Fajin Chen

Guangdong Ocean University · College of Ocean and Meteorology

Previous studies have primarily focused on the impact of human activities on coastal dissolved organic matter (DOM) cycles, while neglecting the role of dynamic processes. This limits our comprehensive understanding of the dynamic processes of coastal DOM, particularly in coastal waters affected by multiple dynamic processes. In this study, the dyn...

Nitrogen oxides (NO x ) in the atmosphere directly affect air quality; however, their oxidation products (e.g., nitrate) are essential nutrients in terrestrial and marine ecosystems. To date, the mechanism and rate of nitrate formation in the global-scale marine boundary layer remains uncertain. Herein, aerosol nitrate isotopes covering the global...

Based on on-site survey data from 26 stations in the surface seawater of Zhanjiang Bay in April (spring), July (summer), September (autumn), and December (winter) of 2017, the spatial distribution characteristics of chlorophyll a (Chl a) and nutrients in the surface seawater of Zhanjiang Bay in different seasons were analyzed, and the regulatory me...

The particulate nitrogen (PN) isotopic composition (δ¹⁵NPN) plays an important role in quantifying the contribution rate of particulate organic matter sources and indicating water environmental pollution. Estimation of δ¹⁵NPN from satellite images can provide significant spatiotemporal continuous data for nitrogen cycling and ecological environment...

Under the influence of many factors, such as climate change, anthropogenic eutrophication, and the development of aquaculture, the area and frequency of algal blooms have showed an increasing trend worldwide, which has become a challenging issue at present. However, the coupled relationship between nitrous oxide (N2O) and algal blooms and the under...

Typhoons can greatly alter the hydrodynamic and nutrient supply in coastal oceans. However, due to the complex conditions of typhoons, such as their intensity, even slight changes may cause substantial changes in hydrodynamics and nutrient supply, which needs to be better understood. In this study, we conducted two cruises before and after Typhoon...

Typhoons exert a profound impact on marine biogeochemical processes, with organic matter (OM) decomposition serving as a key biogeochemical process in coastal waters after typhoons. Despite its significance, the specific contributions of particulate organic matter (POM) and dissolved organic matter (DOM) to OM decomposition triggered by typhoons re...

The Ediacaran–Cambrian (E-C) transition (∼542–517 Ma) witnessed the rapid evolution of Cambrian animals, which was accompanied by carbon cycling anomalies and a significant increase in the concentration of oxygen in Earth’s atmosphere. The mechanisms stimulating the evolution of complex eukaryotes, however, remain problematic, especially concerning...

It has been currently recognized that air pollutants (e.g., carbon and nitrogen) from South and Southeast Asia have a significant impact on the coastal waters of the northern Indian Ocean. However, the understanding of dynamics and fates of these pollutants in aerosols to the remote ocean through long-distance transportation still needs to be impro...

Under global warming, the frequency and intensity of marine heatwaves are increasing. However, the inhibition of atmospheric-forcing marine heatwaves (AMHW) on upwelling and their impacts on marine ecosystems remain poorly understood. To address this issue, the satellite sea surface temperature and reanalysis data during 1998–2021 were analyzed in...

Past hydroclimatic conditions in southern China are poorly constrained owing to the lack of high-resolution marine-sediment records. In this study, we present high-resolution geochemical and grain-size records of marine sediments from the coastal shelf of the northern South China Sea to investigate regional hydrological variations. Results suggest...

The Luzon Strait is a channel where warmer Kuroshio water from the Pacific Ocean intrudes into the South China Sea (SCS). Under climate change impact, the temperature in marginal seas, including the SCS, rises faster than in open oceans. We speculated that the variation of frontal intensity and its eco‐environmental impact in the Luzon Strait may b...

Dual water isotopes were investigated to reveal the seasonal distribution of water masses and their impacts on nutrient supply in southern Beibu Gulf. In summer and winter, the South China Sea (SCS) water (61–69%) contributed the most to the seawater in the southern Beibu Gulf, followed by the diluted water (24–34%), and the west-Guangdong coastal...

The total organic carbon (TOC), total nitrogen (TN), black carbon (BC), δ 13 C TOC , δ 15 N, δ 13 C BC , grain size, and heavy metals of surface sediments collected from Daya Bay were determined to investigate the spatial distributions of these parameters and to evaluate the influences of human activities. Marine organic matter was found to constit...

The decline in ocean productivity has become a consensus due to the weakening vertical supply of nutrients to the upper ocean under global warming. However, ocean productivity in the subtropical gyres, regarded as ocean deserts, has increased over the past few decades. We speculated that the continuous increase in anthropogenic NO x emissions is th...

