Hydrodynamic Connectivity Research Articles

Biophysical drivers of coral trophic depth zonation

Depth is used often as a proxy for gradients in energetic resources on coral reefs and for predicting patterns of community energy use. With increasing depth, loss of light can lead to a reduced reliance on autotrophy and an increased reliance on heterotrophy by mixotrophic corals. However, the generality of such trophic zonation varies across contexts. By combining high-resolution oceanographic measurements with isotopic analyses (δ13C, δ15N) of multiple producer and consumer levels across depths (10–30 m) at a central Pacific oceanic atoll, we show trophic zonation in mixotrophic corals can be both present and absent within the same reef system. Deep-water internal waves that deliver cool particulate-rich waters to shallow reefs occurred across all sites (2.5–5.6 events week−1 at 30 m) but the majority of events remained depth-restricted (4.3–9.7% recorded at 30 m propagated to 10 m). In the absence of other particulate delivery, mixotrophs increased their relative degree of heterotrophy with increasing depth. However, where relatively long-lasting downwelling events (1.4–3.3 times the duration of any other site) occurred simultaneously, mixotrophs displayed elevated and consistent degrees of heterotrophy regardless of depth. Importantly, these long-lasting surface pulses were of a lagoonal origin, an area of rich heterotrophic resource supply. Under such circumstances, we hypothesize heterotrophic resource abundance loses its direct linkage with depth and, with resources readily available at all depths, trophic zonation is no longer present. Our results show that fine-scale intra-island hydrographic regimes and hydrodynamic connectivity between reef habitats contribute to explaining the context specific nature of coral trophic depth zonation in shallow reef ecosystems.

Circulation, dispersion and hydrodynamic connectivity over the Scotian Shelf and adjacent waters

A nested-grid ocean circulation modelling system is used in this study to examine the circulation of surfacewaters over the Scotian Shelf and its adjacent coastal water bodies. The modelling system consists of acoarse-resolution (1/12°) barotropic storm surge (outer) model covering the northwest Atlantic Ocean, and afine-resolution (1/16°) baroclinic (inner) model covering the Gulf of St. Lawrence, Scotian Shelf, and Gulf of Maine.The three-dimensional model currents are used to track trajectories of particles using a Lagrangian particle-trackingmodel. The simulated particle movements and distributions are used to examine the dispersion, retention, andhydrodynamic connectivity of surface waters over the study region. The near-surface dispersion is relatively high overwestern Cabot Strait, the inner Scotian Shelf, and the shelf break of the Scotian Shelf. The dispersion is relatively low inNorthumberland Strait. A process study is conducted to examine the physical processes affecting the surface dispersion,including tidal forcing and local wind forcing. The model results show that the tidal currents significantly influence thedispersion of surface waters in the Bay of Fundy.

Investigating the origin of vagrant dusky groupers, Epinephelus marginatus (Lowe, 1834), in coastal waters of Réunion Island

Due to their geographic isolation, biotas of oceanic islands are likely influenced by episodic long distance dispersal events, but such observations are scarce. In June 2012, fishermen from Réunion Island caught an unknown specimen of grouper, identified as dusky grouper Epinephelus marginatus (Lowe, 1834). This was highly unexpected considering the large distance of its closest verified occurrence (South Africa, ∼2500km). To identify the origin of this specimen and the mechanisms driving this potential long distance colonization, we combined genetic analyses and hydrodynamic connectivity modeling approaches. Molecular markers and samples from various locations across the distribution range resulted in the identification of three putative source populations. The Réunion specimen clustered genetically with South Africa. The estimated spawning period in relation to the connectivity modeling of larvae showed no possible direct connection between South Africa and Réunion. However, connectivity was predicted through intermediate stepping stone populations likely located around the southern tip of Madagascar, where the occurrence of the species has yet to be verified. The results further highlight the potential role of the cyclone Bingiza (February 2011) in the connection between Madagascar and Réunion. This shows that cyclones may be an important driver in long distance colonization of oceanic islands.

