sea state WMO). In contrast, the current variation uses a current with a speed of 10 knots and a current depth of 10 T, 15 T, and 20 T. Based on the data obtained in data processing, it can be seen that the high value of the wave frequency obtained at 90 and 270 degrees wave direction is relatively high. The value of the roll spectrum in the direction of 0 and 270 degrees is large and can cause rolling on the ship. In the direction of 0 and 270 degrees, the wave resistance can be reduced by the ship.

Analysis Of Wave Height To Ship Motion With Displacement Of 7,597 Tons By Finite Element Method

Seakeeping is the ship's ability to stay afloat on the waves. The ship's maneuverability is greatly influenced by external factors related to the state of the sea and the waters in which the ship sails. Calculating seakeeping with various variations of depth, current, and wave height is needed for ship safety when sailing in the calculation of seakeeping using linear strip theory to calculate the response of heaving and pitching movements while roll damping theory for rolling movements. In this study, the ship's motion is calculated using the Finite element method software Hydrodynamic Diffraction and Hydrodynamic Time Response. For variations in wave height and water depth, referring to the conditions of Indonesian waters, from the reference, variations in wave height of 3 m, and 5 m (based on sea state WMO). In contrast, the current variation uses a current with a speed of 10 knots and a current depth of 10 T, 15 T, and 20 T. Based on the data obtained in data processing, it can be seen that the high value of the wave frequency obtained at 90 and 270 degrees wave direction is relatively high. The value of the roll spectrum in the direction of 0 and 270 degrees is large and can cause rolling on the ship. In the direction of 0 and 270 degrees, the wave resistance can be reduced by the ship.

Analysis Of Policy Has Been Established By The Minister On Opening The Export Of Lobster Seed In Indonesia

Seakeeping is the ship's ability to stay afloat on the waves. The ship's maneuverability is greatly influenced by external factors related to the state of the sea and the waters in which the ship sails. Calculating seakeeping with various variations of depth, current, and wave height is needed for ship safety when sailing in the calculation of seakeeping using linear strip theory to calculate the response of heaving and pitching movements while roll damping theory for rolling movements. In this study, the ship's motion is calculated using the Finite element method software Hydrodynamic Diffraction and Hydrodynamic Time Response. For variations in wave height and water depth, referring to the conditions of Indonesian waters, from the reference, variations in wave height of 3 m, and 5 m (based on sea state WMO). In contrast, the current variation uses a current with a speed of 10 knots and a current depth of 10 T, 15 T, and 20 T. Based on the data obtained in data processing, it can be seen that the high value of the wave frequency obtained at 90 and 270 degrees wave direction is relatively high. The value of the roll spectrum in the direction of 0 and 270 degrees is large and can cause rolling on the ship. In the direction of 0 and 270 degrees, the wave resistance can be reduced by th Lobsters are animals that enter into crustaceans that have problematic skin. Adult lobsters can generally be found on a stretch of sand with coral spots with a depth of between 5-100 meters. This condition will cause a low number of young lobsters in the waters. This research was conducted with a case study regarding the policy of opening lobster seed export, which aims to find out how the policy is to open the export of lobster seed. The data obtained is done by reviewing the literature on the internet. Based on the analysis, the export profit of lobster seeds has continued to increase every month since it was again allowed by the government in May 2020. Based on data from the Central Statistics Agency (BPS), lobster seeds began to be re-exported in June 2020 at 32 kilograms, costing the US $ 112,990. The government can help with training and outreach on lobster cultivation. The government can offer Lobster a partnership package to help people start a freshwater crayfish business.

Temperature Influence on the Variability and Emission of CH4 and CO2 from a Former Manchester Landfill

Analysis of datasets in time order was carried out to determine the consequence of atmospheric temperature on the changes in CH4and CO2concentrations at a former landfill site. The Gasclam(in-borehole gas monitor) was used to collect field data of CH4/CO2 concentrations and the environmental parameters. The magnitude of the relationship of ground-gas concentration and the barometric temperature was obtained by linear regression analysis. The result reveals variability in CH4 and CO2 concentrations with poor positive relationships of 0.016 and 0.014, respectively, with barometric temperature over the whole sampling period. Despite slightly improving the R2bytaking into account their concentration over single phases of upward and downward limb temperature, single phases of upward limb temperature, and single phases of downward limb temperature, their correlations remained insignificant at a 95% confidence level. The implicationis that temperature (just like pressure) is not the dominant influence on CH4 and CO2 concentrations changes at this site. Having established barometric pressure and temperature asminor controls, a recommendation was made for the establishment of other potential controls(particularly variations in the site water depth) and their degree of control.

