China Sea Coast Research Articles

Plutonium in the coastal seawater around Chinese nuclear power plants: Sources, distribution, and environmental implications

Coastal surface seawater samples within 30 km around ten Chinese nuclear power plants (NPPs) were systematically investigated. The 239+240Pu activity concentration in the samples varied from 0.226 mBq/m3 to 3.098 mBq/m3, meanwhile the 240Pu/239Pu atom ratios ranged from 0.151 to 0.353. Besides, the Pacific Proving Ground (PPG) close-in fallout and the global fallout were recognized as two primary sources of Pu in these samples. The 239+240Pu activity concentration as well as the PPG contribution showed similar trends as the Kuroshio intrusion path and the coastal currents in the China Seas, illustrating long-range transport and consuming of PPG derived Pu in the coastal China Seas. Moreover, accumulation of PPG sourced Pu in the Beibu Gulf were observed and was attributed to the continuous invasion of the high isotopic Pu that remobilized from the South China Sea (SCS).

Abundant small microplastics hidden in water columns of the Yellow Sea and East China Sea: Distribution, transportation and potential risk

Microplastics (MPs) pose significant concerns for marine ecological security due to their minuteness and ubiquity. However, comprehensive knowledge on their distribution and fate in seawater columns remains limited. This study investigated the abundances and characteristics of MPs across 3–6 water layers in the South Yellow Sea and East China Sea. Results indicate that high-abundance small MPs (< 100 µm) (average 6567 items/m3) were hidden beneath the sea-surface, predominantly fine-grained particles (< 20 µm) and high-density polymers (> 1.03 g/cm3). The total suspended MPs (5.0–834.2 µm) are estimated at 2.9–3.1 × 1017 particles, with most of them occurring in upper layers. In profiles, their distribution varied by physical properties with depth; fragment-shaped and high-density MPs increased in proportion at greater depths, contrasting with fibrous MPs. These MPs originated primarily from the Yangtze River and their winter transport was driven by the Yangtze River Dilution Water, East China Sea Coastal Current, and Yellow Sea Warm Current, resulting in their accumulation in coastal and estuarine regions. Consequently, the Yangtze River Estuary ecosystem faces substantial risks from MP pollution throughout the water column. This work unveils the prevalence of small MPs in coastal water columns and intricate interaction between their fate and hydrodynamic conditions.

Tidal and residual currents in the inner shelf of East China Sea detected from underway ADCP observations

Characterizing the spatial variability of net flow transport in a tide-dominated area like the East China Sea (ECS) is key to understanding the material and heat budget as well as their impacts on local ecosystem. However, the residual circulation in the ECS was much less confirmed by observations as it can only be derived from very sparse mooring data. Here for the first time we obtain the spatial patterns of tidal and residual currents in the inner ECS shelf from ADCP underway measurements conducted in 12 cruises using a spatial least squares (SLS) fitting technique. The SLS method is validated with the traditional harmonic analysis using numerical simulation results and then implemented with the observational data. The tidal current is dominated by two semidiurnal components M2 and S2 in this area, with the major axis of tidal ellipse along northwest-southeast direction. The ADCP-derived tide parameters are in good agreement with those from the mooring data and barotropic tide model. The annual spatial pattern of residual circulation is characterized by a southward coastal current and a northward shelf current, which are identified as the East China Sea Coastal Current (ECSCC) from Changjiang River runoff and the Taiwan Warm Current (TWC) originated from Taiwan Strait and Kuroshio. Their magnitudes are comparable but of one order smaller than tides. The vertical structure of TWC shows a subsurface-intensified feature in line with previous mooring observations. The north limit of TWC is approximately at 31.5°N around the submerged valley, beyond which the northward TWC becomes almost invisible. By a series of virtual cruise experiments, we show that the observation data length is the most crucial factor controlling the SLS fitting accuracy, while the role of other factors like sampling frequency is secondary. With a fixed-length dataset, the degree of polynomial function used for SLS fitting must be properly determined to minimize the under-fitting and over-fitting error, and there is also a trade-off in the fitting accuracy between tidal and residual currents depending on the fitting strategy.

