Submergence Time Research Articles

Forensic study of the mechanical properties of prosthetic materials: Submersion in mangrove environment – A pilot study

IntroductionIt is crucial for dental surgeons to use the mechanical properties of dental prosthetic materials to correlate the submersion time in a mangrove environment. ObjectiveThis study aimed to submerge dental prosthetic materials, such as acrylic resin and zirconia, contained within acrylic resin disks in a mangrove environment, and analyze the alterations in mechanical parameters, such as surface roughness and microhardness, to estimate submergence time in similar forensic situations. Materials and methodsA total of 6 specimens was embedded in acrylic resin disks numbered from 1 to 6. The materials were polished for initial parameter readings a day before submersion, and new readings were obtained 1after submersion. All specimens were subjected to surface roughness analysis, in addition to Knoop microhardness analysis for acrylic resin and Vickers microhardness analysis for zirconia. After the experiment, the data were computed for statistical comparation of the materials properties different parameters. ResultsThere was a significant increase in surface roughness and Knoop microhardness was reduced in the Acrylic Resin samples (p< 0.05); however, no statistically significant differences were observed in the roughness or Vickers microhardness values of the zirconia samples. ConclusionZirconia prosthetics were more resistant to degradation when submerged in a mangrove environment compared to acrylic resin ones; however, owing to the obstacles inherent in this study, we suggest further research on the properties of prosthetic materials submerged in mangroves or other environments, which could bolster the work of dental professionals in forensic medical institutes.

Role of local vasoconstrictors in diving performance of two pinniped species

Diving mammals extend submergence time through bradycardia and reduced peripheral perfusion to certain tissues. Thus, local blood flow regulation under hypoxia may be an essential physiological strategy that fine-tunes metabolic expenditures during breath-hold. We focused on a potent local vasoconstrictor, Endothelin-1 (ET1) and its receptors ETR-A and ETR-B, to determine their potential role in mammalian diving. We hypothesized that less perfused organs (kidney) would have higher signatures of local vasoconstriction (i.e. higher ET1 and receptors), compared to organs known to have higher relative perfusion underwater (heart/left ventricle). Additionally, we compared pinniped species with higher (Weddell seal) and lower (California sea lion) relative dive capabilities. Differences in mRNA expression of vasoconstrictive elements were assessed by 2-way ANOVA to compare tissue and species. In adult animals (n=7 both species) there were significant differences in expression of ET1 between species (F1,16=9.2, p=0.08) and tissues (F1,16=18.4, p=0.0006), with sea lions having consistently higher levels of ET1. ET1 expression was highest in the kidney, with sea lion kidney expressing 25x more ET1 mRNA than heart (posthoc p=0.0007). The expression ratio of ET A and B receptors also differed across tissue (F1,16=19.83 p=0.0004) with B/A highest in the kidney in both species. This is counter to expectations that submergence capability would relate to vasoconstriction potential across species, but supports the hypothesis that within a species, the less-perfused kidney should demonstrate higher potential for local vasoconstriction compared to the heart. Relative expression of ET receptors between tissues also runs counter to our hypothesis. In both divers, the heart expresses relatively more ETR-A, which has a critical role in vasoconstrictive signaling. On the other hand, ETR-B can signal for either vasoconstriction or vasodilation depending on its location within the endothelium or smooth muscle. Kidney in both species expresses relatively more ETR-B, indicating potential for nuanced vasoregulatory control through the endothelin pathway in this tissue. Receptor localization will be determined by immuno-staining to investigate functional differences between tissues. We also investigated the development of diving by comparing the same biomarkers in adults versus pups (n=10 seals, n=3 sea lions) using a separate 2-way ANOVA for each species. We expected that signatures of vasoregulatory potential would be less evident in the novice diving pups. Concordantly, ET1 is lower in sea lion pups than adults (F1,12=5.097, p=0.043); ET1 mRNA is 23x lower in the pup kidney compared to adult (posthoc p=0.02). Receptor expression followed the same patterns in both species, with the highest expression of ETR-A noted in the pup heart, indicating high vasoconstrictive potential in pups, but through tissue specific mechanisms. These results point to differences in the control of local vasoconstriction that occur with development and highlight the physiological components essential to the development of diving. Funding by NSF #2020706. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Propagation of fig (Ficus caricaL.) cuttings under natural rooting at different submergence times