Disparity between planktonic fish egg and larval communities as indicated by DNA barcoding

A genetic identification method (DNA barcoding) was used to compare the commu- nity compositions of planktonic fish eggs and larvae within a coastal embayment, testing the hypothesis that the composition of the planktonic larval fish community proportionately reflects the composition of the planktonic fish egg community (excluding species with non-planktonic eggs). By genetically identifying 843 individual eggs, we preserved the quantitative aspects of tra- ditional community analysis. The studied embayment has restricted hydrodynamic connectivity to other coastal waters. A circulation model containing simulated particles estimated average egg movement of approximately 1 km between times of spawning and sample collection, indicating locally spawned eggs were likely to be retained within the survey area. Thirteen of 14 collected egg taxa (88% of egg specimens) could be genetically identified to species level, with the 14th taxon identified to genus level. This novel approach revealed a high degree of spatial heterogene- ity in fish egg compositions within the embayment. Species that dominated the egg community (Eugerres plumieri, Cynoscion nebulosus, Centropomus undecimalis, and Prionotus spp.) were not particularly abundant amongst the 276 larvae identified, and the most abundant larval species (Achirus lineatus and Cynoscion arenarius) only comprised a minor proportion of the identified eggs. Overall, there was no correlation between the percent compositions of the egg and larval communities (r = −0.07, n = 15, p = 0.81). The clear disparities observed between the species com- positions of the egg and larvae highlight the need for directly identifying eggs when studying habitat connectivity or performing stock assessment with egg production model-based methods.

Modelling of interactions between inshore and offshore aquaculture

Abstract Offshore aquaculture is the subject of intense debate, focusing on feasibility, sustainability, and the potential for effective expansion in the context of competing uses of the coastal zone, and a world requirement for an additional thirty million tonnes of aquatic products by 2050. A modelling framework that integrates the SWAT model for the watershed, Delft3D for ocean circulation, and the EcoWin model for long-term (10 year) ecological simulations, was developed for integrated analysis of catchment, inshore waters, and offshore aquaculture, providing an approach that addresses production, environmental effects, and disease interactions. This framework was tested using a case study in SE Portugal, for a system-scale modelling domain with an ocean area of 470 km2 and a coastal watershed area of 627 km2. This domain contains an inshore area of 184 km2 (Ria Formosa) subject to multiple (often conflicting) uses, including aquaculture of the high value (farmgate price > 10 € kg− 1) clam Tapes decussatus, and one of the first offshore aquaculture parks in the world, located at distance of 3.6 nm from the coast, at a water depth of 30–60 m, with an area of 15 km2. The park contains 60 leases, of which at most 70% are for finfish cage culture, and at least 30% for bivalve longline culture. A substantial part of the dissolved nutrients required to drive primary production that constitutes the food source for clams originates from the coastal catchment. Although stakeholder perception is that nutrients are mainly linked to point-source discharges from wastewater treatment plants, watershed modelling indicates that 55% of the nitrogen and 70% of the phosphorus loads are from diffuse sources. The residence time of waters in the inshore area is low (1–2 days), and consequently pelagic primary production takes place offshore, and drives inshore clam production. The longline culture of Mediterranean mussels (Mytilus galloprovincialis) in the offshore park reduces inshore food availability for clams: simulations suggest that a 3% decrease in clam yields will occur due to offshore mussel cultivation, at a cost of 1.2 million €. This is offset by revenue from offshore culture, but is a source of stakeholder conflict. Potential disease spread between the offshore and inshore systems was analysed using a particle tracking model, and allowed the development of a risk exposure map. This illustrates the challenges posed by hydrodynamic connectivity with respect to biosecurity of aquaculture and fisheries, both inshore and offshore. The model framework was also used for optimisation of stocking density, and analysis of combined culture of finfish and shellfish, both in terms of production and environmental effects. In the offshore aquaculture park, the models suggest that integrated multi-trophic aquaculture (IMTA) of gilthead bream (Sparus aurata) and Mediterranean mussels allows for an increased harvestable biomass of mussels, particularly at higher stocking densities, and offsets some of the negative externalities of finfish culture. By quantifying issues such as reduced yields for inshore stakeholders due to offshore activity, and illustrating the need for strong governance to offset disease risks, dynamic models make a valuable contribution in assessing the feasibility of offshore aquaculture, and the general principles that should underpin licensing and regulation of this sector. We stress the need to go beyond the conventional spatial planning toolset in order to ensure an ecosystem approach to aquaculture, and the opportunities that exist for applying a systems framework in an information economy, where the capital costs of software and data have been sharply reduced.