Deciphering and quantifying nitrate sources and processes in the central Yellow Sea using dual isotopes of nitrate

Anthropogenic activities pose significant challenges to the accumulation of coastal nitrogen (N). Accurate identification of nitrate (NO3−) sources is thus essential for mitigating excessive N in many marginal seas. We investigated the dual isotopes of NO3− in the central Yellow Sea to elucidate the sources and cycling processes of NO3−. The results revealed significant spatial variability in NO3− concentrations among the Yellow Sea Surface Water (YSSW), Changjiang Diluted Water (CDW), Yellow Sea Cold Water Mass (YSCWM), and Taiwan Warm Current Water (TWCW). Stratification played a crucial role in restricting vertical nutrient transport, leading to distinct nutrient sources and concentrations in different water masses. The dual NO3− isotopic signature indicated that atmospheric deposition was the primary source of surface NO3−, contributing approximately 30 % to the NO3− in the YSSW. In the NO3−-rich CDW, the heavier δ15N-NO3− and δ18O-NO3− suggested incomplete NO3− assimilation. Organic matter mineralization and water stratification played crucial roles in the accumulation of nutrients within the YSCWM and TWCW. Notably, regenerated NO3− accounted for approximately half of the NO3− stored in the YSCWM. A synthesis of NO3− dual isotope data across the coastal China seas revealed significant spatial and seasonal variations in the N source. The study emphasized the dynamics of coastal NO3− supply, which are shaped by the complex interconnections among marine, terrestrial, and atmospheric processes. Our approach is a feasible method for exploring the origins of N amidst the escalating pressures of anthropogenic nutrient pollution in coastal waters.

Functional genes and microorganisms controlling in situ methylmercury production and degradation in marine sediments: A case study in the Eastern China Coastal Seas

Dominant microorganisms and functional genes, including hgcA, hgcB, merA, and merB, have been identified to be responsible for mercury (Hg) methylation or methylmercury (MeHg) demethylation. However, their in situ correlation with MeHg levels and the processes of Hg methylation and MeHg demethylation in coastal areas remains poorly understood. In this study, four functional genes related to Hg methylation and MeHg demethylation (hgcA, hgcB, merA, and merB) were all detected in the sediments of the Eastern China Coastal Seas (ECCSs) (representative coastal seas highly affected by human activities) using metagenomic approaches. HgcA was identified to be the key gene controlling the in situ net production of MeHg in the ECCSs. Based on metagenomic analysis and incubation experiments, sulfate-reducing bacteria were identified as the dominant microorganisms controlling Hg methylation in the ECCSs. In addition, hgcA gene was positively correlated with the MeHg content and Hg methylation rates, highlighting the potential roles of Hg methylation genes and microorganisms influenced by sediment physicochemical properties in MeHg cycling in the ECCSs. These findings highlighted the necessity of conducting similar studies in other natural systems for elucidating the molecular mechanisms underlying MeHg production in aquatic environments.

Spatiotemporal Expansion of Algal Blooms in Coastal China Seas.

The coastal seas of China are increasingly threatened by algal blooms, yet their comprehensive spatiotemporal mapping and understanding of underlying drivers remain challenging due to high turbidity and heterogeneous water conditions. We developed a singular value decomposition-based algorithm to map these blooms using two decades of MODIS-Aqua satellite data, spanning from 2003 to 2022. Our findings indicate significant algal activity along the Chinese coastline, impacting an average annual area of approximately 1.8 × 105 km2. The blooms exhibit peak intensity in August, while the maximum affected area occurs in September, featuring multifrequency outbreaks in spring, and pronounced large-scale events in summer and autumn. Notably, our analysis demonstrates a robust 67% increase in bloom occurrences over the study period. This expansion is primarily attributed to increased nutrient inflow from terrestrial sources linked to human activity and precipitation, compounded by rising global sea surface temperatures. These spatiotemporal insights are critical for devising effective management strategies and policies to mitigate the impacts of algal blooms.

