A high accuracy, spatiotemporal coverage, and resolution satellite dataset of water clarity and Forel-Ule Index over China coastal waters (2003–2023)

We investigated the occurrence of imposex in gastropods from the coastal waters of mainland China from November 1999 to July 2004. Imposex was found in 30 species from 8 families, and was recorded in 20 species for the first time. In addition to the already known phenotypes of imposex expression in Cantharus cecillei, we also found aborted egg capsules in specimens with a split ventral channel (stage and type classification: S 6c .) and various extensions of the proximal vas deferens (PVD). The PVD went up to or passed by the vaginal opening, and then it stopped or continued along the capsule gland. In imposex females, the penis shape and the development of the vas deferens were similar to those of the male of the same species. The morphological expressions of imposex showed diverse stages and types. Reproductive failure of females occurred in 13 species. The results suggest that imposex is widespread and severe in the coastal waters of China. Based on our aims of ecological and morphological significance, a typical imposex classification could be further generalized for all 30 species by adding S 6c(*) and 2 subdivisions of the PVD. The generalized scheme was also ascertained to be valid for several morphological variations of imposex in previous work. Sterility at S 6c(*) was proven to be due to the infolding of the capsule gland wall. We thus summed up 4 mechanisms of sterility (a, b, c and *) in females. Furthermore, it was shown that the normal structure of the male genital system also affected the morphological expressions of imposex to some degree, which we referred to as 'effect of male structure'. Finally, we put forward a general classification scheme of imposex with an integrated system of aims, criteria, stages, types (subtypes), pathways and mechanisms of imposex.

Water color, often quantified using the Forel-Ule Index (FUI), is a crucial parameter for assessing the water quality and ecological health of coastal waters. However, there is limited research on the spatiotemporal variations of FUI and the associated influencing factors in the Bohai and Yellow Seas. In this study, we utilized multi-sensor satellite datasets to retrieve monthly FUI products for the Bohai and Yellow Seas spanning the period from September 1997 to December 2019. Subsequently, we examined significant spatial disparities and variations across multiple timescales in the remotely sensed FUI time series. The climatological annual mean FUI map reveals a decreasing trend from nearshore to offshore regions, with similar spatial patterns observed in terms of overall and interannual FUI variability. The annual variations in wind field, sea surface temperature (SST), and ocean stratification play a key role in the seasonal dynamics of FUI by modulating the sediment resuspension process, resulting in low FUI values in summer and high FUI values in winter. Linear regression analysis of FUI anomaly indicates a long-term decreasing trend in FUI for the three bays of the Bohai Sea, while upward trends in FUI predominantly prevail in the central Yellow Sea. Factors related to interannual FUI variations, such as surface winds, SST, river outflow, rainfall, and anthropogenic activities, are qualitatively discussed. The findings of this study provide the first comprehensive evaluation of water color variations and their underlying mechanisms in the Bohai and Yellow Seas.

With the support of Geographical Information System (GIS) technique, boundary of watershed and estuarine drainage areas for fifteen major rivers discharge into coastal waters in China was defined in this study so as to provide the basic geospatial data for further eco-regionalizing and classifying estuarine and coastal waters in China. Using the Hydrology module in ArcGIS environmental, sub-watersheds for fifteen rivers discharge into coastal waters in China were delineated, represented by different spatial levels with five thresholds’ values. Boundary of watershed for fifteen rivers discharge into coastal waters was further delimited, which was verified by the deviation error of delineated areas in this study with other literatures, all within 10%. Forty-one units of estuarine drainage areas were finally defined based on the data regarding spatial distribution of tidehead for fifteen rivers and sub-watersheds delineated before.

China's coastal waters, including the Bohai Sea, the Yellow Sea, the East China Sea and the South China Sea, are rich in marine resources and of strategic importance to the nation’s economic development. However, in recent years, the problem of water safety caused by algae and algal toxins is becoming more and more serious, with the frequency and scale of harmful algal blooms are escalating in China's coastal waters. This dataset collected and organized the survey data of toxic and harmful microalgae and algal toxins in China's coastal waters from 2019 to 2021, containing 3,429 entries of microalgae data, 33,240 entries of microalgae molecular species data, 489 entries of phytoplankton algal toxin data, 76 entries of seawater algal toxin data and 440 entries of economic species algal toxin data. The research teams providing the data ensured the accuracy of the test data through rigorous inter-project and international collation efforts. In order to display the distribution of toxic and harmful microalgae and algal toxins in China's coastal waters, we included 115 microalgae distribution maps and 29 algal toxin distribution maps in the dataset. This dataset can provide data support for studying the spatial and temporal distribution of toxic and harmful microalgae and algal toxins in China's coastal waters, and offers valuable data support for the prevention, warning and control of harmful algal blooms.

China's coastal seawater environment caused by urbanization based on the seawater environmental Kuznets curve

Perfluorinated compounds (PFCs), such as perfluorooctane sulfonate (PFOS), have been identified in the coastal waters of China and Japan. An alkaline digestion method, coupled with solid-phase extraction (SPE), and high-performance liquid chromatography interfaced with high-resolution electrospray tandem mass spectrometry was developed to determine PFCs in mussel and oyster samples from coastal waters of South China and Japan. These techniques produced adequate recoveries and reporting limits with small quantities of PFCs. Concentrations of individual PFCs in mussels and oysters from South China and Japan ranged from 113.6 to 586.0 pg/g, wet weight (ww) for PFOS, 63.1 to 511.6 pg/g, ww for perfluorohexane sulfonate, 9.3 to 30.1 pg/g, ww for perfluorobutane sulfonate and 37.8 to 2957.0 pg/g, ww for perfluorooctane sulfonamide. The quantification of perfluorinated carboxylates was compromised by interferences from carboxylates in the procedural blanks. Perfluoroundecanoate and perfluorononanoate had relatively great blank interferences, which resulted in relatively poor limits of quantification for these compounds. Some PFCs were only identified in a limited number of samples: perfluorododecanoate in samples from Tokyo Bay, Japan (195.9 pg/g, ww); and perfluorodecanoate in Fuzhou, China (131.7 pg/g, ww) and Tokyo Bay (118.6 pg/g, ww). The greatest concentrations of perfluorooctanoate, perfluoroheptanoate, and perfluorohexanoate were observed in samples from Tokyo Bay and Bei Hai, South China.

