Seawater Flow Research Articles

Simulation and Economic Benefit Analysis of Carburetor Combined Transport in Winter at a Liquefied Natural Gas Receiving Station

In the winter, a certain LNG receiving terminal operates exclusively with the submerged combustion vaporizer (SCV). However, due to the high operational costs associated with the SCV, a new combined operation scheme utilizing both the SCV and the open rack vaporizer (ORV) has been proposed. First, models for the SCV and ORV gasification units were developed in Aspen HYSYS and validated using actual operational parameters. Next, the relationship between the seawater inlet–outlet temperature difference and the minimum seawater flow rate for the ORV was determined, and an optimized seawater pump operation strategy, considering LNG export volumes, was formulated. Additionally, the relationship between the SCV fuel gas flow rate and LNG export volume was analyzed, and a comparison was made between the operating costs of SCV running independently and the combined SCV-ORV operation under winter conditions. The results of the combined operation experiments indicated that at a seawater inlet–outlet temperature difference of 3 °C, the joint operation mode could save costs by 70–77%; at 2.5 °C difference, it saves 60–67%; at 2 °C difference, it saves 45–50%; at 1.5 °C difference, it saves 35–38%; and at 1 °C difference, it saves 20–23%. This approach achieves optimized economic performance for LNG terminal operations.

Back cover image

The cover image showcases the application of a cutting‐edge two‐dimensional material in the electrocatalytic direct seawater splitting process. The central figure depicts an electrode made from this two‐dimensional material, featuring easily accessible active sites that symbolize its high efficiency in seawater splitting. The surrounding gradient of green indicates the flow of seawater, while the light spheres around the electrode represent the bubbles of water molecules. The light blue and orange spheres signify the hydrogen and oxygen produced during the electrocatalytic process. The overall design emphasizes the crucial role of two‐dimensional materials in advancing seawater splitting technology, suggesting potential for future sustainable energy production. image

Progress of material degradation: metals and polymers in deep-sea environments

Abstract Given the critical need for ocean exploration, improving the durability of materials in the deep-sea has become a paramount concern. The harshness of deep-sea, such as high pressure, variable seawater flow rates, and corrosive media, lead to premature aging and failure. This work examines the utilization of metals and polymer coatings in deep-sea applications, detailing the characteristics of the deep-sea and its influence on these materials. In particular, chloride ions in seawater pose significant hazards to metal corrosion, which is the main reason for metal failure. Then, the degradation process and the latest research advances of various materials in the deep-sea environment are summarized, and the failure mechanism of the metal/coating system in the deep-sea is analyzed. It was found that the failure of polymer coatings can be divided into three processes, and adding an appropriate amount of fillers to the coating (such as adding 0.2 % graphene to water-based polyurethane) can extend the service life of the coating. Finally, the development trend of the company in the future is predicted. It has guiding and reference significance for the study of the failure behavior of metals and polymers in the deep-sea environment.

Magnetic signals from oceanic tides: new satellite observations and applications.

The tidal flow of seawater across the Earth's magnetic field induces electric currents and magnetic fields within the ocean and solid Earth. The amplitude and phase of the induced fields depend on the electrical properties of both seawater and the solid Earth, and thus can be used as proxies to study the seabed properties or potentially for monitoring long-term trends in the global ocean climatology. This article presents new global oceanic tidal magnetic field models and their uncertainties for four tidal constituents, including [Formula: see text] and even [Formula: see text], which was not reliably retrieved previously. Models are obtained through a robust least-squares analysis of magnetic field observations from the Swarm and CHAMP satellites using a specially designed data selection scheme. We compare the retrieved magnetic signals with several alternative models reported in the literature. Additionally, we validate them using a series of high-resolution global three-dimensional (3D) electromagnetic simulations and place constraints on the conductivity of the sub-oceanic mantle for all tidal constituents, revealing an excellent agreement between all tidal constituents and the oceanic upper mantle structure.This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'.

