Semantic Segmentation of the Intertidal Zone of an Estuary—In Search of the Best Solution

An aerial photographic coverage acquired on two consecutive days in October 2021 with a ground resolution of 20 cm and a spectral resolution of 4 bands (red, green, blue and near infrared), allowed to distinguish most of the classes of interest present in the intertidal zone of the Sado estuary. We explored the possibilities of thematic classification in the powerful and complex software ArcGIS Pro;we presented the methodology used in a detailed way that allows others with minimal knowledge of GIS to reproduce the classification process without having to decipher the specifics of the software. The classification implemented used ground truth from four classes related to the macro-occupations of the area. In a first phase we explore the standard algorithms with object-based capabilities, like K-Nearest Neighbor, Random Trees Forest and Support Vector Machine, and in a second phase we proceed to test three deep learning classifiers that provide semantic segmentation: a U-Net configuration, a Pyramid Scene Parsing Network and DeepLabV3. The resulting classifications were quantitatively evaluated with a set of 500 control points in a test area of 37,500 × 12,500 pixels, using confusion matrices and resorting to Cohen’s kappa statistic and the concept of global accuracy, achieving a Kappa in the range [0.72, 0.81] and a global accuracy between 88.9% and 92.9%;the option U-Net had the most interesting results. This work establishes a methodology to provide a baseline for assessing future changes in the distribution of Sado estuarine habitats, which can be replicated in other wetland ecosystems for conservation and management purposes.

Effect of Intertidal Elevation at Tsuyazaki Cove,Fukuoka,Japan on Survival Rate of Horseshoe Crab Tachypleus tridentatus Eggs

Physical factors affecting the survival of Tachypleus tridentatus eggs were investigated by translocating their eggs between the high intertidal zone and the low intertidal zone of a known spawning site.The mean egg survival rates per day were highest in the mid intertidal zone(45.1%±25.4%)and the lowest in the low intertidal zone(13.3%±27.6%).Differences in the elevation,air exposure time,and water content of the spawning ground were significant factors determining the egg survival rates.Excessive or insufficient air exposure time resulted in inadequate water content at higher and lower intertidal zones and could reduce egg survival.On the other hand,moderate saturation and dehydration were repeated with each tidal movement in the mid intertidal zone.This dynamic is considered as one of the crucial factors for the survival of eggs and is considered optimal for spawning.Therefore,the protection of the mid intertidal zone is imperative for maximizing the egg survival rate in Tsuyazaki Cove where almost all suitable nesting sites have disappeared due to coastal development.By protecting these optimal sites for spawning and recovering other optimal sites on suitable beaches,a positive contribution can be made to future management and conservation.The study also suggests that translocating eggs from marginal to optimal spawning sites might be a recovery strategy for this globally endangered species.

Study on acid-volatile sulfide(AVS), simultaneously extracted metals(SEM) and its toxic effect on the organism in intertidal sediments of Donghai Island, Zhanjiang

The content and distribution of acid-volatile sulfide （AVS） and simultaneously extracted metals （SEM） （Cr Cu, Zn, Cd and Pb） were studied in surface sediments collected from the tidal fiat of Donghai Island, Zhanjiang. The results indicated that for most stations, the AVS concentration was higher in summer with the average of 0.449 μmol/g than that in winter with the average of 1.816 μmol/g. The AVS contents were higher in southern and northern areas and lower in western and eastern areas. The average content of ∑SEM was between 0.56 μmol/g and 4.60 μmol/g in summer and between 0.65μmol/g and 2.21 μmol/g in winter. The concentration change of single metal was Zn〉Cr〉Pb〉Cu〉Cd for most stations. The content percentage in ∑ SEM was below 1% for Cd and over 70% for Zn. SEMZn was the key pattern to control the distribution of T. SEM due to its high concentration percentage. Based on the assessment methods of （∑SEM/AVS） with （∑ SEM-AVS） and thresholds for metal toxicity to benthic organism, most values of （∑ SEM-AVS） in intertidal flats of Donghai Island were between 0 and 5. The most toxicity region was in Tongminghai area located in the west tidal zone of Donghai Island, and the most toxicity metal was zinc in Tongminghai area in summer. The land-based pollution and the environmental parameters such as sunlight, atmosphere temperature and hydrodynamic characteristics were the main affecting factors on the content level and distribution characteristics of AVS and SEM in intertidal sediments of Donghai Island.