There is a possibility that the time of submersion in natural rooting, with respect to vegetative propagation by fig cuttings, may have a significant effect or differences in the formation and characteristics of the roots. For this reason, the research wascarried out in the Multipurpose Nursery, belonging to the Cota Cota Experimental Centre, under a completely randomised design with factorial arrangement, using a mother plant of more than 12 years old, which is an indication that propagation would be difficult, due to the characteristics of the plant material. The response variables evaluated were: days to root formation, percentage of survival, root length, number of roots, and percentage of lodging. The following results were obtained based on the averages of the data collected in the field research: T9 (lentil water, 48 hours) rooted in 54 days, being the best rooting time. The percentage of survival was influenced by the rooting factor directly, with the natural rooters of lentil water and willow infusion responding much better, with 85.70 and 83.66 % respectively. The rooting and submersion time presented a direct significance in root length, which is equal to 7.60 cm, with treatment 5 (willow infusion, 24 hours). In the variable number of roots, both lentil water and willow infusion achieved 8 and 7 root units respectively, both in a submersion time of 24 hours, and it is also important to note the significance in both factors. Treatment 9 (lentil water, 48 hours) with 90 % was the best average in the variable percent rooting. It was confirmed that the longer the soaking time, the more positive the rooting of the cuttings, depending on the rooting agent used.

Response of underwater photosynthesis to light, CO2, temperature, and submergence time of Taxodium distichum, a flood-tolerant tree.

Partial or complete submergence of trees can occur in natural wetlands during times of high waters, but the submergence events have increased in severity and frequency over the past decades. Taxodium distichum is well-known for its waterlogging tolerance, but there are also numerous observations of this species becoming partially or complete submerged for longer periods of time. Consequently, the aims of the present study were to characterize underwater net photosynthesis (PN) and leaf anatomy of T. distichum with time of submergence. We completely submerged 6 months old seedling of T. distichum and diagnosed underwater (PN), hydrophobicity, gas film thickness, Chlorophyll concentration and needles anatomy at discrete time points during a 30-day submergence event. We also constructed response curves of underwater PN to CO2, light and temperature. During the 30-day submergence period, no growth or formation new leaves were observed, and therefore T. distichum shows a quiescence response to submergence. The hydrophobicity of the needles declined during the submergence event resulting in complete loss of gas films. However, the Chlorophyll concentration of the needles also declined significantly, and it was there not possible to identify the main cause of the corresponding significant decline in underwater PN. Nevertheless, even after 30 days of complete submergence, the needles still retained some capacity for underwater photosynthesis under optimal light and CO2 conditions. However, to fully understand the stunning submergence tolerance of T. distichum, we propose that future research concentrate on unravelling the finer details in needle anatomy and biochemistry as these changes occur during submergence.

Water Level Fluctuations Modulate the Microbiomes Involved in Biogeochemical Cycling in Floodplains.

Drastic changes in hydrological conditions within floodplain ecosystems create distinct microbial habitats. However, there remains a lack of exploration regarding the variations in microbial function potentials across the flooding and drought seasons. In this study, metagenomics and environmental analyses were employed in floodplains that experience hydrological variations across four seasons. Analysis of functional gene composition, encompassing nitrogen, carbon, and sulfur metabolisms, revealed apparent differences between the flooding and drought seasons. The primary environmental drivers identified were water level, overlying water depth, submergence time, and temperature. Specific modules, e.g., the hydrolysis of β-1,4-glucosidic bond, denitrification, and dissimilatory/assimilatory nitrate reduction to ammonium, exhibited higher relative abundance in summer compared to winter. It is suggested that cellulose degradation was potentially coupled with nitrate reduction during the flooding season. Phylogenomic analysis of metagenome-assembled genomes (MAGs) unveiled that the Desulfobacterota lineage possessed abundant nitrogen metabolism genes supported by pathway reconstruction. Variation of relative abundance implied its environmental adaptability to both the wet and dry seasons. Furthermore, a novel order was found within Methylomirabilota, containing nitrogen reduction genes in the MAG. Overall, this study highlights the crucial role of hydrological factors in modulating microbial functional diversity and generating genomes with abundant nitrogen metabolism potentials.