Considering species functional and phylogenetic rarity in the conservation of fish biodiversity

AbstractAimRare species make substantial contributions to coastal ecosystem functions. Functional rarity (FR) and phylogenetic rarity (PR) are important features for biodiversity conservation. This work aimed to discuss the necessity and reasonableness of conserving fish FR and PR in coastal seas.LocationChina.MethodsBy compiling historical fish investigation data, joint species distribution modelling (JSDM) was applied to model fish communities in coastal China Seas. Biogeographic patterns of FR and PR were explored, and the effectiveness of current MPA networks in terms of match/mismatch with the hotspots of rarity was assessed.ResultsA total of 44 functionally rare species and 22 phylogenetically rare species were identified. Six of these species were both functionally and phylogenetically rare, and only one was listed as endangered on the Red List of the International Union for Conservation of Nature (IUCN). Functional rarity hotspots covered 10.27% of the coastal areas, which geographically converged in the southern and eastern coast of Taiwan, the Yangtze River Estuary and the Yellow River Estuary. Phylogenetic rarity hotspots only covered 3.06% of the coastal areas, which were sporadically distributed in the coastal East China Sea, the Bohai Sea and the northern Yellow Sea. Current marine‐protected areas (MPAs) only represented 16.16% of the FR hotspots and 20.48% of the PR hotspots, indicating substantial mismatched areas between the MPAs and the hotspots of FR and PR.Main ConclusionsOnly considering threatened species in conservation practices will omit functionally and phylogenetically rare species because FR and PR are not necessarily correlated with species threat status on the IUCN Red List. Functional rarity hotspots do not necessarily overlap with PR hotspots, and current MPAs mismatch the majority of these areas. We therefore advocate that conservation prioritization and expansion of MPA networks should account for FR and PR both at the species and site levels.

Optimizing efficiency and resilience of no-take marine protected areas for fish conservation under climate change along the coastlines of China Seas.

Climate change is one of the major threats to coastal fish biodiversity, and optimization of no-take marine protected areas (MPAs) is imminent. We predicted fish redistribution under climate change in coastal China Seas with joint species distribution modeling and prioritized areas for conservation with Zonation, for which we used core area zonation (CAZ) and additive benefit function (ABF). Based on our results, we devised an expansion plan of no-take MPAs. Under climate change, fish were redistributed northward along the coast. These redistributions were segmented by the Yangtze River estuary and its adjacent waters, indicating a possible biogeographical barrier. Under CAZ and ABF, significantly more fish habitat was conserved than under random prioritization (p<0.001, Cohen's d=-0.36 and -0.62, respectively). The ABF better represented areas with higher species richness, whereas CAZ better represented core habitats for species with narrow distributions. Without accounting for species redistribution, the expanded MPAs were mainly distributed in the northwest of the South China Sea, the East China Sea, the north of the Yellow Sea, and the west of the Bohai Sea. When accounting for species redistribution, the proposed MPAs were mainly distributed in the north of the Bohai Sea and southwest of the Yellow Sea, corresponding to the northern species redistributions. These MPAs conserved less habitat for fishes at present but protected more and better quality habitat for fishes in 2050 and 2100 than those MPAs that did not account for species redistribution, indicating improved fish conservation under climate change. Incorporating species redistribution and trade-offs between areas with high species richness and areas that contain habitats for rare species are suggested to address coastal fish conservation under climate change. This work provides valuable information for fish conservation and is a precursor to systematic conservation planning along the coastlines of China Seas.