Influence of physical environmental parameters on the abundance of Chrysichthys nigrodigitatus of the Cross River, Nigeria.

In this study, the influence of physical environmental factors (rainfall, temperature, water depth, turbidity, transparency and conductivity) on the temporal distribution, abundance and catch of C. nigrodigitatus from the Cross River was investigated. Fish catch and abundance were monitored fortnightly for 12 months. Surface water samples were collected twice monthly and analyzed using standard methods. Seasonal variations in rainfall, water depth, temperature, turbidity, transparency and conductivity were observed across the study period. Correlation analysis showed a positive and significant relationship between rainfall and fish catch (P<0.05), while temperature and conductivity were negatively correlated with fish catch (P<0.05 and 0.01 respectively). Transparency was negatively correlated with fish catch but this relationship was, however, not statistically significant (P>0.05). On the other hand, water depth and turbidity were positively correlated with fish catch but again both relationships were not statistically significant (P>0.05). These findings suggest that rainfall, temperature, conductivity and other environmental variables play important role(s) in the distribution and abundance of Chrysichthys nigrodigitatus in the Cross River, with implication of climate change impact on the species reproductive ecology and population dynamics.

Point of No Return: Determining Depth at Which Sea Turtle Carcasses Experience Constant Submergence

At-sea mortality information is important for understanding the magnitude of threats to protected sea turtle species. When a sea turtle dies, it typically sinks, starts decomposing, and will eventually float to the surface if the carcass remains intact and enough internal gases accumulate. However, few data are available regarding the rate and duration of these processes to allow estimation of time since death once carcasses are recovered. Twenty-seven Kemp's ridley (Lepidochelys kempii) and 15 green (Chelonia mydas) sea turtle cold-stunned carcasses were placed in wire mesh, weighted cages at varying water depths (10–40 m) and temperatures (18.5°C–28.7°C) in the northern Gulf of Mexico from June 2018 to October 2019. Cameras and temperature-depth-orientation recorders were used to document decomposition progression and carcass buoyancy. Decomposition rate was measured using corrected accumulated degree hours and values of observed time-to-float were compared with predictions based on laboratory and field experiments in previous research. Overall, carcasses did not float when deployed in waters > 30 m when temperatures were < 22°C and carcasses tended to float sooner in ≤ 20 m depths, especially if bottom temperatures were > 24°C. Green sea turtle carcasses floated in a variety of environmental conditions, but onset of positive buoyancy was not very predictable. Buoyancy of Kemp's ridley sea turtle carcasses was inconsistent, but float times were fairly predictable. We did not identify the exact depth at which sea turtle carcasses cannot generate enough gases to float, but that depth is likely very close to 40 m. Carcasses that became buoyant in ≥ 30 m depths tended to float for < 24 hrs before sinking again and, therefore, it is unlikely that they have enough time to drift to shore. This information enhances our understanding of the likelihood of carcasses washing ashore and can be incorporated into carcass backtracking analyses to facilitate identification of mortality causes.

Biotic Response to Rapid Environmental Changes During the Permian–Triassic Mass Extinction

The divergent patterns of Permian–Triassic mass extinction (PTME) have been extensively documented in varying water depth settings. We here investigated fossil assemblages and sedimentary microfacies on high-resolution samples from two adjacent sections of the South China Block: Chongyang from shallow-water platform and Chibi from deeper-water slop. At Chongyang, abundant benthos (over 80%), including rugose corals, fusulinids, calcareous algae, and large foraminifers, disappeared precipitously at the topmost of Changxing Formation grainstone, which suggested complete damage of the benthic ecosystem, confirming a sudden single-pulse extinction pattern. The end-Permian regression, marked by a karst surface, provided a plausible explanation for this extinction pattern. Whereas for the fauna in Chibi, the benthos was relatively abundant (20%–55%) with more trace fossils and lacking calcareous algae. Benthic abundance in Chibi reduced by two steps at the two claystone beds (Beds 10 and 18): bioclastic content dropped from an average of 50% in Beds 1–9 to 10% in Beds 11–17 and then to less than 5% in Beds 19–23, suggesting a two-pulse extinction. At the first pulse, large foraminifers were prominent victims in both shallow- and deeper-water settings. A plausible survival strategy for small-sized foraminifers was to migrate to deeper water to avoid extreme heat in shallow water. The early Triassic transgression prompted some small foraminifers to migrate back to original platforms and flourish briefly as disaster forms. At the Early Triassic mudstone with bottom-water settings in Chibi, the appearance of abundant small pyrite framboids (diameters of 4.74–5.96 μm), an indicator of intensified oxygen deficiency, was simultaneous with the two-step reduction of benthic diversity and abundance. Thus, anoxic conditions might be the main cause of the PTME at deeper-water settings. Our study is an example of the wider debate about biotic response to rapid environmental change for both the Permian–Triassic transition and modern days.