Understanding the density patterns of the polychaete Diopatra neapolitana and its relationship with environmental factors in the NW Spain

To understand the density patterns of the tube-forming polychaete Diopatra neapolitana and their relationship with environmental factors, an extensive sampling was conducted in an intertidal, commercially exploited population in the Ría de Vigo (NW Spain). Interpolation of the sampled densities was carried out by Inverse Distance Weighting (IDW). The results showed a heterogeneous, patchy distribution: the average density was 2.56 tubes/0.25 m2, although some areas exhibited a density with more than 30 tubes/0.25 m2 while in others the species was completely absent. Our data also showed that the presence of vegetation (either algae or Zostera) increased the densities of D. neapolitana. To better understand this finding, a second sampling was conducted targeting the three main permanent habitats identified in the study area. This revealed that the spatial location within the intertidal was the most important factor affecting densities. The higher densities observed with increasing latitude and longitude are a consequence of the higher flooding time, that means less water stress and longer submergence time, and involves a reduced likelihood of being caught by shellfish harvesters. The second most important factor explaining D. neapolitana densities was the sediment organic matter content, which is consistent with the observation that the presence of vegetation increases the density of tubes. This work is the first comprehensive approach to understand the spatial structure of densities of D. neapolitana.

Quantifying behavior and collision risk of humpback whales surfacing near large ships: implications for detection and avoidance

Lethal collisions between ships and whales (‘ship strikes’) are a pressing management issue across the globe, and recent work highlights the need for better information to support collision risk avoidance by mariners. Using a ship-based observer stationed on the bow, we recorded the behavior of humpback whales Megaptera novaeangliae surfacing around large cruise ships transiting Glacier Bay National Park, Alaska, one of the largest marine protected areas in North America. We documented surfacing bouts (i.e. series of surfacings when whales breathe between deeper foraging dives) over 460 h of observation from 65 cruises. We detected few surfacings per bout (mean = 2.9) and observed a moderate within-bout submergence time (median = 20.1 s), showing that whales are unavailable for detection during the majority of their time near the surface. We then used these data to parameterize a modified mark-recapture model to estimate the probability of a whale surfacing before and after first detection by mariners. The estimated probability that a whale surfaced prior to detection was moderate (0.54; 95% credible interval [CRI]: 0.52-0.57), indicating that often, the first detected cue (e.g. a blow or a visible fluke) was not the first cue produced (i.e. available to be detected). The probability that a whale remained near the surface following detection was high (median = 0.87; 95% CRI: 0.85-0.88). This indicates that whales likely remain at risk of collision following detection, enabling mariners to evaluate ship-speed-specific avoidance maneuvers based on initial sighting distances to decrease collision risk.

Going under: The implications of sea‐level rise and reduced light availability on intertidal primary production

AbstractEstuarine intertidal flats are known for high rates of primary production, however, globally these ecosystems are under threat from rising sea‐level and accelerated inputs of terrestrial sediments. These stressors simultaneously alter the duration of submersion/emersion periods and water‐column turbidity impacting seafloor photoperiods. To assess how changes in submergence time and water‐clarity can affect benthic primary production, we derived in situ seasonal photosynthesis‐irradiance (P‐I) curves over 2 yr. These were conducted during submerged and emerged periods in a seagrass meadow (Zostera muelleri) and an unvegetated sandflat (dominated by microphytobenthos). P‐I curves showed strong light responses during submergence in both habitats and seagrass during emergence, but in the exposed sandflat there was little relationship between light availability and photosynthesis. Light‐saturated measures of gross primary production (GPPsat) were 2.1 (submerged) and 4.1 times (emerged) higher in the seagrass than the sandflat habitat. Submerged GPPsat was always higher than emerged GPPsat, but this difference was much more pronounced in the sandflat habitat (2.4 vs. 1.3 times for seagrass). Integrating seasonally averaged P‐I curves for both tidal states into a simple model suggests that increasing submergence time could increase primary production in both habitats. However, reductions in water‐clarity will decrease submerged primary production; an effect that will be exacerbated with sea‐level rise. The sandflat trophic state was more sensitive to these environmental stressors because emerged production could not compensate for reductions during submergence. Collectively, regional management of water‐clarity may be key to providing resilience to intertidal habitats, against the inevitable effects of sea‐level rise.