The subseafloor crustal biosphere: Ocean's hidden biogeochemical reactor.

Underlying the thick sediment layer in ocean basins, the flow of seawater through the cracked and porous upper igneous crust supports a previously hidden and largely unexplored active subsurface microbial biome. Subseafloor crustal systems offer an enlarged surface area for microbial habitats and prolonged cell residence times, promoting the evolution of novel microbial lineages in the presence of steep physical and thermochemical gradients. The substantial metabolic potential and dispersal capabilities of microbial communities within these systems underscore their crucial role in biogeochemical cycling. However, the intricate interplay between fluid chemistry, temperature variations, and microbial activity remains poorly understood. These complexities introduce significant challenges in unraveling the factors that regulate microbial distribution and function within these dynamic ecosystems. Using synthesized data from previous studies, this work describes how the ocean crustal biosphere functions as a continuous-flow biogechemical reactor. It simultaneously promotes the breakdown of surface-derived organic carbon and the creation of new, chemosynthetic material, thereby enhancing element recycling and ocean carbon productivity. Insights gained from the qualitative analysis of the extent of biogeochemical microbial activity and diversity across the temperature and chemical gradients that characterize these habitats, as reviewed herein, challenge traditional models of global ocean carbon productivity and provide the development of a new conceptual framework for understanding the quantitative metabolic potential and broad dispersal of the crustal microbial biome.

Prediction of strata settlement in undersea metal mining based on deep forest

Undersea mining encounters challenges due to the presence of seawater. An influx of seawater into stop in undersea can result in enormous disaster. Predicting strata settlement is a crucial measure to ensure the safety of undersea mining. This study proposed an intelligent model based on deep forest (DF) to evaluate the strata settlement during undersea mining. Initially, the strata displacement was monitored in the Xishan mining area of Sanshandao gold mine, China. Comprehensive datasets encompassing roof displacement and twelve influencing factors were compiled from 120 observations. Then, these datasets were statistically analyzed and used to train the DF model. The developed DF model achieved a training R2 of 0.971 and a testing R2 of 0.936. Compared with other machine learning models, the DF model has superior performance in the prediction of strata settlement. Moreover, a graphical user interface was designed to facilitate the application of the DF model. Finally, to validate model feasibility, displacement monitoring was conducted in the Xinli mining area of Sanshandao gold mine. Additional datasets were collected to validate the capability of the DF model. The results suggested that the DF model can be used to predict strata subsidence in undersea mining effectively.

Evidence of 2024 Summer as the Warmest During the Last Four Decades in the Aegean, Ionian, and Cretan Seas

The summer of 2024 witnessed record-high sea surface temperatures (SST) across the Aegean, Ionian, and Cretan Seas (AICS), following unprecedented air heatwaves over the sea under a long-term warming trend of 0.46 °C/decade for the mean atmospheric temperature (1982–2024). The respective mean SST trend for the same period is even steeper, increasing by 0.59 °C/decade. With mean summer surface waters surpassing 28 °C, particularly in the Ionian Sea, the southern Cretan, and northern Aegean basins, this summer marked the warmest ocean conditions over the past four decades. Despite a relatively lower number of marine heatwaves (MHWs) compared to previous warm years, the duration and cumulative intensity of these events in 2024 were the highest on record, reaching nearly twice the levels seen in 2018, which was the warmest until now. Intense MHWs were recorded, especially in the northern Aegean, with extensive biological consequences to ecosystems like the Thermaikos Gulf, a recognized MHW hotspot. The strong downward atmospheric heat fluxes in the summer of 2024, following an interannual increasing four-decade trend, contributed to the extreme warming of the water masses together with other met-ocean conditions such as lateral exchanges and vertical processes. The high temperatures were not limited to the surface but extended to depths of 50 m in some regions, indicating a deep and widespread warming of the upper ocean. Mechanisms typically mitigating SST rises, such as the Black Sea water (BSW) inflow and coastal upwelling over the eastern Aegean Sea, were weaker in 2024. Cooler water influx from the BSW decreased, as indicated by satellite-derived chlorophyll-a concentrations, while upwelled waters from depths of 40 to 80 m at certain areas showed elevated temperatures, likely limiting their cooling effects on the surface. Prolonged warming of ocean waters in a semi-enclosed basin such as the Mediterranean and its marginal sea sub-basins can have substantial physical, biological, and socioeconomic impacts on the AICS. This research highlights the urgent need for targeted monitoring and mitigation strategies to address the growing impact of MHWs in the region.