Marsh bird response to restored shallow lakes: Implications for future management

AbstractThe restoration of shallow lakes has the potential to provide habitat for obligate breeding marsh birds, including secretive marsh birds. However, the degree of marsh bird response to wetland restoration may vary over time as prairie wetlands are subject to variation in water depth and vegetation characteristics (e.g., height, density, distribution) because of management and biotic and abiotic factors. We investigated the effects of shallow lake restoration age and habitat covariates on the abundance of 3 secretive marsh bird species and marsh bird species richness at shallow lakes in northern Iowa from 2009–2010 and again from 2016–2017. We found that the interspersion of water and emergent vegetation, shallow lake area, and water depth influenced the abundance of pied‐billed grebes (Podilymbus podiceps). Restoration age (β = −0.52, 95% CI = −0.87, −0.18) had a quadratic effect on abundance of pied‐billed grebes, peaking at 6 years post‐restoration. Percent cattail (β = 1.95, 95% CI = 0.55, 3.35) and restoration age (β = 0.51, 95% CI = 0.14, 0.87) were important predictors for Virginia rail (Rallus limicola) abundance. Species richness was greater at restored shallow lakes ( = 2.72, 95% CI = 2.23, 3.23) compared to non‐restored shallow lakes ( = 3.91, 95% CI = 3.41, 4.56) and at shallow lakes with a greater percentage of cattail ( = 2.54, 95% CI = 2.13, 3.07 at 0% cattail to = 4.27, 95% CI = 3.47, 5.15 at 100% cattail). Restoration age did not significantly influence least bittern (Ixobrychus exilis) abundance or species richness, but both variables tended to peak between 5 to 8 years after restoration. Our findings illustrate the need to evaluate habitat characteristics of individual shallow lake restorations as they age to inform continued management efforts for breeding marsh birds.

Differential behavioral responses of benthic and nektonic tadpoles to predation at varying water depths

Predators influence microhabitat selection and activity level of tadpoles, but it is still unclear how such responses to predators differ among species and how water column's depth influences this predator–prey interaction. Here, we experimentally tested whether the presence of Odonata water nymphs influenced the spatial use and activity of benthic and nektonic tadpoles in different food availability contexts. Benthic tadpoles occupied and consumed more food at the bottom level, irrespective of predator's presence. However, when predators were at the bottom, benthic tadpoles remained close to the cages, suggesting a typical “stay-still” defensive behavior known for Physalaemus nattereri (Steindachner, 1863). Nektonic tadpoles occupied shallower depths on predator presence, and they also consumed less food and avoided the predator by selecting food sources far from it. When the predator was at the bottom level and food was available, the distance of tadpoles to the cage tended to be smaller. Scinax fuscovarius (Lutz, 1925) tadpoles were more active when food was absent regardless of predator's presence. When food was available, these tadpoles generally occupied and consumed more food at the bottom level. Tadpole responses depended not only on predator presence but also on a complex net of factors, which included tadpole habit, antipredatory behavior, and availability and location of food.

An authigenic response to Ediacaran surface oxidation: Remarkable micron-scale isotopic heterogeneity revealed by SIMS

