Tidal Flat Research Articles

Sea level and temperature extremes in a regulated Lagoon of Venice

Increasing sea levels and water temperatures have been detected at several coastal locations worldwide with severe consequences on the communities and ecosystems. Coastal lagoons are particularly vulnerable to such changes due to their low land elevation and limited connections with the open sea. Here the recent and future climatic changes in the Lagoon of Venice (Italy) are investigated using in-situ observations and high-resolution hydrodynamic modeling. Trend analysis was applied to observed time series of meteorological and oceanographic climate essential variables to identify significant long-term changes in mean and extreme values. The mean relative sea level rose at a rate of 4.9 mm per year in Venice due to the combined action of eustacy and subsidence while air and sea temperatures increased on average by 1.8 and 1.1°C in 30 years, respectively. These rates, as well as climate projections, were used following a pseudo-global-warming approach to investigate the near future (up to 2050) evolution of the lagoon's dynamics focusing on sea level and temperature extremes. The lagoon will amplify the temperature changes expected for the Adriatic Sea, especially in the shallow tidal flats where the intensity of the marine heat waves will be more than four times larger than that in the open sea. Moreover, the model allowed us to perform “what-if” scenarios to explore to which extent the flood protection MoSE barriers will modify the lagoon's dynamics. According to the simulations, the number of floods and therefore of the MoSE closure strongly increases with sea level rise. In the most severe scenario, MoSE will have to close for more than 20% of the time in October, November, and December resulting in the reduction of water exchange with the open sea and exacerbation of marine cold spells. Some considerations on the implications of the expected changes on the lagoon's ecology are proposed.

Restoration of Aegiceras corniculatum Mangroves May Not Increase the Sediment Carbon, Nitrogen, and Phosphorus Stocks in Southeastern China

Mangrove ecosystems play important roles in mitigating climate change but are suffering from an area decrease. The sediment in a mangrove ecosystem is a crucial component in estuarine carbon and nutrient cycles. However, it is unclear whether the restoration of mangroves enhances their sediment carbon sequestration and nutrient storage. To investigate the restoration effects of native Aegiceras corniculatum mangrove forests, the contents and density of sediment organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) were quantified in an unvegetated mudflat (MF), an area with mature A. corniculatum (AC), and two restored A. corniculatum mangroves planted in 2002 (02AC) and 2008 (08AC) in Quanzhou, southeastern China. Compared with the MF, mangrove restoration increased the SOC and TN contents in the sediment, primarily at the 0–40 cm depth for SOC and 0–20 cm for TN, while the TP content was not impacted by restoration. The sediment under AC showed a higher SOC content only at the 0–10 cm and 20–40 cm depths compared to restored 02AC and 08AC. The restoration of A. corniculatum mangroves did not significantly increase the stock of sediment SOC, TN, and TP relative to the MF, which might be attributed to the decrease in bulk density and the relatively short restoration period. Thus, further continuous monitoring is needed to verify whether the sediment carbon pool can be promoted on a longer-term scale by the restoration of A. corniculatum.

Effects of Polycyclic Aromatic Hydrocarbons on the Composition of the Soil Bacterial Communities in the Tidal Flat Wetlands of the Yellow River Delta of China.

Polycyclic aromatic hydrocarbons (PAHs) are pervasive organic pollutants in coastal ecosystems, especially in tidal flat wetlands. However, the mechanisms through which PAHs impact the soil bacterial communities of wetlands featuring a simple vegetation structure in the Yellow River Delta (China) remain largely unclear. In this study, we examined soil samples from two sites featuring a single vegetation type (Suaeda salsa) in the Yellow River Delta. Specifically, we investigated the impacts of PAHs on the diversity and composition of soil bacteria communities through high-throughput 16 S rRNA sequencing. PAHs significantly increased the soil organic carbon content but decreased the total phosphorus content (p = 0.02). PAH contamination notably reduced soil bacterial community α diversity (Shannon index) and β diversity. Furthermore, PAHs significantly altered the relative abundance of bacterial phyla, classes, and genera (p < 0.05). Specifically, PAHs increased the relative abundance of the bacterial phyla Acidobacteriota and Gemmatimonadota (p < 0.05), while decreasing the relative abundance of Bacteroidota, Desulfobacterota, and Firmicutes compared to the control wetland (p < 0.05). Moreover, PAHs and certain soil properties [total nitrogen (TN), soil organic carbon (SOC), total phosphorus (TP), and total salt (TS)] were identified as key parameters affecting the community of soil bacteria, with the abundance of specific bacteria being both negatively and positively affected by PAHs, SOC, and TN. In summary, our findings could facilitate the identification of existing environmental problems and offer insights for improving the protection and management of tidal flat wetland ecosystems in the Yellow River Delta of China.