Modeling of Liquefied Natural Gas Cold Power Generation for Access to the Distribution Grid

Cold energy generation is an important part of liquefied natural gas (LNG) cold energy cascade utilization, and existing studies lack a specific descriptive model for LNG cold energy transmission to the AC subgrid. Therefore, this paper proposes a descriptive model for the grid-connected process of cold energy generation at LNG stations. First, the expansion kinetic energy transfer of the intermediate work mass is derived and analyzed in the LNG unipolar Rankine cycle structure, the mathematical relationship between the turbine output mechanical power and the variation in the work mass flow rate and pressure is established, and the variations in the LNG heat exchanger temperature difference, seawater flow rate, and the turbine temperature difference in the cycle system are investigated. Secondly, based on the fifth-order equation of state of the synchronous generator, the expressions of its electromagnetic power, output AC frequency, and voltage were analyzed. Finally, the average equivalent models of the machine-side and grid-side converters are established using a direct-fed grid-connected structure, thus forming a descriptive model of the overall drive process. The ORC model is built in Aspen HYSIS to obtain the time series expression of the torque output of the turbine; based on the ORC output torque, the permanent magnet synchronous generator (PMGSG) as well as the direct-fed grid-connected structure are built in MATLAB/Simulink, and the active power and current outputs of the grid-following-type voltage vector control method and the grid-forming-type power-angle synchronous control method are also verified.

Mineral formation and element migration in fractures and pores of hydrogenetic ferromanganese nodules

Ferromanganese (Fe-Mn) nodules composed of nano-sized Fe-Mn (oxyhydr)oxides are significant mineral resources rich in multiple critical metals (e.g., Co, Ni, Cu, and REY). The ubiquitous high porosity, large pore size, and pore connectivity in hydrogenetic nodules enable the constant influx of seawater and/or porewater driving widespread diagenetic processes (i.e., mineral dissolution and recrystallization) in the abundant fractures and pores. These diagenetic processes are critical to understanding the migration, partitioning, and distribution of the critical metals, but remain unclear yet. In this study, high-resolution in-situ analyses were conducted to investigate the mineralogical and geochemical characteristics of diagenetic precipitates in fractures and pores of a hydrogenetic Fe-Mn nodule (MP5D33) from the central Pacific. Both oxic and suboxic processes were found in the fracture. The oxidized diagenetic products exhibit geochemical and mineralogical characteristics similar to those of hydrogenetic precipitates (e.g., vernadite), while the suboxic diagenetic processes primarily produced large-size 10 Å phyllomanganate. The diagenetic conditions within this studied fracture gradually shifted from oxic to suboxic, causing changes in the contents of multiple critical metals. The minerals in pores are mainly composed of 10 Å phyllomanganate that crystallized forms through heterogeneous nucleation on small-size vernadite in a suboxic environment. Additionally, minor todorokite likely transformed from 10 Å phyllomanganate undergoing long-term diagenesis. These findings shed some insights into the diagenetic process in the interior fractures and/or pores of Fe-Mn nodules and enhance the understanding of the migration of critical elements associated with Fe-Mn (oxyhydr)oxides during diagenesis in Fe-Mn deposits.

