Low Tidal Zone Research Articles

Distribution characteristics and influencing factors of benthic diatoms on several typical beaches along the southern coast of China

Benthic diatoms are the primary beach vegetation on sandy coasts, acting as the main primary producers in such environments. Changes in their community structure and biomass can have substantial impact on both the entire micro-food web and the nearshore shallow marine ecosystem. This study focused on four typical beaches along the southern coast of China (Fuzhou Changle Beach, Xiamen Huizhan Beach, Xiamen Guanyinshan Beach, and Beihai Silver Beach). Analysis of benthic diatoms and environmental factors revealed that the distribution of benthic diatom communities on the studied beaches is influenced by elevation, salinity changes due to freshwater inputs, sediment composition, and hydrodynamic factors. The most important factor is elevation, which reflects the location of the beach in the tidal zone. On Beihai Silver Beach and the Xiamen beaches, the mid-tidal and low tidal zones are more conducive to growth and reproduction of benthic diatoms, and some diatom species show preference for different tidal zones. On dissipative beaches, benthic diatom abundance peaks in the mid-tidal zone, whereas on low tidal terrace beaches, diatom abundance is generally low in the high tidal zone and relatively high in the low tidal zone. Additionally, low tidal terrace beaches exhibit a “steep increase zone” of diatom abundance at the junction of the steep and gentle slopes, indicating that benthic diatom abundance responds more to this type of beach landform than to that of dissipative beaches.

Evaluation of the stock enhancement effect of Phascolosoma esculenta on macrobenthic communities using diversity and biotic indices in Yueqing Bay, East China Sea

Stock enhancement activities have many benefits but also negative impacts. The macrobenthic diversity index and the M-AMBI index were adopted to assess the effects of stock enhancement of Phascolosoma esculenta on macrobenthic communities and the local ecosystem in Yueqing Bay. The results revealed that the Shannon–Wiener diversity index (H’) and Margalef richness index (d) increased in October 2022 after stock enhancement, indicating a positive ecological restoration effect. The average M-AMBI in the intertidal zone of Yueqing Bay was 0.59, indicating good benthic ecological quality. Excluding seasonal factors, the M-AMBI in the intertidal zone increased after stock enhancement, indicating that stock enhancement by Phascolosoma esculenta had a certain positive effect on the intertidal ecological environment of Yueqing Bay. The increase in the M-AMBI occurred mainly in the low-tide zone, increased slightly in the mid-tide zone, and remained basically unchanged in the high-tide zone. On the one hand, Phascolosoma esculenta can accumulate heavy metals from the environment and release a large amount of organic matter throughout its lifecycle, promoting nutrient cycling, which plays a positive role in the environment. On the other hand, Phascolosoma esculenta is an economic species; however, the planting of mangroves in the low tide zone causes fishers to fish in the mid- and high-tide zones, so the changes in the M-AMBI values in each tidal zone are related mainly to Phascolosoma esculenta and anthropogenic disturbances.

Occurrence, Source Apportionment, and Risk Assessment of Antibiotics in Mangrove Sediments from the Lianzhou Bay, China.

In recent years, the widespread application of antibiotics has raised global concerns, posing a severe threat to ecological health. In this study, the occurrence, source, and ecological risks of 39 antibiotics belonging to 5 classes in mangrove sediments from Lianzhou Bay, China, were assessed. The total concentrations of the antibiotics (∑39 antibiotics) ranged from 65.45 to 202.24 ng/g dry weight (dw), with an average of 142.73 ± 36.76 ng/g dw. The concentrations of these five classes of antibiotics were as follows: Sulfonamides (SAs) > Tetracyclines (TCs) > Fluoroquinolones (QUs) > Penicillin (PCs) > Macrolides (MLs). The spatial distribution of antibiotics varied as high tidal zone > middle tidal zone > low tidal zone. The total organic carbon (TOC), pH, nitrate (NO3--N), and nitrite (NO2--N) of the sediment significantly influenced the distribution of antibiotics (p < 0.05). A source analysis identified untreated sewage from aquaculture as the primary source of antibiotics in the local mangrove. A risk assessment revealed that ciprofloxacin, norfloxacin, ofloxacin of QUs, and tetracycline of TCs exhibited medium risks to algae in certain sampling sites, while other antibiotics exhibited low or no risks to all organisms. Nevertheless, the total risk of all the detected antibiotics to algae was medium in 95% of the sites. The overall ecological risk level of antibiotics in the middle tidal zone was slightly lower than in the high tidal zone and the lowest in the low tidal zone. In summary, the experimental results provided insights into the fate and transport behaviors of antibiotics in mangrove sediments from Lianzhou Bay.