Tidal asymmetry and mud transport in Oualidia Lagoon: Actual conditions in 2012 and rehabilitation scenarios

Oyster aquaculture in Oualidia Lagoon, Morocco, has suffered from poor water quality and water confinement in its upstream region. Tidal asymmetry (TA) has been suggested as a possible cause, and a sediment trap was dredged in 2011 to mitigate this condition. This study addresses TA in the lagoon using field measurements and numerical modeling in the presence of the sediment trap. Results indicate that the lagoon is flood-dominated mostly in its upstream end, where frictional forces exceed inertia accelerations during the tidal cycle and fine sediments settle on the tidal flats and inside the sediment trap. However, this study shows that a large mass of suspended sediments is exported to the ocean, which is contrary to expectations in flood-dominated lagoons. Defining the sediment trap as the rehabilitation scenario S1, the impacts of three additional scenarios on TA are examined. These are scenario S2 (dredging the upstream section of the main channel), scenario S3 (dredging the channels surrounding the flood delta near the inlets), and scenario S4 (raising the ocean level by 0.5 m following climate change predictions). Results show that none of these scenarios modify the tidal flood dominance in the lagoon, although scenarios S2 and S4 decrease its intensity in the upstream region. Nevertheless, all scenarios still contribute to a significant export of sediments to the ocean. This suggests that lagoon management activities should not rely on tidal asymmetry analyses that normally predict upstream sediment transport in flood-dominated lagoons.

Sediment temperature characteristics and their relation to distribution patterns of two sentinel crab species in intertidal flats in western Japan

In the context of global climate change, monitoring focused on temperature and benthic animals in intertidal flats and the development of metrics to assess climate change and ecosystem responses are essential for a sustainable society. However, few studies have assessed the relationship between intertidal sediment temperature and the distribution of benthic animals. To address this gap, in the present study, intertidal sediment temperatures were observed in 12 intertidal flats in 11 survey areas over 335 days, from October 2, 2019, to August 31, 2020, using water temperature data loggers. The characteristics of intertidal sediment temperatures were variable among the survey areas, and a correlation analysis suggested that such characteristics are possibly influenced by various spatial-scale factors, such as geographical, basin, and habitat scales. Furthermore, two sentinel crab species, Macrophthalmus japonicus and Macrophthalmus banzai were collected, and the number of wintering individuals of each species was estimated based on their carapace width to analyze the changes in abundances of the two species in each survey area. The results show that the number of days with daily minimum temperature ≥ 19 °C was the factor that influenced the abundance rate, suggesting that M. japonicus and M. banzai populations may decrease and increase, respectively, according to future climate change in Japan. Our findings emphasize the importance of long-term monitoring of sediment temperatures and benthic animals in intertidal flats to evaluate the influence of future climate change.

Dynamic Evolution of Aquaculture along the Bohai Sea Coastline and Implications for Eco-Coastal Vegetation Restoration Based on Remote Sensing.

The expansion and intensification of coastal aquaculture around the Bohai Sea in China has reduced the tidal flats and damaged the coastal vegetation environment. However, there are few studies on the relationship between the evolution of coastal aquaculture and the variability of coastal vegetation, which limits our understanding of the impact of human activities on the coastal ecosystem. In this study, based on remote sensing technology, we firstly used a combination of a neural network classifier and manual correction to monitor the long-term dynamic changes in aquaculture in the Bohai Sea from 1984 to 2022. We then analyzed its evolution, as well as the relationship between the evolution of coastal aquaculture and the variability of coastal vegetation, in detail. Our study had three main conclusions. Firstly, the aquaculture along the coast of the Bohai Sea showed an expanding trend from 1984 to 2022, with an increase of 538%. Secondly, the spatiotemporal changes in the aquaculture centroids in different provinces and cities varied. The centroid of aquaculture in Liaoning Province was mainly distributed in the Liaodong Peninsula, and moved northwest; that in Hebei Province was distributed in the northeast and moved with no apparent pattern; the centroid of aquaculture in Tianjin was mainly distributed in the southeast and moved westward; and the centroid of aquaculture in Shandong Province was mainly distributed in the northwest and moved in a northwesterly direction. Finally, the expansion of aquaculture of the Bohai Sea has increased the regional NDVI and length of the corresponding coastline, and has made coastlines move toward the sea. Our results provide reliable data support and reference for ecologically managing aquaculture and coastal environmental protection in the Bohai Sea.