The health of an ecosystem and the quality of water can be determined by the clarity of the water. The Persian Gulf and Oman Sea have a unique ecosystem, and monitoring their water clarity is necessary for sustainable development. Here, various criteria such as hue angle, chlorophyll-a, Forel-Ule index, organic carbon (OC), precipitation, sea surface salinity (SSS), Secchi disk depth (SDD), and sea surface temperature (SST) were analyzed from 2002 to 2018 using MODIS-Aqua Imagery, statistical tests, and deep learning (DL) models to monitor the water clarity of the Persian Gulf and the Oman Sea. The study found differences in criteria across different regions, with coastal areas showing higher Forel-Ule index and chlorophyll-a values. Positive trends in the Persian Gulf and the Oman Sea were attributed to the Forel-Ule index and OC, while negative trends were seen in SSS and SST in the Persian Gulf. The convolutional neural network (CNN) model was found to perform better than long short-term memory (LSTM) in predicting water clarity. Interpretation techniques were used to determine the importance of criteria in monitoring water clarity, with the Forel-Ule index, hue angle, and OC showing the greatest interaction. Sensitivity analysis revealed that chlorophyll-a and SSS had the most significant impact on water clarity prediction. Overall, this study using DL models and MODIS-Aqua Imagery can help improve water quality and protect the environment.

Salinity-dependent aquatic life criteria of inorganic mercury in coastal water and its ecological risk assessment

The genetic relationships of mantis shrimp Oratosquilla oratoria between the coastal waters of China and Japan were not well studied. To reveal the genetic differentiation and genetic structure among populations, we collected populations of mantis shrimp O. oratoria from the coastal waters of China and Japan to analyze the mtDNA control region variation. A total of 309 individuals of O. oratoria were collected from 13 localities (11 from China and 2 from Japan) and a segment of mitochondrial DNA control region was sequenced. Three hundred nine haplotypes were defined, yielding a very high haplotype diversity and nucleotide diversity. Two lineages of O. oratoria were revealed and displayed strong differences in the geographical distribution. In the coastal waters of China, the geographic distribution of the two lineages was completely separated by the Yangtze River estuary; however, the lineages showed geographic sympatry in two populations from Japan. Based on the lineage distribution, three groups were defined. There was no significant genetic differentiation among the populations within the three groups, indicating high gene flow within each group. Significant and negative values for Tajima D and Fu's Fs tests, and mismatch distributions for two lineages indicated population expansion. The present result confirmed that the freshwater outflow from the Yangtze River formed a physical barrier and affected gene exchange. The different distribution patterns of the two lineages in coastal waters of China and Japan indicated that the larvae of O. oratoria were transferred from China to the coastal waters of Japan with a one-way gene flow.

Earth observation reveals the shifting patterns of China's lake colour driven by climate change and land cover

Between the years 1933–2001, 460 red tide events were found in China's coastal water. The scope of red tide occurrence has extended over all the coastal provinces of China, and the three major areas with high red tide frequency are the Bohai sea, the sea area near the Shengsi Archipelago and Huaniaoshan Island on the outer side of the Changjiang River estuary and the Hangzhou Bay, and the coastal waters on the east side of the Zhujiang River estuary from Hong Kong to East Guangdong. In the past 20 years, the frequency of red tides has been tending upwards. The years of 1988–1990 and 1998–2001 saw the most serious red tides along China's coastal waters, with the latter period as the peak. The average area of a single red tide, i.e., the scale of red tides, is expanding every year, and in 2001 rose to about 500 km2. Every year, China's red tides occur from south to north, with those in the South China Sea occurring from March to May, those in the East China Sea from April to August and those in the Bohai and Huanghai Seas from May to September.

Typhoon waves possess significant destructive potential, and their numerical simulation relies on accurate sea surface wind fields. An evaluation of different combinations of the radial air pressure distribution coefficient B and the radius of maximum wind speed (Rmax) in the Holland wind field (HWF) model was conducted to determine the optimal configuration. The HWF and the ERA5 wind field (EWF) were used as input wind fields to drive the typhoon wave model for China’s coastal waters. Validation results indicated that neither wind field accurately reflected real conditions; therefore, a hybrid wind field (HBWF) was created by combining HWF and EWF using weighting coefficients that vary with the radius of wind speed to enhance accuracy. Simulation results showed that the HBWF improved the accuracy of significant wave heights (SWHs), with a mean relative error of 25.29%, compared to 32.48% for HWF and 27.94% for EWF. Additionally, HBWF also demonstrated the best performance in terms of root mean square error (RMSE) and consistency index. Overall, the HBWF enhances the simulation accuracy of typhoon waves in China's coastal waters.

福建中部近海浮游动物数量分布与水团变化的关系

Mercury concentrations in China's coastal waters and implications for fish consumption by vulnerable populations

The surface nutrients in China's coastal waters in the winter of 2025.