Ocean Surface Gravity Waves Excited by the 2022 Eruption of Hunga Tonga‐Hunga Ha'apai Volcano

AbstractOn 15 January 2022, a massive underwater eruption occurred at the Hunga Tonga‐Hunga Ha'apai Volcano. The plume reached the mesosphere, and the eruption excited a significant atmospheric Lamb wave, which forced the tsunami. The complicated tsunami waveforms due to ocean‐atmosphere coupling prevented inferring the force history of the excitation. To address this, we analyze ocean surface gravity waves (OSWs) from 15 to 40 mHz, which are decoupled from the Lamb wave due to their slower phase velocities. Modeling these OSWs, we infer that the excitation started at 4:00 UTC with an amplitude of N and lasted for 5 hr, followed by a sub‐event at 8:40 UTC. The observations suggest an initial blowout of seawater above the summit and a subsequent outflow that excited a tsunami below 5 mHz. The 2 hr delayed OSW excitation from 6 to 15 mHz may indicate seawater inflow into the crater.

Low microbial abundance and community diversity in the egg capsule of the oviparous cloudy catshark (Scyliorhinus torazame) during oviposition.

Vertebrate embryos are protected from bacterial infection by various maternally derived factors, yet little is known about the defence mechanisms in elasmobranchs. This study aimed to characterize the intracapsular environment of freshly laid eggs of the oviparous catshark (Scyliorhinus torazame) by investigating the microbial abundance and microbiota to understand its potential contribution to embryonic defence. The egg capsule of oviparous elasmobranchs is tightly sealed until pre-hatching, after which seawater flows into the capsule, exposing the embryos to the surrounding seawater. We found that early embryos were highly vulnerable to environmental pathogens, suggesting that the embryos are somehow protected from infection before pre-hatching. Indeed, the intracapsular environment of freshly laid eggs exhibited significantly low bacterial density, maintained until pre-hatching. Furthermore, the microbiome inside eggs just after oviposition differed markedly from those of rearing seawater and adult oviducal gland epithelia; these eggs were predominantly populated by an unidentified genus of Sphingomonadaceae. Overall, this study provides compelling evidence that early embryos of oviparous cloudy catshark are incubated in a clean intracapsular environment that potentially plays a significant role in embryonic development in oviparous elasmobranchs.

Protecting a complex intertidal habitat in the Severn Estuary affected by jetty construction

This case study presents a coastal engineering scheme that addressed a unique environmental challenge on a marine construction site. Artificially bunded reservoirs were constructed on the rocky shore of the Bristol Channel, UK, to mitigate the potential impact to ecological features of the Severn Estuary/Môr Hafren Special Area of Conservation resulting from the construction of a jetty at the Hinkley Point C construction site. The installation of piles irreversibly altered the natural supply of seawater from several large rock pools to Corallina officinalis (red seaweed) waterfalls, that the developer, Electricité de France, was obliged to protect. Corallina can die within 30 min of drying out. Following rigorous topographic surveys of the foreshore, hydrodynamic modelling and an evolution of protective measures, concrete structures were designed and installed to ensure the Corallina waterfalls were passively supplied with a constant flow of seawater throughout the tidal cycle. The artificial bunds had to be sympathetic to the natural environment while sufficiently durable to withstand the high-energy conditions of the intertidal site. A local wave buoy 13.5-year dataset shows that the scheme has withstood the two highest wave heights recorded, one of which was the third highest storm peak.

Observations of waves and currents on the fore-reef and reef flat of a coral reef atoll in the South China Sea

