导读

海岸带-河口-近海连续体是陆地和大洋的过渡地带，分布其间的大型水生植物能够提供生物栖息地和改善水质等生态系统服务价值。大型水生植物可以通过强盛的光合作用，固定大气二氧化碳和释放氧气，具有缓解海洋酸化和河口缺氧等生态环境问题的潜力。目前对大型水生植物的种类、生物量和周边河口环境因子的时空分布规律，以及它们如何交互作用进而影响生态系统结构，是否能够缓解海洋酸化和河口缺氧，仍然欠缺长时间的观测数据与有力的科学解析。本文对上述问题进行了详细探究，相关研究成果近日发表于Science合作期刊Ocean-Land-Atmosphere Research (OLAR) 上。

图1  图文摘要

研究结果

本文选取了Coos Bay河口上、中、下游三个代表性站点，获取现场调查数据，并集成了15年大型水生植物和环境因子数据。分析结果表明，该河口海草的生物质从下游向上游递减，大型海藻的生物质整体上低于海草，海草和海藻在过去15年间整体呈现衰退趋势，不同站点存在着不同的年际变化特征。大型水生植物的衰退可能由温度、流域的人类活动扰动和河流泥沙的增加导致。当地的大型水生植物的群落呼吸和生产能够贡献超过一半的生态系统代谢活动，因此水生植物的衰退与水体溶解氧和pH的日变幅减小存在紧密联系。作者观测到在大型水生植物生物量高的区域，其白天的光合作用能够使水体DO和pH分别增加超过2 mg/L和0.3，对局域水质提升明显，而且这种植物改善水质的潜力存在空间差异，即河口中上游高于中下游。同时，作者也指出大型水生植物缓解海洋酸化和缺氧的成效取决于植物的种类和丰度，以及周边水体的体量与停留时间。

图2  2004-2019年，South Slough内3个地点（Coos Bay, OR, USA）的季节性大叶藻（圆形）和巨藻（三角形）生物量的平均值（±标准误差）。图中蓝色代表冬季（1-4月），绿色代表夏季（5-9月），黄色代表秋季（10-12月）。

总结与展望

本文探讨了大型水生植物衰退与多种环境因子的互作关系，指出植物能够缓解近海酸化和缺氧的环境问题，为近海生态修复和海洋经济发展提供了科学理论依据。同时，本研究工作也表明滨海蓝碳植物的兴衰具有极其复杂的诱因与严重的生态后果，后续可进一步研究流域变化与河流物质输入、植物地上地下生物质、生长周期、植物和藻类生理差异等对河口近海水质或热点环境问题的调控机理。

原文链接：https://spj.science.org/doi/10.34133/olar.0023

文章标题：

Eelgrass and Macroalgae Loss in an Oregon Estuary: Consequences for Ocean Acidification and Hypoxia

文章作者：

Caitlin L. Magel, Sally D. Hacker, Francis Chan and Alicia R. Helms

文章摘要：

Estuarine macrophytes are proposed to influence ocean acidification and hypoxia (OAH) via the uptake (release) of inorganic carbon (oxygen) during photosynthesis. The extent to which macrophytes mitigate OAH in estuaries depends on the interaction between variable environmental conditions and macrophyte production over space and time. To explore these complexities in detail, we considered the potential causes and consequences of intertidal eelgrass and macroalgae declines in a U.S. Pacific Northwest estuary. We compiled and analyzed a record of eelgrass (Zostera marina) and ulvoid macroalgae along with a broad suite of environmental conditions over 15 years (2004 to 2019) at 3 sites along an estuarine gradient in South Slough, Oregon. The analysis showed that declining macrophyte biomass coincided with increasing temperature (water and air), watershed disturbance, and possibly turbidity. Coincident with macrophyte loss, diel dissolved oxygen (DO) and pH variability were reduced, indicating an influence of macrophytes on water quality at an ecosystem scale. Eelgrass loss was correlated with declining gross production and respiration, which altered the diel dynamics of pH, DO, and partial pressure of carbon dioxide at some sites. Under certain conditions, there was an association between eelgrass biomass and changes in DO and pH of more than 2 mg/l and 0.3 units, respectively. We found that daytime amelioration of low DO and pH was possible at certain locations when macrophyte biomass (especially eelgrass) was high. However, our analyses suggested that the efficacy of macrophyte mitigation of OAH depends on macrophyte abundance and the volume and residence time of overlying water.

文章引用：

Magel CL, Hacker SD, Chan F, Helms AR. Eelgrass and Macroalgae Loss in an Oregon Estuary: Consequences for Ocean Acidification and Hypoxia. Ocean-Land-Atmos. Res. 2023;2:Article 0023.

DOI:10.34133/olar.0023

作者简介

Caitlin Magel

University of Washington

Tacoma

Caitlin Magel is a coastal ecologist at the Puget Sound Institute where she primarily focuses on modeling the linkages between terrestrial and aquatic habitats, water quality, and social-ecological outcomes to support management decisions. Particular areas of interest include the ecology and ecosystems services of important estuarine habitats, including seagrass beds and salt marshes, with a focus on nutrient and carbon cycling. Caitlin completed her Ph.D. in the Department of Integrative Biology at Oregon State University in 2020, where she was trained to use transdisciplinary and collaborative approaches to address marine and coastal management challenges. She also holds a M.S. in Marine Science from the University of North Carolina – Chapel Hill and a B.A. in Biology and Environmental Science at Lawrence University in Appleton, Wisconsin.

联系邮箱：magelcai@uw.edu

OLAR 期刊简介

Ocean-Land-Atmosphere Research (OLAR) 由南方海洋实验室和美国科学促进会合作出版，入选2022年度中国科技期刊卓越行动计划高起点新刊项目，海洋负排放国际大科学计划（Ocean Negative Carbon Emissions, ONCE）学术出版合作平台，已被全球最具影响力的开放存取期刊目录DOAJ（Directory of Open Access Journals）数据库收录。本刊以海洋相关学科为重点，刊稿主题包括但不限于：海陆气相互作用、海洋碳中和、物理海洋学、海洋生物与生态、海洋地质与地球物理、化学海洋学、海洋气象学、大气物理与大气环境、冰冻圈科学、河口海岸学、海洋工程与海洋技术、海洋资源开发与利用。OLAR 投稿系统目前已正式开放，热烈欢迎相关研究领域科学家踊跃投稿。分享卓见，探索前沿，OLAR 诚邀您一起荟萃科学发现，共享学术盛筵！

期刊官网：https://spj.science.org/journals/olar/

投稿系统：https://www.editorialmanager.com/olar/