Cue rates and surfacing characteristics of sei whales (Balaenoptera borealis) in the Falkland Islands

The cue rate (CR: blows per whale per hour), surfacing characteristics and swim speeds of sei whales (Balaenoptera borealis) were quantified fromfocal follows carried out at Berkeley Sound (East Falkland) between January and May 2017 and off the west coast of West Falkland betweenFebruary and April 2018. In Berkeley Sound, focal follows were conducted from Cape Pembroke lighthouse and from a small boat. In West Falklandall focal follows were conducted from a yacht. Thirty-seven focal follows of sei whale individuals or groups (2–5 individuals) were analysed toproduce CRs ranging from 21.99 to 46.73, with a mean of 31.46 (SD = 5.12). There was no significant difference in the CRs observed from shorevs. boat platforms or between the two study areas. Maximum submergence times exceeding 13min were recorded from both individuals and groups.The durations of 51 whale surfacing events had a mean of 6.4s (SD = 1.7). The average swim speed during boat-based sei whale focal follows was5.7kmh−1. The inter-breath intervals (IBIs) recorded from 13 solitary individuals ranged from 77.2 to 180.1s, with an overall mean of 118.6s (SD= 137.6). A combined approach incorporating IBI parameters and sequence pattern was used to classify 270 IBIs into surface dives (mean = 37.2s),intermediate dives (mean = 113.7s) and true dives (mean = 332.6s). Individuals showed marked variation in dive pattern, with some exhibitingclear cycles of true dives interspersed with surface bouts while others routinely took intermediate-duration dives interspersed by single surfacings.Sei whales in Berkeley Sound exhibited a higher proportion of surface dives than whales in West Falkland, and those surface dives were of lowermean and median IBI. Individual sei whales had surface bouts comprising a mean of 3.8 blows and a mean IBI of 33.4s. These are the firstquantifiable data on surfacing-dive patterns and CRs for sei whales in the Falkland Islands and across the wider range of the species. The data haveconservation and management relevance, including addressing availability bias for line transect and cue count abundance estimates, incorporationinto vessel strike modelling, and understanding foraging behaviour.

Nutrient Release from Immersed Foliar Biomass during Caruachi Dam Reservoir Filling: Caroni River, Venezuela

Background: Decomposition process controls the release and the availability of essential nutrients, which affects the structure and the functioning of plant communities. Freshwater reservoirs are largely known to have impacts on the water quality, especially during the first phases of filling. The aim of the study was to conduct a nutrient release experiment where decomposition of fresh leaves and litter from vegetation of a low dry tropical forest was flooded. Selected species were Leguminosae species Albizia glabripetala (H. S. Irwin) G. P. Lewis & P. E. Owen (AG), Bauhinia aculeata L. (BA), Centrolobium paraense Tul. (CP) and Piptadenia leucoxyllon Barneby & J. W. Grimes (PL). Freshwater decomposition experiments were carried out at 50 cm depth inside nine floating containers in a protected area of the reservoir: litter (HJ), leaves of AG and BA (E2), and CP and PL (E3) were used. It was over 20 weeks period. Every week for two months and at week 20, a bag of each sample was extracted for analysis of Carbon, Ca, Mg, Na, K, P and S. Results: Results indicate that residual dry mass decreased by 71% for HJ, 81.4% for E2, and more than 86.8% for E3 after twenty weeks. The higher content of carbon (%) at the beginning of the experiment was E2 > E3 > HJ. After 20 weeks, the percentage of carbon loss was 2.09% for HJ, 3.02% for E2, and 1.69% for E3. S decreased between 50% - 60% during the first week; at 20 weeks, the remaining amount of S was 13% for HJ and E3 and 7% for E2. P showed a different pattern, where the second week was more important for the release. HJ and E3 followed the pattern of nutrient release: K > Mg > Na > Ca while E2 was K > Ca > Mg > Na. Conclusions: P and S release depends on the time of submergence and the species. Fresh leaves decay faster than necromass. Nutrient loss is higher than 50% for the three first weeks and seems constant between week 8 - 20. C and S concentrations incorporated in the reservoir can result in a high release of gases CH4 and S2 to the atmosphere. This study is the first publication in relation to nutrient release from the submergence of species in dry tropical forests.