Heavy metal pollution in intertidal sediments from Quanzhou Bay, China

The concentrations of eight heavy metals （Cu, Zn, Pb, Cd, Cr, Ni, Hg, and As） in the intertidal surface sediments from Quanzhou Bay were determined to evaluate their levels and spatial distribution due to urbanization and economic development of Quanzhou region, southeast China. The ranges of the measured concentrations in the sediments are as follows： 24.8-119.7 mg/kg for Cu, 105.5-241.9 mg/kg for Zn, 34.3-100. 9 mg/kg for Pb, 0.28-0. 89 mg/kg for Cd, 51.1-121.7 mg/kg for Cr, 16.1-45.7 mg/kg for Ni, 0.17-0.74 mg/kg for Hg, and 17.7-30.2 mg/kg for As. The overall average concentrations of above metals exceed the primary standard criteria but meet the secondary standard criteria of the Chinese National Standard of Marine Sediment Quality. Several contents of Cu and Hg exceed the secondary standard criteria at some stations. The results of geoaccumulation index （Igeo） show that Cd causes strong pollution in most of the study area. There are no significant correlations among most of these heavy metals, indicating they have different anthropogenic and natural sources. Some locations present severe pollution by heavy metals depending on the sources, of which sewage outlets, aquatic breeding, and commercial ports are the main sources of contaminants to the area.

Effect of an Alien Species Spartina alterniflora Loisel on Biogeochemical Processes of Intertidal Ecosystem in the Jiangsu Coastal Region,China

Spartina alterniflora Loisel, a species vegetating in intertidal flats along the eastern coast of the United States, was introduced in China almost 30 years ago and has become an urgent topic due to its invasiveness in the coastal zone of China. The impacts of this alien species S. alterniflora on intertidal ecosystem processes in the Jiangsu coastland were investigated by comparing the sediment nutrient availability and trace element concentration characteristics in a mud flat and those of a four-year old Spartina salt marsh that had earlier been a mudflat. At each study site, fifteen plots were sampled in different seasons to determine the sediment characteristics along the tidal flats. The results suggested that Spartina salt marsh sediments had significantly higher total N, available P, and water content, but lower pH and bulk density than mudflat sediments. Sediment salinity, water content, total N, organic C, and available P decreased along a seaward gradient in the Spartina salt marsh and increased with vegetation biomass. Furthermore, the concentrations of trace elements and some metal elements in the sediment were higher under Spartina although these increases were not significant. Also, in the Spartina marsh, some heavy metals were concentrated in the surface layer of the sediment. The Spartina salt marsh in this study was only four years old; therefore, it is suggested that further study of this allen species on a longer time frame in the Jiangsu coastland should be carried out.

Observations of boundary layer parameters and suspended sediment transport over the intertidal flats of northern Jiangsu, China

A current-turbidity monitoring system (CTMS) was deployed on the intertidal flat at Wanggang, northern Jiangsu during October 16-17, 2000, to measure the tidal current speeds and seawater turbidities at 5 levels above the seabed. Based upon the logarithmic-profile equation, the boundary layer parameters, i.e., u, z0 and C60, were obtained for 247 tidal flow velocity profiles. Around 90% of the profiles were logarithmic according to the critical correlation coefficient. Internal consistency analysis shows that these parameters derived by different methods are consistent with each other. In addition, the height of the bedforms observed is close to the seabed roughness lengths calculated from the velocity profiles, indicating that the boundary layer parameters obtained can reveal the conditions at the sediment-water interface on the intertidal flats. Suspended sediment concentrations were obtained from the 5 CTMS turbidity meters using laboratory and in-situ calibrations. The results show that the in-situ calibrated SSCs have a much higher accuracy than the laboratory calibrated ones. Calculation of suspended sediment fluxes on the intertidal flats, with a magnitude of 104 kg/m per spring tidal cycle, indicates that suspended sediment moves towards the northwest, which is reversal to the transport pattern controlled by the southward Northern Jiangsu Coastal Current in the sub-tidal zone and adjacent shallow waters.