Surface transport in the Northeastern Adriatic Sea from FSLE analysis of HF radar measurements

This study focuses on the surface transport in the Northeastern Adriatic Sea and the related hydrodynamic connectivity with the Gulf of Trieste (GoT) under calm or typical wind conditions: Bora (from the NE) and Sirocco (from the SE). The surface transport in the area has been investigated by evaluating the Finite-Size Lyapunov Exponents (FSLE) on the current field measured by the High Frequency (HF) coastal radar network. FSLE allow us to estimate Lagrangian Coherent Structures (LCSs), which provide information on the transport patterns associated with the flow and identify regions characterized by different dynamics. This work includes the development and set-up of the FSLE algorithm applied for the first time to the specific Adriatic area considered. The FSLE analysis during calm wind reveals an attractive LCS crossing the GoT entrance, marking the convergence between the Northern Adriatic and the outflowing gulf waters. During Bora episodes this attractive LCS is displaced westward with respect to the calm wind case, indicating that Bora drives an extended coherent outflow from the GoT. On the other hand, Sirocco wind piles up the water along the northern end of the basin. In this area an attractive LCS is found, extending mainly in the SW–NE direction. The sirocco-induced inflow of Adriatic waters in the GoT is mainly driven along its northern (Italian) side, as evidenced by the orientation of the LCS. Under Sirocco condition, as in the Bora case, there is no barrier in front of the gulf. No relevant LCSs are observed in the southern radar coverage area except for Bora cases, when a repulsive LCS develops in front of the Istrian coast separating water masses to the North and the South of it.

Quantitative characterization of connectivity and conductivity of sandstone carriers during secondary petroleum migration, applied to the Third Member of Eocene Shahejie Formation, Dongying Depression, Eastern China

Studies on migration pathways remain qualitative, albeit extensive quantification of migration forcing. In this study, hydrocarbon carriers are defined as carrier units and their corresponding carrier beds for the Third Member of Eocene Shahejie Formation in the Dongying Depression, Bohai Bay Basin, eastern China, on the basis of their lithofacies and physical properties, spatial relationships, and data availability; secondary migration conduits are then quantified. A carrier unit is defined as a stratigraphic unit that contains microscopically porous and permeable carrier beds and is covered by regional seals. The carrier beds are macroscopically and physically connected to each other within a carrier unit and are hydrodynamically connected during secondary migration. A method of quantifying sandstone carrier units using common physical properties is developed. First, a carrier unit containing potential carrier beds is identified on the basis of lithofacies and their lateral changes. Second, physical connectivity of sandstone carrier beds is assessed on the basis of percolation theory. Third, the hydrodynamic connectivity of a sandstone carrier unit is analyzed using effective parameters that may reflect the hydraulic circulation in the carrier unit. Last, the conductivity of a sandstone carrier bed is quantitatively characterized using appropriate physical property parameters. The results for sandstone carrier units in the Third Member of the Shahejie Formation are used in numerical models addressing Pleistocene secondary migration. The model results explain the discovered accumulation and hydrocarbon shows well; and the model predictions on exploration targets have been confirmed by drilling.

Scenarios involving future climate and water extraction: ecosystem states in the estuary of Australia's largest river

Management of natural resources, particularly water, increasingly requires that likely benefits of particular actions (e.g., allocating an environmental flow) are quantified in advance. Therefore, new techniques are required that enable those potential benefits to be objectively compared among competing options for management (e.g., compared to a "do nothing" scenario). Scenario modeling is one method for developing such an objective comparison. We used existing hydrologic, hydrodynamic, and ecosystem response models for a case study location, the Coorong, an inverse estuary in South Australia, to illustrate the potential for such scenario modeling to inform natural resource management. We modeled a set of 12 scenarios that included different levels of water extraction, potential future climate change, and sea-level change, thereby enabling a comparison of the different drivers of possible future reductions in water availability in the Coorong. We discovered that potential future climate change combined with current extraction levels has the capacity to devastate the ecology of the Coorong, but also that much of the degradation could be averted by reducing upstream extractions of water. The inclusion of possible sea-level change had a surprising effect, whereby higher sea levels increased hydrodynamic connectivity between the Coorong's two lagoons. Increased hydrodynamic connectivity limited the occurrence of extremely low water levels and high salinities due to evapoconcentration that were simulated for dry future climates in the absence of sea-level rise. These findings strongly suggest that future ecological degradation in the Coorong is not a foregone conclusion, and that management decisions regarding water allocations upstream will determine the ecological future of this coastal lagoon.