The two salinity peaks mode of marine salt supply to coastal underground brine during a single tidal cycle

Seawater salt is constantly supplied from the marine environment to coastal underground brine deposits, meaning that brine has the potential for continuous extraction. There is currently a lack of information about the processes that drive the fluxes of seawater salt to underground brine deposits in tidal-driven brine mining areas. We chose the Yangkou salt field on the southern coast of Laizhou Bay, a brine mining area, as our study site. We monitored the spatial and temporal distribution of the underground brine reserve and the changes in water level and salinity in the mining area and adjacent tidal flats using electrical resistivity tomography and hydrogeological measurements. We monitored cross-sections along two survey lines and observed that the underground brine reserve receives a stable supply of seawater salt, and calculated that the rate of influx into the brine body in the mining area near the boundary of the precipitation funnel was 0.226−0.232 t/h. We calculated that a total salt flux of approximately 5.50 t enters the underground brine body every day through a 150 m long shoreline and a 1322.3 m2 window, which is sufficient to sustain the daily extraction of one brine well. During tidal cycles, there are two peaks in the salinity of the water supplied to the underground brine reserve, which means that the brine supply is from at least two high-salinity salt sources in different tidal stages. The first salinity peak occurs during the initial stage of the rising tide after seawater inundates the tidal flat. At this time, seawater, which is a solution and carries a large amount of evaporated salt, is transported into the brine layer through highly permeable areas or biological channels and replenishes the brine in the mining area. The second salinity peak occurs during the early stage of the falling tide. Influenced by hysteresis-driven tidal pumping, high-salinity brine from the lower intertidal zone is rapidly transported into the mining area, thereby increasing the salinity of the underground brine.

Mean Particle Size, Organic Carbon, and Porewater Salinity Distribution of Surface Sediments Using a Dataset from the Hwangdo Tidal Flat, Taean, Western Korea

Mean Particle Size, Organic Carbon, and Porewater Salinity Distribution of Surface Sediments Using a Dataset from the Hwangdo Tidal Flat, Taean, Western Korea

Isolation and Cultivation of Carotenoid-Producing Strains from Tidal Flat Sediment and Proposal of Croceibacterium aestuarii sp. nov., a Novel Carotenoid-Producing Species in the Family Erythrobacteraceae

Carotenoids are extensively used in drugs, cosmetics, nutrients, and foods, owing to their antioxidant and anti-inflammatory characteristics. Diverse marine heterotrophic prokaryotes can accumulate carotenoids and become promising alternatives for the advancement of carotenoids production. In this research, 55 strains were isolated and cultivated from tidal flat sediment in Zhoushan and classified into the phyla Pseudomonadota (n = 24), Bacillota (n = 18), Bacteroidota (n = 9), and Actinomycetota (n = 4). Nine of them accumulated carotenoids, and most of them belonged to the families Flavobacteriaceae (n = 4) and Erythrobacteraceae (n = 4). Among those carotenoid-producing strains, one strain, designated as D39T, was proposed as one novel species belonging to the genus Croceibacterium through polyphasic taxonomy approaches. Genomic annotations and carotenoid compound determinations revealed that strain D39T encoded crtEBIYZG genes and mainly accumulated zeaxanthin as major carotenoids. Furthermore, carotenoid biosynthesis pathway in the majority of Croceibacterium strains were identical with that in the strain D39T, implying that Croceibacterium members can be sources of producing zeaxanthin. This study enhances knowledge of microbial biodiversity in tidal flats, proposes a novel carotenoid-producing Croceibacterium species, and elucidates carotenoid biosynthesis pathway in the genus Croceibacterium, which contribute to enriching marine carotenoid-producing strains and promoting a comprehensive insight into genomic contents of them.