The Ediacaran Shuram excursion (SE) records a global decrease in carbonate carbon isotope (δ13Ccarb) values from +6‰ down to ca. –10‰, representing the largest δ13Ccarb negative anomaly in Earth history. While the SE is widely recorded in the upper Doushantuo Formation of South China, it shows highly variable δ13Ccarb profiles among correlative sections. This inconsistent expression of the SE challenges the conventional view of a homogeneous marine dissolved inorganic carbon (DIC) reservoir. A potential process that could explain δ13Ccarb variability is local mineralization of isotopically distinct authigenic carbonates near the sediment–water interface during early diagenesis. However, a direct test of such authigenic carbonates is still limited. Here, following a recent study on the SE in an intra-shelf environment, we revisited an outer-shelf section, identified and analyzed μm-scale, syn-depositional authigenic calcite cements via integrated cathodoluminescence (CL), micro-X-ray fluorescence (μXRF), scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), and secondary ion mass spectrometry (SIMS). Our new SIMS results reveal remarkable micron-scale heterogeneity of δ13Ccarb in authigenic calcite cements, including extremely negative values down to –37.5‰ (VPDB). We interpret these calcite cements as methane-derived authigenic calcite (MDAC) resulting from microbial sulfate reduction (MSR) and anaerobic oxidation of methane (AOM) during early diagenesis. Based on the new results, we propose that the heterogeneous SE in South China — manifest on micrometer, centimeter, and basinal scales — was modulated by methane oxidation under variable local redox and water depth conditions. The SE, therefore, was coupled with different degrees of methane oxidation in individual basins, and globally triggered by enhanced seawater sulfate during an atmospheric oxygenation event. In light of this study, the potential role of redox variability in methane oxidation during the SE may have been underestimated. Our study demonstrates that integrated SIMS-SEM analysis can distinguish different generations of isotopically distinct carbonates otherwise undetected by conventional analysis, and is thus an effective approach to assess the origin and diagenetic history of δ13Ccarb anomalies in the sedimentary record.

Wave-current interactions at the Tagus Estuary Mouth (Portugal) under storm wave conditions

This study investigates interactions between waves, water levels and currents at the mouth of the second largest estuary in Europe (the Tagus Estuary, Portugal) under storm waves, combining field observations and a three-dimensional fully coupled wave-current modelling system. Tidal-induced water depth variations substantially modulate waves over the ebb shoal. During energetic conditions, low tide levels promote depth-limited wave breaking and energy transfer towards higher harmonics (triad interactions), which reduces wave heights and periods. Furthermore, for a given water level, tidal currents also influence wave propagation and drive strong modulations over shallow regions characterized by cross-channel current gradients. Flood currents change the mean wave direction by about 10–15° and tend to focus the wave energy flux towards coastal regions of the southern margin compared to a run without currents (20 to 30% increase of wave heights), while ebb currents reduce the wave heights. In addition, model results suggest that the saturation level associated with wave and current conditions at shallow locations may be close to the threshold where waves start to dissipate by whitecapping. At the peak of the storm, waves become a main driver of the circulation at the mouth scale, even in the 45-m deep main channel. Wave breaking acceleration over the ebb-shoal locally increases flood currents by 50 to 300% and reduces ebb currents by 20 to 50%.

EFFECT OF FREEBOARD HIGH ON WAVE REFLECTION ON ZIGZAG MODEL WCSP-DS BUILDING

&lt;p&gt;The Wave Catcher Shore Protection Dual-Slope (WCSP-DS) model in this study is a model of a dual function beach building as a beach protector and a catcher of wave energy, which has two walls, namely upright and inclined walls with an angle of 45°. The WCSP-DS building also has a reservoir at its top to accommodate wave runoff (overtopping). This study aims to determine the reflection in front of the model with variations in the freeboard height of the Wave Catcher Shore Protection Dual-Slope (WCPS-DS) building in a zigzag position. The test was carried out using a 1:20 scale 3D physical model at the Coastal and Environmental Engineering Laboratory, Faculty of Engineering, Hasanuddin University, Makassar. Simulation and data acquisition were carried out in a wave basin measuring 15 meters long, 10 meters wide using a regular wave generation system and the wave height data on the wave probe was recorded automatically. The simulation was carried out with 5 variations of freeboard height on 3 variations of waves, namely wave height and period and 3 variations of water depth. The results showed that there was a significant effect of freeboard height, wave steepness and water level position on WCSP-DS vertical wall height or water depth relative to the wave reflection coefficient in front of the model. The value of the reflection coefficient (Kr) in the relationship between freeboard height and water depth (Fb/d) at a depth of 0.4 meters (d/z = 1.143) ranges from 0.42 – 0.74, at a depth of 0.35 meters (d /z = 1) ranged from 0.44 – 0.74 and at a depth of 0.3 meters (d/z = 0.857) ranged from 0.35 – 0.71.&lt;/p&gt;

Water depth determines spatial and temporal phosphorus retention by controlling ecosystem transition and P-binding metal elements

