Dispersive Model Research Articles

Direct sampling of ultrashort laser pulses using third-harmonic generation with perturbation in ambient air.

We propose a simple and robust all-optical pulse sampling method to characterize the temporal profiles of ultrashort laser pulses. The method is based on a third-harmonic generation (THG) process with perturbation in ambient air, which requires no retrieval algorithm and can be potentially applied to electric field measurement. The method has been successfully used to characterize multi-cycle and few-cycle pulses with a spectral range from 800 nm to 2200 nm. Considering the broad phase-matching bandwidth of THG and extremely low dispersion of air, this method is suitable for ultrashort pulse characterization even for single-cycle pulses in the near- to mid-infrared range. Thus, the method provides a reliable and highly accessible approach for pulse measurement in ultrafast optics research.

Coupling large-spatial scale larval dispersal modelling with barcoding to refine the amphi-Atlantic connectivity hypothesis in deep-sea seep mussels

In highly fragmented and relatively stable cold-seep ecosystems, species are expected to exhibit high migration rates and long-distance dispersal of long-lived pelagic larvae to maintain genetic integrity over their range. Accordingly, several species inhabiting cold seeps are widely distributed across the whole Atlantic Ocean, with low genetic divergence between metapopulations on both sides of the Atlantic Equatorial Belt (AEB, i.e. Barbados and African/European margins). Two hypotheses may explain such patterns: (i) the occurrence of present-day gene flow or (ii) incomplete lineage sorting due to large population sizes and low mutation rates. Here, we evaluated the first hypothesis using the cold seep mussels Gigantidas childressi, G. mauritanicus, Bathymodiolus heckerae and B. boomerang. We combined COI barcoding of 763 individuals with VIKING20X larval dispersal modelling at a large spatial scale not previously investigated. Population genetics supported the parallel evolution of Gigantidas and Bathymodiolus genera in the Atlantic Ocean and the occurrence of a 1-3 Million-year-old vicariance effect that isolated populations across the Caribbean Sea. Both population genetics and larval dispersal modelling suggested that contemporary gene flow and larval exchanges are possible across the AEB and the Caribbean Sea, although probably rare. When occurring, larval flow was eastward (AEB - only for B. boomerang) or northward (Caribbean Sea - only for G. mauritanicus). Caution is nevertheless required since we focused on only one mitochondrial gene, which may underestimate gene flow if a genetic barrier exists. Non-negligible genetic differentiation occurred between Barbados and African populations, so we could not discount the incomplete lineage sorting hypothesis. Larval dispersal modelling simulations supported the genetic findings along the American coast with high amounts of larval flow between the Gulf of Mexico (GoM) and the US Atlantic Margin, although the Blake Ridge population of B. heckerae appeared genetically differentiated. Overall, our results suggest that additional studies using nuclear genetic markers and population genomics approaches are needed to clarify the evolutionary history of the Atlantic bathymodioline mussels and to distinguish between ongoing and past processes.

Early prehistory of South America and population dynamics: Issues and hypotheses

People were in the Americas before, during, and immediately after the Last Glacial Maximum. Multiple data converge toward a deep chronology model for Homo genre exploration, dispersal, occupation, and settlement across the continent. South America is not an exception. This paper is an attempt to think of South America record in terms of population dynamics within a Paleolithic reflection: What are the anthropological implications of a longer and therefore slower peopling process? What modes of expansion, rhythms, adaptations, routes could be traced base especially in lithic records? What kind of archaeological manifestations should we expect in the different environments that make up an immense and highly diverse geography? What modes of technological continuity and change could be linked to these manifestations? Although further research is still needed to address these questions, our goal is to contribute to posing the problem in the most holistic way possible, linking climate, environment, and techno-cultural data within and beyond South America, in order to model how populations might have expanded and contracted at different periods throughout this subcontinent.