Hydrodynamic connectivity between two macrotidal Amazonian estuaries

ABSTRACT Araujo Jr., W.P. and Asp, N.E., 2013. Hydrodynamic connectivity between two macrotidal Amazonian estuaries The hydrodynamic connectivity between the Taperacu and the Caete estuaries at the east sector of the Amazon Coastal Zone, through the Taici channel was investigated. Water levels, currents, salinity and suspended solid concentration (SSC) were measured at both ends and at the middle of the channel. The measuring campaigns were carried out during neap and spring tides, including also the wet and dry seasons. The results have showed a strong tidal asymmetry, with ebb phases lasting approx. 40% longer than the flood. On the other hand, the flood phase is longer and takes place first and reaches higher levels at the Caete side in comparison to the Taperacu side, despite neap/spring or wet/dry variations. During the wet season the depth-integrated ebb current velocity reached 1.5 m.s−1 at the Taperacu side and 1.4 m.s−1 at Caete side, whereas during the flood it reached 0.9 and 0.8 m.s−1 at Taper...

Connectivity modelling and network analysis of sea lice infection in Loch Fyne, west coast of Scotland

AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 3:51-63 (2012) - DOI: https://doi.org/10.3354/aei00052 Connectivity modelling and network analysis of sea lice infection in Loch Fyne, west coast of Scotland Thomas Adams1,*, Kenny Black1, Craig MacIntyre2, Iain MacIntyre3, Rebecca Dean4 1SAMS, Scottish Marine Institute, Dunbeg, Oban, Argyll PA37 1QA, UK 2Argyll Fisheries Trust, Cherry Park, Inveraray, Argyll PA32 8XE, UK 3The Scottish Salmon Company, Arkinglas Estate, Cairndow, Argyll PA26 8BH, UK 4The Scottish Salmon Company, Mid-Strome, Lochcarron, Ross-Shire IV54 8YH, UK *Email: tom.adams@sams.ac.uk ABSTRACT: Sea lice are a persistent threat in many areas where salmon farming is practised. In common with the management of disease, infection levels are typically controlled by operating sites within distinct geographical areas, allowing for coordinated treatment and fallow cycles. However, the hydrodynamic connectivity and consequent transmission of lice larvae between sites is often not well understood, which limits our ability to optimise the spatial distribution of farms to minimise infection. We used a multistage modelling approach to investigate the transmission of sea lice larvae between salmon aquaculture sites in Loch Fyne, Scotland. A finite element hydrodynamic model was forced using meteorological data collected over the study period. Output from this model was used to drive a particle-tracking model. The latter model implemented the development and mortality of larvae to estimate the probability of successful larval dispersal between sites. In turn, these dispersal probabilities were used to define a network describing the sea lice metapopulation (its habitat defined by the aquaculture sites). Methods from graph theory allow the identification of those sites in the network that are likely to be key for the control of sea lice in the loch population as a whole. Model outputs were compared with data from a campaign of plankton tows and with lice abundance data from aquaculture sites. The general pattern of abundance was reasonably well replicated, albeit with some notable discrepancies. These differences are worth investigating further, as they may be suggestive of sources of infection by wild fish or of inadequacies in the model. KEY WORDS: Sea lice · Connectivity · Biophysical model · Larval dispersal · Population dynamics · Lepeophtheirus salmonis Full text in pdf format Supplementary material PreviousNextCite this article as: Adams T, Black K, MacIntyre C, MacIntyre I, Dean R (2012) Connectivity modelling and network analysis of sea lice infection in Loch Fyne, west coast of Scotland. Aquacult Environ Interact 3:51-63. https://doi.org/10.3354/aei00052 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 3, No. 1. Online publication date: December 19, 2012 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2012 Inter-Research.

Numerical study of dispersion and hydrodynamic connectivity of near-surface waters in Lake Huron

A nested-grid hydrodynamic modeling system is used to examine the circulation and dispersion in Lake Huron and adjacent areas with specific attention to physical parameters pertinent to the estimation of hydrodynamic connectivity of near-surface waters. The nested system is forced by monthly mean surface heat flux and 12-hourly wind stress computed from wind speeds extracted from the National Centers for Environmental Prediction of the National Center for Atmospheric Research (NCEP/NCAR) 40-year reanalysis data. The three-dimensional model currents are used to calculate the retention and dispersion of conservative, near-surface particles carried by the currents. The near-surface dispersion is relatively low in Saginaw Bay, eastern Georgian Bay and the eastern North Channel; and relatively high over the western part of the main lake and the coastal region of south Lake Huron. The hydrodynamic connectivity in the surface water and connectivity matrices are calculated from particle movements carried passively by model currents superposed by a random walk process. The model results demonstrate that the hydrodynamic connectivity in the North Channel and Georgian Bay (ranging from 0.9 to 2.2%) is much weaker than those in the main lake (5.3 to 21.9%).