Modern sedimentation rates in the intertidal zone on the west coast of the Bohai Gulf

On the basis of the measurement of 210Pbex and 137Cs activities in the sediment cores taken from the intertidal zone on the west coast of the Bohai Gulf, the average sedimentation rates of modern sediments are calculated. The results indicate that in the sandy area of the intertidal zone (from Daogouzi to the Duliujian River), the sedimentation rate from 1955 to 1963 is 3.43-4.06 cm/a, and is within the range of 0.65￣1.59 cm/a since 1963. The average sedimentation rate in the muddy area (around Qikou) is approximately 1.81 cm/a. The results above suggest that the sandy area of the intertidal zone has experienced rapid sedimentation from the 1950s to the 1960s, and the sedimentation slows down after the 1960s, and the sedimentation rates increase from north to south spatially. The rapid sedi- mentation from the 1950s to the 1960s in the sandy area is due to the fact that North China has plentiful precipitation during this period and the intertidal zone is supplied with abundant matter sources for sedimentation. After the 1960s, the weakened sedimentation may be a result of the reduction of sand transported to the intertidal zone, which is a consequence of diminished rainfall in North China and intensive human activities in the Haihe basin.

Degradation kinetics and products of triazophos in intertidal sediment

This work presents taboratory studies on the degradation of triazophos in intertidat sediment. The overall degradations were found to follow the first-order decay model. After being incubated for 6 d, the percentage of degradations of triazophos in unsterilized and sterilized sediments were 94.5% and 20.5%, respectively. Between the temperatures of 15℃ and 35℃, the observed degradation rate constant（kob,d） enhanced as the incubation temperature increased. Triazophos in sediment degraded faster under aerobic condition than under anaerobic one. The water content of sediment had little influence on the degradation when it was in the range of 50%-100%. The values of kobsd decreased with increasing initial concentration of triazophos in sediment, which could result from the microorganism inhibition by triazophos. Four major degradation products, o, o-diethyl phosphorothioic acid, monoethyl phosphorothioic acid, phosphorothioic acid, and 1-phenyl-3-hydroxy-1, 2,4-triazole, were tentatively identified as their corresponding trimethylsilyl derivatives with a gas chromatography-mass spectrometer. The possible degradation pathway of triazophos in intertidal sediment was proposed. The results revealed that triazophos in intertidal sediment was relatively unstable and coutd be easily degraded.

Using benthic macrofauna to assess environmental quality of four intertidal mudflats in Hong Kong and Shenzhen Coast

Intertidal zone is a significant wetland between land and ocean. It plays an important rolein maintaining local ecological balance. Both Mai Po and Futian intertidal mudflats are located in Shenzhen Bay and are important 'refueling' point along the East Asian/Australian flyway of migratory birds. The environmental quality of Mai Po and Futian mudflats have aroused great concern due to rapid economic developments in Hong Kong and Shenzhen in recent decades. Macroinfauna of Mai Po and Futian mudflats was investigated in December 2000 and the faunal data were used to assess their environmental quality. Two other mudflats, namely Ma Wan Typhoon Shelter (a more disturbed area) and Luk Keng intertidal mudflat (a place with relatively less human disturbance), were also sampled for macroinfauna and used as reference mudflats. Shannon - Weaver species diversity index (Isd), biotic coefficient (Cb) and macrofaunal pollution index (Imp) of the macrofauna community on four intertidal mudflats were used to determine their environmental quality. The results showed that Luk Keng intertidal mudflat was unpolluted, Mai Po and Futian mudflats were slightly polluted, and Ma Wan was moderately polluted. The pollution in Ma Wan Typhoon Shelter mainly came from various types of rubbish and fishing boats that disturbed the sediment, while pollution sources in Mai Po and Futian mudflats were discharges of industrial water, municipal sewage and from nearby rivers.