Typhoons and rainstorms (rainfall >250 mm day-1) are extreme weather events that seriously impact coastal oceanography and biogeochemical cycles. However, changes in the mixing of water masses and nutrient supply induced by typhoons and rainstorms can hardly be identified and quantified by traditional methods owing to the complex hydrological condi...

Typhoons are extreme weather events that can not only affect marine dynamics, but also change marine biogeochemistry, considerably impacting the climate. Based on the satellite remote sensing data, the upwelling of abundant nutrients induced by typhoons from deeper eutrophic water to the upper oligotrophic layer triggers phytoplankton blooms in the...

The Kuroshio Extension (KE) System exhibits highly energetic mesoscale phenomena, but the impact of mesoscale eddies on marine ecosystems and biogeochemical cycling is not well understood. This study utilizes remote sensing and Argo floats to investigate how eddies modify surface and subsurface chlorophyll-a (Chl-a) concentrations. On average, cycl...

The source information of coastal particulate organic carbon (POC) with high spatial and temporal resolution is of great significance for the study of marine carbon cycles and marine biogeochemical processes. Over the past decade, satellite ocean color remote sensing has greatly improved our understanding of the spatiotemporal dynamics of ocean par...

The Kuroshio Extension(KE) System exhibits highly energetic mesoscale phenomena, but the impact of mesoscale eddies on marine ecosystems and biogeochemical cycling is not well understood. This study utilizes remote sensing and Argo floats to investigate how eddies modify surface and subsurface chlorophyll (Chl-a) concentrations. On average, cyclone...

We recently reported that decomposition (as a carbon source) of organic matter (OM) is the dominant process in coastal waters after typhoons, which is contrary to phytoplankton blooms (as a carbon sink) in previous studies. However, the characteristics and mechanisms of typhoon‐induced decomposition and the question whether the decomposition mainly...

Since offshore waters are less affected by human activities and nutrient‐rich water masses, existing theories on periodic offshore blooms (POB) consider that the POB is proportional to the intensity of ocean fronts (nutrient supply from enhancing vertical mixing), ignoring external nutrient supply and external forcing (climatic oscillations). This...

The Devonian-Carboniferous (D-C) transition coincides with the Hangenberg Crisis, carbon isotope anomalies, and the enhanced preservation of organic matter associated with marine redox fluctuations. The proposed driving factors for the biotic extinction include variations in the eustatic sea level, paleoclimate fluctuation, climatic conditions, red...

Although great efforts have been made to decrease nutrient (notably nitrogen and phosphorus) loads and lighten related environmental damages, coastal eutrophication remains a persistent environmental crisis. To estimate whether the rapid development of the local economy has accelerated the eutrophication in Zhanjiang Bay, a newly developing industr...

The concentration of nitrogenous aerosols is influenced by air mass transition, local meteorological conditions, local emissions, and the wet removal effect driven by precipitation. Deposited nitrogenous aerosols influence nitrogen availability in the canopy, affecting the amount of plant carbon sequestration. However, the factors controlling nitro...

Few studies have incorporated the tools of stable isotopes and optical properties to study the biogeochemical process of organic matter (OM), including particulate organic matter (POM) and dissolved organic matter (DOM), which prevents our comprehension of the interactions between POM and DOM in the marine environment. In this study, the origin, di...

The assessment of nitrogen cycle processes in paleomarine and paleolake systems commonly relies solely on total nitrogen isotopes. If organic nitrogen and adsorbed nitrate can be effectively extracted from samples, the application of nitrogen isotopic systematics in different N forms would be beneficial for reconstructing the nitrogen cycle process...

Coastal upwelling along the northern South China Sea controls regional marine productivity and thereby influences blue economies. However, centennial-scale upwelling variability and its associated forcing mechanisms are poorly understood, primarily due to the lack of high-resolution upwelling records beyond the instrumental and historical periods....

Severe human activities in coastal areas have greatly impacted the sources and biogeochemical behaviors of organic matter (OM), including particulate OM (POM) and dissolved OM (DOM). However, few studies have incorporated the indices of POM and DOM to address this issue. Here, a dataset of the combination of stable isotopes of carbon and nitrogen i...

The issue of whether the increase in nutrients is supplied by increasing runoff or by enhancing upwelling in coastal marine ecosystems after a typhoon is considered controversial. This is because it is relatively difficult to quantify water mixing using traditional methods. Dual water isotopes in the northwestern South China Sea during Typhoon Wiph...

The decrease of river runoff caused by the intensified human activities (e.g. artificial dams) and increasing intrusion of high salinity water in the coastal bays have become a worldwide environmental problem. However, the mixing can hardly be identified by traditional method with temperature and salinity due to the complicated water sources in the...