The DiSCPersal model: A simple model for the small-scale atmospheric transport of spheroidal carbonaceous particles (SCPs)

Spheroidal carbonaceous particles (SCPs) are atmospherically mobile by-products of anthropogenic, high-temperature fossil fuel combustion. Since they are preserved in many geologic archives across the globe, SCPs have been identified as a potential marker for the onset of the Anthropocene. Our ability to reliably model the atmospheric dispersal of SCPs remains limited to coarse spatial scales (i.e., 102–103 km). We address this gap by developing the DiSCPersal model, a multi-iterative and kinematics-based model for dispersal of SCPs at local spatial scales (i.e., 10°–102 km). Although simple and limited by available measurements of SCPs, the model is nonetheless corroborated by empirical data of the spatial distribution of SCPs from Osaka, Japan. We find that particle diameter and injection height are the primary controls of dispersal distance, whereas particle density is of secondary importance. Further, stark differences in the modelled dispersal distances of SCPs between non-point vs. smokestack sources could explain the ambiguity of dispersal distances and the relative magnitude of long-range vs. localized sourcing of SCPs reported in the literature. This research underscores the need to incorporate understanding of the localized dispersal patterns of SCPs when interpreting their preservation in geologic archives. By extension, our findings have implications for the reliability of SCPs as a globally synchronous marker for the onset of the Anthropocene.

Investigating the genetic basis of vertebrate dispersal combining RNA-seq, RAD-seq and quantitative genetics.

Although animal dispersal is known to play key roles in ecological and evolutionary processes such as colonization, population extinction and local adaptation, little is known about its genetic basis, particularly in vertebrates. Untapping the genetic basis of dispersal should deepen our understanding of how dispersal behaviour evolves, the molecular mechanisms that regulate it and link it to other phenotypic aspects in order to form the so-called dispersal syndromes. Here, we comprehensively combined quantitative genetics, genome-wide sequencing and transcriptome sequencing to investigate the genetic basis of natal dispersal in a known ecological and evolutionary model of vertebrate dispersal: the common lizard, Zootoca vivipara. Our study supports the heritability of dispersal in semi-natural populations, with less variation attributable to maternal and natal environment effects. In addition, we found an association between natal dispersal and both variation in the carbonic anhydrase (CA10) gene, and in the expression of several genes (TGFB2, SLC6A4, NOS1) involved in central nervous system functioning. These findings suggest that neurotransmitters (serotonin and nitric oxide) are involved in the regulation of dispersal and shaping dispersal syndromes. Several genes from the circadian clock (CRY2, KCTD21) were also differentially expressed between disperser and resident lizards, supporting that the circadian rhythm, known to be involved in long-distance migration in other taxa, might affect dispersal as well. Since neuronal and circadian pathways are relatively well conserved across vertebrates, our results are likely to be generalisable, and we therefore encourage future studies to further investigate the role of these pathways in shaping dispersal in vertebrates.

Molecular data, ecological niche, and dispersal models reveal a trans-Atlantic shallow-water octopus species

The tropical Octopus insularis is a shallow-water species widely distributed in the western Atlantic. Recent studies of niche models have identified suitable habitats for its settlement also on the east coast of the Atlantic. Considering the pelagic larval period and the high tolerance of this species to environmental variations, this study aimed to analyze the possibility of O. insularis occurrence in the West Atlantic (São Tomé Island) through molecular analyses, dispersion, and niche models. The molecular analyses were performed using fragments of 481 bp of the mitochondrial gene (cox1) from three muscle samples collected in São Tomé Island. The O. insularis long-range connectivity between South America and Western Africa was analyzed using a Lagrangian particle tracking model. Additionally, O. insularis records across its entire known distribution were applied to run the ecological niche model (ENM) using the Maxent algorithm. The Bayesian phylogenetic reconstruction showed that two of the three octopus sequences from São Tomé island (Central-Western Africa) belong to a monophyletic and well-supported O. insularis clade. The third octopus sample revealed a new species related to the clade with the Octopus vulgaris species complex. The dispersal models pointed out that passive particles could potentially reach the seamounts region at Africa coast via oceanic currents (mainly the North Equatorial Countercurrent) from São Pedro and São Paulo archipelago (Central-Western Region of the Atlantic) in a period of ∼30–60 days. This suggests that São Pedro and São Paulo archipelago could act as a potential source of paralarvae to Western Africa, although we hypothesize that this connection was more common during the Pleistocene, when sea level was around 120 m lower. In addition to the already known areas of O. insularis occurrence, the ENM pointed suitable habitats to the octopus settlement from Guinea-Bissau down to Equatorial Guinea and Gabon, and African Islands, such as São Tomé and Príncipe. The new record of O. insularis in Africa raises important questions regarding regional fisheries management. Considering that O. insularis is highly tolerant to environmental variations and very adapted to warm shallow waters, there is a possibility that octopus fisheries stocks on the African coast have a mixed composition (O. vulgaris, O. insularis, and Octopus sp.) and therefore the fisheries must follow management measures suitable for each species. In addition, further studies should be carried out in order to characterize and describe the potential new octopus species found only in São Tomé Island according to our genetic survey.

