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Biological processes in intertidal species follow tidal rhythms that enhance survival and fitness. Whereas tidal effects on behaviour and metabolic rates have been widely studied, impacts on other key process such as protein synthesis are still poorly understood. To date, no studies have examined the effect of immersion/emersion and tidal cycles on protein synthesis rates ( k s ). Patella vulgata is an intertidal limpet present in North-Eastern Atlantic rocky shores from high to low shore. Previously reported P. vulgata respiration and heart rate measurements suggest aerobic metabolism is maintained during emersion and growth rates increase from high to low shore, but whether these patterns are reflected in k s is currently unclear. Here, we measured for the first time in any intertidal organism, k s , RNA to protein ratios and RNA translational efficiency ( k RNA ) in P. vulgata over a full tidal cycle, at three different shore heights. k s increased during emersion ( p  < 0.001) and was significantly higher in low shore animals compared to the other shore heights ( p  < 0.001), additionally k s was negatively correlated to body mass ( p  = 0.002). RNA to protein ratios remained unchanged over the tidal cycle ( p  = 0.659) and did not vary with shore height ( p  = 0.591). k RNA was significantly higher during emersion and was also higher in low shore limpets ( p  < 0.001). This study demonstrates that P. vulgata increases k s during emersion, an important adaptation in a species that spends a considerable amount of its lifecycle emersed. Intertidal species are highly exposed to increasing air temperatures, making knowledge of physiological responses during emersion critical in understanding and forecasting climate warming impacts.

The carbon cycle process of coastal ecosystems is extremely complex subjected to the coupling effects of hydrodynamics from land and sea. To investigate the distribution and biogeochemistry of organic carbon in estuaries area, particulate organic carbon (POC) and dissolved organic carbon (DOC) in water and total organic carbon (TOC) in surface sediments were measured over four tidal cycles at Sanjiagang (121.8°E, 31.2°N) in the Yangtze River estuary (YRE) from November 2022 to February 2023. Our results showed that the concentration of POC and DOC in water was positively correlated during the autumn and winter. Additionally, the significant positive correlation between tidal elevation and TOC concentrations indicated that organic carbon accumulation to estuarine areas was greatly influenced by tides. According to the principal component analysis (PCA) and stepwise multiple regression, the tidal dynamics and physicochemical properties of water, including salinity, dissolved oxygen (DO), temperature, turbidity, and pH, showed significant correlations to organic carbon. DOC and TOC concentrations were significantly higher in autumn than in winter. Due to the tidal asymmetry in the YRE, the POC and DOC concentrations during ebb tides were higher than those during flood tides. Furthermore, the influence of hydrometeorological conditions such as monthly precipitation and average temperature on the accumulation of organic carbon cannot be ignored in coastal areas. In addition, the grey correlation analysis revealed that strong relevance between the development of the processing manufacturing industry and the TOC in sediments at Site SJG. The socio-economic development and anthropogenic activities along the YRE interfered with the biogeochemical cycle of organic carbon through the massive discharge of wastewater and CO2.

Underground brine in beach and neritic zones (UBBN), widely distributed on muddy coasts in arid coastal regions, undergoes dynamic salt cycling driven by a “salt pump” system, composed of hydraulic gradients, salinity gradients, and tidal forces. This study investigates the fate of UBBN along the southern coast of Laizhou Bay, China, where salt depletion threatens sustainable resource management. Combining field observations, we developed a bay‐scale numerical model incorporating geomorphological diversity, submarine groundwater discharge hotspots, and sediment heterogeneity to quantify UBBN dynamics during tidal cycles and evaluate the impacts of coastal underground brine (CUB) mining and suspension. Results show that tidal fluctuations control groundwater flow fields, which drive spatiotemporal salt transport and persistent UBBN depletion. Salt outflow rates peak at the sediment‐water interface in beach zones and decline seaward. Discharge hotspots exhibit salt outflow rates 4–8 times greater than adjacent neritic areas. Despite net losses, approximately 9% (offshore)–60% (nearshore) of salt from tidal recharge (evaporated beach salt and seawater) is retained and replenishes the aquifer per tidal cycle, accumulating predominantly in the top‐section of silt cover layers. CUB mining and suspension enhance seawater and evaporated salt influx while reducing leakage from high‐salinity confined brine, effectively slowing UBBN salt loss. These findings advance large‐scale UBBN cycling mechanisms and provide actionable insights for sustainable development of UBBN resources in bay‐scale beach and neritic zones.