Microplastic accumulation and resulting degradation are significant threats to the coastal ecosystems around the world. Baseline information on microplastics and their sources is of great importance for a permanent waste management system. The present study focused on the vertical distribution and characteristics of microplastics in the mid-interti...

The mixing of different water masses is important for local physical and biogeochemical processes as well as for ecosystems in the ocean. In this study, a new dataset of stable water isotopes (δD and δ¹⁸O) combined with temperature–salinity profiles was used to quantitatively understand the mixing of water masses in the Pearl River Estuary (PRE) an...

A new data set of seasonal stable water isotopes (δD and δ¹⁸O) and temperature‐salinity profiles was applied to improve our understanding of water mass distributions and their impact on the environment of the Beibu Gulf (BG). Our study revealed that the coastal current (CC), West‐Guangdong coastal current (WGCC), and South China Sea water (SCSW) we...

This study investigated the total concentrations and geochemical compositions of metals (Cd, Cr, Cu, Ni, Pb, Zn, Fe and Mn) in surface sediments of Zhanjiang Bay (ZJB) in spring and summer, to assess the contamination status, mobility and influencing factors of spatial-seasonal changes of these metals. The average total concentration for each studi...

Heavy metal pollution in the mariculture areas is of considerable attention due to its potential ecological effects and public concern for seafood safety. A better understanding of the current contamination status and historical trend of heavy metals in the ecosystems of mariculture areas has an important implication for the sustainable development...

The eutrophication degree in the coastal bay has been increasing significantly for the past years, due to the increasing nutrient discharge. However, the factors controlling sources and nitrogen (N) cycling in the different types of bays are still poorly understood. In this comparative study, nitrate dual isotopes ( δ 15 N − NO 3 − and δ 18 O − NO...

The Northwest Pacific Ocean (NWPO) is a significant sink for atmospheric CO2 but a paucity of large-scale phytoplankton surveys in the upper and lower euphotic zone results in uncertainties in estimates of the efficiency of the biological carbon pump there. Here, we report the spatial distribution of lipid biomarkers from diatoms (brassicasterol/ep...

Atmospheric ammonia (NH3) is a precursor of the ammonium (NH4⁺) in rainwater and aerosol. However, relations among them are largely unknown, which preventing our understanding from the sources and spatio-temporal variability of the NH4⁺ in rainwater and aerosol. Concentration and stable nitrogen isotope (δ¹⁵N) of NH4⁺ were measured in bulk depositi...

Dual isotope measurements were performed on nitrate (δ¹⁵N‐NO3⁻ and δ¹⁸O‐NO3⁻) in the Pearl River Estuary (PRE) and the adjacent northern South China Sea (NSCS) to investigate nitrate sources and its biogeochemical processes during rainy season. Our results indicated that in the PRE, high nitrate levels were associated with the intense human activit...

In this study, we present high-resolution δ¹⁵N records of organic nitrogen (δ¹⁵Norg) from the northern inner shelf of the South China Sea (SCS) to reveal nitrogen processes in the coastal environment over the last 7500 years. To remove the bias effect from inorganic nitrogen (IN), mainly terrestrial clay lattice-fixed ammonia, on total/bulk nitroge...

Microplastic (MP) was investigated in Zhanjiang Bay, a semi-enclosed bay in south China and famous for considerable mariculture industry, to evaluate whether mariculture activities accelerated MP pollution. The MP abundances ranged from 0 to 2.65 n/m³ (number/m³), showing seasonal variances with higher levels in May and September and lower levels i...

Dual nitrate isotopes (δ¹⁵N–NO3⁻ and δ¹⁸O–NO3⁻) and NO3⁻ concentration were measured in aerosol and precipitation in Zhanjiang, a tropical city in the southmost tip of China mainland, between November 2018 and October 2019. Measurements aimed to identify possible formation processes of NO3⁻, sources and the difference of dual nitrate isotope betwee...

The impact of typhoons on the ecology of the ocean has been observed using high‐accuracy satellite remote sensing data. However, few field observations in the ocean have been conducted to understand the effect of typhoons on the biogeochemistry because typhoon is furious, dangerous, and unpredictable. Here, we investigated the impact of Typhoon Wip...

Global climate change is an indisputable fact, and anthropogenic disturbances are the likely driving mechanisms; moreover, marginal seas tend to respond faster than the global ocean. In this study, the transit time distribution method was used to estimate the anthropogenic carbon (Cant) in the typical marginal seas along the west side of North Paci...