Benthic foraminifera and pore water carbonate chemistry on a tidal flat and salt marsh at Ria Formosa, Algarve, Portugal

Benthic foraminifera showed a vertical zonation in tidally influenced salt marshes, which has been used for sea level reconstructions. Growing evidence suggested that freshwater influx, salinity, or the pH of interstitial waters has also an impact on the foraminiferal distribution. A tidal flat and salt marsh transect was investigated in the north-western Ria Formosa coastal lagoon, Algarve, Portugal, to constrain the relationship of benthic foraminifera, halophytes, and pore water properties. The dominance of saltworts from the subfamily Salicornioideae and landward increasing soil salinities depicted evaporation as governing environmental factor. The carbonate chemistry from lagoonal and pore waters identified anoxic tidal flat sediments of as main source of total alkalinity. The alkalinity was lower in the salt marsh, where the pCO2 was extremely high. Salt marsh pore waters showed a high variability of carbonate system parameters, which mirrored small-scale spatial heterogeneities in the soil. The distribution of textulariid salt marsh foraminifera was confined to the vegetated zones, where their abundance increased with elevation. Calcareous species were frequent on the tidal flat and in the highest salt marsh. Many of them were specialised to high salinities or to extreme and variable environmental conditions. Two levels of faunal change in the salt marsh coincide with vegetation zonal boundaries, mean tide or mean high water levels. The two other faunal changes were related to changes in calcite saturation state or organic carbon concentrations. The proportion of textulariids showed a negative correlation with submergence time or elevation, and a significant correlation with pore water pCO2. The faunal distribution, pore water calcite saturation, and Ammonia dissolution patterns indicated that calcareous species specialised to tolerate carbonate-corrosive conditions prevailed even at lowest saturation levels.

Investigating Blasting Demolition Dust Micromorphology, Microscopic Agglomeration Process With Wetting Droplet and Suppression Effectiveness by Explosion Water Mist

Blasting demolition has been widely used in the safe and efficient demolishing of construction buildings. Blasting demolition dust is the most visible and realistic harmful material during the blasting process. The characteristics and suppression of the blasting dust are scarcely addressed in the literature. This article investigated the micromorphology characteristic of blasting demolition dust from a typical building demolition project. The dust median size value D50 was 65.890 μm, and it showed a character of smooth edge, fluffy structure, and cracks. It consists of higher content of heavy metals than conventional cement powder particles, which include Mn, Ni, Zn, and As elements. The dust cannot be wet by municipal water for its hydrophobic character. A novelty method was proposed to set a methodology to form a stable, larger volume, and surface area water droplet on a rod stand, which provided more opportunities to find out and verify the microscopic agglomeration phenomenon and effectiveness between dust and different wetting droplets. The single dust-droplet collision results can be accurately recorded by the high-speed camera with a microscope, the collision and submergence time between blasting demolition dust particle and municipal water droplet on the stand was 2 ms, while the time was 1.125 ms with surfactant solution droplet, which was much shorter than the time of municipal water. The dust-droplet microscopic collision results were shown that the blasting demolition dust can be better wet and agglomerated by a surfactant solution. In blasting demolition projects, the BDD suppression methods with surfactant solution explosion mist have the highest efficiency, which can restrict the BDD’s concentration to 10 mg/m3.

