College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China.
Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, No. 164, West Xingang Road, Guangzhou 510301, China.
Sci Total Environ. 2019 Jul 15;674:592-602. doi: 10.1016/j.scitotenv.2019.04.176. Epub 2019 Apr 13.
We present the first concurrent measurements of N fixation rates (N uptake), primary production (C uptake), dissolved organic carbon (DOC) concentrations, and diazotrophic community composition derived from nitrogenase (nifH) abundance in the subtropical Daya Bay (DB) of the coastal northern South China Sea (NSCS) from 2015 to 2017. N fixation rates ranged from n.d. - 4.51 nmol N L h. Such values were generally higher than those reported in the neighbouring NSCS open waters and several well-studied oligotrophic waters, thereby suggesting that N-replete conditions do not prevent N fixation in coastal waters. N fixation rates were positively and significantly correlated with the primary production and the concentration of DOC in DB in the spring and summer. Combined with other lines of evidence, we suggest that N fixation may be facilitated by non-diazotrophic phytoplankton via a probable regulation of the quantity and quality (bioavailability) of DOC in DB. Since DB represents a suitable site that has experienced dramatic human-induced changes in environmental conditions, our results likely provide insights in understanding how N fixation and relevant biogeochemical processes may respond to intensified global anthropogenic forcing in similar coastal settings.
我们首次同时测量了亚热带大亚湾（DB）从 2015 年到 2017 年的固氮速率（N 吸收）、初级生产力（C 吸收）、溶解有机碳（DOC）浓度和源自固氮酶（nifH）丰度的固氮生物群落组成。固氮速率范围从 n.d. - 4.51 nmol N L h。这些值通常高于南海北部邻近开阔水域和几个经过充分研究的贫营养水域的报告值，因此表明富氮条件不会阻止沿海水域的固氮。在春季和夏季，DB 中的固氮速率与初级生产力和 DOC 浓度呈正显著相关。结合其他证据，我们认为固氮可能通过非固氮浮游植物对 DB 中 DOC 的数量和质量（生物可利用性）的可能调节而得到促进。由于 DB 是一个经历了环境条件剧烈人为变化的合适地点，因此我们的结果可能提供了对固氮和相关生物地球化学过程如何响应类似沿海环境中强化的全球人为胁迫的理解。