Seawater quality criteria and ecotoxicity risk assessment of zinc oxide nanoparticles based on data of resident marine organisms in China

Water quality criteria (WQC) for zinc oxide nanoparticles (ZnO NPs) are crucial due to their extensive industrial use and potential threats to marine organisms. This study conducted toxicity tests using marine organisms in China, revealing LC50 or EC50 values for ZnO NPs ranging from 0.36 to 95.6 mg/L across seven species, among which the salinity lake crustacean zooplankton Artemia salina exhibited the highest resistance, while diatom Phaeodactylum tricornutum the most sensitive. Additionally, the EC10 or maximum acceptable toxicant concentration (MATC) values for ZnO NPs were determined for five species, ranging from 0.03 to 2.82 mg/L; medaka Oryzias melastigma demonstrated the highest tolerance, while mysis shrimp Neomysis awatschensis the most sensitive. Based on the species sensitivity distribution (SSD) method, the derived short-term and long-term WQC for ZnO NPs were 138 μg/L and 8.37 μg/L, respectively. These values were further validated using the sensitive species green algae Chlorella vulgaris, confirming effective protection. There is no environmental risk observed in Jiaozhou Bay, Yellow River Estuary and Laizhou Bay in the northern coastal seas of China. This study provides important reference data for the establishment of water quality standards for nanoparticles.

Causes of 2022 summer marine heatwave in the East China Seas

Recent occurrences of marine heatwaves (MHWs) in coastal China seas have caused serious impacts on marine ecosystem services and socio-economics. Nevertheless, the underlying physical process, including local drivers and remote associations, remains poorly understood, thereby hindering accurate predictability. In this study, we reported an extreme MHW event in the East China Seas (ECSs, including the Bohai, Yellow, and East China Sea), lasting for 75 d with a maximum intensity of 1.96 °C relative to 1982–2011 during the summer 2022. This ECSs MHW event was triggered by a combination of anomalous atmospheric and oceanic conditions, including enhanced insolation, weakened surface wind speed, suppressed latent heat loss from ocean, a shallower mixed layer, and upper ocean current anomaly. Mixed-layer temperature budget diagnosis suggested that changes in the ECSs temperature were dominated by the surface net heat flux, largely due to strong shortwave radiation flux, during the development and decay of the MHW event. Oceanic advection also created favorable conditions for the maintenance of the MHW. These physical drivers were further regulated by the westward expanded and intensified western Pacific subtropical high (WPSH), potentially linked to the negative phase of Indian Ocean Dipole (IOD). Despite the three years (2020–2022) consecutive La Niña events, the ECSs summer MHWs appeared to be more closely linked to negative IOD events, with a lagging period of 1–3 mon. The seasonal precursor signals of the negative IOD have the potential to affect local physical drivers of ECSs MHWs through regulating the strength and position of WPSH, thus serving as a promising predictor for the ECSs MHWs. The future likelihood and intensity of the ECSs MHWs are projected to increase substantially in the coming decades, largely due to broad-scale warming attributed to anthropogenic climate change. Consequently, there is an urgent need to develop MHW forecasting and early warning systems, and robust approaches to address climate change.

South China Sea: Battle of the Diplomatic Notes among China and Non-Claimant States

Abstract The South China Sea disputes are becoming increasingly tense with more and more countries expressing their views on legal issues and actions of claimant Statess in the South China Sea. In December 2019, Malaysia deposited a partial submission to the United Nations Commission on the Limits of the Continental Shelf to establish the limits of its extended continental shelf beyond 200 nautical miles in the northern part of the South China Sea. The submission sparked a new legal battle of diplomatic notes with the participation of South China Sea coastal States which can also be regarded as claimant States in the contet of the South China Sea disputes (Brunei, China, Malaysia, the Philippines and Viet Nam) as well as non-claimant States (Australia, France, Germany, Indonesia, Japan, New Zealand, the United Kingdom and the United States). Following the article “South China Sea: New Battle of the Diplomatic Notes among claimants in 2019–2021” published in the Asia-Pacific Journal of Ocean Law and Policy 6 (2021), this paper provides an analysis of the exchange of diplomatic notes between China and non-claimant States with the aim of understanding the impact of these exchanges on the prospect for the peaceful settlement of the maritime disputes in the South China Sea.