Biogenic silica in intertidal marsh plants and associated sediments of the Yangtze Estuary

Biogenic silica （BSi） contents in the marsh plants （Phragmites australis, Scirpus mariqueter and Spartina alterniflora） and associated sediments in Chongming Island eastern intertidal flat of the Yangtze Estuary were determined. The BSi contents in P. australis, S. mariqueter and S. alterniflora varied from 25.78–42.74 mg/g, 5.71–19.53 mg/g and 6.71–8.92 mg/g, respectively. Over the entire growth season, P. australis and S. mariqueter were characterized by linear accumulation patterns of BSi. The aboveground biomass （leaves and culms） of the marsh plants generally contained more BSi than underground biomass （roots）. BSi contents were relatively higher in dead plant tissues than in live tissues which was probably due to the decomposition and the leaching of labile components of plant tissues such as organic carbon and nitrogen. Comparing with the habitats of S. mariqueter and S. alterniflora, the highest BSi content was recorded in sediments inhabited by P. australis, with an annual average of 15.69 mg/g. Overall, the intertidal marshes in the Yangtze Estuary may act as a net sink of BSi via plant uptake and sedimentary burial.

Spatial and temporal distributions of nitrogen,phosphorus and heavy metals in the intertidal sediment of the Chang jiang River Estuary in China

Spatial and temporal distributions of nutrients （N and P） and heavy metals （Cu, Zn, Pb and Cd） in the intertidal sediments at Dongtan wetland of the Changjiang River （Yangtze River） Estuary were examined by laying one transect running seaward to landward during January, April, June, August and October of 2005. Total nitrogen （TN） and heavy metal concentrations in the intertidal sediment showed an increasing trend from open bare flat to the high marsh, with the maximum concentrations in the high marsh and the minimum values in open bare flat. In contrast, sediment total phosphorus （TP） concentrations changed little among sampling sites. One-way ANOVA found that there were significantly temporal variations of nutrients and heavy metals concentrations in the intertidal sediment （P 〈0.05）. The concentrations of heavy metals generally showed an increasing trend from January to October. As compared with other large estuaries, heavy metal contamination in the intertidal sediment of the Changjiang River Estuary was relatively low.

Distribution and accumulation of biogenic silica in the intertidal sediments of the Yangtze Estuary

Sedimentary biogenic silica is known to be an important parameter to understand biogeochemical processes and paleoenviromental records in estuarine and coastal ecosystems. Consequently, it is of great significance to investigate accumulation and distribution of biogenic silica in sediments. The two-step mild acid-mild alkaline extraction procedure was used to leach biogenic silica and its early diagenetic products in intertidal sediments of the Yangtze Estuary. The results showed that total biogenic silica （t-BSi） in the intertidal sediments varied from 237.7-419.4 μmol Si/g, while the mild acid leachable silica （Si-HCl） and the mild alkaline leachable silica （Si- Alk） were in the range of 25.1-72.9 μmol Si/g and 208.1-350.4 μmol Si/g, respectively. Significant correlations were observed for the grain size distributions of sediments and different biogenic silica pools in intertidal sediments. This confirms that grain size distribution can significantly affect biogenic silica contents in sediments. Close relationships of biogenic silica with organic carbon and nitrogen were also found, reflecting that there is a strong coupling between biogenic silica and organic matter biogeochemical cycles in the intertidal system of the Yangtze Estuary. Additionally, the early diagenetic changes of biogenic silica in sediments are discussed in the present study.