Examination of circulation, flushing time and dispersion in Halifax Harbour of Nova Scotia

This study examines the circulation, flushing time and hydrodynamic connectivity in Halifax Harbour based on three-dimensional currents produced by a multi-nested coastal ocean circulation modelling system. The time-mean currents produced by the modelling system feature two-layer estuarine circulation with a seaward flow in the upper layer and a landward flow in the lower layer in the Harbour. The hydrodynamics in the Harbour are also affected significantly by tides and wind forcing. Based on numerical passive tracer experiments, the estimated e-folding flushing time is about 40 and 90 days in the upper and the entire Bedford Basin, respectively. By comparison, the flushing time is about 2–5 days over the Inner and Outer Harbour, and only about 1 day in the Narrows. Analysis of passive particle trajectories carried by the model currents demonstrates that movements of particles in the Harbour are strongly affected by tidal and storm-induced currents. Hydrodynamic connectivity in the study region is also quantified in terms of a connectivity matrix calculated from particle trajectories.

Hydrogeological framework and its implication on water level rise in Eastern ArRiyadh, Saudi Arabia

Excessive water usage together with limited capacity of local hydrogeological environment to dispose excess water or waste water has emerged as a problem of water level rise in many parts of ArRiyadh, the capital city of Saudi Arabia. In the past, groundwater rise to shallow horizons has caused considerable impact on public health, environment and infrastructure. In order to reduce and maintain groundwater to safe level, ArRiyadh Development Authority has constructed a gravity drainage system in the affected areas. During the initiation of the gravity drain project, water level in eastern ArRiyadh was >15 m; therefore, the area was not included in the project but was subjected to regular groundwater monitoring. During the recent decade, eastern ArRiyadh has witnessed quick water level rise, with an average rate of 0.55 m/year. This water level rising trend seems persistent with time which may impart serious damage to the environment and infrastructure. The study shows that the presence of thick clays within eastern alluvium retards hydrodynamic connectivity and inhibits vertical groundwater movement.

Simulation of the dynamic (frequency-dependent) permeability and electrical conductivity in porous materials based on the concept of an ensemble of pores

The class of models of porous media based on the concept of an ensemble of pores with a certain distribution of the main geometrical parameters (e.g., pore size) is studied. The case of the saturation of the pore space with a single-phase multicomponent fluid mixture is studied with and without taking into account the transfer of electric charges. Transfer laws are derived from the condition of decreasing free energy. The hydrodynamic connectivity of pores (and electrical conductivity) is described by two kernels: one kernel describes the connectivity of pores in space, and the other describes the connectivity of pores in the elementary macrovolume. The frequency dependences of the dynamic permeability determined in laboratory experiments and the electrical conductivity of the porous medium were determined using the concept of an ensemble of pores. The relationship between the models considered and relaxation filtration models is established.

Modeling Circulation and Hydrodynamic Connectivity in Bras d'Or Lakes using Nested-Grid Approach

Abstract The Bras d'Or Lakes (BdOL) is a land-locked estuarine system in central Cape Breton Island. Nova Scotia, Canada. Recent outbreaks of waterborne diseases at several sites in the BdOL have decimated shellfish populations and threaten its unusual biodiversity. Assessing the potential for spread of invasive pathogens is a priority for management. A nested-grid hydrodynamic modeling system is used to simulate the three-dimensional (3D) circulation and temperature-salinity distributions for summer 1974, when currents and hydrographic measurements suitable for model calibration were made at several locations. The modeled 3D velocity fields are then used in Eulerian-Lagrangian transform to study the spatial patterns of retention and dispersion of passive particles, as a proxy for the spread of disease by water flow in the estuary. Probabilities of transfers (connectivity) among 10 sub-domains of the BdOL are calculated from the statistics of the 3D particle trajectories and portrayed in a transition matr...

