Tidal Channel Research Articles

Longshore changes in the microfacies and distribution of clastic barrier coastal sandbodies: a case from the Benxi formation in the Ordos Basin, China

AbstractThe Benxi Formation in the Ordos Basin is an important gas-producing layer in the Yanchang gas field. There are critical changes in the microfacies type and extension trend of sandbodies, which affects the understanding of reservoir formation and the deployment of development wells. Based on many core and thin section observations, as well as statistical analyzes of sandstone thickness and percentage of sandstone content from 1446 wells, we analyzed the coastal changes and control factors of the microfacies type, planar morphology and distribution of the Benxi Fm sandbodies in the field. The results indicate that the Benxi Fm of the Yanchang gas field is generally composed of terrigenous coastal clastic barrier deposits in a medium to small tidal range environment, but the wave action in the southern region is weak, forming typical barrier sandbars and backbarrier deposits. The wave actions in the north change more strongly, forming three major microfacies sandbodies: reworked barriers, shoals and incised valley filled tidal channels. The barrier sandbodies are arranged in a belt or bead-like pattern parallel to the shoreline and are distributed longshore near the provenance. The oval-shaped shoal sandbodies are dispersed further from the shoreline, and the filling of tidal channel sandbodies is controlled by ancient geomorphic grooves. This research has important guiding significance for the identification and evaluation of reservoirs in the Yanchang gas field and similar geological settings.

Case Study of Contaminant Transport Using Lagrangian Particle Tracking Model in a Macro-Tidal Estuary

This study presents a comprehensive analysis of contaminant transport in estuarine environments, focusing on the impact of tidal creeks and flats. The research employs advanced hydrodynamic models with irregular grid systems and conducts a detailed residual current analysis to explore how these physical features influence the movement and dispersion of contaminants. The methodology involves simulating residual currents and Lagrangian particle trajectories in both ‘Creek’ and ‘No Creek’ cases, under varying tidal conditions. The results indicate that tidal creeks significantly affect particle retention and transport, with notable differences observed in the dispersion patterns between the two scenarios. The ‘Creek’ case demonstrates enhanced material retention along the creek pathways, while the ‘No Creek’ case shows broader dispersion, potentially leading to increased sedimentation in open sea areas. The discussion highlights the implications of these findings for sediment dynamics, contaminant transport, and estuarine ecology, emphasizing the role of tidal creeks in modulating flow and material transport. The research underlines the necessity of incorporating detailed environmental features in estuarine models for accurate contaminant transport prediction and effective estuarine management. This study contributes to a deeper understanding of estuarine hydrodynamics and offers valuable insights for environmental policy and management in coastal regions.

Creek systems in restored coastal wetlands: Morphological evolution and design implications

Saltmarsh restoration such as managed realignment (MR) projects often include excavation of simplified tidal creek networks to improve drainage and marsh functioning, but their design is based on limited evidence. This paper compares the morphological evolution of creek networks in current MR projects in the UK with creek networks in natural saltmarshes, in order to provide improved guidance.The evolution of creek networks was monitored for 2–20 years post-breach at 10 MR sites across the UK by semi-automatically extracting 12 morphological creek parameters from lidar. The rates of creek evolution in MR sites are linked to the initial tidal, morphological and sedimentological conditions using principal component analysis, then compared with power law relationships of morphological equilibrium defined from 13 mature natural saltmarshes.MR creeks evolved into larger, more complex, better distributed systems, with a total creek length and volume statistically similar to their natural counterparts. However, the creek volume remains poorly distributed, with a mean distance between creeks ranging from 33 to 101 m versus 5–15 m for natural mature saltmarshes. MR creeks are also clustered around the breach area, leaving the marsh interior poorly drained. MR creek network morphologies remain strongly influenced by the initial creek template, as evidenced by unnaturally straight creeks inherited from former drainage ditches.A combination of external conditions (i.e., tidal range, sediment concentration in the wider estuary) and local conditions (i.e., site elevation, topographical heterogeneity, soil compaction) controls how easily creeks can form within MR sites. This in turn determines the amount of engineering effort required to help achieve reference site conditions. The end goal of creek design is to create MR sites that closely resemble reference site conditions, however the final design is also likely to be affected by a range of practical factors (e.g. engineering/cost) unique to each site and project.