New charged aggregate mathematical models to predict the behavior, structural parameters, and geometrical features of microemulsions

Experimental characterization techniques can provide qualitative and quantitative information on the behavior and properties of microemulsion systems. However, they suffer from several inherent drawbacks that often restrict their application to research settings rather than routine practice in various industries. Also, the majority of theoretical studies on microemulsion systems have focused on nonionic surfactants and suffer from restrictive assumptions and limitations that can be violated under realistic conditions. Therefore, their practical applications to real-world problems such as surfactant-based enhanced oil recovery (EOR) processes require the exercise of extreme caution. This work is intended to fill existing research gaps and solve industrial challenges by developing new mathematical models for predicting micelle size besides other structural and geometrical parameters in ionic surfactant-induced oil-in-water (O/W) and water-in-oil (W/O) microemulsions. The main purpose of the present study is to derive novel models that are not only fitting-free, objective, independent of iterative algorithms and experimental data, and inclusive of intermicellar interactions, but also applicable to complex systems containing real crude oil, experiencing compositional changes, and under any thermodynamic conditions. First, a recently proposed surface charging model for dispersions of charged particles in electrolyte solutions is combined with the DLVO theory of colloidal interactions to develop a thermodynamic model for the structural description of O/W microemulsions. Then, upon coupling a surface charging model for non-electrolyte dispersions of charged aqueous cavities with the DLVO theory, another thermodynamic model is developed for W/O microemulsions. Next, the developed mathematical models are supplemented with an auxiliary material balance equation and an equilibrium condition to calculate the radius of micelles in each type of systems. After determining the radii of oil- and water-swollen micelles using the new models, other geometrical and structural parameters such as solubilized phase-to-surfactant molar ratio, aggregation number, the volumes of microemulsion and excess phases, intermicellar distance, and periodicity are readily calculated in an explicit manner using the derived relationships. Afterwards, some reliable complementary tools are discussed for calculations of the associated physical parameters to avoid the need for experimental measurements, thereby making the models more practical and operational. Finally, the validity of the developed models is verified using literature experimental data.

Design of frontal chromatography separation of 1-phenylethanol and acetophenone using a hydrophobic resin

Adsorption and chromatographic processes havegood potential in the purification of natural aromas produced via biocatalytic routes. This work deals with the recovery of 1-phenylethanol (PE) from mixtures containing different amounts of acetophenone (AP). Amberlite FPX68, an industrial adsorbent with high selectivity with respect to acetophenone, was chosen for the separation of PE and AP by frontal chromatography. Small-scale experiments were performed for two different feed compositions and various flow rates and bed lengths. Using the target purity of 99 %, promising yields close to 90 % were obtained. The breakthrough curves were fitted with the equilibrium dispersive model, which provided HETP values under the different conditions. The obtained dependences of HETP on flow velocity complied with the Van Deemter equation. The contributions of individual phenomena responsible for adsorption zone broadening were analyzed. The experimental and modelling results obtained for the small-scale column became the basis for the scale-up of frontal chromatography separation of PE with an annual capacity up to 500 kg.