Within the coastal flow-field system, the hydrodynamic coupling between the tidal channel and surf zone is among the most important, implicated in shoreline morphodynamics, river mouth bar dynamics, and the recreational quality of nearshore waters. The nature of the coupling has seldom been empirically evaluated at tidal frequencies spanning lunar cycles. This investigation is directed at filling this gap in information based on 50-day successive tidal cycle flow monitoring in an estuary-surf zone setting, S. E. coast of Nigeria. Results show a reversing flow pattern at all monitoring stations at tidal frequencies. The estuary indicated ebb-asymmetric tidal cycle residual flow velocities which at spring tide (30-38 cm/s range) act as an expanding jet relative to the flanking surf zone residual longshore current counterparts (typically ≤ 5 cm/s). The western and eastern flanking surf zones showed westwardand eastward-asymmetric tidal cycle residual flows, respectively with coastwise decreasing asymmetry reflecting the weakening impact of the estuary outflow. Coupling of surf zone - estuarine residual flow vectors indicated a higher frequency of threshold coefficient (r ≥ 0.7) at ebb than at flood stage. The observed pattern of strong estuarine residual outflow velocities and modally divergent weak surf zone flows is a favourable condition for the estuary mouth bar development. However, the eastward-skewed bar configuration fits more to the effect of eastward-directed momentum flux associated with water mass transport of the obliquely-shoaling southwesterly waves given that breaking wave-generated longshore currents in the western surf zone display a westward-asymmetry over a tidal cycle.

Carbon export from mangrove forests to the oceans partly acts as a sink for atmospheric CO2, exceeding the rate of carbon burial in mangrove soils. Primary production in ecosystems adjacent to mangroves may prevent degassing and enhance further carbon export from mangroves to the oceans. In this study, we continuously monitored carbonate chemistry parameters (pCO2, dissolved inorganic carbon (DIC), total alkalinity (TA)) and dissolved organic carbon (DOC) in a tidal flat adjacent to a fringe mangrove forest over a spring-neap tidal cycle. Mean pCO2 during the entire period was 923 ± 318 μatm, and the export of TA, DIC, and DOC from the mangroves to the ocean was 36 ± 26 mmol m−2 d−1, 42 ± 39 mmol m−2 d−1, and 10 ± 9 mmol m−2 d−1, respectively. Semi-monthly pCO2 variations in the mangrove front were controlled by the tidal level during spring tide and by photosynthesis and respiration on the tidal flat during neap tide. This means that during neap tide, photosynthesis on the tidal flat offset the increase in pCO2 caused by the porewater export from the mangrove soil. The DIC/TA export ratio in this study was 1.17 ± 0.08, which was lower than the global average of 1.41 ± 1.39, indicating that the tidal flat adjacent to the mangrove forest may act as a buffer zone to mitigate the increase in pCO2, resulting in much of the exported DIC being stored in the ocean.

Tessier, B.; Poirier, C.; Weill, P.; Dezileau, L.; Rieux, A.; Mouazé, D.; Fournier, J., and Bonnot-Courtois, C., 2019. Evolution of a shelly beach ridge system over the last decades in a hypertidal open-coast embayment (western Mont-Saint-Michel Bay, NW France). In: Castelle, B. and Chaumillon, E. (eds.), Coastal Evolution under Climate Change along the Tropical Overseas and Temperate Metropolitan France. Journal of Coastal Research, Special Issue No. 88, pp. 77–88. Coconut Creek (Florida), ISSN 0749-0208. The behavior of the shelly beach ridge system forming a more or less continuous barrier lying along the southern coast of the hypertidal Mont-Saint-Michel bay (NW France) is examined using a set of various data including aerial photographs since 1947, sediment cores collected in back-barrier salt marshes, ground penetrating radar profiles, and differential digital elevation models (DEMs). The latter shows that since the middle of the 20th century, the tidal flats extending in front of the ridge system experience erosion and accretion that alternate spatially according to cross-shore corridors. The shelly ridges are better developed on line with the erosional bands. The reasons for this erosion/accretion compartment pattern are not totally elucidated. It probably results from the combined influence of shellfish farms, tidal channels and reef present on the tidal flats on wave and current dynamics. At the decadal to pluri-decadal scale, the shelly beach ridge system behavior as well as its internal organization can partly be related to the fluctuations of hydrodynamic conditions controlled by the 18.6 years nodal tidal cycle. Periods of intense landward migration alternate with periods of relative stability during the peak and the trough of the cycle respectively. This general scheme is complicated due to variations in storm wave dynamics. The most morphogenic events happen potentially during coinciding nodal cycle peaks and enhanced storminess. Such conditions actually occurred around 1995-2000, resulting in the most prominent washover fan deposit preserved within the back-barrier infilling successions. These sediment successions evidence as well that no beach ridge system older than the 19th century is preserved in front of the Medieval dike built during the 11th century on a relict beach ridge, and on which the present-day system is backed. We suggest that the enhanced storminess conditions of the Little Ice Age provoked the reworking of beach ridges formed between the 11th and 19th centuries. Changes in quantity and type of mollusk shells, related to the shellfish farming development during the 20th century are also thought to have had positive consequences on the barrier building and stability.