Characteristics of storm deposits in Wangcun Lagoon on the southern China coast during Typhoon Rammasun

Through study of the 210Pb, sedimentology, geochemistry, and microfossil characteristics of six core samples taken in Wangcun Lagoon on the Guangdong Province coast (China) before and after the passage of Typhoon Rammasun (2014), we determined the modern storm depositional dynamic process and its deposition characteristics. During Typhoon Rammasun, a storm deposit with thickness of 40–70 cm was formed in Wangcun Lagoon. The storm deposit gradually thickened from the entrance to the interior of the lagoon, and from the edge of the tidal channel to the tidal flat, and it showed an obvious three-layered structure. The lowest layer had finer grain size, higher total organic carbon (TOC) and C/N contents, and higher abundance of diatoms. The middle layer had coarser grain size, lower TOC and C/N contents, and lower abundance of diatoms, especially near the entrance and the tidal channel. The upper layer mainly existed in the interior of the lagoon, with finer grain size, higher TOC content, higher (lower) C/N contents in the tidal channel (tidal flat), and the second-highest diatom abundance. The fragmentation rate of diatoms was very high in all storm deposit layers. We believe the most likely explanation for the formation of such storm deposit layers is attributable to special storm dynamic processes that are influenced by tides and storm waves. The erosion maximum was reached when the hydrodynamic force was strongest, and then a fine-grained layer was formed during the sedimentary window that occurred as the hydrodynamic force of the ebb tide weakened. Later, part of the fine-grained matter was resuspended under the sub-strong dynamic environment of the subsequent flood tide. Finally, as the hydrodynamic force of the storm weakened further, two layers that were coarser at the bottom and finer at the top were formed. The numbers of storm sediment sequences depend on whether there are multiple sedimentary windows in which sediments can be retained. Storm deposits can be recorded continuously and completely in a lagoon, different from event sedimentary records, and they have specific sedimentological, geochemical, and microfossil characteristics.

Changes of Yancheng coastline near 20 years based on remote sensing technology

The study of coastline changes is crucial for the monitoring, development, and management of coastal environments. This article specifically focuses on the coastline of Yancheng. To analyze the changes of coastline, latest remote sensing images of Landsat series from 2002 to 2021 were selected. Threshold segmentation was employed to extract the coastline from these images. Subsequently, tidal level correction was applied to rectify the instantaneous water edge in the binary image of the target coastal area based on tidal channels, resulting in the acquisition of the target coastline. Finally, the obtained target coastline from different time periods were inputted into the Digital Shoreline Analysis System (DSAS). DSAS can be used to assess coastline changes using the end point change rate (EPR) and linear regression change rate (LRR). The research findings reveal that the average siltation rate of various sections along the Yancheng coastline is 105.62 m/y, with the maximum siltation length measuring 12,048 m, located in the Tiaozini reclamation area. Conversely, the maximum erosion length is 1820 m, situated near the mouth of the Shuangyang River. Taking the Sheyang River mouth as the boundary, the northern coastline of the river mouth experiences predominantly erosion, while the southern coastline is primarily affected by sedimentation. Moreover, the rate of coastline change gradually increases from north to south. The transformation of artificial coastline is the outcome of a combination of natural and human factors. Agricultural reclamation, port construction, and coastal protection engineering are identified as the main reasons for the artificial and seaward advancement of coastline. This study provides a foundation for the construction and protection of Yancheng’s coastal zone and offshore engineering. It holds significant practical implications for urban planning and development.