Numerical modeling of a potential landslide-generated tsunami in the southern Strait of Georgia

We report results of numerical simulations of a potential subaerial landslide on the coast of Orcas Island and the resultant tsunami waves in the southern Strait of Georgia near the US/Canada border. A likely trigger is strong ground shaking during large earthquakes on the nearby Holocene active Skipjack Island fault zone. For a worst-case scenario, we assume a 0.17 {textrm{km}}^3 rigid subaerial failure on the steep northeast coast of the island, spanning the sim 5 km between previous landslide deposits on the adjacent seafloor. The landslide motion and resulting tsunami generation are modeled using the three-dimensional (3D) non-hydrostatics physics-based NHWAVE model. The simulated failure moves downslope with a peak velocity of 13.64ṁ/s and travels 732 m before coming to rest after 85 s in 75-m water depth. Tsunami propagation is then continued using the 2D fully nonlinear and dispersive Boussinesq wave model FUNWAVE-TVD in a succession of layered and nested grids. The modeling reveals susceptible locations, particularly as waves will arrive with little or no warning. In the near-source region, modeled waves have peak amplitudes of 15–20 m, current speeds of up to 10 m/s, and runup of up to 30 m. Smaller, but significant, wave amplitudes and runup occur throughout the region surrounding Orcas Island. In the tsunami propagation direction, runup reaches 7.5 m at Neptune Beach near Lummi Bay. Both initial and reflected waves cause significant runup (> 1.5 m) along much of the shoreline between Point Roberts and Lummi Bay.

Non‐reproductive dispersal: an important driver of migratory range dynamics and connectivity

Dispersal is the primary ecological process underpinning spatial dynamics in motile species by generating flux in reproductive locations over time. In migratory species, dispersal can also occur around non‐breeding ranges, but this form currently lacks a unifying theoretical framework. We present a novel conceptual model for dispersal in migrants that builds upon existing literature, differentiating ‘reproductive' dispersal (i.e. changes in breeding locations) from ‘non‐reproductive' dispersal, which we define as movements resulting in inter‐annual or inter‐generational changes in non‐breeding locations. Crucially, unlike reproductive dispersal where movement outcomes are naturally propagated between generations, the outcomes of non‐reproductive dispersal can be non‐heritable. We use simulations of a solo‐migrant population with a genetically encoded migratory programme to illustrate how variation in this heritability exerts a strong influence on both migratory connectivity and range shift propensity. When exposed to spatially uncoupled shifts in habitable ranges (i.e. seasonal climate niches shifting at different rates), long‐term persistence of simulated populations required changes in migratory programmes to arise through heritable forms of non‐reproductive dispersal (e.g. mutations in migratory gene complexes). By contrast, non‐heritable dispersal mechanisms (e.g. navigation errors) cannot drive long‐term shifts in non‐breeding ranges, despite being a major component of realised dispersal and migratory connectivity patterns. Migratory connectivity metrics conflate these heritable and non‐heritable drivers of non‐reproductive dispersal, and therefore have limited power in predicting population responses to environmental change. Our models provide a framework for improving our understanding of spatial dynamics in migratory populations, and highlight the importance of teasing apart the mechanisms that drive migratory variability in order to evaluate and predict range plasticity in migrants.

Larval Dispersal Modeling Reveals Low Connectivity among National Marine Protected Areas in the Yellow and East China Seas.

Marine protected areas (MPAs) are vital for protecting biodiversity, maintaining ecosystem integrity, and tackling future climate change. The effectiveness of MPA networks relies on connectivity, yet connectivity assessments are often skipped in the planning process. Here we employed a multi-species biophysical model to examine the connectivity patterns formed among the 21 national MPAs in the Yellow and East China Seas. We simulated the potential larval dispersal of 14 oviparous species of five classes. Larvae of non-migratory species with pelagic larval duration (PLD) were assumed to be passive floating particles with no explicit vertical migration. A total of 217,000 particles were released according to spawning period, living depth, and species distribution, and they were assumed to move with currents during the PLD. Most larvae were dispersed around the MPAs (0-60 m isobaths) and consistent with the currents. Larval export increased with PLD and current velocity, but if PLD was too long, few larvae survived due to high daily mortality during pelagic dispersal. The overall connectivity pattern exhibited a north-to-south dispersal trend corresponding to coastal currents. Our results indicated that the national MPAs in the Yellow and East China Seas did not form a well-connected network and nearly 30% of them were isolated. These MPAs formed three distinct groups, one in the Yellow Sea ecoregion and two in the East China Sea ecoregion. Four MPAs (all in coastal Zhejiang) emerged as key nodes for ensuring multi-generational connectivity. Under the pressure of future climate change, high self-recruitment and low connectivity present significant challenges for building well-connected MPA networks. We suggest adding new protected areas as stepping stones for bioecological corridors. Focused protection of the Yellow Sea ecoregion could have a good effect on the southern part of the population recruitment downstream. Conservation management should be adjusted according to the life cycles and distributions of vulnerable species, as well as seasonal changes in coastal currents. This study provides a scientific basis for improving ecological connectivity and conservation effectiveness of MPAs in the Yellow and East China Seas.