Tracing microplastic pollution in Mahi River estuary, Gulf of Khambhat, Gujarat, and their influence on functional traits of macrobenthos.

Most maritime habitats contain microplastic (MPs) contamination. The quality of the benthic ecosystem's habitat is declining as MPs accumulate in marine system. The contamination of MPs must therefore be investigated. We studied MPs pollution in the Mahi River, estuary, and macrobenthos. In the present study, the abundance of MPs fragments gradually decreased from the high tide zone to the low tide zone and muddy sediment has high MPsconcentrations due to sediment characteristics and particle size. The majority of sediment and biota MPs were fibrous and black. MPs in both silt and biota have identical chemical compositions (modified cellulose), shapes, and colors. A significant source of pollutants and MPs fluxing into the ocean is well within the river system. Perinereis aibuhitensis ingested the most MPs out of 11 species, whereas Amphipods did not show any presence of MPs. Our findings showed that functional characteristics are essential for macrobenthos MPs intake. MPs in macrobenthos are high due to biological functions such as feeding, ecological groups, feeding mechanisms, body size, and bioturbation. MPs in marine sediment and organisms aretracked down to the Mahi River exceeding 50km. The present work has investigated the idea that the macrobenthos that live in the sediment are ingesting the MPs that are building up there and this ingestion relies on the macrobenthos' functional characteristics.

Seaweed Community Structure in the Waters of Kelombok Village, Lingga District, Linga District

Kelombok Village, Lingga Regency is an island with a large water area (99% of the water area) and has a high wealth of biological resources, especially algae or seaweed. This research was conducted in the coastal waters of Kelombok Village with three stations (stations 1, 2, and 3), and two zones (tide zone and low tide zone). The research was carried out for one month, namely in January 2024. Sampling was carried out using the line transect technique. Data analysis was carried out descriptively. Based on the research results, it is known that 12 types of seaweed live in the coral coastal waters of Kelombok Village, consisting of 3 types of green algae (Chlorophyta), 4 types of brown algae (Phaeophyta), and 5 types of red algae (Rhodophyta). The abundance of seaweed in zone A is 99,913 ind /m2, and in zone B is 99,981 ind /m2. Water conditions were recorded for brightness 1-1,7 m, temperature 29-30,1 oC, salinity 29,5-30‰, current speed 0,071 m/sec, DO 6,78-7,23 ppm, depth 0,75-1,7 m, pH 7,8-8, nitrate 0,01 mg/l, and phosphate 0,073 mg/l.

Tide-induced infiltration and resuspension of microplastics in shorelines: Insights from tidal tank experiments

In the present study, the infiltration and resuspension of microplastics (MPs) in a slope substrate under the influence of repeated tidal forces were investigated using a tidal tank. In the scenario in which MPs were placed on the top of the slope, increasing numbers of particles were observed on the water surface with the increase in tidal cycles. More particles of smaller equivalent particle diameter (dMP) and low density floated to the water surface. The horizontal positions (positive toward the lower tide zone) of MPs showed significant positive correlation with the shortest length c of MPs, MP density, MP weight, dMP, and Corey shape factor, whereas they showed significant negative correlation with the rate of tidal level change and the longest length a of MPs. The vertical positions (positive in the downward direction) of MPs showed significant positive correlation with the shortest length c of MPs, MP density, MP weight, dMP, and Corey shape factor, while they demonstrated significant negative correlation with the largest cross-section area and surface tension of MPs. In the scenario in which MPs were placed at the bottom of the tank, the smaller and low-density particles had a higher possibility of moving upward to the water surface under repeated tidal forces. High-density particles also migrated to the water surface due to the surface tension force. Further, a lower rate of tidal level change contributed to more floating of particles. The horizontal positions of MPs showed significant positive correlation with MP density, while they demonstrated significant negative correlation with the largest cross-section area and surface tension of MPs. The vertical positions of MPs showed significant positive correlation with the longest length a of MPs, MP density, MP weight, and dMP. These results imply that large, high-density, and less flatty particles tend to be distributed in the lower tidal zone and deeper substrate layers. These findings can help understand the redistribution of MPs and assess their risk in the shoreline environment.

