Shenzhen Key Laboratory of Marine Microbiome Engineering, Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
Guangxi Key Lab of Mangrove Conservation and Utilization, Guangxi Mangrove Research Center, Guangxi Academy of Sciences, Beihai 536000, China; Marine Environmental Monitoring Center of Guangxi, Beihai 536000, China.
Water Res. 2020 Dec 15;187:116431. doi: 10.1016/j.watres.2020.116431. Epub 2020 Sep 25.
To offset estuarine eutrophication, interest is increasing in restoring oyster reefs and expanding oyster aquaculture. However, ecosystem-scale evidence is lacking on oyster assemblages' impacts on estuarine pelagic nitrogen (N) cycling. Using a multiple-isotope approach and isotope-mixing model, we examined the sources, transformations, and influence of intensive oyster aquaculture on N pollution in a subtropical estuary. The salinity-dependent NO and NH concentrations and their correlations with isotopic signals (δN-NO, δO-NO, δN-NH) indicated the nutrient spatial distribution in low-salinity areas was largely regulated by mixing between freshwater and seawater. However, the intensive oyster aquaculture greatly increased nitrification in the estuary. In high-salinity areas where oyster assemblages were absent, the assimilation of NO by phytoplankton became dominant and sharply increased the δN-NO and δO-NO. Soil organic nitrogen and fertilizer, domestic sewage, and wastewater treatment plants were the major NO sources in the estuary, while internal nitrification contributed 20.6% to the NO pool. Oyster biodeposits comprised up to one-third of the particulate organic matter in the water column, and as much as 47.3% of the NH pool could be from the oysters. Our study shows that oysters significantly contribute to the pelagic nutrient pools and N transformations, adding an important dimension to our understanding of oyster assemblages' impacts on estuarine N cycling.
为了抵消河口富营养化，人们越来越感兴趣的是恢复牡蛎礁和扩大牡蛎养殖。然而，缺乏牡蛎生物群落在河口浮游氮（N）循环中的影响的生态系统尺度证据。本研究使用多种同位素方法和同位素混合模型，研究了密集型牡蛎养殖对亚热带河口 N 污染的来源、转化和影响。盐度依赖的 NO 和 NH 浓度及其与同位素信号（δN-NO、δO-NO、δN-NH）的相关性表明，低盐度地区的营养物质空间分布在很大程度上受淡水和海水混合的调节。然而，密集型牡蛎养殖大大增加了河口的硝化作用。在没有牡蛎生物群的高盐度地区，浮游植物对 NO 的同化作用变得占主导地位，并急剧增加了 δN-NO 和 δO-NO。土壤有机氮和肥料、生活污水和污水处理厂是河口 NO 的主要来源，而内部硝化作用对 NO 库的贡献为 20.6%。牡蛎生物沉积物占水柱中颗粒有机物质的三分之一，多达 47.3%的 NH 库可能来自牡蛎。本研究表明，牡蛎显著促进了浮游营养物质库和 N 转化，为我们理解牡蛎生物群落在河口 N 循环中的影响增加了一个重要维度。