The diffusive fluxes of inorganic nitrogen across the intertidal sediment-water interface of the Changjiang Estuary in China

Ammonium and nitrate concentrations were analyzed in near-bottom water and pore water collected from ten stations of the intertidal flat of the Changjiang Estuary during April, July, November and February. The magnitudes of the benthic exchange fluxes were determined on the basis of concentration gradients of ammonium and nitrate at the near-bottom water and interstitial water interface in combination with calculations of a modified Fick＇ s first law. Ammonium fluxes varied from - 5.05 to 1.43 μg/（ cm^2·d） and were greatly regulated by the production of ammonium in surface sediments, while nitrate fluxes ranged from - 0. 38 to 1.36 μg/ （ cm^2·d） and were dominated by nitrate concentrations in the tidal water. It was found that ammonium was mainly released from sediments into water columns at most of stations whereas nitrate was mostly diffused from overlying waters to intertidal sediments. In total, 823.75 t/a ammonium-N was passed from intertidal sediments to water while about 521.90 t/a nitrate-N was removed from overlying waters to intertidal sediments. This suggests that intertidal sediments had the significant influence on modulating inorganic nitrogen in the tidal water.

Food sources of the Manila clam Ruditapes philippinarum in intertidal areas:evidence from stable isotope analysis

Based on stable isotope analysis, we characterized the dietary regime of the Manila clam Ruditapesphilippinarum inhabiting intertidal areas along the Liaodong Peninsula, Northern China. Samples, including particulate organic matter （POM; n=30）, benthic microalgae （BMI; n=30） and R. philippinarum （n=60）, were collected from six sampling sites displaying the same ecological conditions. Of the two primary food sources, POM was more depleted in δ13C （-20.61‰ to -22.89%0） than BMI was （-13.90‰ to -16.66‰）. With respect to 15N, BMI was more enriched （2.90%0 to 4.07%0） than POM was （4.13‰ to 5.12‰）. The δ13C values of R. philippinarum ranged from -18.78‰ to -19.35‰ and the δ15N values from 7.96%0 to 8.63‰, which were intermediate between the POM and BMI values. In a two-source isotope mixing model, we estimated the relative contributions of POM and BMI to the diet ofR. philippinarum to be 74.2% and 25.8%, respectively. We conclude that R. philippinarum feeds mainly on POM, and BMI is also an important supplemental food source in intertidal areas.

Intensive use of an intertidal mudflat by foraging adult American horseshoe crabs Limulus polyphemus in the Great Bay estuary, New Hampshire

Although concerns about harvesting levels of the American Horseshoe Crab, Limulus polyphemus have prompted increased research into its ecology, current understanding of the species＇ foraging ecology is mostly limited to mid-Atlantic populations. This study elucidates the spatial and temporal pattern of Limulus foraging on an intertidal mudflat of a northern New Eng- land estuary. A novel survey method was used to monitor Limulus foraging activity without disturbing the sediment. A fixed 50 mx2 m transect was monitored with monthly surveys of the number of Limulus feeding pits from June to October 2009, May and June 2010. Snorkelling surveys were also carried out to observe individual behavior and examine the spatial scale of activity of individual animals. Results showed frequent and intensive use of the mudflat by foraging Limulus. Limulus were actively foraging within the survey area during all months surveyed. Foraging patterns exhibited a seasonal pattern with activity levels peaking in August 2009 and increased significantly towards the end of the study in June 2010. It was also shown that Limulus intertidal foraging persisted and peaked after the spring breeding season. Observations of foraging Limulus revealed that individual predators dig multiple pits within a single high tide, with little disturbance to the sediment in between. In addition to altering the perception of Limulus as a subtidal predator outside of the breeding season, findings from this study suggests a segregation of spawning and feeding habitats, thus underscoring the need to consider a wider range of critical habitats in the management of Limulus populations

Investigation of Macrobenthos in the Intertidal Zone of Tianjin and Discussion on Bioremediation

An investigation of macrobenthos in the littoral zone was carried out in Tanggu District, Tianjin City in June 2003. This investigation was the only integrated one since 1983 there. Something about macrobenthos investigation was reported in this paper. The results showed that the biomass of macrobenthos of that area was almost at the same level as that of 1983, and the density of macrobenthos increased a little. The biomass of Mactra veneriformis has great effect on the average biomass of that area. The diversity of macrobenthos has changed obviously, and 5 or 6 kinds of macrobenthos have become extinct or decreased greatly. So the ecological structure of macrobenthos has become simpler and unstable. In addition, some ecological methods to remedy the area are discussed in this paper.