Tidal variation shaped microplastic enrichment patterns in mangrove blue carbon ecosystem of northern Beibu Gulf, China

Mangroves are considered to be a sink for microplastics (MPs) due to their unique characteristics. Previous studies mainly focused on the spatial distribution of MPs, but few researchers have addressed the influence of tidal variation on this distribution, especially since the MP total number in mangroves was unknown. In this study, surface sediment samples were collected in mangroves from the Beibu Gulf, South China Sea, and the abundance, composition, and number of MPs were investigated. The results showed that MPs were widely present in all mangrove sediment samples, with abundances ranging from 26.67 ± 9.43 to 239.94 ± 37.80 items/kg. The distribution of MPs was heterogeneous among different sampling sites, with the highest levels in the Shankou (SK) area. The MP abundance in the same mangrove forest gradually increased from the low tidal zone to the high tidal zone, with the enrichment factor ranging from 1.50 to 4.00. The MP abundance was significantly correlated with particulate organic carbon (POC) (n = 12, R = 0.664, p &amp;lt; 0.05). Results showed that mangroves had an interception effect on MPs and factors affecting MP distribution in mangrove sediments included not only tides but also human activities, such as aquaculture, agriculture, and residential life. Finally, this paper estimated the MP total number in mangroves at different sampling areas and tidal zones, and the middle tidal zone was considered to be more accurate for MP pollution assessment in mangroves.

Corrosion behavior of low-alloy steel in tidal zone: A simulated investigation

Corrosion behaviors of low-alloy steel were investigated in the simulated tidal zones using stereoscopic microscope, field emission scanning electron microscope, X-ray diffraction, open circuit potential, and electrochemical impedance spectroscopy. The result shows that the corrosion in various tidal zones is much more severe than that of the immersion (IM) zone, and more severe corrosion takes place in the low tide (LT) and middle tide (MT) zones compared with the high tide (HT) zone. In the present test-time scale, uniform corrosion predominantly occurs in the IM and LT zones, and non-uniform corrosion occurs in the MT and HT zones. The main corrosion products in the LT and MT zones are Fe3O4 while α-FeOOH dominates the composition of rust layers in the HT zone.

Development and characterization of 135 SNP markers in chiton Acanthochitona rubrolineatus

Acanthochitona rubrolineatus (Lischke, 1873) (Polyplacophora, Neoloricata, Cryptoplacidae) is an important species widely distributed in the middle and low tide zone of coastal intertidal zone along the China Sea coast. In recent years, the serious pollution of seawater has caused a sharp decline in the number of wild populations of A. rubrolineatus. Lacking of effective molecular markers limits the effective protection and management of this species. Studies for the isolation and characterization of 135 A. rubrolineatus SNP markers were carried out. The frequency of minor allele ranges from 0.0125 to 0.5000. The observed heterozygosity and expected heterozygosity are 0.0000-0.9750, 0.0731–0.6696, respectively. The inbreeding value varies from − 0.2902 to 0.9966. Among them, there are 27 sites markablely differently from Hardy-Weinberg equilibrium (P < 0.05). The study of the polymorphic SNPs will provide a therotical basis for further analysis of population genetic analysis on A. rubrolineatus.

Corrosion behavior of marine structural steel in tidal zone based on wire beam electrode technology and partitioned cellular automata model

The initial corrosion evolution of marine structural steel in tidal zone is studied using wire beam electrode (WBE). The electrochemical experiment results show that the WBE in the high and middle tidal zones are in the anodic dissolution state for less time than that in the low tidal and immersion zones. The fitting results of WBE experiment provide the boundary conditions for the partitioned cellular automata (PCA) model, which is adopted to simulate the initial corrosion evolutions of steel in the tidal zone. The proposed independent variable of the electrolyte concentration (ρ), corrosion probability (Pc), passivation probability (Pp), and movement direction probability (Pm) on the corrosion behavior of steel are studied. The calculated results demonstrate that ρ and Pm can well characterize the corrosion evolutions of the steel in ocean tidal zones. This model is effective in predicting the corrosion evolution of marine structural steel in tidal zone. It provides a new method for predicting the corrosion evolution of marine structural steel in tidal zone.