Understanding the wave and current conditions of coral reef ecosystems is essential for maintaining their health, as many reef processes are controlled by these hydrodynamic conditions. In this study, high-frequency measurements of tides, waves, and currents were made using acoustic, electromagnetic, and pressure instruments over a 28-d period on the fore-reef and reef flat of a coral reef atoll in the South China Sea. The research revealed wave transformation, tidal and wave modulation of flow, and wave setup conditions for the first time at this typical atoll. Three large wave processes dominated by gravity waves (GWs) are observed in the fore-reef. The GWs are significantly attenuated on the reef flat, whereas infragravity (IG) waves strengthened. The tidal modulation of GWs and IG waves on the reef flat is significant when the incident wave height exceeded 1 m. In the fore-reef, the modulation of progressive tidal waves and large waves leads to relatively stronger upper-layer currents, and weak near-bottom currents are primarily attributed to the dissipation of tidal wave energy by the rough coral terrain. In calm conditions, flow variations on the reef flat are modulated by tides, thereby allowing seawater flow to pass through the reef flat during spring tides. Conversely, during periods with large waves, tidal modulation of flow on the reef flat is less significant, and the cross-reef flow velocity increases with increasing incident wave height. The occurrence of wave setup on the reef flat enhances cross-reef flow towards the lagoon. The wave setup is positively linearly correlated with the incident wave height. The magnitude of wave setup is associated with the distance between the measurement sites on the fore-reef and reef flat.

Experimental study of a high-power generation platform for ocean thermal energy conversion

Ocean Thermal Energy Conversion (OTEC) is a form of power generation that utilizes the temperature difference between the upper and lower layers of the ocean. This paper presents the design and construction of a land-based experimental platform for OTEC using R134a as the working fluid. Through experimental research, we investigated the performance of the thermal energy cycle system under varying external environmental conditions, such as temperature and flow rate. The results show that the net output power of the system increases with the temperature and flow rate of the warm seawater. Similarly, an increase in the cold seawater temperature and flow rate leads to an increase in net output, though the increase is less significant at higher power levels when compared to changes in warm seawater conditions. Adjusting the evaporation pressure to increase the turbine inlet and outlet pressure difference initially increases the output power but then remains constant. The highest recorded output power during testing was 48kW, with the turbine achieving an isentropic efficiency of 80%, and the maximum system efficiency reached 2%. This study provides theoretical basis and empirical data for system design, which can promote the application in the field of OTEC and contribute to the development of renewable energy.

Bronze Age to Roman period salt production in the coastal areas of peninsular Italy: Palaeoenvironments, production methods and archaeological evidence

The landscape characteristics and salt production methods along the coasts of peninsular Italy from the Bronze Age to the Roman period are examined, with a focus on the significance of marine salt for Italy's ancient food economy, given the limited availability of rock salt. Two main methods of marine salt production are highlighted. Briquetage involves using clay or pottery containers to evaporate seawater, which requires specific environmental conditions such as clay availability and significant human labour and technological skill. Conversely, salterns consist of creating shallow ponds or pools for seawater evaporation, demanding flat coastal areas, a stable climate, and controlled seawater flow. While this method is less labour-intensive, it requires substantial initial infrastructure.The potential for salt production in Italy's coastal palaeoenvironments using either method has been evaluated. Key factors include coastal geomorphology, climate stability, and access to raw materials. This environmental data supports an analysis of archaeological remains from salt production sites active from the Bronze Age to the Roman period. The assessment focuses on the material evidence such as clay containers from briquetage and structural remains of salterns, aiming to understand the spatial and temporal distribution of these sites.The discussion also explores the geopolitical implications of salt production, examining how the distribution and development of these sites were affected by broader geopolitical shifts in Italy, including the impact of (proto)urbanization on the expansion and adaptation of salt production practices.

Experimental and numerical study on the flow and heat transfer of ring-ribbed tank in deep-sea manned submersible

The ring-ribbed tank is the key equipment of cooling system of deep-sea manned submersible. The heat transfer characteristics of the outer wall and the heat transfer and flow characteristics of the inner flow channel of the ring-ribbed tank for different inlet and outlet temperatures and flow rates were studied through a water tank test. The results indicate that Nusselt number for the inner flow channel correlates with Reynolds and Prandtl numbers, while for the outer wall, it correlates with Grashof and Prandtl numbers with an overall error within 5%. A numerical study using the Realizable k-ε turbulence model and Boussinesq approximation of the flow-solid conjugate heat transfer is conducted, which can accurately determine the heat exchange capacity and the import and export differential pressure with an average relative error of 1.98% for hot water temperature and 7.73% for shell wall temperature. Additional simulations for determining the heat transfer capacity and flow resistance characteristics of the ring-ribbed tank in open water results demonstrate that the differential pressure and its coefficient are basically consistent with model test results. The cooling system can achieve a heat transfer rate of up to 17 kW with an external seawater flow velocity of approximately 2 knots.