Contributions of plant‐ and microbial‐derived residuals to mangrove soil carbon stocks: Implications for blue carbon sequestration

Abstract Coastal blue carbon ecosystems, particularly mangroves, are becoming increasingly recognised for their importance in mitigating climate change. Still, the specific patterns and drivers of plant lignin components and microbial necromass accumulation in these ecosystems are unclear. In response, we carried out a study along a 40‐year mangrove restoration chronosequence, measuring lignin phenol and amino sugar concentrations in soil profiles (0–100 cm) as indicators of plant‐based and microbial‐derived residues, respectively. Our results showed that restoration significantly increased plant lignin phenol and amino sugar concentrations, with mature mangroves having much higher concentrations than tidal flats. During restoration, the fungal necromass was greater than the bacterial necromass. The factors influencing the lignin phenols were tree biomass, total nitrogen, pH and salinity, while those influencing the formation of amino sugars were total biomass, soil C: N ratio and pH. While the amino sugars decreased, the lignin phenols increased with the content of SOC, providing evidence of the important role lignin phenol components play in the formation of SOC in mangrove. Synthesis: By separating soil carbon into plant‐based and microbial‐derived components, our results demonstrate that the carbon stock in mangrove sediments is vulnerable to disturbances and that changes from anaerobic to aerobic conditions cause significant carbon mineralisation. The precise identification of soil carbon sources in blue carbon ecosystems could aid in elucidating the mechanisms of soil carbon sequestration and their responses to environmental changes. Read the free Plain Language Summary for this article on the Journal blog.

Evaluation of historical and future coastal wetland change in the Yellow and Bohai Seas using satellite images and a land use model

Predicting the future distribution of coastal wetlands and characterizing changes in the area of wetlands between historical and future periods are important for the formulation of wetland conservation and management plans. Here, we used a cellular automata–Markov model and satellite images to simulate the future distribution of coastal wetlands under the business-as-usual scenario (BAU) and ecological protection scenario (EP) along the Yellow and Bohai Seas in China; we also explored historical (from 1990 to 2020) and future (from 2020 to 2050) changes in wetlands and the factors driving these changes. We found that the area of tidal flats gradually decreased because of increases in the area of saltpans, and the aquaculture area increased because of land reclamation and the invasion of Spartina alterniflora; most of the tidal flat area was fragmented into multiple small patches. If the current rate of degradation continues (BAU), the area of tidal flats will decrease by 21.25%, and the area of saltpans and aquaculture will increase by 13.83% and 21.25%, respectively. By contrast, under EP, the area of tidal flats will increase by 13.81%, and this increase will mainly stem from the conversion of areas with S. alterniflora (174.49 km2, 33.22%) to aquaculture areas (155.17 km2, 29.54%). Clear differences between historical and future periods were observed among Liaohe Estuary, Bohai Bay, Laizhou Bay, and the Yancheng–Nantong coasts. Land reclamation is the main factor inducing changes in the area of tidal flats, saltpans, and aquaculture in Liaohe Estuary, Bohai Bay, and Laizhou Bay. Land reclamation and the S. alterniflora invasion both affect the distribution of wetlands along the Yancheng–Nantong coasts.

Spatiotemporal variations in migratory bird diversity and abundance along the coast of Gochang getbol.

Tidal flats provide critical habitat for migratory waterbird species; however, populations of migratory waterbirds have significantly declined due to tidal flat loss and degradation caused by human activities, particularly in Asia. Gochang getbol is one of tidal flats located on the southwest coast of South Korea and a center of clam production. Using bird monitoring data collected at five zones (zone1 to zone5) established across Gochang getbol and near coastal area, we examined distribution patterns of migratory bird diversity and conservation-related species along the coast of Gochang getbol. The intensity of human activity ‒ mudflat culture (mostly bivalve) and aquaculture was relatively high at zone2 and zone3, occupying > 30% of 2km circular area surrounding most sample points of these zones. Zone1 and particularly zone4 contained more natural/semi-natural habitats (less disturbed mudflats and wetlands) and zone5 had smallest mudflat than others. Shannon diversity, species richness, and abundance of migratory birds differed between zones (Anova test, P ≤ 0.02) except Shannon diversity in winter. In fall, all values were higher at zone4 than zone3 and zone5. In winter, zone1 showed greatest species richness and higher abundance than zone2, zone3, and zone5. In spring, while most differences were found between zone4 and zone5, abundance at zone4 was somewhat higher than zone2. The results from the fourth corner analysis indicated that abundance of species foraging at mudflat level was positively associated with zone1 (winter) but negatively with zone3 (fall). Sandpipers were positively associated with zone4. Abundance distribution maps of conservation-related species, created by inverse distance-weighted interpolation modeling, also showed high abundance of most conservation-related species at zone4 and 1. The findings of our study suggest the importance of natural/semi-natural habitat, and the possible link between human activity and distribution patterns of migratory birds in Gochang getbol. While we need further investigation on direct response of migratory birds to human activity, areas with low human activity with more natural/semi-natural habitat, e.g., zone4 and zone1 may be crucial for the conservation of migratory birds.