Effects of Environmental and Spatial Variables on Bacteria in Zhanjiang Mangrove Sediments.

The bottom mud of mangroves contains numerous microbial groups that play an important role in the main ecological functions of the mangrove ecosystem. The diversity and functional and environmental factors related to microbial communities, in terms of the assembly process and in environmental adaptation of the abundance and rare bacterial communities in the mangrove ecosystem, have not been fully explored. We used 16S high-throughput sequencing and operational taxonomic unit analysis to compare the diversity and composition of bacterial communities in different tidal zones in the sediments of the Zhanjiang Gaoqiao Mangrove Nature Reserve, compare the ecological adaptation thresholds and phylogenetic signals of bacterial communities under different environmental gradients, and examine the factors affecting the composition of the bacterial community. The diversity of microbial species and structure and function of the mangrove sediments were affected by the environment, showing the trend: mid tide zone > climax zone > low tide zone. Organic matter content, oxygen content, pH, and total phosphorus were identified as important environmental factors determining the functional diversity of bacterial communities and survival, while pH influences species evolution. The abundant taxa showed a wider response threshold and stronger phylogenetic signals of ecological preference across environmental gradients compared to rare taxa. The abundant bacterial groups have broader environmental adaptability than rare bacterial groups, and different environmental factors affect different communities and functions in the mangrove ecological environment. These results elucidate the mechanism underlying the generation and maintenance of bacterial diversity in response to global environmental changes.

Influence of coastal engineering on the intertidal macrobenthic community in the Dongtou Islands, China

Abstract Coastal areas have been intensively urbanized in Asia, causing changes to the structure and function of intertidal macrobenthic communities. In this study, the intertidal assemblages on two natural rocky shores, two rocky shores disturbed by construction works, and two shores with mixed artificial seawalls and mudflats in the Dongtou Islands were studied. We examined the influence of coastal engineering by comparing macrobenthic community structures in different transects. The statistical results revealed significant differences between macrobenthic community structures in natural and influenced transects, although all the high tidal zones shared common species. The most common species on mudflats were opportunistic polychaetes; however, historical evidence suggests that the mudflats in Dongtou used to be dominated by Mollusca. We inferred that this change in community structure occurred when the seawalls were constructed five5 years previously. The macrobenthic community does not appear to have subsequently recovered. We also observed an absence of habitat-forming macroalgae in our study area, although similar investigation results revealed that they still prevail on an uninhabited island in Dongtou. The increasing disturbance caused by construction work may explain the decline in brown algae, which are mainly distributed in the low tidal zone.

