Microbial pterin biomolecules facilitate algal blooms in response to nutrient pressure in estuarine and coastal continuum.

Pterins are ubiquitous biomolecules synthesized by diverse phytoplankton, serve as pigments, cofactors, precursors, and redox sensors, playing crucial roles in ocean carbon fixation and nutrient cycling. However, the mechanisms driving their production, distribution, and fate in marine ecosystems are not well understood. This study examines the generation and behavior of microbial pterins in the Jiulong River Estuary, a system affected by nutrient-rich discharges.

Geographical and Environmental Factors Differentially Shape Planktonic Microbial Community Assembly and Resistomes Composition in Urban Rivers.

Global urbanization accelerates pollution challenges in urban rivers, including increased transmission of bacterial antibiotic resistance genes (ARGs), severely threatening the health of aquatic ecosystems and human health. Yet, systematic knowledge of differences in distribution and community assembly patterns of bacterial resistance across urban rivers at a continental scale is still insufficient. In this study, we conducted extensive sampling in nine representative urban rivers across China.

Inorganic nitrogen and phytoplankton dynamics in a subtropical reservoir during low-flow winter periods: Implications for nitrogen management.

The dynamics of nutrient cycling in inland waters, particularly during algal blooms, play a critical role in shaping aquatic ecosystems. However, the interaction between phytoplankton and inorganic nitrogen during low-flow periods remains poorly understood. This study presents high-frequency monitoring of ammonium (NH-N), nitrate (NO-N), nitrite (NO-N) and phytoplankton communities in a subtropical river-type reservoir during the low-flow winter period, characterized by blooms dominated by cryptophytes and green algae.

Harmful algal blooms in inland waters.

Harmful algal blooms can produce toxins that pose threats to aquatic ecosystems and human health. In this Review, we outline the global trends in harmful algal bloom occurrence and explore the drivers, future trajectories and potential mitigation strategies. Globally, harmful algal bloom occurrence has risen since the 1980s, including a 44% increase from the 2000s to 2010s, especially in Asia and Africa.

Drought reduces nitrogen supply and NO emission in coastal bays.

Severe droughts are increasingly prevalent under global climate change, disrupting watershed hydrology and coastal nitrogen cycling. However, the specific effects of drought on nitrogen transport from land to sea and subsequent nitrogen dynamics remain inadequately understood. In this study, we evaluated the consequences of the 2020-2022 drought on nitrogen supply and NO emissions in Xiamen Bay, Southeast China.

S-containing molecular markers of dissolved organic carbon attributing to riverine dissolved methane production across different land uses.

The emission of methane (CH) from streams and rivers contributes significantly to its global inventory. The production of CH is traditionally considered as a strictly anaerobic process. Recent investigations observed a "CH paradox" in oxic waters, suggesting the occurrence of oxic methane production (OMP).

Urbanization and greenhouse gas emissions from municipal wastewater in coastal provinces of China: Spatiotemporal patterns, driving factors, and mitigation strategies.

Coastal cities, as hubs of social and economic activity, have witnessed rapid urbanization and population growth. This study explores the transformative changes in urban municipal wastewater treatment practices and their profound implications for greenhouse gas (GHG) emissions in Chinese coastal provinces. The approach employed in this study integrates comprehensive data analysis with statistical modeling to elucidate the complex interplay between urbanization, wastewater treatment practices, and GHG emissions.

Seasonal hypoxia enhances sediment iron-bound phosphorus release in a subtropical river reservoir.

Dams worldwide commonly accelerate the eutrophication of reservoirs. While the seasonal hypoxia in deep reservoirs is widely acknowledged, there is limited research on its impact on benthic phosphorus (P) cycling and P fraction release from the reservoir sediments. Here we show that seasonal hypoxia enhances sediment P release and P fluxes at the sediment-water interface (SWI) which might alter P dynamics in deep reservoirs.

Assessing ammonium pollution and mitigation measures through a modified watershed non-point source model.

Watershed water quality modeling is a valuable tool for managing ammonium (NH) pollution. However, simulating NH pollution presents unique challenges due to the inherent instability of NH in natural environment. This study modified the widely-used Soil and Water Assessment Tool (SWAT) model to simulate non-point source (NPS) NH processes, specifically incorporating the simulation of land-to-water NH delivery.

Storm-induced nitrogen transport via surface runoff, interflow and groundwater in a pomelo agricultural watershed, southeast China.

The storm-induced export of nitrogen (N) from agricultural watersheds significantly impacts aquatic ecosystems, yet the mechanisms of source supply and transport behind N species remain unclear. Here, we investigated the hydrological factors influencing the timing and magnitude of river N species export in a Chinese pomelo agricultural watershed. We conducted continuous observations of watershed hydrology, N species, and their isotopic ratios along a soil-groundwater-river continuum during two storm events in 2018-2019.

Prioritizing ecological restoration in hydrologically sensitive areas to improve groundwater quality.

Greening is the optimal way to mitigate climate change and water quality degradation caused by agricultural expansion and rapid urbanization. However, the ideal sites to plant trees or grass to achieve a win-win solution between the environment and the economy remain unknown. Here, we performed a nationwide survey on groundwater nutrients (nitrate nitrogen, ammonia nitrogen, dissolved reactive phosphorus) and heavy metals (vanadium, chromium, manganese, iron, cobalt, nickel, copper, arsenic, strontium, molybdenum, cadmium, and lead) in China, and combined it with the global/national soil property database and machine learning (random forest) methods to explore the linkages between land use within hydrologically sensitive areas (HSAs) and groundwater quality from the perspective of hydrological connectivity.

Dynamics and geochemical responses of dissolved metals (Mn and Cu) in a subtropical estuary, China.