Dense Water Formation Variability in the Aegean Sea from 1947 to 2023

The formation of dense water in the Aegean Sea is important as it affects the deep circulation and the hydrography of the Eastern Mediterranean Sea. In this study, the variability of dense water formation is investigated in relation to forcing mechanisms from 1947 to 2023 in the subbasins of the Aegean Sea, utilising in situ observations from various sources, which have been analysed in combination with satellite altimetry and reanalyses products. The analysis reveals that the Aegean Sea has been in a state of increased dense water formation since 2017 due to the combination of increased surface buoyancy loss and reduced Black Sea water inflow. Extremely high salinity has been recorded in the intermediate layers of the Aegean Sea since 2019. The anticyclonic circulation of the North Ionian gyre during 2017 and 2018 probably also contributed to the rapid transport of highly saline waters in the intermediate and, through dense water formation, the deep layers of the Aegean Sea in 2019. Until 2022, the dense waters formed during the peak of the Eastern Mediterranean Transient still occupied the bottom layers of some deep subbasins of the North and South Aegean; however, the 29.4 kg m−3 isopycnal in the North Aegean and the 29.3 kg m−3 isopycnal in the Southeastern Aegean have gradually deepened by 800 m, permitting the waters forming in the last ten years in the Aegean Sea to settle at ever greater depths. Temperature controls the density variability of the Cretan intermediate water up to the decadal time scale. Increased data availability since 2010 was sufficient to clarify that intrusions of dense water from the North–Central Aegean Sea contributed to the erosion of the Eastern Mediterranean transitional waters in the South Aegean Sea after 2017, as well as to raising the intermediate water masses of the South Aegean to shallower depths. The erosion of the transitional Mediterranean waters in the South Aegean Sea between 1947 and 1955 and 1973 and 1980 coincided with increased dense water formation in the North–Central Aegean Sea. During the peak of the Eastern Mediterranean Transient, the North Ionian circulation, the Black Sea water inflow, the Atlantic Multidecadal Oscillation, and the surface buoyancy fluxes favoured dense water formation in the Aegean Sea.

Quaternary floodings in the Zanzibar Channel (NW Indian Ocean, Tanzania) – Identifying palaeoceanographic patterns and palaeoenvironment using a multiproxy study

Multiproxy palaeoenvironmental analyses represent a promising tool for complex reconstructions of continent-sea or air-sea interactions in shallow marine environments. This is in particular illustrated by the case of strong climatic variations in the late Pleistocene to mid-Holocene. A unique combination of geochemical proxies (143Nd/144Nd, 87Sr/86Sr, δ18O and δ13C isotope analyses, n-alkane analysis and biomarker study) together with micropalaeontological data (foraminifera, calcareous nannoplankton and diatoms) allowed to precisely characterise two marine floodings (mid-Holocene and late Pleistocene) in the Zanzibar Channel (NW Indian Ocean, Tanzania). The climate of the late Pleistocene interval was arid compared to the Holocene. The fully oligotrophic environment characteristic of the late Pleistocene flooding (∼115–130 ka) was episodically interrupted by intervals of intense rainfall with episodes of increased nutrient input during the mid-Holocene (∼5–10 ka). The dominance of seaweed meadows in the Holocene and late Pleistocene contrasts with the modern environment dominated by seagrass ecosystems. Relatively non-radiogenic εNd signatures in the Zanzibar Channel during the Holocene and late Pleistocene indicate a strong influence of riverine input draining the Precambrian basement on the African mainland. The main inflow of seawater was from the south, consistent with the flow direction of the East African Coastal Current and the directions of the March to October monsoon winds. A promising tool for future applications as indicators of seagrass/seaweed meadow type ecosystems may be the presence of specific diatom taxa.