长江口潮间带底栖生物生态及变化趋势

PDF HTML阅读 XML下载 导出引用 引用提醒 长江口潮间带底栖生物生态及变化趋势 DOI: 10.5846/stxb202009012276 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 海市科委科研计划项目（18DZ1206503）；长江三角洲河口湿地生态系统教育部/上海市野外科学观测研究站开放基金项目（K202003）；自然资源部海洋生态监测与修复技术重点实验室开放基金资助项目（MEMRT202009） Ecological evaluation and variation trend analysis of macrobenthos in intertidal zone of Changjiang Estuary Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:基于长江口3个区域潮间带（崇明东滩、南汇边滩和嵊山岛）监测数据，对长江口区域潮间带底栖生物生态现状及变化趋势进行评价。结果表明，2019年长江口海域泥相和岩相潮间带共鉴定大型底栖生物9门57种，软体动物、甲壳类和多毛类构成主要类群。崇明东滩、南汇边滩两个泥相潮间带底栖生物平均栖息密度分别为96.4个/m2和160.4个/m2，平均生物量分别为68.42 g/m2和45.71 g/m2；嵊山岛岩相潮间带平均栖息密度和生物量分别为488.9个/m2和763.72 g/m2。各断面多样性、丰富度和均匀度指数分别位于1.36-3.24、0.75-2.88和0.48-0.77，泥相潮间带低潮区生物多样性优于中潮区和高潮区，岩相潮间带中潮区生物多样性最好。聚类分析可见长江口海域潮间带底栖生物分为泥相和岩相2个大组群，物种分布存在明显的分潮区现象，高潮区站位成群或与个别中潮区站位成群，低潮区站位成群或与个别中潮区站位成群，表明底质类型和潮汐是影响潮间带大型底栖生物群落结构的主要因子。近30年来，崇明东滩和南汇边滩底栖生物种类数存在一定波动，嵊山后陀湾断面生物种类数明显下降；3个区域潮间带底栖生物密度和生物量均呈波动下降的趋势，应与长江口海域湿地围垦、外来物种入侵、人类过度采捕和环境污染等相关。 Abstract:Using macrobenthos monitoring data of 3 intertidal zones (Chongming eastern shoal, Nanhui nearshore and Shengshan Island being CM, NH and SS for short) in Changjiang estuary, biodiversity dynamics were evaluated in this study. The results showed that 9 phyla and 57 species of macrobenthos were identified in the intertidal zone of the Changjiang Estuary in 2019, and molluscs, crustacea and polychaeta were the main groups. The CM and NH were muddy intertidal zones, SS was rocky. The average density was 96.4 ind/m2, 160.4 ind/m2, and 488.9 ind/m2 in CM, NH and SS, the average biomass was 68.42 g/m2, 45.71 g/m2 and 763.72 g/m2 in the three areas. There were 3 sections in every area. The diversity, richness and evenness index were in 1.36-3.24, 0.75-2.88 and 0.48-0.77 with every section. The biodiversity of low tide zone was better than that of middle and high tide zone in muddy intertidal zone, but the middle tide zone was the best in rocky intertidal zone. All the macrobenthos were divided into two groups-muddy and rocky. Different species distributed in high, middle and low intertidal zones. Some species in high intertidal zone formed groups with very view in middle intertidal zone and some species in low intertidal zone formed groups with very view in middle intertidal zone. It showed that the sediment environment and tide were the most significant factors to affect community structure of intertidal macrobenthos. During the past 30 a, the species number of macrobenthos undulated in CM and NH, but decreased in SS; the average density and biomass were decreased in 3 areas, which should be related to wetland reclamation, species invasion, human over fishing and pollution. 参考文献 相似文献 引证文献

N2O emission dynamics along an intertidal elevation gradient in a subtropical estuary: Importance of N2O consumption

Studying nitrous oxide (N2O) production and consumption processes along an intertidal elevation gradient can improve the understanding of N2O dynamics among coastal wetlands. A natural-abundance isotope technique was applied to characterize the processes responsible for N2O emission in high, middle and low intertidal zones in the Yangtze Estuary. The results showed that N2O emission rates in high tidal zones (0.84 ± 0.35 nmol g−1 h−1) were significantly higher than those in middle (0.21 ± 0.04 nmol g−1 h−1) and low tidal zones (0.26 ± 0.05 nmol g−1 h−1). Gross N2O production and consumption rates were greater in high and low tidal zones than in middle tidal zones, whereas N2O consumption proportions generally increased from high to low tidal zones. N2O consumption was quite pronounced, implying that N2O emission in estuarine wetlands accounts for only a small fraction of the total production. Higher degrees of N2O consumption were the pivotal driver of less N2O emission in low tidal zones. Bacterial denitrification (>84%) was the dominant pathway, although hydroxylamine (NH2OH) oxidation/fungal denitrification contributed substantially to N2O production in high tidal flats. The contribution to N2O production exhibited a decrease in NH2OH oxidation/fungal denitrification and an increase in bacterial denitrification with decreasing elevation. Changes in N2O dynamics along the elevation gradient were affected by carbon and nitrogen substrate availabilities as well as the redox environments. Overall, our findings highlight the importance of N2O consumption in controlling N2O emission in intertidal wetlands, especially with higher inundation frequencies and durations.