The upper-ocean physical and biochemical responses to sequential tropical cyclones (TCs) Kyarr and Maha in the Arabian Sea (AS) were investigated using data from satellites and Bio-Argo floats. Corresponding to slow and strong sequential TCs, two cooling processes and two short chlorophyll a (chl-a) blooms occurred on the sea surface, separated by...

Few systematic investigations use isotopic compositions (δ¹⁸O and δD) of seawater together with water temperature and salinity to trace the water dynamic processes in the upwelling area. This study presents depth‐specific δ¹⁸O, δD, salinity (S), and temperature data of water samples collected from the northwestern South China Sea (NWSCS) during spr...

Due to the intensive human activities and rapid economic development during the past few decades, the anthropogenic sourced nitrogen (N) input into coastal waters has increased dramatically. In this study, the net anthropogenic nitrogen input (NANI), including the deposition of atmospheric N, the application of N fertiliser, the fixation of biologi...

The Late Devonian Frasnian-Famennian (FF) transition at ca. 367 Ma was a key event in Phanerozoic Eon involving a massive biotic crisis, which coincided with a positive carbon isotope anomaly and large climate changes associated with eustatic fluctuations. The details underpinning the initiation of the mass extinction, however, remain problematic....

The El Niño–Southern Oscillation is one of the most important drivers of climate change on Earth, and is characterised by warmer (El Niño) or colder (La Niña) ocean surface temperatures in the equatorial Pacific. Tropical cyclones (TCs) and meridional circulation are the most influential weather events and climate phenomena, respectively. However,...

Surface currents play an essential role in the worldwide distribution of microplastics in the coastal seas and open oceans. As a branch of the western boundary currents (WBCs), Kuroshio changes seawater properties and pollutant levels of the South China Sea (SCS) during its intrusion process. To study the impact of Kuroshio intrusion on microplasti...

The δ¹³C, δ¹⁵N and C/N ratio of the particulate organic matter (POM) in western Guangdong waters were determined to evaluate the impacts of the coastal currents on the POM in spring and summer. The predominance of photosynthetic organic matter in the nearshore was triggered by nutrients brought by the coastal currents in spring and summer, while th...

Isotope measurements were performed on dissolved nitrate (NO3−) and ammonium (NH4+) in the coastal waters of the northeastern Beibu Gulf, China, to investigate the seasonal nitrate sources and their biogeochemical processes, which are due to the rapid development of local industrialisation and urbanisation. The high N/P ratio observed in the coasta...

In order to understand origin and fate of particulate organic matter, the isotopic composition (δ13C and δ15N), total organic carbon content, total nitrogen content, and C/N ratios were measured for suspended particulate organic matter (POM) collected from the northern South China Sea (NSCS) during summer. Our study revealed that δ13C generally dec...

Typhoons frequently induce algal blooms in the open ocean based on the satellite remote sensing data. However, the effects of typhoons on nearshore areas are not fully clarified due to the inaccessibility of in situ sampled data and the low accuracy of satellite data in the nearshore areas. To understand the biogeochemical and ecological changes in...

A comprehensive, depth specific (near‐surface to 3,700 m) water isotope (δD and δ¹⁸O) data set of 237 water samples collected from 20 different locations from the Northwest Pacific through the Luzon Strait to the Northern South China Sea (NSCS) are used to clarify the deeper understanding of water mass processes using δ¹⁸O‐salinity (S) and δD‐δ¹⁸O...

High‐resolution stalagmite oxygen isotope (δ¹⁸O) records are widely employed in palaeoclimate studies as indicators of East Asian Monsoon intensity in southern China. A key issue is whether the East Asian Monsoon or other factors control δ¹⁸O in precipitation in southern China, which requires modern observations to confirm. To understand which fact...

Abrupt climatic events and the history of human activities on Hainan Island are poorly understood, due to the lack of high-resolution records. We present high-resolution multiproxy records from the coastal shelf off eastern Hainan Island in China to investigate abrupt climate change and regional human–environment interaction over the last 7,000 yea...

We investigated the distributions of phosphate (PO4-P) and used the oxygen isotope composition of phosphate (δ¹⁸OP) to quantify PO4-P sources in the waters of Huangbai River. According to the environmental characteristics of Huangbai River basin, the sampling stations in the Huangbai River were divided into three groups: sampling stations in the ph...

The presence of polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethanes (DDTs) was determined in the sediments of Beibu Gulf, a newly developing industry and port in South China, to evaluate whether the rapid development of coastal cities has accelerated the organic pollution in the region. The levels of PCBs and DDTs ranged from 1.17...