Mineralogy and sulfur isotopic compositions of sulfides from Yunzang (25.3°S) hydrothermal field, South Mid-Atlantic Ridge: Implications for formation mechanism and maturation of sulfide chimneys

A newly discovered hydrothermal field, named Yunzang and predominantly hosted by mafic rocks, was recently identified at 25.3°S on the South Mid-Atlantic Ridge (SMAR). This is the first report on the sulfide mineralogy and sulfur isotopic composition of sulfide chimney and massive sulfide ores collected from Yunzang field, SMAR. Based on mineralogical morphology, texture, crystallinity, assemblage and zonation, five specific stages of mineralization can be divided for the sulfide chimney at Yunzang. These stages range from low- to high-temperature hydrothermal conditions, along with an additional stage of seafloor weathering. The observed variations in morphology and crystallinity from low- and medium-temperature stages to high- and high- to medium-temperature stages suggest an evolution in the ore-forming conditions. Initially, the environment was characterized by instability and low-temperature conditions, with significant seawater influx. Subsequently, there was a shift towards a more stable regime dominated by high-temperature ore-forming fluid condition. The positive δ34S values of all the sulfides from Yunzang hydrothermal field suggest 79–92 % and 69–79 % of sulfur were generated from the leaching of basalt for sulfide chimney and massive sulfide, respectively, the rest sulfur were from reduced seawater sulfate. The δ34S values of massive sulfide (3.5–6.8 ‰, average = 5.1 ± 0.9 ‰) are mostly higher than that of sulfide chimney (1.1–4.5 ‰, average = 2.8 ± 0.8 ‰) are mainly caused by sub-surface reactions between preexisting sulfate and re-circulating fluid. An incremental increase of δ34S values from the external edge to the interior orifice indicating the Yunzang chimney maturation is relatively lower and the duration of hydrothermal activity was short. These results enrich our comprehension of mineralization in the seafloor hydrothermal system.

Mapping tidal restrictions to support blue carbon restoration

Blue carbon ecosystems (BCEs), encompassing mangroves, saltmarshes, and seagrasses, are vital ecosystems that deliver valuable services such as carbon sequestration, biodiversity support, and coastal protection. However, these ecosystems are threatened by various anthropogenic factors, including tidal restrictions like levees, barriers, and embankments. These structures alter the natural seawater flow, often converting coastal ecosystems into freshwater environments. Identifying tidal restrictions and assessing their suitability for tidal restoration in areas amenable for coastal management is a crucial first step to successfully restore BCEs and the associated ecosystem services they provide, i.e., managed realignment. This study presents a novel approach for detecting tidal restrictions in the state of Victoria, Australia, using high-resolution LiDAR data, geospatial analysis techniques, and a multi-criteria scoring system. Our model successfully identified 90 % of known tidal restrictions from an existing dataset, while also detecting an additional 118 potential tidal restrictions, representing a 35 % increase. The model performance analysis revealed trade-offs between precision, recall, and noise ratio when using different noise reduction thresholds, highlighting the importance of selecting an appropriate threshold based on project objectives. The multi-criteria scoring system, which considered factors such as proximity to BCEs and current land use, enabled the selection of tidal restrictions based on their hydrological suitability for restoration. The results of this study have significant implications for BCE restoration efforts not only in Victoria, but more broadly across Australia and globally, providing a systematic approach to identifying and targeting areas with the greatest potential for successful restoration projects. While the approach is low-cost and user-friendly, it is dependent on the availability of LiDAR data for the study area. This can make it accessible to researchers and practitioners worldwide, allowing for its adaptation and application in diverse regions to support global efforts in restoring BCEs through tidal restoration.