The research delved into the occurrence and dynamics of dissolved metals, specifically manganese (Mn) and copper (Cu), within the Jiulong River Estuary, South China, a medium-sized subtropical estuary. Our findings unveiled a nuanced seasonal and spatial variability of dissolved metals throughout the entire estuarine system. Notably, dissolved Mn concentrations peaked (~ 3.

Carbonate chemistry and carbon sequestration driven by inorganic carbon outwelling from mangroves and saltmarshes.

Mangroves and saltmarshes are biogeochemical hotspots storing carbon in sediments and in the ocean following lateral carbon export (outwelling). Coastal seawater pH is modified by both uptake of anthropogenic carbon dioxide and natural biogeochemical processes, e.g.

Per- and polyfluoroalkyl substances in a subtropical river-mangrove estuary-bay system.

Mangrove estuaries are one of the most economically valuable and biologically diverse coastal ecosystems. However, knowledge of emerging pollutants in mangrove estuaries is limited. This study provided insight into the PFAS in a river (Zhangjiang River, ZR)-mangrove estuary (Zhangjiang River Estuary, ZRE)-bay (Dongshan Bay, DSB) continuous system in Fujian Province, China.

Pollution abatement reducing the river NO emissions although it is partially offset by a warming climate: Insights from an urbanized watershed study.

Global nitrogen (N) pollution has resulted in increased river nitrous oxide (NO) emissions, which contribute to climate change. However, little is known about how pollution abatement conversely reduces river NO production in a warming climate. Here, field observations and microcosmic experiments were conducted in a coastal urbanized watershed (S.

Response and recovery mechanisms of river microorganisms to gradient concentrations of estrogen.

As an important ecological system on the earth, rivers have been influenced by the rapid development of urbanization, industrialization, and anthropogenic activities. Increasingly more emerging contaminants, such as estrogens, are discharged into the river environment. In this study, we conducted river water microcosmic experiments using water to investigate the response mechanisms of microbial community when exposed to different concentrations of target estrogen (estrone, E1).

Impacts of a subtropical storm on nitrogen functional microbes and associated cycling processes in a river-estuary continuum.

Storms, in subtropical regions such as S.E. China, cause major changes in the physical and biogeochemical fluxes of anthropogenic N species through the river-estuary continuum to the coast.

Seasonal hydrological dynamics govern lifestyle preference of aquatic antibiotic resistome.

Antibiotic resistance genes (ARGs) are a well-known environmental concern. Yet, limited knowledge exists on the fate and transport of ARGs in deep freshwater reservoirs experiencing seasonal hydrological changes, especially in the context of particle-attached (PA) and free-living (FL) lifestyles. Here, the ARG profiles were examined using high-throughput quantitative PCR in PA and FL lifestyles during four seasons representing two hydrological phenomena (vertical mixing and thermal stratification) in the Shuikou Reservoir (SR), Southern China.

[Spatiotemporal Characteristics of Dissolved Oxygen and Control Mechanism of Hypoxia (Low Oxygen) in the Watershed-Coastal System in Fujian Province].

Dissolved oxygen is a key parameter to measure water environment quality and ecosystem health. Currently, the problem of hypoxia (low oxygen) is prominent in coastal areas in China, but there is a lack of research on the spatiotemporal characteristics of dissolved oxygen and the control mechanism of hypoxia in the watershed-coastal system. Based on the data of 135 surface water (including estuaries) and 66 coastal water monitoring sites in Fujian Province from 2011 to 2020, this study analyzed the spatiotemporal variation pattern of dissolved oxygen at seasonal and interannual time scales.

[Spatial and Temporal Distribution and Influencing Factors of Dissolved Trace Metals in Jiulong River Estuary and Xiamen Bay].

Trace metals play an important role in some biogeochemical processes in the marine system. The physical and hydrological conditions in estuaries and coastal seawater are complicated and significantly affected by human activities. Therefore, the biogeochemical behavior and influencing mechanism of trace metals in nearshore water have become a research hotspot.

Hydrological connectivity affects nitrogen migration and retention in the land‒river continuum.

Land use change and excessive nitrogen (N) loading threaten the health of receiving water bodies worldwide. However, the role of hydrological connectivity in linking watershed land use, N biogeochemistry and river water quality remain unclear. In this study, we investigated 15 subwatersheds in the Jiulong River watershed (southeastern China) during a dry baseflow period in 2018, combined with 3‒year (2017-2019) nutrient monitoring in 5 subwatersheds to explore river N dynamics (dissolved nutrients, dissolved gases and functional genes) and their controlling factors at three hydrological connectivity scales, i.

Predicting Dynamic Riverine Nitrogen Export in Unmonitored Watersheds: Leveraging Insights of AI from Data-Rich Regions.

Terrestrial export of nitrogen is a critical Earth system process, but its global dynamics remain difficult to predict at a high spatiotemporal resolution. Here, we use deep learning (DL) to model daily riverine nitrogen export in response to hydrometeorological and anthropogenic drivers. Long short-term memory (LSTM) models for the daily concentration and flux of dissolved inorganic nitrogen (DIN) were built in a coastal watershed in southeastern China with a typical subtropical monsoon climate.

The spatiotemporal variations in microalgae communities in vertical waters of a subtropical reservoir.

The construction of cascade reservoirs increases eutrophication and exacerbates algal blooms and thus threatens water quality. Previous studies on the microalgae in reservoir have mainly focused on the spatio-temporal patterns of surface microalgae communities at the horizontal scale, while few studies have simultaneously considered the successions of microalgae in vertical profiles including the sediments and the effects of the nutrients release and microalgae in sediments on microalgae in upper waters. In this study, we investigated the effects of microalgae and physico-chemical parameters in waters and sediments on the successions of vertical microalgae communities in Xipi Reservoir, Southeast China.