Wu Di, Wang Kui, Wang Guoquan, Mu Qinglin, Fan Wei, Xu Dawei
Ocean College, Zhejiang University. Zhoushan, Zhejiang, 316021, China.
Ocean College, Zhejiang University. Zhoushan, Zhejiang, 316021, China; Key Laboratory of Ocean Space Resource Management Technology, Ministry of Natural Resources, Hangzhou, Zhejiang, 310012, China.
Mar Environ Res. 2025 Sep;210:107302. doi: 10.1016/j.marenvres.2025.107302. Epub 2025 Jun 14.
The Changjiang River Estuary (CRE) supports critical fisheries and aquaculture industries. Net Ecosystem Metabolism (NEM) serves as a key indicator for assessing aquaculture ecosystem health, providing early warning of hypoxia risks, determining environmental carrying capacity, and guiding scientific aquaculture management. However, the hydrologic regime of the CRE, influenced by monsoons and strong tides, makes the combined effects of high-frequency wind and tidal variations on NEM dynamics poorly understood. In this study, we deployed a high-resolution in-situ profiler at a mussel aquaculture site in the CRE during September-October 2022 to continuously measure parameters, including dissolved oxygen (DO), at 1-min intervals. We then applied a one-dimensional DO mass balance model to quantify NEM variations and elucidate the driving mechanisms under contrasting wind and tidal conditions. Results indicated a predominantly heterotrophic ecosystem, with a mean NEM value of -6.0 ± 27.4 mmol m h. Mechanistic analysis revealed that wind and tidal forces regulate NEM by modulating the frontal dynamics between the Changjiang River Diluted Water (CDW) and the Taiwan Warm Current (TWC). Northerly winds enhanced heterotrophy by intensifying CDW dominance and terrestrial organic matter inputs. In contrast, easterly winds coupled with spring tides promoted autotrophy through the onshore advection of shelf surface waters (SSW). Tidal cycles further regulated NEM through vertical mixing-mediated benthic nutrient output, resulting in higher autotrophy during spring tides. These findings, derived from high-frequency observations, highlight the acute sensitivity of estuarine metabolism to shifts in dominant water masses. They provide essential insights for adaptive management strategies, such as implementing real-time environmental monitoring and selecting species aligned with water mass dynamics, to enhance aquaculture sustainability amidst climate variability. Nevertheless, limitations in the temporal scope (mid-autumn period) and localized geography necessitate future investigations into seasonal/interannual NEM variations across broader spatial scales. Integrating wider drivers, including river discharge and climate change, will yield more robust data support and mechanistic analysis for developing predictive models.
长江河口（CRE）支撑着重要的渔业和水产养殖业。净生态系统代谢（NEM）是评估水产养殖生态系统健康状况的关键指标，可对缺氧风险发出早期预警、确定环境承载能力并指导科学的水产养殖管理。然而，受季风和强潮汐影响，长江河口的水文状况使得高频风和潮汐变化对NEM动态的综合影响尚不清楚。在本研究中，我们于2022年9月至10月在长江河口的一个贻贝养殖场地部署了一台高分辨率原位剖面仪，以1分钟的间隔连续测量包括溶解氧（DO）在内的参数。然后，我们应用一维溶解氧质量平衡模型来量化NEM变化，并阐明不同风和潮汐条件下的驱动机制。结果表明该生态系统主要为异养型，平均NEM值为-6.0±27.4 mmol m⁻² h⁻¹。机理分析表明，风和潮汐力通过调节长江冲淡水（CDW）和台湾暖流（TWC）之间的锋面动态来调节NEM。北风通过加强CDW的主导地位和陆地有机物质输入来增强异养作用。相比之下，东风与大潮相结合，通过陆架表层水（SSW）的向岸平流促进了自养作用。潮汐周期通过垂直混合介导的底栖营养物质输出进一步调节NEM，导致大潮期间自养作用增强。这些基于高频观测得出的结果突出了河口代谢对优势水体变化的高度敏感性。它们为适应性管理策略提供了重要见解，例如实施实时环境监测以及选择与水体动态相匹配的物种，以在气候变化的背景下提高水产养殖的可持续性。然而，时间范围（中秋期间）和局部地理条件的限制使得未来有必要在更广泛的空间尺度上对季节性/年际NEM变化进行调查。纳入更广泛的驱动因素，包括河流流量和气候变化，将为开发预测模型提供更有力的数据支持和机理分析。