Sedimentary and stratigraphic architecture in the geoarchaeological context of Late-Holocene deposits in the eastern coastal plain of Belgium: Zwin region – Hoeke

A sedimentary investigation was carried out into the rise and fall of mediaeval Bruges’ maritime access. Because the mediaeval metropolis had no direct connection with the North Sea, its maritime connectivity during the High- and Late-Middle Ages depended on a tidal channel, known as the ‘Zwin’. In order to reconstruct the mediaeval physical environmental situation correctly, the entire Holocene sedimentary record was studied through undisturbed mechanically-drilled cores and electrical cone penetration tests (CPT-e). A detailed sedimentary analysis was complemented with radiocarbon dating and datable archaeological finds to resolve a timeframe for the sedimentary evolution. Tidal channel systems with diverse morphologic and sedimentologic characteristics prevail and cover a period from at least the Roman period till the Late-Middle Ages. The presence of a single peat layer directly on top of the Pleistocene substrate and the stratigraphic position of the tidal channel deposits relative to this peat layer, proves that no seawater entered this part of the Belgian coastal plain before the Late-Holocene. The tidal channel system that was active during the heydays of Bruges (the Zwin) was the last natural one. It silted up due to a further reduction of the accommodation space as a consequence of new embankments, possibly expedited by storms.

Seasonal drivers and patterns of sediment temperatures in a New England salt marsh

AbstractSalt marshes are globally important ecosystems and thus their resilience to climate change holds societal importance. To date, studies addressing salt marsh responses to climate change have focused on sea‐level rise and biogeochemical feedbacks with increasing inundation. Less is known about how salt marsh sediment temperatures, which impact physical, biological, and chemical ecosystem processes, will respond to climate change. In this study, we present multi‐depth sediment temperature and porewater level data from low‐, mid‐, and high‐marsh sites at a New England salt marsh for a 1‐year period and investigate how salt marsh sediment temperatures respond to atmospheric and oceanic forcing. We use spectral analyses to identify the frequencies at which sediment temperatures vary and link the temperature variations to specific forcing mechanisms. We find that all sites across the marsh responded to air temperature with roughly equal amplitude whereas the responses to radiative heating and ocean tides varied spatially. The high‐marsh site is more sensitive to radiative heating than the mid‐ and low‐marsh sites. The low‐marsh is affected by tidal processes and inundation whereas the high‐ and mid‐marsh sites are not. In addition, we find that the bulk thermal diffusivity of the saturated sediments decreases with distance from the tidal channel. These factors contribute to considerable temporal and spatial variability in sediment temperatures with elevation, distance from the tidal channel, and time of year (season) being most important.

Opposing life history strategies allow grass shrimp parasites to avoid a conflict of interest.

A conflict of interest occurs when parasites manipulate the behavior of their host in contradictory ways to achieve different goals. In grass shrimp (Palaemonetes pugio), trematode parasites that use shrimp as an intermediate host cause the shrimp to be more active than usual around predators, whereas bopyrid isopod parasites that use shrimp as a final host elicit the opposite response. Since these parasites are altering the host's behavior in opposing directions, a conflict of interest would occur in co-infected shrimp. Natural selection should favor attempts to resolve this conflict through avoidance, killing, or sabotage. In a field survey of shrimp populations in four tidal creeks in the Cape Fear River, we found a significant negative association between the two parasites. Parasite abundance was negatively correlated in differently sized hosts, suggesting avoidance as a mechanism. Subsequent mortality experiments showed no evidence of early death of co-infected hosts. In behavior trials, co-infected shrimp did not show significantly different behavior from singly infected or uninfected shrimp, suggesting that neither parasite sabotages the manipulation of the other. Taken together, our results suggest that rather than sabotaging or killing one another, bopyrid and trematode parasites tend to infect differently sized hosts, thus avoiding a conflict and confirming the importance of testing assumptions in natural contexts.

