Alleviated photoinhibition on nitrification in the Indian Sector of the Southern Ocean  

作　　者：Lingfang Fan Min Chen Zifei Yang Minfang Zheng Yusheng Qiu 

机构地区：[1]College of Ocean and Earth Sciences,Xiamen University,Xiamen 361102,China

出　　处：《Acta Oceanologica Sinica》2024年第7期52-69,共18页海洋学报（英文版）

基　　金：The National Natural Science Foundation of China under contract No.41721005;the Fund of the Ministry of Natural Resources of the People’s Republic of China under contract Nos IRASCC 02-01-01 and 01-01-02C.

摘　　要：Nitrification,a central process in the marine nitrogen cycle,produces regenerated nitrate in the euphotic zone and emits N_(2)O,a potent greenhouse gas as a by-product.The regulatory mechanisms of nitrification in the Southern Ocean,which is a critical region for CO_(2)sequestration and radiative benefits,remain poorly understood.Here,we investigated the in situ and dark nitrification rates in the upper 500 m and conducted substrate kinetics experiments across the Indian Sector in the Cosmonaut and Cooperation seas in the late austral summer.Our findings indicate that light inhibition of nitrification decreases exponentially with depth,exhibiting a light threshold of 0.53%photosynthetically active radiation.A positive relationship between dark nitrification and apparent oxygen utilization suggests a dependence on substrate availability from primary production.Importantly,an increased NH_(4)^(+) supply can act as a buffer against photo-inhibitory damage.Globally,substrate affinity(α)increases with depth and transitions from light to dark,decreases with increasing ambient NH_(4)^(+)and exhibits a latitudinal distribution,reflecting substrate utilization strategies.We also reveal that upwelling in Circumpolar Deep Water(CDW)stimulates nitrification through the introduction of potentially higher iron and deep diverse nitrifying microorganisms with higherα.We conclude that although light is the primary limiting factor for nitrification in summer,coupling between substrate availability and CDW upwelling can overcome this limitation,thereby alleviating photoinhibition by up to 45%±5.3%.

关 键 词：NITRIFICATION light inhibition substrate affinity circumpolar deep water(CDW)upwelling the Southern Ocean 

分 类 号：P734[天文地球—海洋化学]