Combining artificial intelligence and laboratory experiments to explore behavior process of sunken and submerged oil: A typical oil drift and diffusion detection technology

This paper aims to use laboratory experiments to study the behavior process of sunken and submerged oil under different breaking waves and then combines the experimental results with deep learning technology to establish a typical oil drift and diffusion model. Using the image data of real oil pollution moving under breaking wave energy in the laboratory, this research established and compared the ‘You Only Look Once v4 model’, ‘CenterNet model’, ‘You Only Look Once v3 model’, and ‘Single Shot MultiBox Detector model’. The results show that the average detection speed values of ‘You Only Look Once v4’, ‘You Only Look Once v3’, ‘CenterNet’, and ‘Single Shot MultiBox Detector’ are 42.47 frames per second, 26.80 frames per second, 35.37 frames per second, and 38.90 frames per second, respectively. In terms of detection accuracy, the ‘You Only Look Once v4’ algorithm exceeds the other three algorithms by 10.59%, 22.62%, and 31.69%. Considering its detection speed and detection accuracy, the ‘You Only Look Once v4’ algorithm has strong robustness to changes in the shape and movement of sunken and submerged oil. In addition, by using ‘You Only Look Once v4’ model for oil detection, it is found that the submergence time of oil droplet for 10 cm, 15 cm, 20 cm, 25 cm and 30 cm breaking waves is 2.32 s, 2.52 s, 2.62 s, 3.20 s, 7.12 s, respectively. The speed of sinking to the deepest point is 0.208 m/s, 0.222 m/s, 0.212 m/s, 0.359 m/s, 0.303 m/s.

Research on sunken & submerged oil detection and its behavior process under the action of breaking waves based on YOLO v4 algorithm

Marine oil spill pollution is one of the most serious marine pollution issues. Aiming at the problems of low accuracy and slow speed in the process of detecting the behavior of sunken and submerged oil by traditional methods, a technology of sunken & submerged oil tracking based on YOLO v4 (YOLO refers to ‘you look only once’) algorithm is proposed in this paper. The image data used in this study are pictures of real oil pollution moving under breaking waves, and they are collected in the laboratory. First, the YOLO v4 model under CSPDarknet53 framework was established. Then, in order to simplify the oil detection model and ensure the efficiency of the model, this research used Mosaic data enhancement, random flipping, and Gaussian noise fuzzy data enhancement, as well as Cosine Annealing Learning Rate, and Label Smoothing to improve the effect of deep learning model. After data enhancement, the final data set was divided into a training set and a test set proportionally. The training set had 878 pictures, and the test set had 1945 pictures. The test set contained the situation where oil droplets were completely occluded by waves, so that the detection accuracy was closer to the real situation. The results show that the oil droplet is hit and then sunk, forming ‘sunken and submerged oil’ under the action of breaking waves of wave heights of 10 cm, 15 cm, 20 cm, 25 cm and 30 cm. The submergence time enhances with the increase of wave height of breaking wave, that is, the residence time of oil droplet for 10 cm, 15 cm, 20 cm, 25 cm and 30 cm breaking waves is 2.32 s, 2.52 s, 2.62 s, 3.20s, 7.12 s, respectively. The deepest position of oil droplet under the water for 10 cm, 15 cm, 20 cm, 25 cm and 30 cm breaking waves is 0.165 m, 0.179 m, 0.226 m, 0.297 m, 0.428 m, respectively. However, the drift velocity and sinking velocity of oil droplet show nonlinear variation. The speed of sinking to the deepest is 0.208 m/s, 0.222 m/s, 0.212 m/s, 0.359 m/s, 0.303 m/s, respectively.

The controlled impact of elastic plates on a quiescent water surface

The impact of flexible rectangular aluminum plates on a quiescent water surface is studied experimentally. The plates are mounted via pinned supports at the leading and trailing edges to an instrument carriage that drives the plates at constant velocity and various angles relative to horizontal into the water surface. Time-resolved measurements of the hydrodynamic normal force ($F_n$) and transverse moment ($M_{to}$), the spray root position ($\xi _r$) and the plate deflection ($\delta$) are collected during plate impacts at 25 experimental conditions for each plate. These conditions comprise a matrix of impact Froude numbers${Fr} = V_n(gL)^{-0.5}$, plate stiffness ratios$R_D= \rho _w V_n^2 L^3D^{-1}$and submergence time ratios$R_T= T_sT_{1w}^{-1}$. It is found that$R_D$is the primary dimensionless ratio controlling the role of flexibility during the impact. At conditions with low$R_D$, maximum plate deflections on the order of$1$ mm occur and the records of the dimensionless form of$F_n$,$M_{to}$,$\xi _r$and$\delta _c$are nearly identical when plotted vs$tT_s^{-1}$. In these cases, the impact occurs over time scales substantially greater than the plate's natural period, and a quasi-static response ensues with the maximum deflection occurring approximately midway through the impact. For conditions with higher$R_D$($\gtrsim 1.0$), the above-mentioned dimensionless quantities depend strongly on$R_D$. These response features indicate a dynamic plate response and a two-way fluid–structure interaction in which the deformation of the plate causes significant changes in the hydrodynamic force and moment.