A historical overview of water quality in the coastal seas of China

Using historical data, long-term variations in pollutant sources and water quality in China’s coastal waters over the last three decades are reviewed. The results show that the total area of non-clean water, which reflects state of total water quality, increased rapidly before 2000, but then underwent two stages of decline, with a modest decline by one-quarter between 2001 and 2015, followed by a sharp decline of more than half of that in 2015 since then. Consequently, water quality at present is better than it was at the beginning of the 1990s. The total area of polluted water fluctuated without any trend from the end of the 1990s until 2015, but has declined sharply by nearly two-thirds since 2015, indicating that the water quality in China’s coastal seas has improved substantially. Geographically, the Bohai Sea was the first to see a turning point in water quality, followed by the Yellow Sea and East China Sea, while the South China Sea was the last. The main pollutants that govern the water quality grade and area are dissolved inorganic nitrogen and phosphate as well as petroleum hydrocarbons. As a response to variations in water quality, changes in both the frequency and total area affected by harmful algal blooms were similar to those of water quality over the last three decades, albeit with a slight lag. Analysis showed that variations in water quality were closely related to the land- and sea-sourced pollutant inputs. The combination of shift in the mode of economic growth from high-speed growth to high-quality development and the enforcement of the new, strictest ever Environmental Protection Law resulted in a significant decline of pollutant emissions, inducing a turning point in the water quality in the coastal seas of China in the mid-2010s.

Estimations of Secchi depth from the turbid Eastern China Coastal Seas using MODIS data

ABSTRACT In this study, a neural network-based Secchi depth retrieval model (NNSD) was developed using observations obtained during 2003–2012 in the Bohai, Yellow, and China East Seas (Eastern China Coastal Seas, ECCS). Based on the results of the analyses, the NNSD model produced less than 25% uncertainty in quantifying the Secchi depth in the optically complex ECCS. The slope of the linear relationship between the field-measured and NNSD model-derived Secchi depth varied from 0.98 to 1.08 among the datasets. However, the corresponding determination coefficients were not any lower than 0.91. To determine the effectiveness of the NNSD model in deriving the Secchi depth in the ECCS, the performances of the three existing models were also evaluated, and the results are presented in this study. By comparison, using the NNSD model decreased the uncertainty by 26% when compared with the three existing models in deriving the Secchi depth in the ECCS. Finally, the NNSD model was further applied to the MODIS data over the ECCS to briefly illustrate its applicability to general oceanographic studies. The NNSD model could produce 24.62% MRE and 0.14 RMSE values in deriving the Secchi depth from the ECCS, which was > 26% MRE and > 0.07 RMSE values better than all the BGSD, KDSD and SASD models. In regards to the spatial distribution pattern of the Secchi depth, the eastern and northern sections of the ECCS were much higher than the western and southern areas. Additionally, the temporal distribution mode indicated that the winter season was higher than the summer season. These spatiotemporal characteristics were caused primarily by the regional climate, river discharges, and strong tidal currents and winds, among other factors.

The impact of ocean acidification on the eye, cuttlebone and behaviors of juvenile cuttlefish (Sepiella inermis)

The cuttlefish (Sepiella inermis) is an economically important species in the coastal seas of China. The impacts of ocean acidification on the ability of juvenile cuttlefish to select a suitable habitat, its hunting and swimming behavior, remains unknown. We examined behavior-related responses and the eye and cuttlebone structure of juvenile cuttlefish following short-term exposure to CO2-enriched seawater. The predation success rate decreased with the elevation in CO2 concentration. In the CO2 treatment groups, cuttlefish spent more time in the dark zone and the average swimming speed and total swimming distance significantly decreased. The structure of the retina and cuttlebone was affected by seawater acidification. Moreover, apoptotic cells were significantly increased in the eyes. In the wild, the impairment of the eye and cuttlebone may decrease the predation ability of juvenile cuttlefish and negatively affect their ability to select a suitable habitat, which would be detrimental to its population.