In this study, the isotopic composition (δ13C and δ15N), total organic carbon content, total nitrogen content, and C/N ratios of suspended particulate organic matter (POM) in Zhanjiang Bay, which is a semi-enclosed bay with concentrated artificial activities in Southern China, were analyzed in order to investigate the seasonal variations in the pri...

The isotopic compositions (δ 13 C and δ 15 N) and C/N ratios of suspended particulate organic matter (POM) were investigated off the east coast of Hainan Island in the South China Sea during summer. Coastal upwelling influenced the nearshore stations of transects S2 and S3, and higher δ 13 C and δ 15 N values suggested that coastal upwelling played...

Using cruise observations before and after the typhoon Chebi in August 2013 and those without the typhoon in July 2012, this study investigates variations in current structure, nutrient distribution, and transports disturbed by a typhoon in a typical coastal upwelling zone east of Hainan Island in the northwestern South China Sea. The results show...

The tidal dynamics and the characteristics of pollutant migration in the drowned-valley tidal inlet, a typical unit of coastal tidal inlets, are strongly influenced by geomorphological features. Along with the development of society and the economy, the hydrodynamic and water quality environment of the tidal inlet is also becoming more disturbed by...

BIO-Argo float (chlorophyll a (Chl-a), temperature, and salinity profiles) and remote sensing data (Chl-a, photosynthetic available radiation (PAR), and wind) located south of the Kuroshio current near Shikoku from September 2018 to May 2019 were used to study phytoplankton bloom and their mechanisms of development in open oceans. Results show that...

Dichlorodiphenyltrichloroethane (DDT) is well known for its harmful effects and has been banned around the world. However, DDT is still frequently detected in natural environments, particularly in aquaculture and harbor sediments. In this study, 15 surface sediment samples were collected from a typical tropical bay (Zhanjiang Bay) in the South Chin...

During the Late Cretaceous period (~100.5–65 million years ago), two episodes of expansive lake anoxia occurred in the Songliao Basin (~3× the size of Lake Superior), NE China, either lasting less than one million years. These events, known as lacustrine anoxic events (LAEs), were the factors driving the development of the main source rocks for the...

The isotopic composition (δ¹³C and δ¹⁵N), organic carbon and nitrogen contents and C/N ratios of suspended particulate organic matter (POM) collected from the Pearl River Estuary and the adjacent shelf during spring and summer of 2017 were determined to understand the main controlling factors of spatiotemporal distribution and to elucidate the sour...

High-resolution Holocene marine sediment records are limited, which hampers our understanding of paleomonsoon evolution. Continental shelf sediment records are derived mainly from terrestrial weathering products and are thus often sensitive to paleoclimate variations. In this study, the grain size and magnetic mineral composition of a well-dated se...

The multiple and complex N sources in coastal upwelling areas make it difficult to understand the behaviour of the N cycle. Stable N and O isotopes (δ¹⁵N and δ¹⁸O) of nitrate (NO3⁻) from coastal upwelling off eastern Hainan Island in the South China Sea (SCS) identified the main NO3⁻ sources and the processes that control NO3⁻ distribution in the a...

The distribution of aerosols and their impacts on chlorophyll‐a (Chl‐a) distribution were studied in the South China Sea (SCS). Seventeen years of aerosol optical depth (AOD) data, Chl‐a concentration data, wind speed (WS), and sea surface temperature (SST) from satellite observations were employed along with 2 years of in situ aerosol total suspen...

Dissolved oxygen (DO) is one of the most important factors for maintaining a healthy marine ecosystem. The information of DO in large estuaries or bays with large entrances has been widely studied, while it is relatively limited for a bay with a narrow entrance which is vulnerable to human activities. The Zhanjiang Bay, located in the northwestern...

Nitrogen isotope of ammonium (δ¹⁵N-NH4 ⁺) in the wet deposition in Zhanjiang, a typical tropical city in the southernmost region of mainland China, were analyzed from October 2015 to November 2018 in order to examine the monthly variations and identify the sources of ammonia. The NH4 ⁺ exhibited higher concentrations during the dry season than the...

Upper ocean responses to the passage of sequential tropical cyclones over the northwestern South China Sea (SCS) in 2011 were investigated using satellite remote sensing data, Argo reanalysis data, and an array of mooring data. We found that the sea surface low temperature region lasted for more than 38 days and two phytoplankton blooms occurred af...

Nitrate (NO3−) dual isotope analysis was performed in Zhanjiang Bay, which is a closed bay with intensive human activities in South China, to investigate seasonal changes in the main NO3− sources and their biogeochemical processes in the monsoon-controlled climate. The relatively low N/P ratios in Zhanjiang Bay suggests that nitrogen (N) is a limit...