The long-term spatiotemporal changes of surface biogenic elements in the Changjiang River Estuary and adjacent waters during the summer of 2008−2016 were analyzed in this study. The concentrations of dissolved inorganic nitrogen (DIN), soluble reactive phosphate (${{\rm {PO}}_4^{3-}} $) and silicate (${{\rm {SiO}}_3^{2-}} $) were generally stable, with a slight decrease of DIN and ${{\rm {PO}}_4^{3-}} $, and a slight increase of ${{\rm {SiO}}_3^{2-}} $, which mainly occurred in the estuarine waters. The grey correlation analysis was carried out between biogenic elements and chlorophyll a (Chl-a). Results showed that compared with the absolute values of biogenic elements, the correlations between the concentration ratio of nitrogen to phosphorus (N/P), ratio of silicon to nitrogen (Si/N) and Chl-a were closer, indicating the important influence on phytoplankton by the structure of biogenic elements. The study area was generally in a state of potential P limitation, and could have potential impact on the phytoplankton community, triggering the shift of red tide dominant species from diatoms to dinoflagellates.

The sedimentary record of climate change in the Arctic region is useful for understanding global warming. Kongsfjord is located in the subpolar region of the Arctic and is a suitable site for studying climate change. Glacier retreat is occurring in this region due to climate change, leading to an increase in meltwater outflow with a high debris content. In August 2017, we collected a sediment Core Z3 from the central fjord near the Yellow River Station. Then, we used the widely used chronology method of ²¹⁰Pb, ¹³⁷Cs, and other parameters to reflect the climate change record in the sedimentary environment of Kongsfjord. The results showed that after the mid-late 1990s, the mass accumulation rate of this core increased from 0.10 g/(cm²·a) to 0.34 g/(cm²·a), while the flux of ²¹⁰Pb_ex increased from 125 Bq/(m²·a) to 316 Bq/(m²·a). The higher sedimentary inventory of ²¹⁰Pb_ex in Kongsfjord compared to global fallout might have been caused by sediment focusing, boundary scavenging, and riverine input. Similarities between the inventory of ¹³⁷Cs and global fallout indicated that terrestrial particulate matter was the main source of ¹³⁷Cs in fjord sediments. The sedimentation rate increased after 1997, possibly due to the increased influx of glacial meltwater containing debris. In addition, the ¹³⁷Cs activity, percentage of organic carbon (OC), and OC/total nitrogen concentration ratio showed increasing trends toward the top of the core since 1997, corresponding to a decrease in the mass balance of glaciers in the region. The results of δ¹³C, δ¹⁵N and OC/TN concentration ratio showed both terrestrial and marine sources contributed to the organic matter in Core Z3. The relative contribution of terrestrial organic matter which was calculated by a two-endmember model showed an increased trend since mid-1990s. All these data indicate that global climate change has a significant impact on Arctic glaciers.

Here, we report the results of high-resolution nitrate measurements using an optical nitrate profiler (in situ ultraviolet spectrophotometer, ISUS) along transect across a high-turbidity shelf (East China Sea) and a low-turbidity shelf (Chukchi Sea). The ISUS-measured nitrate concentrations closely reproduced the results measured by conventional bottle methods in low-turbidity waters. However, for high-turbidity waters of the East China Sea (salinity<30), a correction factor of 1.19 was required to match the standard bottle measurements. The high-resolution ISUS data revealed subtle spatial variability (e.g., a subsurface nitrate minimum) that may have been missed if based solely on bottle results. Four main structures of the nitracline on the East China Sea are apparent from the ISUS nitrate profile. High-resolution nitrate data are important for studying nitrate budgets and nutrient dynamics on continental shelves.