Cataclysmic Disturbances to an Intertidal Ecosystem: Loss of Ecological Infrastructure Slows Recovery of Biogenic Habitats and Diversity

Understanding the resilience and recovery processes of coastal marine ecosystems is of increasing importance in the face of increasing disturbances and stressors. Large-scale, catastrophic events can re-set the structure and functioning of ecosystems, and potentially lead to different stable states. Such an event occurred in south-eastern New Zealand when a Mw 7.8 earthquake lifted the coastline by up to 6 m. This caused widespread mortality of intertidal algal and invertebrate communities over 130 km of coast. This study involved structured and detailed sampling of three intertidal zones at 16 sites nested into four degree of uplift (none, 0.4–1, 1.5–2.5, and 4.5–6 m). Recovery of large brown algal assemblages, the canopy species of which were almost entirely fucoids, were devastated by the uplift, and recovery after 4 years was generally poor except at sites with &amp;lt; 1 m of uplift. The physical infrastructural changes to reefs were severe, with intertidal emersion temperatures frequently above 35°C and up to 50°C, which was lethal to remnant populations and recruiting algae. Erosion of the reefs composed of soft sedimentary rocks was severe. Shifting sand and gravel covered some lower reef areas during storms, and the nearshore light environment was frequently below compensation points for algal production, especially for the largest fucoid Durvillaea antarctica/poha. Low uplift sites recovered much of their pre-earthquake assemblages, but only in the low tidal zone. The mid and high tidal zones of all uplifted sites remained depauperate. Fucoids recruited well in the low zone of low uplift sites but then were affected by a severe heat wave a year after the earthquake that reduced their cover. This was followed by a great increase in fleshy red algae, which then precluded recruitment of large brown algae. The interactions of species’ life histories and the altered physical and ecological infrastructure on which they rely are instructive for attempts to lessen manageable stressors in coastal environments and help future-proof against the effects of compounded impacts.

Mangrove diversity and community structure of Mimika District, Papua, Indonesia

Abstract. Setyadi G, Pribadi R, Wijayanti DP, Sugianto DN. 2021. Mangrove diversity and community structure of Mimika District, Papua, Indonesia. Biodiversitas 22: 3562-3571. Despite being one the largest mangrove forest in the world, there are few studies on mangrove diversity and community structure in Mimika, Papua Province. The study collected data from 4 estuaries of Mimika Region, i.e. Kamora, Tipuka, Ajkwa and Minajerwi. Mangrove species, tree diameter at breast height and canopy height data were collected in 10 m x 10 m plot with three replicates for distance, specifically 0, 250, and 500m perpendicular to the riverbank. This study found 66 mangroves species consisting of 20 major, 10 minor, and 36 associate mangrove species. Their density ranged from 577-1,345 trees ha-1 with diversity Shannon-Weiner diversity indices (H’) ranging from 0.62-1.19 and Evenness Index (J’) ranging from 0.09-0.18. The canopy height of the mangrove trees was ranged from 9-42.5 m. The highest density species was Rhizophora apiculata (333 ha-1) followed by Avicennia marina, Bruguiera gymnorrhiza, and Camptostemon schultzii, while B. parviflora, S. alba, and X. granatum were the least dominant. Regarding basal area, R. apiculata and B. gymnorrhiza were the highest with medians of 7,853 cm2 ha-1 and 5,201 cm2 ha-1 respectively. In the low tidal zone area, mangrove was dominated by A. marina, Sonneratia alba and R. mucronata. Medium low to medium high tidal zones were dominated by B. gymnorrhiza, R. apiculata, and B. parviflora. The high tidal zone was more dominated by Nypa fruticans.

The Physicochemical Properties of Sediment and Ground Cover for a Secondary Mangrove System in Thailand