Shallow lakes are more susceptible to eutrophication than deep lakes. The geochemical and biogeochemical mechanisms controlling the vulnerability to eutrophication for deep lakes and shallow lakes remain unknown. Therefore, we investigated the combined Phosphorus (P) retention mechanism with P fractions, water depth, distribution of P-binding metal elements, and macrophytes coverage in a degrading ecosystem of Erhai Lake. We concluded that different mechanisms control the P retention in deep-water areas and shallow-water areas. In shallow areas covered by macrophytes, the biogeochemical process manipulates the P retention by changing the total organic carbon (TOC), calcium (Ca) distributions and turbulence. In deep areas without macrophyte coverage, the aluminum (Al) and iron (Fe) distributions control the P retention by a physicochemical process. Manganese (Mn) was found to be a potential proxy in tracking the kinetic release and readsorb of redox-sensitive P (BD-P) in deep areas. The historical record and core sample indicate that the hydrological engineering induced water depth variation is a vital factor changing the ecosystem of Erhai Lake by forming a large area of intermediate area where macrophytes could only survive at low water level. The uplift of water level in the 1990s gradually changed the ecosystem of Erhai Lake from macrophyte-dominated to algal-macrophyte concomitant that reduced the accumulation of stable P fractions and their binding metals. Macrophytes were capable to preserve P in biomass in the macrophyte-dominated ecosystem, which released 150% and 72% of more labile organic P (NaOH25-nrP) and BD-P in the sediment after the deterioration than before, respectively. Therefore, water depth is a prerequisite to restoring the P preservation capacity of sediment and the macrophyte ecosystem. Further hydraulic engineering projects should consider the effect of water-level-variation-induced ecosystem transition.

Godunov-type solutions for free surface transient flow in pipeline incorporating unsteady friction

AbstractA finite-volume second-order Godunov-type scheme (GTS) combining the unsteady friction model (UFM) is introduced to simulate free surface flow in pipelines. The exact solution to the Riemann problem calculates the mass and momentum fluxes while considering the Brunone unsteady friction factor. One simple boundary treatment with double virtual cells is proposed to ensure the whole computation domain with second-order accuracy. Results of various transient free-surface flows achieved by the proposed models are compared with exact solution, experimental data, the four-point implicit Preissmann scheme solution, as well as predictions by the classic Method of Characteristics (MOC). Results show that the proposed second-order GTS UFMs are accurate, efficient, and stable even for Courant numbers less than one and sparse grid. The four-point implicit Preissmann scheme may produce severe numerical attenuation in the case of large time steps and unsuitable weighting factors, while the MOC scheme may produce severe numerical attenuation in the case of a low Courant number and could not maintain mass conservation. The numerical simulations considering the unsteady friction factor are closer to the measured water depth variations. The effect of unsteady friction becomes more important as the initial water depth difference increases significantly.

Analysis of a solar still with photovoltaic modules and electrical heater - Energy and exergy approach.

The availability of drinkable water, along with food and air, is a fundamental human necessity. Because of the presence of higher amounts of salt and pollution, direct use of water from sources such as lakes, sea, rivers, and subsurface water reservoirs is not normally suggested. Solar is still a basic technology that can use solar energy to transform accessible waste or brackish water into drinkable water. Exergy analysis is a strong inferential technique for evaluating the performance of thermal systems. Exergy is becoming more popular as a predictive tool for analysis, and there is a rising interest in using it. In this paper, performance analysis on the aspect of energy and exergy from the proposed solar still (PSS) (conventional solar still with the photovoltaic modules-AC heater) was analyzed on three different water depths (Wd) conditions (1, 2, and 3 cm). Using a solar still with an electric heater, the daily potable water production was found as 8.54, 6.37, and 4.43 kg, for the variations in water depth (Wd) of 1, 2, and 3 cm respectively. The energy and exergy efficiency of the PSS at the Wd of 1, 2, and 3 cm were 75.67, 51.45, and 37.21% and 5.08, 2.29, and 1.03%, respectively. At 1 cm Wd, PSS produced the maximum freshwater yield as compared to the other two water depths. When the Wd is increased from 1 to 2 cm and from 1 to 3 cm, the yield is decreased up to 27.3 and 52.7%, respectively. Similarly, the energy and exergy efficiency is decreased up to 36.8 and 53.2% and 50.4 and 80.6%, respectively. The water cost of the modified solar still is calculated as 0.028 $/kg for the least water thickness.