A Numerical Study of Lossy Multipole Debye Dispersive Media Using a Recursive Integral-FDTD Method

A dispersive finite-difference time-domain (FDTD) method based on the recursive integration (RI) technique for the modeling of the lossy multipole Debye dispersive media is described in this article. The interaction between the electromagnetic (EM) field and the human tissues is simulated by means of the RI method, and the frequency-dependent formulations which possess good compatibility with the main FDTD algorithm are achieved. Next, the expression of the multipole Debye dispersion model is similar to the multipole complex frequency shift (CFS) stretching function which is utilized to build the multipole perfectly matched layer (MPML). Therefore, a significant feature of using the RI method is its overall modeling of both multipole Debye dispersive media and MPML boundary conditions. Furthermore, the stability analysis of the RI method in solving the lossy multipole Debye dispersive model indicates that the Courant–Friedrich–Levy (CFL) stability limit of the regular FDTD can be maintained. At last, the numerical cases performed in this work demonstrate the correctness of the RI method in modeling dispersive media.

Acute and Sublethal Effects of Deltamethrin Discharges from the Aquaculture Industry on Northern Shrimp (Pandalus borealis Krøyer, 1838): Dispersal Modeling and Field Investigations.

Pharmaceutical deltamethrin (Alpha Max), used as delousing treatments in aquaculture, has raised concerns due to possible negative impacts on the marine environment. A novel approach combining different scientific disciplines has addressed this topic. Acute (mortality) and sublethal effects (i.e., fitness, neurological, immunological, and oxidative responses) of exposure of northern shrimp (Pandalus borealis) were studied in laboratory experiments. Passive water sampling combined with sediment analyses revealed environmental concentrations. Finally, dispersal modeling was performed to predict environmental concentrations. Ecotoxicological analyses showed mortality in shrimp after 1 h of exposure to 2 ng L-1 (1000-fold dilution of treatment dose), revealing a high sensitivity to deltamethrin. Sublethal effects included induction of acetylcholinesterase and acyl CoA oxidase activities and oxidative impairment, which may be linked to neurotoxic responses. Field concentrations of 10-200 ng L-1 in water (100 m from the pens) and <LOD-0.19 ng g-1 dw in sediment (0-400 m from pens) were measured. Ecotoxicological values were compared with measured and modeled concentrations. They showed that concentrations higher than those causing mortality could be expected up to 4-5 km from point of release, in an area of 6.4 km2, with lethal concentrations remaining up to 35 h in some areas. Hence, the study demonstrates that there is a considerable risk for negative effects on the ecologically and commercially important shrimp.

Broad host-range pathogens as bioherbicides: managing nontarget plant disease risk.

Plant pathogens with a broad host range are commercially more attractive as microbial bioherbicides than strictly host-specific pathogens as a result of the wider market potential of a product capable of controlling multiple species. However, the perceived spatiotemporal disease risk to nontarget plants is a barrier to their adoption for weed control. We consider two approaches to managing this risk. First, we consider safety zones and withholding periods for bioherbicide treatment sites. These must ensure inoculum spreading from, or surviving at the site, exposes nontarget plants to no more inoculum than from natural sources. They can be determined using simple dispersal models. We show that a ratio of added:natural inoculum of 1.0 is biologically reasonable as an 'acceptable risk' and a sound basis for safety zones and withholding periods. These would be analogous to the 'conditions of use' for synthetic chemical herbicides aimed at minimizing collateral damage to susceptible plants from spray drift and persistent soil residues. Second, weed-specific isolates of broad host-range pathogens may avoid the need for safety zones and withholding periods. Such isolates have been found in many broad host-range pathogen species. Their utilization as bioherbicides may more easily meet the requirements of regulators. Mixtures of different weed-specific isolates of a pathogen could provide bioherbicides with commercially attractive spectrums of weed control activity. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