Response of vegetation to submergence along Jingjiang Reach of the Yangtze River.

This work explores the changes in vegetation coverage and submergence time of floodplains along the middle and lower reaches of the Yangtze River (i.e., the Jingjiang River) and the relations between them. As the Three Gorges Dam has been operating for more than 10 years, the original vegetative environment has been greatly altered in this region. The two main aspects of these changes were discovered by analyzing year-end image data from remote sensing satellites using a dimidiate pixel model, based on the normalized difference vegetation index, and by calculating water level and topographic data over a distance of 360 km from 2003–2015. Given that the channels had adjusted laterally, thus exhibiting deeper and broader geometries due to the Three Gorges Dam, 11 floodplains were classified into three groups with distinctive features. The evidence shows that, the floodplains with high elevation have formed steady vegetation areas and could hardly be affected by runoff and usually occupied by humans. The low elevation group has not met the minimal threshold of submerging time for vegetation growth, and no plants were observed so far. Based on the facts summed up from the floodplains with variable elevation, days needed to spot vegetation ranges from 70 to 120 days which happened typically near 2006 and between 2008 and 2010, respectively, and a negative correlation was detected between submergence time and vegetation coverage within a certain range. Thus, floods optimized by the Three Gorges Dam have directly influenced plant growth in the floodplains and may also affect our ability to manage certain types of large floods. Our conclusions may provide a basis for establishing flood criteria to manage the floodplain vegetation and evaluating possible increases in resistance caused by high-flow flooding when these floodplains are submerged.

Evidence of morphological adaptation to life underwater: sternal keel affects swimming speed in giant water scavenger beetles (Coleoptera: Hydrophilidae: Hydrophilini)

Fundamentally, insects evolved on land and secondarily inhabited aquatic environments multiple times. To live underwater, aquatic insects have acquired enormously variable morphological, developmental, physiological, and ecological traits, such as gas exchange systems and swimming-related characteristics. Giant water scavenger beetles of the tribe Hydrophilini (Coleoptera: Hydrophilidae) are characterized by the presence of a sternal keel, which often extends posteriorly. Despite being a conspicuous morphological trait, its function remains unclear. Here, I verified two hypotheses: keel affects (1) submergence time following air replacement and (2) speed and oscillatory movement during forward swimming in Hydrophilus acuminatus Motschulsky, 1854. Submergence time was affected by body mass rather than keel removal; in other words, larger individuals replaced their gas gills more frequently. Keel removal reduced swimming speed by 12.5%. These observations support the second hypothesis, and are also consistent with previous speculations that the sternal keel is a key adaptation for swimming, but the results showed that the degree of oscillation was closely related to body mass but not to keel removal. Further studies are warranted to elucidate precise factors through which the presence of the keel increases swimming speed. Such studies would provide clues into understanding the associations among body size, swimming methods, and morphological traits.

Hunting by the Stroke: How Foraging Drives Diving Behavior and Locomotion of East-Greenland Narwhals (Monodon monoceros)