Field hydrometric studies at the estuaries of the White Sea basin yielded data on some hydrodynamic features of reverse tidal currents. Among the mouth areas of tidal rivers studied in 2015–2022, the most interesting results were obtained at the mesotidal Kyanda estuary, flowing into Onega Bay, and at the macrotidal Syomzha estuary, flowing into Mezen estuary. The essence of the method used in the field studies is synchronic measurements of water flow by acoustic Doppler profilers and water levels by autonomous barometric recorders in two cross-sections, located at different distances from the river mouth, during an entire semidiurnal tidal cycle. The results of these measurements were used to evaluate the terms of Saint-Venant equation of motion and the roughness coefficients. It was found that in the tidal rivers, the flow resistance varies considerably during a tidal cycle. In periods of quasi-steady water flow in both directions during flood and ebb, the values of the Darcy–Weisbach friction factor are 0.04–0.07, as is typical for rivers with similar morphological channel pattern and characteristics. However, in several cases, in periods close to slack water, the friction factor took negative values. A possible explanation of this phenomenon is a negative turbulent viscosity, which manifests itself in some phases of the tidal cycle, when the energy of eddy formations can be transferred to the translational motion of the water mass.

This study investigates the effects of tidal cycles on the zooplankton community within the Cotonou Channel, an important waterway connecting the large Nokoué Lagoon to the Atlantic Ocean in Benin. From the determination of zooplankton composition from 25-hour samples collected in July 2020, alpha diversity indices and abundance were assessed, while relationships between biotic and abiotic parameters were analyzed through Pearson correlation, analysis of variance, and principal component analysis. A total of 66 zooplankton taxa were identified, with rotifers exhibiting the highest species richness (35 taxa), while copepods dominated in abundance (71%). Zooplankton abundance varied significantly, ranging from 2 to 95 ind L−1 depending on the tidal phase. A negative correlation was found between species richness (r = −0.51, p < 0.01) and increasing salinity (3–37), indicating that higher salinity reduced diversity (r = 0.06, p > 0.05). Resilient species like Synchaeta bicornis persisted despite salinity changes. The tidal cycle structurally altered the zooplankton community, with abundance and diversity peaking at different phases, notably higher at high tide (15 ind L−1.) These initial findings underscore the complex interactions between tidal dynamics and estuarine biodiversity, suggesting the need for further research across different tidal and seasonal conditions to inform effective management and conservation efforts.

Han, Z.; Li, H.; Xie, H.; Yang, H.; Ouyang, Q., and Gong, S., 2022. Dredging of the Shenzhen-Zhongshan Link in the Pearl River Estuary, China: Short-term siltation mechanism for a trial trench. Journal of Coastal Research, 38(5), 988–998. Coconut Creek (Florida), ISSN 0749-0208. Understanding the short-term, particularly daily, siltation mechanism of a dredged trench is critical for immersed tunnel construction, as well as for offshore engineering and coastal management. This study explored the short-term siltation mechanism of the trial trench dredged for the Shenzhen-Zhongshan Link in the Pearl River Estuary, China. Monthly silting characteristics over a period of ∼11 months indicate that the silting intensity during the flood season was much larger than during the dry season. Local suspended sediment concentrations (SSCs) also varied on a flood–dry seasonal cycle, which were impacted by the suspended load from the Pearl River. Daily silting characteristics indicate that the silting intensity during spring tides were higher than during neap and moderate tides and that the local SSCs and flow velocities also varied on a spring–neap tidal cycle, which was dominated by periodic variations in the astronomical tide. The flow velocity deceased substantially from the surface to the bottom of the trench, and flow circulation occurred at the bottom of the trench, which aided the silting process. Seasonal changes in the sediment load from the Pearl River were the dominant cause of the changes in suspended sediment around the trench, which produced seasonal siltation changes in the trench. Daily changes in trench siltation were directly caused by the amount of sediment that entered the trench, which was affected by changes in the flow velocity and bottom SSC around the trench during the neap–spring tidal cycle. Although the high-siltation intensity during the flood season was unhelpful, the low-siltation intensity during neap and moderate tides was helpful for the construction of immersed tunnel during the flood season.

Estuaries are often a significant source of atmospheric CO 2 . However, studies of carbonate systems have predominantly focused on large estuaries, while smaller estuaries have scarcely been documented. In this study, we collected surface and bottom seawater carbonate samples in the subtropical Jiulong River Estuary across different tidal levels from 2019 to 2021. The results showed that estuarine mixing of freshwater from the river with seawater was the dominant factor influencing the estuarine carbonate system. Moreover, estuarine mixing is concomitantly impacted by the net metabolism of biological production and decomposition, groundwater input, release of CO 2 from the estuary, and precipitation or dissolution of calcium carbonate. The estuarine partial pressure of CO 2 ( p CO 2 ) varied from 530 µatm to 7 715 µatm, which represents a strong source of atmospheric CO 2 . The mean annual air-sea CO 2 flux estimated from three different parameterized equations was approximately (25.63 ± 10.25) mol/(m 2 ·a). Furthermore, the annual emission to the atmosphere was approximately (0.031 ± 0.012) Tg C, which accounts for a mere 0.007 7%–0.015% of global estuarine emissions. Dissolved inorganic carbon (DIC), total alkalinity (TA) and the p CO 2 exhibited high variability throughout the tidal cycle across all cruises. Specifically, the disparities observed between DIC and TA during low and high tides at identical stations during all cruises ranged from approximately 15% to 30%. The variance in the p CO 2 was even more pronounced, ranging from approximately 30% to 40%. Thus, tidal discrepancies may need to be taken into consideration to estimate the CO 2 flux from estuarine systems more accurately.