Examination of circulation, dispersion, and connectivity in Lunenburg Bay of Nova Scotia using a nested-grid circulation model

A coastal ocean observatory has been established in Lunenburg Bay, Nova Scotia since summer 2002 as part of a multi-agency research program of marine environmental observation and prediction over Atlantic Canada coastal waters. The observatory was operational when a category-2 hurricane (Juan) made land fall within 50-km of the bay in September 2003. The coastal response of the bay to Hurricane Juan is examined using a nested-grid coastal circulation modelling system. The nested-grid system is forced by the local wind, tides, and remotely generated coastal waves. A comparison of model results with observed surface elevations and currents demonstrates that the nested-grid system has reasonable skills in simulating the three-dimensional (3D) storm-induced circulation in the study region. The 3D model currents are used to examine the transport and dispersion of passive tracers, local flushing time, and retention and connectivity of passive particles in the bay during Hurricane Juan. Numerical results demonstrate that local wind forcing plays a dominant role in generating large dispersion and hydrodynamic connectivity in the bay during the storm.

Shallow water processes govern system-wide phytoplankton bloom dynamics: A modeling study

A pseudo-two-dimensional numerical model of estuarine phytoplankton growth and consumption, vertical turbulent mixing, and idealized cross-estuary transport was developed and applied to South San Francisco Bay. This estuary has two bathymetrically distinct habitat types (deep channel, shallow shoal) and associated differences in local net rates of phytoplankton growth and consumption, as well as differences in the water column's tendency to stratify. Because many physical and biological time scales relevant to algal population dynamics decrease with decreasing depth, process rates can be especially fast in the shallow water. We used the model to explore the potential significance of hydrodynamic connectivity between a channel and shoal and whether lateral transport can allow physical or biological processes (e.g. stratification, benthic grazing, light attenuation) in one sub-region to control phytoplankton biomass and bloom development in the adjacent sub-region. Model results for South San Francisco Bay suggest that lateral transport from a productive shoal can result in phytoplankton biomass accumulation in an adjacent deep, unproductive channel. The model further suggests that turbidity and benthic grazing in the shoal can control the occurrence of a bloom system-wide; whereas, turbidity, benthic grazing, and vertical density stratification in the channel are likely to only control local bloom occurrence or modify system-wide bloom magnitude. Measurements from a related field program are generally consistent with model-derived conclusions.

Modeling of isothermal processes in porous materials on the basis of the concept of an ensemble of pores

A class of models of porous media based on the concept of an ensemble of pores with a certain distribution of the main geometric parameters (for example, the pore size) is considered. The cases of pores saturated with single-and two-phase multicomponent liquid mixtures are investigated. The properties of equilibrium states of the mixture are derived from the minimum free energy condition and the transfer laws from the decreasing free energy condition. The hydrodynamic connectivity of the pores is described by two types of kernels: one describes the spatial connectivity and the other the connectivity in an elementary macrovolume. Analytically and numerically, the one-dimensional problems of establishment of a steady-state regime, propagation of a passive admixture, and two-phase flow (an analog of the Buckley-Leverett problem) are investigated. A relationship between the models in question and relaxational filtration models is demonstrated. A simple model of capillary hysteresis related with the non-monotonicity of the pore area to volume ratio function is proposed.

Numerical study of circulation, dispersion, and hydrodynamic connectivity of surface waters on the Belize shelf

A nested grid ocean circulation modeling system is used to examine the circulation, dispersion, and hydrodynamic connectivity of surface waters on the Belizean shelf. The nested grid system consists of a coarse‐resolution (∼19 km) outer model of the western Caribbean Sea, an intermediate‐resolution (∼6 km) middle model of the southern Meso‐American Barrier Reef System (MBRS), and a fine‐resolution (∼2 km) inner model of the Belizean shelf. The nested system is forced by climatological monthly mean surface forcing and integrated over 5 years. The near‐surface circulation on the Belize shelf produced by the inner model is characterized by a strong and persistent northwestward flow as a direct influence of the Caribbean Current on the northwestern shelf and a weak and spatially variable flow on the inner and southern shelf. The monthly mean model currents are used to calculate retention and dispersion of conservative, near‐surface particles carried by the ocean currents. The near‐surface dispersion is relatively higher in areas seaward (east) of Lighthouse and Glovers Reef atolls and lower on the inner shelf, particularly within the Inner Channel and in the vicinity of South Water Cay. To examine hydrodynamic connectivity of reefs in the surface waters of the Belize shelf, we calculate upstream and downstream retention areas for coral reefs at Turneffe Islands and Glovers Reef atolls. The potential sources of passive, near‐surface particle supply reaching these two reef atolls within 30 days include both the shallow waters surrounding the two sites, the deep waters between them, and the coastal waters of the Bay Islands (Honduras). The 30‐day downstream retention areas of the Turneffe and Glovers Reef atolls cover the central and southern Belize shelf, respectively.