Deep diving air-breathing species by necessity must balance submergence time and level of exercise during breath-holding: a low activity level preserves oxygen stores and allows longer duration submergence whereas high activity levels consume oxygen quickly and shorten submergence time. In this study, we combined high-resolution multi sensor animal-borne tag data to investigate diving behavior and locomotion styles of the narwhal (Monodon monoceros) (n= 13, mean record length 91 h)–a deep diving Arctic species. Narwhals in this study dove down to &amp;gt;800 m but despite the deep diving abilities, one-third of the dives (33%) were shallow (&amp;gt;100 m) and short in duration (&amp;lt;5 min). Narwhals utilized energy saving measures such as prolonged gliding during descent with increasing target depth but stroked actively throughout the ascent indicating excess oxygen storages. Foraging behavior, as detected by the presence of buzzes, was a key factor influencing dive depth and spinning behavior—the rolling movement of the animal along its longitudinal axes. Narwhals in East Greenland utilized two foraging strategies, while transiting and while stationary, with different target depths and buzzing rates. The first targeted deep-dwelling, possibly solitary prey items and the latter, more schooling prey closer to the surface. The buzzing rate during stationary foraging was on average twice as high as during transiting foraging. Spinning was an integrated part of narwhal swimming behavior but the amount of spinning was correlated with foraging behavior. The odds for spinning during all dive phases were 2–3 times higher during foraging than non-foraging. Due to the spinning behavior, stroking rate might be better suited for estimating energy consumption in narwhals than ODBA (overall dynamic body acceleration). The narwhal is considered as one of the most sensitive species to climate change–the results from this study can act as a baseline essential for evaluating changes in the behavior and energy usage of narwhals caused by stressors evolving in the Arctic.

Geomorphology and Species Interactions Control Facilitation Cascades in a Salt Marsh Ecosystem.

Facilitation cascades are chains of positive interactions that occur as frequently as trophic cascades and are equally important drivers of ecosystem function, where they involve the overlap of primary and secondary, or dependent, habitat-forming foundation species [1]. Although it is well recognized that the size and configuration of secondary foundation species' patches are critical features modulating the ecological effects of facilitation cascades [2], the mechanisms governing their spatial distribution are often challenging to discern given that they operate across multiple spatial and temporal scales [1, 3]. We therefore combined regional surveys of southeastern US salt marsh geomorphology and invertebrate communities with a predator exclusion experiment to elucidate the drivers, both geomorphic and biotic, controlling the establishment, persistence, and ecosystem functioning impacts of a regionally abundant facilitation cascade involving habitat-forming marsh cordgrass and aggregations of ribbed mussels. We discovered a hierarchy of physical and biological factors predictably controlling the strength and self-organization of this facilitation cascade across creekshed, landscape, and patch scales. These results significantly enhance our capacity to spatially predict coastal ecosystem function across scales based on easily identifiable metrics of geomorphology that are mechanistically linked to ecological processes. Replication of this approach across vegetated coastal ecosystems has the potential to support management efforts by elucidating the multi-scale linkages between geomorphology and ecology that, in turn, define spatially explicit patterns in community assembly and ecosystem functioning.

Filtration rates of the manila clam, Ruditapes philippinarum, in tidal flats with different hydrographic regimes.

The manila clam Ruditapes philippinarum is widely distributed in the sandy mud sediments of tidal flats and plays a role in seawater purification by filtering suspended organic matter. This study was designed to evaluate differences in seawater purification based on the filtration rate of the manila clam in terms of particulate organic matter (POM) between two tidal flats with different hydrographic regimes. In situ experiments were carried out at Geunso and Sihwa tidal flats, along the west coast of Korea. The amount of POM removed from the water column by the feeding activity of the clam was measured in the field using a closed circulation chamber. The filtration rate of clams for POM at Sihwa tidal flat (2.86 for POC, 2.29 for PON and 5.46 L h-1 gDW-1 for Chl a) was higher than that at Geunso tidal flat (0.61 for POC, 0.89 for PON and 2.54 L h-1 gDW-1 for Chl a) which resulted from differences in the hydrographic regime, including tide characteristics, current speed and submergence time, and food quantity and quality. The current speed was much greater at Geunso tidal flat than at Sihwa tidal flat, but the submergence time by tide was longer at the latter site than the former, resulting in different feeding times for clams. The food quantity in terms of chlorophyll a was higher at Sihwa tidal flat than at Geunso tidal flat, and the food quality based on the C/N ratio of POM was better at the former site than the latter, with values of 12.8 and 15.6, respectively. These findings suggest that hydrographic regime could be important in understanding in situ filtration rates of R. philippinarum.