Empirical Dynamic Modeling Reveals Complexity of Methane Fluxes in a Temperate Salt Marsh

AbstractMethane dynamics within salt marshes are complex because vegetation types, temperature, oscillating water levels, and changes in salinity and redox conditions influence CH4 production, consumption, oxidation, and emissions. These non‐linear and complex interactions among variables affect the traditionally expected functional relationships and present challenges for interpreting and developing process‐based models. We employed empirical dynamic modeling (EDM) and convergent cross mapping (CCM) as a novel approach for characterizing seasonal/multiday and diurnal CH4 dynamics by inferring causal variables, lags, and interconnections among multiple biophysical variables within a temperate salt marsh using 5 years of eddy covariance data. EDM/CCM is a nonparametric approach capable of quantifying the coupling between variables while determining time scales where variable interactions are the most relevant. We found that gross primary productivity, tidal creek dissolved oxygen, and temperature were important for seasonal/multiday dynamics (rho = 0.73–0.80), while water level was most important for diurnal dynamics during both the growing and dormancy phenoperiods (rho = 0.72 and 0.56, respectively). Lags for the top‐ranked variables (i.e., gross primary productivity, dissolved oxygen, temperature, water level) occurred between 1 and 5 weeks at the seasonal scale and 1–24 hr at the diurnal scale. The EDM had high prediction capabilities for intra‐/inter‐seasonal patterns and annual CH4 sums but had limitations in representing large, infrequent fluxes. Results highlight the importance of non‐linearity, drivers, lag times, and interconnections among multiple biophysical variables that regulate CH4 fluxes in tidal wetlands. This research introduces a novel approach to examining CH4 fluxes, which will aid in evaluating current paradigms in wetlands and other ecosystems.

Evolution of a tidal channel network in the Yellow River Delta, China, and simulation of optimization scenarios

Tidal channel networks, which characterize all river deltas, control the exchange of water and nutrients (hydrological connectivity) between the ocean and the delta area. Therefore, a tidal channel network in optimal conditions ensures the maintenance of the diversity and stability of the deltaic ecosystem. However, the developmental status of channel networks in the Yellow River Delta, China, has not been clearly determined. Here, we selected a typical tidal channel network in this delta that showed different spatial patterns (e.g., connectivity attributes) in the past three decades and explored its evolution using entropy as an index of connectivity. Seven scenarios were set up to determine the optimal status of the tidal channel network by optimizing its structure. The optimization effect was evaluated by comparing the connectivity attributes of the channel network before and after optimization. The results showed that the network experienced two obviously different developmental phases: an evolution before 2005 and a regression after 2005. Mann–Kendall analysis indicated that the channel network achieved dynamic stability before 2014 and became unstable thereafter. The simulations conducted to optimize the system showed that adding outlets changed the current patterns of the network’ structural and functional connectivity. As the optimization proceeded, structural connectivity increased while functional connectivity decreased, and the tidal channel network tended to be dynamically stable. Our study elucidated the quantitative relationship between outlet number and stability within tidal channel networks, providing reference information that could be incorporated into future projects for the restoration and management of river deltas.

Coastal Compound Flood Simulation through Coupled Multidimensional Modeling Framework

Coastal watersheds are prone to compound flooding caused by heavy rainfall, storm surge, and high tide. Accurate prediction and modeling of coastal compound floods (CCF) require precise physical representation in numerical models with appropriate numerical approximation associated with multi-driver physical processes for simulating the flood dynamics. To address this, an integrated and tightly coupled modeling approach is implemented to capture the nonlinear and complex processes involved in CCF and interconnectivity among Multidimensional Hydraulics (pipe and channel), Hydrodynamics (2D overland flow), and distributed Hydrologic (MH3) models are developed. The coupled modeling framework focuses on the development of interconnected meshes of the node-link-basin using the Interconnected Channel and Pond Routing (ICPR) model. This framework effectively incorporates the complex drainage network system of tidal creeks, tidal channels, underground sewer networks, and detention ponds of the Charleston Peninsula of South Carolina (SC). The dynamics of the urbanized floodplain in the peninsula are represented using high-resolution LiDAR-derived Digital Elevation Model (DEM) and Digital Surface Model (DSM). The overland flow is simulated using energy balance, momentum balance, and diffusive wave methods. The performance of the CCF model is tested for the 2015 SC historical flood and a high tide flood event. The momentum balance-based CCF model shows 98.35% accuracy in identifying street-level flooding locations. Furthermore, the model shows that incorporating DSM processing in the current study improves the accuracy of urban flood simulation by approximately 15% to 33% compared to LiDAR DEM. It is revealed that the momentum balance method outperforms to simulate the flood dynamics. Consequently, this study contributes to the modeling of CCF by developing an integrated MH3 system that enhances the physical representation of coastal hydrology at a fine scale.