A point particle source model for conjugate heat and mass transfer in dispersed two-phase flows by BEM based methods

The paper reports on development of a Boundary Element Method (BEM) based two phase dispersed flow model, that allows an accurate and efficient heat and mass transfer coupling by using a moving point source model to account for particle–fluid interaction. The two-way coupling model highlights the efficient use of the elliptic fundamental solution and the Dirac delta distribution properties to accurately evaluate the heat and mass point particle source impact on the continuous phase, solved by the Boundary Domain Integral Method (BDIM). In addition to the BDIM model of the particle–fluid heat and mass transfer interaction, the two-phase flow case under consideration is extended to the case of porous spherical particle drying with internal moving drying front, which is solved by the Boundary Element Method. As the two-phase flow is considered to be dilute, the particle–fluid momentum exchange is covered by a one-way coupling algorithm, with Lagrangian particle tracking used for determination of particle positions and velocities in the flow. Two computational cases are presented, where 1000 and 10000 particles are dried in a stream of hot air. Comparison between the obtained drying times for the cases of the one-way and the two-way heat and mass transfer coupling results shows, that the developed two-way coupling model accurately captures the effect of moisture accumulation and temperature decrease in the fluid phase, leading to realistic computations of drying rates of particles in the flow.

A three-step approach for assessing landscape connectivity via simulated dispersal: African wild dog case study

ContextDispersal of individuals contributes to long-term population persistence, yet requires a sufficient degree of landscape connectivity. To date, connectivity has mainly been investigated using least-cost analysis and circuit theory, two methods that make assumptions that are hardly applicable to dispersal. While these assumptions can be relaxed by explicitly simulating dispersal trajectories across the landscape, a unified approach for such simulations is lacking.ObjectivesHere, we propose and apply a simple three-step approach to simulate dispersal and to assess connectivity using empirical GPS movement data and a set of habitat covariates.MethodsIn step one of the proposed approach, we use integrated step-selection functions to fit a mechanistic movement model describing habitat and movement preferences of dispersing individuals. In step two, we apply the parameterized model to simulate dispersal across the study area. In step three, we derive three complementary connectivity maps; a heatmap highlighting frequently traversed areas, a betweenness map pinpointing dispersal corridors, and a map of inter-patch connectivity indicating the presence and intensity of functional links between habitat patches. We demonstrate the applicability of the proposed three-step approach in a case study in which we use GPS data collected on dispersing African wild dogs (Lycaon pictus) inhabiting northern Botswana.ResultsUsing step-selection functions we successfully parametrized a detailed dispersal model that described dispersing individuals’ habitat and movement preferences, as well as potential interactions among the two. The model substantially outperformed a model that omitted such interactions and enabled us to simulate 80,000 dispersal trajectories across the study area.ConclusionBy explicitly simulating dispersal trajectories, our approach not only requires fewer unrealistic assumptions about dispersal, but also permits the calculation of multiple connectivity metrics that together provide a comprehensive view of landscape connectivity. In our case study, the three derived connectivity maps revealed several wild dog dispersal hotspots and corridors across the extent of our study area. Each map highlighted a different aspect of landscape connectivity, thus emphasizing their complementary nature. Overall, our case study demonstrates that a simulation-based approach offers a simple yet powerful alternative to traditional connectivity modeling techniques. It is therefore useful for a variety of applications in ecological, evolutionary, and conservation research.Graphical abstract

Info-gap theory to determine cost-effective eradication of invasive species

Invasive species eradication campaigns often fail due to stochastic arrival events, unpredictable detectability and incorrect resource allocation. Severe uncertainty in model parameter estimates may skew the eradication policy results. Using info-gap decision theory, this research aims to provide managers with a method to quantify their confidence in realizing successful eradication of particular invasive species within their specified eradication budgets (i.e. allowed eradication cost) in face of information-gaps. The potential introduction of the Asian house gecko Hemidactylus frenatus to Barrow Island, Australia is used as a case study to illustrate the model. Results of this research demonstrate that, more robustness to uncertainty in the model parameters can be earnt by (1) increasing the allowed eradication cost (2) investment in pre-border quarantine and border inspection (i.e. prevention) or (3) investment in post-border detection surveillance. The combination of a post-border spatial dispersal model and info-gap decision theory demonstrates a novel and spatially efficient method for managers to evaluate the robustness of eradication policies for incursion of invasive species with unexpected behaviour. These methods can be used to provide insight into the success of management goals, in particular the eradication of invasive species on islands or in broader mainland areas. These insights will assist in avoiding eradication failure and wasteful budget allocation and labour investment.