Variations in dissolved oxygen and aquatic biological responses in China's coastal seas

Coastal areas can represent an ecological transition zone with the function of biodiversity conservation, and good water quality is fundamental to maintaining this function. In this study, we analyzed data from 2011 to 2020 to reveal the variation in dissolved oxygen (DO) and the aquatic biological response in China's coastal seas. Results showed that DO in coastal waters exhibited an upward trend from 2011 to 2020 because of reduction in terrestrial anthropogenic pollutant (TAP) input. In comparison with DO in other seas, the DO content in the East China Sea was lower owing to higher TAP input, i.e., the proportion of DO of <5 mg L−1 accounted for approximately 60% of the total. Species numbers, density, and the species diversity index of phytoplankton, zooplankton, and macrobenthos were different in the different sea areas because phytoplankton, zooplankton, and macrobenthos have different responses to changes in DO. In comparison with the species numbers of zooplankton and macrobenthos, the species numbers of phytoplankton were more significantly related to DO, and showed a negative linear relationship with a better DO environment (DO ≥ 5 mg L−1; r2 = 0.39, p < 0.01) and positive correlation with a poor DO environment (DO < 3 mg L−1; r2 = 0.52, p < 0.01). A better DO environment is conducive to increased density of macrobenthos. Studies have shown that a good DO environment contributes to coastal ecosystem health, and continuous control of TAP input is an effective means of ensuring DO recovery.

Typhoon-induced destruction and reconstruction of the coastal current system on the inner shelf of East China Sea

Typhoons frequently occur in the East China Sea, which significantly affect the material transport, marine hydrodynamics, and sedimentary environment of coastal currents in a relatively short time scale. Based on the in-situ observation and satellite remote sensing data, this paper analyzes the influence of five typhoons on the coastal currents of East China Sea in 2019 during different seasons. The typhoons Lekima and Mitag, which passed directly, greatly influenced the coastal current, resulting in the disappearance of the tide signal, and stimulated the current to generate new periodic signals of 3–6 days and 1–3 days, respectively. Typically, the wind of Lekima changed the flow field of the East China Sea Coastal Current (ECSCC) from northeastward to southwestward in summer in a short period, and the southwestward volume transport of the ocean current was 4 times that during periods without typhoon occurrence. The remaining water levels of the Haimen, Jiantao, and Damutu tidal level stations showed maximum water level increases during the observation period, whose values were 1.89, 1.26, and 0.90 m, respectively. Mitag only caused a northeastward current transport during autumn, and the water levels of tidal level stations along the coast increased by more than 0.5 m. However, weak and distant typhoons (Danas, Lingling, and Tapah) caused relatively small changes in ocean currents, along with the corresponding change in water transport and deposition. The results show that local wind accompanying typhoons is the main factor affecting the evolution (destruction and reconstruction) of the coastal current system. Therefore, the evolution of the ECSCC under different typhoons can provide a more comprehensive understanding of the impact of typhoons with different paths and intensities on the coastal current.

Northward Expansion of a Warm-Water Doliolid Dolioletta gegenbauri (Uljanin, 1884) into a Temperate Bay, China

A warm-water doliolid species Dolioletta gegenbauri (Uljanin, 1884) was firstly recorded in Jiaozhou Bay (JZB) during the autumn of 2019–2020. As a warm-water species, its native habitat lies in the East China Sea Shelf, &gt;1000 km south of JZB. Distribution, abundance, stage composition, size frequency distribution, and relationships with environmental factors were studied. Both asexual and sexual reproduction stages were observed. Gonozooids generally dominated the population, indicating an active population development status. Abundance was significantly correlated to temperature. Water temperature in the two consecutive years was among the highest levels during the recent 3–4 decades. The continuous warming trends both in the China coastal seas and JZB likely expanded the biogeographic range. The sub branches of a boundary current, the Kuroshio Current, especially the Yellow Sea Warm Current, may play a central role during the northward extension. Moreover, its feeding, growth, reproduction, and recruitment could also be benefited from the neritic food environment. Finally, when the temperature dropped below 15 °C in the early winter, it disappeared in JZB. The seasonal expansion of D. gegenbauri in JZB could be facilitated by current transportation, warming, and the neritic environment.