Geographical characteristics that promote persistence and accumulation of PFAS in coastal waters and open seas: Current and emerging hot spots

Poly- and perfluoalkyl substances (PFAS) have been found in ocean water, sediments, and marine organisms. The objective of this study was to identify coastal and open water conditions that affect accumulation and transport characteristics of PFAS in coastal areas and open waters. Coastal conditions were compared based on the classification for Shoreline Cleanup and Assessment Technique (SCAT). Open sea conditions were evaluated in relation to ocean currents. PFAS data available in the literature from different coastal areas and open seas were compiled. Tidal flats, sheltered shores, salt and brackish marshes, bays and estuaries, mangroves, and areas with coral reefs, sea grasses, kelp have conditions that are favorable for PFAS accumulation and ecosystems in these environments are vulnerable to long term PFAS exposure and bioaccumulation. The areas near the centers of gyres in oceans trap and accumulate floating debris as well as PFAS contaminated particles. PFAS accumulation in highly productive coastal areas with mangrove forests, seagrasses and salt marshes can affect the ecosystems in these locations. PFAS data from marine environments indicate that some areas in the Indian Ocean (41.1 ng/L), North Pacific Ocean (12.8 ng/L), and North Atlantic Ocean (4.0 ng/L) relatively high levels of PFAS. Marine organisms with long life spans are likely to accumulate high levels of PFAS over their lifespan. PFAS concentrations at vulnerable coastal waters and open seas should be monitored systematically and periodically to establish the baseline conditions and evaluate the changes in PFAS levels water column and sediments overtime.

Evaluation of Soft CaO-improved Soil as Tidal Flat and Shallow Sediment Material: A Comparative Experimental Study Using Mesocosm Tanks

Evaluation of Soft CaO-improved Soil as Tidal Flat and Shallow Sediment Material: A Comparative Experimental Study Using Mesocosm Tanks

Short-Term Prediction of Vertical Deformation in Tidal Flat Terrains Based on PSO-VMD-LSTM

Short-Term Prediction of Vertical Deformation in Tidal Flat Terrains Based on PSO-VMD-LSTM

A More Accurate Method of Extracting Tidal Flats Data Affected by Irregular Tides Using Surface Humidity Difference: Reducing the Dependence on High Matching Between High and Low Tide Times and Satellite Transit Times

A More Accurate Method of Extracting Tidal Flats Data Affected by Irregular Tides Using Surface Humidity Difference: Reducing the Dependence on High Matching Between High and Low Tide Times and Satellite Transit Times

Spatio-Temporal Evolution Monitoring and Analysis of Tidal Flats in Beibu Gulf From 1987 to 2021 Using Multisource Remote Sensing

Spatio-Temporal Evolution Monitoring and Analysis of Tidal Flats in Beibu Gulf From 1987 to 2021 Using Multisource Remote Sensing

Thermal Tolerance of the Shallow-Water Ostracod Cyprideis from a Lagoon in Bahrain, Western Arabian Gulf

Laboratory experiments were conducted to determine the thermal tolerance of the living ostracod Cyprideis sp. from a lagoon known as Murray’s Pool on the east coast of Bahrain, in the western Arabian Gulf. Our experimental trials, run in duplicate using a semi-controlled thermal incubator, demonstrate the resilience of the ostracod community to elevated temperatures. We observed that ostracod specimens begin to enter an inactive condition or become comatose at about 39.4 °C, and with increase in temperatures, half of the specimens died or did not recover at 51.8 °C. At 53.5 °C, total mortality is observed with no indication of recovery. These observations have implications for climate change predictions in the western Gulf region, as water temperatures in the lagoon reach 42 °C in summer, while the substrate temperatures on mud flats exposed during low tide exceed the lethal limit of the ostracods during the summer months.

유아를 위한 지속가능발전교육(ESD) 기반 갯벌 체험학습 프로그램 개발

유아를 위한 지속가능발전교육(ESD) 기반 갯벌 체험학습 프로그램 개발

｢가고 싶은 섬｣의 갯벌과 토양환경 특성(Ⅶ) - 연도, 옥도 중심으로 -

｢가고 싶은 섬｣의 갯벌과 토양환경 특성(Ⅶ) - 연도, 옥도 중심으로 -