Coupling numerical models of deltaic wetlands with AirSWOT, UAVSAR, and AVIRIS-NG remote sensing data

Abstract. Coastal marsh survival relies on the ability to increase elevation and offset sea level rise. It is therefore important to realistically model sediment fluxes between marshes, tidal channels, and bays as sediment availability controls accretion. Traditionally, numerical models have been calibrated and validated using in situ measurements at a few locations within the domain of interest. These datasets typically provide temporal information but lack spatial variability. This paper explores the potential of coupling numerical models with high-resolution remote sensing imagery. Products from three sensors from the NASA Delta-X airborne mission are used. Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) provides vertical water level change on the marshland and was used to adjust the bathymetry and calibrate water fluxes over the marsh. AirSWOT yields water surface elevation within bays, lakes, and channels, and was used to calibrate the Chezy bottom friction coefficient. Finally, imagery from AVIRIS-NG provides maps of total suspended solids (TSS) concentration that were used to calibrate sediment parameters of settling velocity and critical shear stress for erosion. Three numerical models were developed at different locations along coastal Louisiana using Delft3D. The coupling enabled a spatial evaluation of model performance that was not possible using simple point measurements. Overall, the study shows that calibration of numerical models and their general performance will greatly benefit from remote sensing.

Multi-data settlement prediction along a road section integrating InSAR and coastal subsurface information with data assimilation

This paper presents a novel approach to examining the impact of soil settlement and its spatial distribution on infrastructure. The study focuses on a specific road section in the Friesland coastal plain in the north of the Netherlands, investigating how the Holocene coastal subsurface architecture influences settlement patterns. Our study underscores the importance of integrating multiple datasets, providing data at varying resolutions. The road segment traverses lithostratigraphical units, which include tidal channel and tidal flat deposits, overlaying an older tidal basin system and intercalated peat beds. Through data assimilation of a settlement model optimized with InSAR measurements, we have identified settlement heterogeneities that can be explained by combining high-resolution variations in lithology with gradual changes in lithostratigraphy. This was accomplished by utilizing a medium-resolution model (MRM) based on borehole descriptions and a high-resolution data (HRD) approach based on cone penetration tests along the road. The HRD method proved more effective in capturing abrupt changes in lithology between channel structures, while the MRM provided a continuous representation of the lithostratigraphic setting of the area. Our study demonstrates that subsurface heterogeneities have significant implications for subsidence along roads. Settlement rates increase from 2–4 mm/year towards 9 mm/year along the road section, resulting in a differential settlement of more than 5 mm/year over a distance of less than a kilometer. This is primarily attributed to variations in lithostratigraphy. Overall, this new innovative approach offers a practical and cost-effective solution for predicting subsidence due to settlement, eliminating the need for expensive laboratory tests. By integrating lithology and lithostratigraphy, more efficient road maintenance and management become possible.