A flexible fully nonlinear potential flow model for wave propagation over the complex topography of the Norwegian coast

Coastal wave propagation and transformation are complicated due to the significant variations of water depth and irregular coastlines, which are typically present at the Norwegian fjords. A potential flow model provides phase-resolved solutions with low demands on computational resources. Many potential flow models are developed for offshore waves and lack of numerical treatments of coastal conditions. In the presented work, several modifications are introduced to a fully nonlinear potential flow model with a σ-grid for the purpose of coastal wave modelling: Shallow water breaking criteria are included in addition to deepwater breaking algorithms to approximate breaking waves over a complete range of water depth. A new coastline algorithm is introduced to detect complex coastlines and ensure robust simulations near the coast. The algorithm is compatible with structured grid arrangement in the horizontal plane and allows for high-order discretisation schemes for the free surface boundary conditions for an accurate representation of complex free surfaces. A parallelised solver for the Laplace equation is utilised to ensure fast simulations for large domains with multi-core infrastructures.The proposed model is validated against theories and experiments for various two- and three-dimensional nonlinear wave propagation and transformation cases that represent typical coastal conditions. The simulations show a good representation of nonlinear waves, and the results compare well with experiments. Furthermore, two large-scale engineering scenarios are simulated, where the applicability of the coastline algorithm and the parallel commutation capability of the model are demonstrated.

Depth and habitat are important drivers of abundance for predatory reef fish off Pemba Island, Tanzania

Coral reefs across the world face significant threats from fishing and climate change, which tends to be most acute in shallower waters. This is the case off Pemba Island, Tanzania, yet the effects of these anthropogenic stressors on the distribution and abundance of economically and ecologically important predatory reef fish, including how they vary with depth and habitat type, is poorly understood. Thus, we deployed 79 baited remote underwater videos (BRUVs) in variable water depths and habitats off Pemba Island, and modeled the effects of depth and habitat on abundance of predatory reef fish. Predatory reef fish types/taxa were significantly predicted by depth and habitat types. Habitats in relatively deeper waters and dominated by hard and soft corals hosted high species richness and abundance of predatory reef fish types/taxa compared to mixed sandy and rubble habitats. The findings add to the growing evidence that deep waters around coral reefs are important habitats for predatory reef fish. Thus, careful management, through effective area and species protection measures, is needed to prevent further depletion of predatory reef-associated fish populations and to conserve this biologically important area.

Experimental and numerical investigation of shallow water effects on resistance and propulsion of coupled pusher-barge convoys

Model tests for three representative configurations of modern inland coupled pusher-barge convoys were performed to experimentally and numerically assess calm water resistance and propulsion characteristics in deep and shallow waters. The configurations consisted of a pusher boat coupled with one, two, and four barges. Obtained was insight into calm water resistance of such systems and benchmark data to validate numerical methods. Although the barges being pushed were identical, their arrangement had a significant effect on the efficiency of the convoys. Power required to transport a unit payload was lowest for the third configuration. Numerical resistance tests were carried out using a Reynolds-Averaged Navier–Stokes solver for the first configuration in deep and shallow waters, with varying water depth to draft ratios of H/T=∞,2.0,1.5 and 1.2. The computations were validated against model test measurements.

Effect of Water Depth on Heart Rate and Core Temperature During Underwater Treadmill Walking

Exercising using an underwater treadmill (UTM) has become a popular modality; however, few studies have focused on the physiological demands of UTM walking at varying water depths. Thus, the objective of this study was to investigate changes in heart rate (HR) and core temperature (CT) values in college-aged males and females while exercising at different water immersion depths using an UTM. Twenty participants (age = 21.50 ± 2.19 years; height = 169.04 ± 10.85cm; weight = 75.56 ± 22.28kg) walked at water depths of 10cm below the xiphoid process and at the level of the superior iliac crest (I.C.). Each UTM session lasted 15 minutes, consisting of 5-minute bouts at 1, 2, and 3 mph. Polar HR monitors and ingestible thermoregulatory pills were used to measure HR and CT. Results indicated that HR at 1 (p = .305) and 2 mph (p = .864) were not significantly different between water depths. Heart rate was significantly higher at 3 mph (p = .003) at the I.C. water level. No significant differences were found in CT at 1 (p = .919), 2 (p = .392), or 3 mph (p = .310) during either immersion depth. As a result, higher immersion depths resulted in a lower average HR during higher intensity exercise due to the increased buoyancy effects and the reduced gravity environment of the water. Thus, exercising in higher immersion depths allows participants to exercise at a higher intensity with less overall stress placed on the lower extremities.