Marine sediments represent a major carbon reservoir on Earth. Dissolved organic matter (DOM) in pore waters accumulates products and intermediates of carbon cycling in sediments. The application of excitation-emission matrix spectroscopy (EEMs) in the analysis of subseafloor DOM samples is largely unexplored due to the redox-sensitive matrix of anoxic pore water. Therefore, this study aims to investigate the interference caused by the matrix on EEMs and propose a guideline to prepare pore water samples from anoxic marine sediments. The parameters determined by fluorescence spectra include 3D-index derived from EEMs after parallel factor analysis (PARAFAC), fluorescence index (FI) (contribution of terrigenous DOM), biological index (BIX) and humification index (HIX) derived from 2D emission spectra. First, we investigated the impacts of extensively-presented ions as typical electron acceptors, which are utilized by anaerobic microbes and stratified in marine sediments: Fe(II), Fe(III), Mn(II) and sulfide in anoxic pore water resulted in biases of fluorescent signals. We proposed threshold concentrations of these ions when the interference on EEMs occurred. Effective removal of sulfide from sulfide-rich samples could be achieved by flushing with N₂ for 2 min. Second, the tests based on DOM standard were further verified using pristine samples from marine sediments. There was a significant change in the fluorescence spectra of DOM in anoxic sediments from the Rhône Delta. This study demonstrated that the change was caused by oxidation of the matrix rather than the intrinsic alteration of DOM. It was confirmed by extracted DOM via both EEMs analysis and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Slight oxidation of sulfur-containing compounds (e.g., sulfhydryl) and polyphenol-like compounds occurred. Finally, a sample preparation sequence is proposed for pore water from anoxic sediments. This method enables measurement with small volumes of the sample (e.g., 50 µL in this study) and ensures reliable data without the interference of the redox-sensitive matrix. This study provides access to the rapid analysis of DOM composition in marine sediments and can potentially open a window into examining the carbon cycling of the marine deep biosphere.

The estuarine tapertail anchovy (Coilia nasus) is a high-value commercial fish. Estimating the spawning site or hatchery origin and habitat is essential for its conservation. This study aimed to determine the habitat use and life history characteristics of C. nasus from the Changjiang River Estuary. We investigated the environmental signatures of strontium (Sr) and calcium (Ca) in the otoliths of the collected specimens using electron probe microanalysis; additionally, we examined their gonadal maturity stage. Our results indicate that the 31 adult C. nasus specimens used in this study could be classified into two types based on their otolith Sr:Ca concentration ratios and their gonadal maturity stage. The long freshwater early life history type (Type LF) had wider central region in the otolith with low Sr:Ca concentration ratios ranging from 1.24±0.62 to 1.92±0.78 and a bluish pattern of low Sr content level. These fish are of riverine origin and had a relatively long early life history in freshwater and low gonadal maturation when captured. The short freshwater early life history type (Type SF) had a shorter central region in the otolith with low Sr:Ca concentration ratios ranging from 1.35±0.5 to 2.82±0.97 and a correspondingly bluish pattern. These fish also had a relatively short-term early life history in freshwater and high gonadal maturation when captured. The results of the otolith microchemical analysis indicated that Type LF and Type SF originated in spawning/hatching sites far from and close to the estuary, respectively. The mature gonads of Type SF fish indicated that they may breed in areas close to the estuary, whereas the immature gonads of Type LF fish indicated that they may breed in areas far from the estuary. This study is the first to reveal that the Changjiang River Estuary contains stocks of anadromous C. nasus originating in different spawning sites during the same season. The estuarine habitat plays a critical role in the connectivity between freshwater recruitment and the marine resources available to adult spawners of this commercially valued species. From a conservation perspective, this study provides important information for identifying anadromous C. nasus stocks originating in different spawning sites in the Changjiang River Basin.

The internal energy distribution of waves can be described using ocean-wave spectra. In many ways, obtaining wave spectra on a global scale is critical. Surface waves investigation and monitoring onboard the Chinese-French oceanography satellite is the first space-borne instrument for detecting wave spectra specially, which was launched on October 29, 2018. It can avoid the shortage of synthetic aperture radar detection results while still having some problems, especially with the effects of speckle noise. In this study, a method to suppress the speckle noise is proposed. First, the empirical formula for background speckle noise is established. Second, many spatio-temporal representative fluctuation spectra are classified and averaged. Third, rational transfer function filtering is used to obtain speckle noise close to the along-track direction. Finally, a signal-to-noise ratio threshold is used to suppress the abnormal speckle noise. This method solves the problems existing in previous denoising methods, such as excessive denoising in the along-track direction and the inability of some abnormal noises to be denoised in the two-dimensional directional wave spectra.