Sediment fluxes within salt marsh tidal creek systems in the Yangtze Estuary

Creeks are essential for salt marshes by conveying water and sediment through this geomorphic system. In this paper, we investigate the mechanisms that determine the residual sediment flux using measurements conducted in tidal creeks in salt marshes of the Yangtze Estuary. A main creek and a secondary creek were studied to explore whether the mechanisms determining residual sediment fluxes through the main creek differ from those in the secondary creek. Measurements in creeks were carried out over 5 years, spanning different months. Sediment import was found during most tides, both in the main creek and the secondary creek, implying that creeks in Chongming generally function as a conveyor belt of sediment into the marsh. However, sediment export can occur during certain overbank tides. When comparing the role of creeks in drainage and sediment delivery, the main creek functions more in delivering sediment while the secondary creek primarily serves as a drainage conduit. To better understand the mechanisms behind sediment fluxes, the residual sediment flux was compared with the residual discharge and the sediment differential (differences in sediment concentration between flood and ebb). Overbank tides generally lead to a net outward discharge as more water from saltmarshes can be concentrated into the marsh creek during ebb tides. This net outward discharge tends to export more sediment during ebb tides. However, due to the sediment abundance during the flood phase in the turbid environment, sediment import can be expected even with the residual export of water. Export of sediment was only found for the few tides with a net outward discharge and a small positive sediment concentration differential. Large negative sediment differentials (larger averaged suspended sediment concentration during ebb tides) have not been observed because the sediment supply during ebb is limited. This paper unravels how the sediment differential and residual discharge contribute to the residual sediment flux, providing a better understanding of sediment dynamics in marsh creek systems.

Morphometry of Tidal Meander Cutoffs Indicates Similarity to Fluvial Morphodynamics

AbstractSinuous channels wandering through coastal wetlands have been thought to lack lateral‐migration features like meander cutoffs and oxbows, spurring the broad interpretation that tidal and fluvial meanders differ morphodynamically. Motivated by recent work showing similarities in planform dynamics between tidal and fluvial meandering channels, we analyzed meander neck cutoffs from diverse tidal and fluvial environments worldwide, and show that tidal cutoffs are widespread. Their perceived paucity stems from pronounced channel density and hydrological connectivity in coastal wetlands, comparatively small size of most tidal channels, and typically dense vegetation cover. Although these factors do not efface tidal meander cutoffs, they collectively inhibit oxbow formation and make tidal cutoffs ephemeral features that can escape detection. We argue that similar morphodynamic processes drive cutoff formation in tidal and fluvial landscapes, with differences arising only during post‐cutoff evolution. Such process similarity has important implications for understanding coastal wetland ecomorphodynamics and predicting their long‐term evolution.

Small-scale spatial distribution of ghost shrimp and macrobenthic fauna in an Amazon macrotidal dissipative sandy beach

ABSTRACT Spatial changes in environmental characteristics strongly influence the structure of benthic communities on sandy beaches, where the patterns of occurrence are mainly controlled by morphodynamic characters and biological interactions. Despite being very abundant and extensive, the Amazonian sandy beaches are among the coastal environments less well known to science. On these beaches, the ghost shrimp Lepidophthalmus siriboia Felder and Rodrigues, 1993 is an important component of the intertidal macrofauna. The present study describes the small-scale distribution patterns of L. siriboia and of the macrobenthic communities in a dissipative macrotidal Amazonian sandy beach. Samples were collected in the intertidal zone of two areas: Area 1, next to a tidal channel; and Area 2, away from the tidal channel. In Area 1, with finer sediments, there was a higher burrow density of L. siriboia and higher density and species richness of macrofauna. In both areas, the burrow density of L. siriboia increased towards the sea. The faunal distribution patterns can be explained by changes in flooding and the type of substratum across the shore and alongshore. These findings add to our knowledge of tropical sandy beach ecology and reinforce the idea that tropical macrotidal beaches have a complexity of morphological features, which are drivers of macrofaunal structure.

Diet of the European Shag Gulosus aristotelis during the non-breeding season at a roost within a tidal channel

ABSTRACT The diet of the European Shag Gulosus aristotelis was assessed at one of their most northerly roosts in the UK; Bluemull Sound, Shetland. One pellet and 40 faecal samples were collected during the non-breeding season. The most frequent prey was Velvet Swimming Crab Necora puber, while the highest number of otoliths were from Saithe Pollachius virens and estimated mean (±sd) fish length was 143.9 ± 66.9 mm (range 81.4–223.6 mm).