Jumprom, N.; Rodcharoen, E., and Wichachucherd, B., 2021. The physicochemical properties of sediment and ground cover for a secondary mangrove system in Thailand. Journal of Coastal Research, 37(4), 784–792. Coconut Creek (Florida), ISSN 0749-0208.Mangrove forests serve various positive aspects for human use and accumulate sediment and filter impurities from the land and sea. In this study, the investigation was performed on the year-round changes in the physicochemical characteristics of sediment and the percentage of cover of the bottom in a secondary mangrove where public-access mangrove areas and the mouth of the Mae Klong River to the sea at Samut Songkhram province, Thailand. Organic carbon (OC), organic matter (OM), bulk density, and grain size were measured in the sediment samples. The percentage of cover and litter dry weight were estimated using 50-cm2 quadrats. Conductivity, total dissolved solids, pH, and salinity were measured from the sediment. Air and water temperatures were recorded. The study site was divided into upper-, middle-, and low-tide levels. The results showed that tidal levels and months had significantly different (p < 0.05) influences on all of the factors examined. The percentage of OC and percentage of OM increased continuously at the upper levels but were low at the middle and lower levels. The bulk density, however, was low in value in the low-tide zone. In addition to the percentage of cover, the percentage of soil and percentage of aerial root were found mostly in the middle to low zones. The percentage of garbage waste and percentage of litter were not different at different levels, and nor was the dry weight, throughout the period of study. The grain size in each month was classified as clay type, pH, conductivity, total dissolved solid, and salinity obtained from sediment varied significantly (p < 0.05) among levels and months. In summary, the upper level is influenced by the terrestrial runoff. Environmental factors such as climate and geography affect the sediment quality at the middle and lower levels.

Pattern of soil extracellular enzyme activities along a tidal wetland with mosaic vegetation distributions in Chongming Island, China

Soil extracellular enzymes play an important role in the biochemical cycling in the coastal tidal wetland. Previous results revealed the factors affecting the soil extracellular enzyme activity (EEA) in the terrestrial ecosystems with acid soils, while it is still unknown what factors mainly affect the EEAs in the tidal wetland with neutral or alkaline soils. To reveal the factors affecting the variations of soil EEAs along the tidal wetland with mosaic distributions of vegetation types, the activities of nine types of soil enzymes, whose functions closely related to the cycling of soil C, N and P, respectively, were investigated in the Chongming Dongtan tidal wetland, East China. The soil samples with different layers were collected from the unvegetated area (S1), Spartina alterniflora area (S2), Scirpus mariqueter area (S3), and Phragmites australis area (S4), respectively, over the high tidal zone (HT), mid-tidal zone (MT) and low tidal zone (LT), respectively. The results showed that the soil EEA profiles were observably (p < 0.05) among the vegetation types, soil layers and tidal levels, based on the multi-response permutation procedure (MRPP) method. Variation partitioning analysis revealed that soil properties, soil layer, tidal level and vegetation type explained 28.2% variation of EEAs. Soil properties explained 17.5% variation of EEAs. The most variations of EEAs explained by soil layer, tidal level and vegetation type were soil characteristics, and 3.6% variations of EEAs were explained by the others three variables. NH3–N, C/N and BD were the most important factors affecting the variations of EEAs. Therefore, the most variations of EEAs were well explained by the soil properties in the Dongtan tidal wetland, East China.

Mollusks in the rocky tidal zone of the Phu Quoc island

Results of the survey of mollusks in the rocky tidal zones at 22 sites along the Phu Quoc island in April 2019 has identified 42 taxa of Mollusks, belonging to 3 classes: Gastropoda (25 taxa), Bivalvia (16 taxa) and Polyplacophora (1 taxon). Species composition between stations varies from 2 to 9 species. The average density was 21.07 individuals/m2, ranging from 3.67 individuals/m2 in Southeastern Kim Qui to 84.22 individuals/m2 in Hon Dam Ngoai. Density of mollusks was highest in the middle tide zones (42.42 individuals/m2), followed by high tide zones (14.55 individuals/m2) and lowest in the low tide zones. Density dominance belongs to two species Patella sp. and Siphonaria sp. distributed in the middle tide zones.

Effects of tidal zones and seasons on nutritional properties of commercially importance gastropods

Gastropods are important protein sources for coastal communities. This study performed a case study in Nan'ao Island to compare the spatial and temporal variations of lipids, proteins, carotenoids and antioxidant capacity of commercially important gastropods. Seven commercially important gastropods were identified from the rocky shores of Nan'ao Island. All the gastropods analysed had medium to high fat, low protein, and a considerable amount of total carotenoids. From low tide zone to high tide zone, the total antioxidant capacity of gastropods increased dramatically. In terms of fatty acid composition, all analysed gastropods had PUFA/SFA >0.45, but only three species had n-3/n-6 >1.00. In conclusion, some gastropods, especially Lunella coronata coreensis and Monodonta labio, have good nutritional value and potential health effects. This study is the first comprehensive assessment of the nutritional properties of commercially important gastropods in different rocky shore microenvironments and different seasons.