Insights into community-based bioassessment of environmental quality status using microphytobenthos in estuarine intertidal ecosystems

The feasibility of community-based bioassessment of environmental quality status was studied using microphytobenthos（MPB） in estuarine intertidal ecosystems.The sediment samples of MPB were collected monthly during a 1-year cycle（September 2006-August 2007） at four sampling stations in the Nakdong River Estuary,Korea.Environmental variables,such as salinity,radiation,grain size of sediment,Si（OH）4（Si）,nitrate（NO3^-）,nitrite（NO2^-）,ammonium（NH4~＋） and phosphates（PO4^（3-））,were measured synchronously for comparison with biotic parameters.The statistical analyses were carried out for assessment the relationship between biotic and environmental parameters.The results showed that：（1） the MPB community structures were significant differences among four sampling stations;（2） spatial variation in the MPB communities were significantly correlated with environmental variables,especially the nutrient NH4＋ in combination with salinity and grain size;（3） three species（Navicula lacustris,Pleurosigma anglulatum and Fragilaria sp.1） were significantly correlated with nutrients and/or Si;and（4） the species richness and diversity were significantly correlated with the grain size.It is suggested that MPB communities may be used as a potentially robust bioindicator for assessing environmental quality status in estuarine intertidal ecosystems.

Geochemical Characteristics of Rare Earth Elements in Intertidal Sediments of Tianjin Coastal Zone

The geochemical characteristics of rare earth elements (REEs) in intertidal sediments in Tianjin coastal zone were systematically studied. The environmental behaviors of REEs in polluted river were also examined. The source of REEs in intertidal sediments was discussed on the basis of distribution pattern of REEs. The results can be summed up in the following aspects: (1) The average content of total REEs in the intertidal sediments is 164.5 mg·kg -1, and different in different sections of the coast. (2) Residual REEs in the coastal zone decrease from north to south, and Fe-Mn oxides and organic matter-bound REEs increase. Compared with those in Changjiang River, ratio between residual and carbonate REEs is obviously low. (3) Distribution patterns of REEs show that light REEs is relatively high and Eu-anomaly is slightly negative. They are similar to the patterns in coastal and inland rivers and different from those in continental shelf.

Studies on island intertidal benthic ecology in Fujian

A total of 862 benthic species were identified in the island intertidal zone in Fujian, of which 734 species are animals and 128 species algae. Determination of Jaccard's similarity index of species was made on the intertidal communities around 11 major islands. Based on hierarchical clustering (WPGMA) and polar ordination, the benthic communities may be classified into three types; the estu-arine type, the bay and harbour type and open sea type. The distribution of the benthic community is related to the location of the island and its habitats of which, salinity and hydrodynamics are the major factors controlling the distribution of the communities.

Enoplus taipingensis,a new species of marine nematode from the rocky intertidal seaweeds in the Taiping Bay,Qingdao

One new species of free-living marine nematodes Enoplus taipingensis sp. nov. from the rocky intertidal seaweeds in the Taiping Bay, Qingdao is described and illustrated with scanning electron microscopy observation and 18S rRNA gene sequence analysis. Enoplus taipingensis is characterized by special arrangement of lateral setae on the tail, three cervical setae, distal structure on the supplement, and much longer body length with bigger De Man ratio ＂a＂. Type specimens are deposited in the College of Marine Life Science, Ocean University of China.