Quantifying Drivers of Methane Hydrobiogeochemistry in a Tidal River Floodplain System

The influence of coastal ecosystems on global greenhouse gas (GHG) budgets and their response to increasing inundation and salinization remains poorly constrained. In this study, we have integrated an uncertainty quantification (UQ) and ensemble machine learning (ML) framework to identify and rank the most influential processes, properties, and conditions controlling methane behavior in a freshwater floodplain responding to recently restored seawater inundation. Our unique multivariate, multiyear, and multi-site dataset comprises tidal creek and floodplain porewater observations encompassing water level, salinity, pH, temperature, dissolved oxygen (DO), dissolved organic carbon (DOC), total dissolved nitrogen (TDN), partial pressure of carbon dioxide (pCO2), nitrous oxide (pN2O), methane (pCH4), and the stable isotopic composition of methane (δ13CH4). Additionally, we incorporated topographical data, soil porosity, hydraulic conductivity, and water retention parameters for UQ analysis using a previously developed 3D variably saturated flow and transport floodplain model for a physical mechanistic understanding of factors influencing groundwater levels and salinity and, therefore, CH4. Principal component analysis revealed that groundwater level and salinity are the most significant predictors of overall biogeochemical variability. The ensemble ML models and UQ analyses identified DO, water level, salinity, and temperature as the most influential factors for porewater methane levels and indicated that approximately 80% of the total variability in hourly water levels and around 60% of the total variability in hourly salinity can be explained by permeability, creek water level, and two van Genuchten water retention function parameters: the air-entry suction parameter α and the pore size distribution parameter m. These findings provide insights on the physicochemical factors in methane behavior in coastal ecosystems and their representation in local- to global-scale Earth system models.

Performance of three hydrophone flow shields in a tidal channel.

Pseudosound caused by turbulent pressure fluctuations in fluid flow past a hydrophone, referred to as flow noise, can mask propagating sounds of interest. Flow shields can mitigate flow noise by reducing non-acoustic pressure fluctuations sensed by a hydrophone. We evaluate the performance of three hydrophone flow shields (two nylon fabrics and an oil-filled enclosure) in a tidal channel with peak current speed of 1.3 m s-1. All three flow shields reduced flow noise without attenuating propagating sound below 20 kHz. The oil-filled enclosure performed best, reducing flow noise by over 30 dB at frequencies below 40 Hz.

Seasonal regulation of tidal creek burrow distribution: Unveiling the dynamic interplay of biotic and abiotic factors

Intertidal creek ecosystems in saltmarsh wetlands provide crucial ecological services, with burrows facilitating material exchange between these environments. Investigating burrow distribution in tidal creeks is essential, yet the underlying mechanisms remain poorly understood. Our study conducted field observations during two seasons, dividing the typical creek section into microhabitats: flat (F), gentle edge (GE), gentle slope (GS), steep slope (SS), and steep edge (SE). Comprehensive analysis of sediment samples encompassed assessments of water content, organic matter, particle size, and salinity. Burrow parameters were extracted using a deep learning method applied to sample images. Benthic biodiversity and community compositions were characterized through eDNA analysis. Our findings revealed significant variations in burrow distribution, sediment properties, and community compositions, both between and within creek sections. Temporal heterogeneity emerged as a substantial influencer of burrow characteristics, while the propensity of benthic communities to respond to topography and sediment properties constituted a chief determinant of burrow distribution. Utilizing a structural equation model based on field data, we illuminated four response pathways governing burrow distribution. Abiotic factors, especially under temporal heterogeneity, had a paramount impact, highlighting the need to explore relative biotic and abiotic influences, considering seasonal regulation. These findings establish a foundational understanding of burrow distribution and its driving mechanisms in creek ecosystems. They offer valuable insights for future field observations and research directions in this field.