Change in cephalopod species composition in the overexploited coastal China seas with a closer look on Haizhou Bay, Yellow Sea

Climate change and intensive fishing have affected not only population abundance, but also species composition. Cephalopods have been increasing in abundance in the world ocean under climate change due to their flexible life-history traits, including the over-exploited China Seas. Despite the increasing importance of coastal cephalopods in the China Seas, there have been no reports of changes in either species composition, nor the ecological roles of species with different life-history traits. Thus, this study first presents the changes in species composition of coastal cephalopods throughout the China Seas as summarized from fishery-independent survey reports over the last six decades. This is followed by an investigation of species composition of cephalopods in Haizhou Bay in the Yellow Sea. The ecological roles of two currently targeted cephalopods, Amphioctopus fangsiao and Loliolus spp. (Loliolus beka and Loliolus japonicus), are evaluated using an ecosystem model. The species composition of coastal cephalopods in the China Seas has changed since the 1960s, from species of large size and high value to small-size, low-value species. Cephalopod species composition in Haizhou Bay shows great seasonality, which is probably due largely to the characteristics of their life cycle. The population abundance of A. fangsiao and Loliolus spp. appear to be affected by ambient water temperature, and population distribution of Loliolus spp. seems to correlate with water depth. Occupying the highest trophic level in this ecosystem, A. fangsiao potentially displays strong top-down control over other organisms. Loliolus spp. are keystone species showing higher keystoneness in the autumn, owing to a low abundance of fish species which normally prey on them. The species-specific life-history traits and ecological roles of cephalopods are therefore important factors to consider in order to manage them effectively.

Evaluation and adjustment of the radiometric degradation of HY-1B satellite COCTS via a stable marine site

ABSTRACT The Chinese Ocean Color and Temperature Scanner (COCTS) on-board the Chinese second ocean color satellite, HY-1B, obtained approximately 6 years of data between 2007 and 2013 in China coastal seas and the adjacent waters. However, its radiometric performance has hardly been analyzed, which confuses its applicability in ocean remote sensing. This study tracked the long-term radiometric responsivity trend of HY-1B COCTS based on a stable marine target. Firstly, we identified a temporally stable maritime site of 12° ~ 15°N and 116°~119°E according to the water and atmospheric optical properties using Aqua MODIS products. Then, the time-series of top-of-atmosphere (TOA) reflectance was obtained for each band of HY-1B COCTS and Aqua MODIS over this site according to the criteria of sun-target-view geometry. Finally, exponential or linear degradation models were built and used to adjust the radiometric levels of HY-1B COCTS. Results indicate that the radiometric performance exhibited continuous degradation for all bands at varying levels between 0.4% and 8.1% yr−1. The worst degradation occurred at 412 nm, with an annual average rate of 8.1%. The degradation at 443 nm reached 5.5% yr−1 following 412 nm. The radiometric performance at 490 nm, 520 nm, and 565 nm was relatively stable with a drift of ~3% yr−1. The 670 nm, 750 nm, and 865 nm bands remain most stable with the degradation of ~1% yr−1. Taking Terra MODIS as a reference, the temporal consistency of HY-1B COCTS was significantly improved for each band after radiometric adjustment. Cloud-free imageries between 2007 and 2013 showed relatively high spatial consistency. The bias of TOA reflectance was ~5% in visible bands and ~10% in near-infrared bands after degradation correction. These improvements confirm the application potentials of HY-1B COCTS in ocean remote sensing.

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.