The importance of resolving nearshore currents in coastal dispersal models

Biophysical models often require shelf-scale domains to map larval dispersal over several weeks, presenting a computational challenge. This can be overcome by decreasing model spatial resolution; however, nearshore processes, which potentially play a significant role in larval dispersal, will inevitably be unresolved. Here, we evaluate how simulated larval dispersal in the nearshore is sensitive to model spatial resolution. We use an unstructured, finite element, hydrodynamic model of a topographically-complex coastline in North Wales, UK (which includes headlands, bays and channels) at four different spatial scales (50, 100, 250, 500 m) to compare the influence of spatial resolution on transport and dispersal patterns of particles released within the nearshore region (within 1 km of the shore). In the higher resolution (50 and 100 m) simulations, particles generally travelled offshore more quickly and further (∼18%) than in the coarser (250 and 500 m) simulations. This had important implications for potential connectivity along the coast: for the lower resolution simulations, retention of particles near source sites was increased by ∼50% and, whilst the magnitude of connectivity among discrete regions along the coast was also increased (by ∼27%), the number of connected regions was reduced (by ∼9%), compared with the higher resolution simulations. Our results, based on a case study in a highly energetic and topographically complex region, suggest that model spatial resolution of ≤100 m should be used for dispersal studies in the nearshore zone. These findings add to growing evidence of the importance of using appropriately scaled models when simulating the transport of material within – and out of – the coastal zone, with many applications, such as marine ecology, marine biosecurity, marine spatial planning and marine pollution.

A Non-Hydrostatic Model for Simulating Weakly Dispersive Landslide-Generated Waves

The aim of this study is to develop an efficient numerical scheme that is capable of simulating landslide-generated waves. The numerical scheme is based on the one-layer non-hydrostatic (NH-1L) model, a phase-solving model that can account for weakly dispersive waves. In this paper, the model is extended to include a time-varying solid bed. This NH-1L scheme is very efficient because, at each time step, only a tridiagonal Poisson pressure matrix needs to be solved. In this study, the capability of the NH-1L scheme to simulate landslide-generated waves is demonstrated by executing two types of landslide motion: constant speed and with acceleration and deceleration. Validation was performed using analytical solutions of the linear weakly dispersive (LWD) model, as well as experimental data. The NH-1L model was capable of describing the generation and propagation of water waves by a submarine landslide from relatively intermediate water to shallow water depths.

Patterns of dreissenid mussel invasions in western US lakes within an integrated gravity model framework

Freshwater invasive species, such as the quagga mussel (Dreissena rostriformis bugensis), are causing over $1 billion USD annually in damages to water infrastructure, recreation, and the environment. Once established, quagga and other dreissenid mussels are extremely difficult to eradicate. Preventing the spread of these invasives is critical and of high management concern. Invasive dreissenid establishment is predicated upon both successful dispersal from a source and suitable habitat in the uninfested waterbody to which they are transported. Recreational boaters have become predominant dispersal vectors making it possible to forecast the risk of invasion of waterbodies for more targeted management and prevention. We developed an integrated mussel dispersal model that couples a constrained gravity model and habitat suitability model to forecast future invasions. The model simulates boater movement between lakes, the likelihood of boats transporting mussels, and the likelihood that those mussels survive in the environmental conditions of the new lake. Model output was most sensitive to changes in boater threshold, then buffer zones, while not as sensitive to changes in habitat suitability. From an initial infested source pool of 11 among 402 Western inland US lakes, we forecast additional lakes infested in several possible simulation scenarios. Constraining movement reduced connectivity between waterbodies with amplifying effects at different distance levels. This model can be used to determine waterbodies most at risk for dreissenid mussel invasion and to highlight the importance of multifactor integrated models in environmental management.