{"title":"Dynamics of blue carbon across various estuaries: Key drivers and pathways","authors":"Sha Lou, Zhongyuan Yang, Shizhe Chen, Shuguang Liu, Gangfeng Ma, Irina Viktorovna Fedorova","doi":"10.1016/j.watres.2025.124644","DOIUrl":null,"url":null,"abstract":"Coastal wetlands are vital organic carbon (OC) sinks. This study examined OC dynamics and the implications for trophic status in the salt marsh-dominated Yangtze River Estuary (YRE) in China and four mangrove-dominated estuaries under varying anthropogenic influence within the Rookery Bay National Estuarine Research Reserve (RBNERR) in the USA, including natural (FHE), agricultural (BWE), canal-modified (FUE), and urbanized (HCE) estuaries. The research focused on three thematic areas: total organic carbon (TOC) composition and degradation, key drivers and their cascading effects, and estuarine eutrophication assessment, employing stable isotope tracing (δ<sup>13</sup>C, C/N), machine learning (BRT models), partial least squares path modeling (PLS-PM), and trophic indices (TRIX, TSI). Results showed that FHE had the highest organic carbon concentrations (4-19.82 mg/L). While terrestrial sources contributed >85% of total OC across estuaries, composition varied: YRE's OC was derived mainly from freshwater algae and soil organic matter, whereas in the RBNERR estuaries, it was dominated by mangrove-derived, marine phytoplankton, and anthropogenic sources. Anthropogenic organic matter (OM) inputs (e.g., from agriculture and wastewater) and phytoplankton growth promoted r-strategists and enhanced degradation, likely decreasing burial efficiency in YRE, BWE, and HCE compared to FHE and FUE. In the FHE and FUE, TOC was primarily driven by the degradation of mangrove-derived OM (with hydrodynamic influence in FUE). In contrast, TOC in the YRE, BWE, and HCE estuaries was mainly governed by anthropogenic and phytoplankton inputs, which manifested in distinct ways: tidal dilution, light-limited photosynthetic growth, and degradation of phytoplankton-derived and soil organic matter in the YRE; agricultural organic matter degradation in the BWE; and phytoplankton photosynthesis in the HCE. PLS-PM further revealed that meteorological factors indirectly influenced TOC concentrations through salinity, biological environment, hydrodynamics and nutrients. Overall, the driving mechanisms resulted in the YRE and BWE being eutrophic, while the other estuaries were mesotrophic. In summary, these findings demonstrate that local environmental factors and human activities are key drivers of OC dynamics. This understanding of specific mechanisms is essential for refining blue carbon assessments under global change.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"22 1","pages":""},"PeriodicalIF":12.4000,"publicationDate":"2025-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Water Research","FirstCategoryId":"93","ListUrlMain":"https://doi.org/10.1016/j.watres.2025.124644","RegionNum":1,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, ENVIRONMENTAL","Score":null,"Total":0}
引用次数: 0
Abstract
Coastal wetlands are vital organic carbon (OC) sinks. This study examined OC dynamics and the implications for trophic status in the salt marsh-dominated Yangtze River Estuary (YRE) in China and four mangrove-dominated estuaries under varying anthropogenic influence within the Rookery Bay National Estuarine Research Reserve (RBNERR) in the USA, including natural (FHE), agricultural (BWE), canal-modified (FUE), and urbanized (HCE) estuaries. The research focused on three thematic areas: total organic carbon (TOC) composition and degradation, key drivers and their cascading effects, and estuarine eutrophication assessment, employing stable isotope tracing (δ13C, C/N), machine learning (BRT models), partial least squares path modeling (PLS-PM), and trophic indices (TRIX, TSI). Results showed that FHE had the highest organic carbon concentrations (4-19.82 mg/L). While terrestrial sources contributed >85% of total OC across estuaries, composition varied: YRE's OC was derived mainly from freshwater algae and soil organic matter, whereas in the RBNERR estuaries, it was dominated by mangrove-derived, marine phytoplankton, and anthropogenic sources. Anthropogenic organic matter (OM) inputs (e.g., from agriculture and wastewater) and phytoplankton growth promoted r-strategists and enhanced degradation, likely decreasing burial efficiency in YRE, BWE, and HCE compared to FHE and FUE. In the FHE and FUE, TOC was primarily driven by the degradation of mangrove-derived OM (with hydrodynamic influence in FUE). In contrast, TOC in the YRE, BWE, and HCE estuaries was mainly governed by anthropogenic and phytoplankton inputs, which manifested in distinct ways: tidal dilution, light-limited photosynthetic growth, and degradation of phytoplankton-derived and soil organic matter in the YRE; agricultural organic matter degradation in the BWE; and phytoplankton photosynthesis in the HCE. PLS-PM further revealed that meteorological factors indirectly influenced TOC concentrations through salinity, biological environment, hydrodynamics and nutrients. Overall, the driving mechanisms resulted in the YRE and BWE being eutrophic, while the other estuaries were mesotrophic. In summary, these findings demonstrate that local environmental factors and human activities are key drivers of OC dynamics. This understanding of specific mechanisms is essential for refining blue carbon assessments under global change.
期刊介绍:
Water Research, along with its open access companion journal Water Research X, serves as a platform for publishing original research papers covering various aspects of the science and technology related to the anthropogenic water cycle, water quality, and its management worldwide. The audience targeted by the journal comprises biologists, chemical engineers, chemists, civil engineers, environmental engineers, limnologists, and microbiologists. The scope of the journal include:
•Treatment processes for water and wastewaters (municipal, agricultural, industrial, and on-site treatment), including resource recovery and residuals management;
•Urban hydrology including sewer systems, stormwater management, and green infrastructure;
•Drinking water treatment and distribution;
•Potable and non-potable water reuse;
•Sanitation, public health, and risk assessment;
•Anaerobic digestion, solid and hazardous waste management, including source characterization and the effects and control of leachates and gaseous emissions;
•Contaminants (chemical, microbial, anthropogenic particles such as nanoparticles or microplastics) and related water quality sensing, monitoring, fate, and assessment;
•Anthropogenic impacts on inland, tidal, coastal and urban waters, focusing on surface and ground waters, and point and non-point sources of pollution;
•Environmental restoration, linked to surface water, groundwater and groundwater remediation;
•Analysis of the interfaces between sediments and water, and between water and atmosphere, focusing specifically on anthropogenic impacts;
•Mathematical modelling, systems analysis, machine learning, and beneficial use of big data related to the anthropogenic water cycle;
•Socio-economic, policy, and regulations studies.