Pituitary gland, or pituitary for short, is characteristic of all vertebrates. As a “master gland” controlling a multitude of important functions in the body, its evolutionary origin has been an object of investigations of evolutionary biology for two centuries. Previous morphological, ultrastructural and immunohistochemical studies suggested the homology of the Hatschek’s pit of amphioxus and vertebrate pituitary. Developmental genetics study showed that the development of Hatschek’s pit and vertebrate pituitary is both subject to regulation by the common genes such as Pit1, Lhx3 and BMP3b. Our recent studies demonstrated that the Hatschek’s pit is able to secrete growth hormone (GH)-like hormone and thyroid-stimulating hormone (TSH)-like hormone that both play functions similar to vertebrate GH and TSH. We thus think that the emergence of Hatschek’s pit represents one of important events during endocrine network evolution, which laid a foundation for the subsequent formation of a hypothalamic-pituitary system in vertebrates.

The most important marine coastal ecosystem in the Chilean coast are kelp forests. This review is based on ecological studies regarding different aspects of subtidal kelp ecosystems along the Chilean coast. It highlights the most interesting findings in (1) biology of subtidal kelp in Chile, with particular reference to (2) habitats formed by kelp, and considered the successful examples and promising results in the (3) kelp as an industrial resource (Biotechnological approach of kelps and aquaculture). The impact caused by (4) El Niño-Southern Oscillation is discussed as an important climatic event that could help to forecast the future of the kelp ecosystem. In addition, this literature review outlines the knowledge gaps on subtidal kelp along the Southeast Pacific Coast of Chile, so that research can be strengthened in the future.

Based on long-term tide gauge observations in the last 60 years, the temporal and spatial variation characteristics of sea level change along the coast of China are analyzed. The results indicate that the sea level along the coast of China has been rising at an increasing rate, with an estimated acceleration of 0.07 mm/a². The rise rates were 2.4 mm/a, 3.4 mm/a and 3.9 mm/a during 1960–2020, 1980–2020 and 1993–2020, respectively. In the last 40 years, the coastal sea level has risen fastest in the South China Sea and slowest in the Yellow Sea. Seasonal sea levels all show an upward trend but rise faster in winter and spring and slower in autumn. Sea level change along the coast of China has significant periodic oscillations of quasi-2 a, 4 a, 7 a, 11 a, quasi-19 a and 30–50 a, among which the 2–3 a, 11 a, and 30–50 a signals are most remarkable, and the amplitude is approximately 1–2 cm. The coastal sea level in the most recent decade reached its highest value in the last 60 years. The decadal sea level from 2010 to 2019 was approximately 133 mm higher than the average of 1960–1969. Empirical orthogonal function analysis indicates that China’s coastal sea level has been changing in a north-south anti-phase pattern, with Pingtan and Fujian as the demarcation areas. This difference was especially obvious during 1980–1983, 1995–1997 and 2011–2013. The coastal sea level was the highest in 2016, and this extreme sea level event was analyzed to be related mainly to the anomalous wind field and ENSO.

Bathing beaches are usually the first to suffer disasters when tsunamis occur, owing to their proximity to the sea. Several large seismic fault zones are located off the coast of China. The impact of each tsunami scenario on Chinese bathing beaches is different. In this study, numerical models of the worst tsunami scenarios associated with seismic fault zones were considered to assess the tsunami hazard of bathing beaches in China. Numerical results show that tsunami waves from the Pacific Ocean could affect the East China Sea coast through gaps between the Ryukyu Islands. The Zhejiang and Shanghai coasts would be threatened by a tsunami from Ryukyu Trench, and the coasts of Hainan and Guangdong provinces would be threatened by a tsunami from the Manila Trench. The tsunami hazard associated with the Philippine Trench scenario needs particular attention. Owing to China’s offshore topography, the sequential order of tsunami arrival times to coastal provinces in several tsunami scenarios is almost the same. According to the tsunami hazard analysis results, Yalongwan Beach and eight other bathing beaches are at the highest hazard level. A high-resolution numerical calculation model was established to analyze the tsunami physical characteristics for the high-risk bathing beaches. To explore mitigating effects of a tsunami disaster, this study simulated tsunami propagation with the addition of seawalls. The experimental results show that the tsunami prevention seawalls constructed in an appropriate shallow water location have some effect on reducing tsunami hazard. Seawalls separated by a certain distance work even better. The analysis results can provide a scientific reference for subsequent preventive measures such as facility construction and evacuation.