基于同位素的极区海洋生物泵运转及机制研究

Isotopic insights into the operation and mechanisms of biological pumps in polar oceans

生物泵是极区海洋净吸收大气CO_(2)的重要路径之一,也是连接海洋上层和底栖生态系统的关键环节。本文概述近10年来应用放射性核素和稳定同位素的独特指示功能,系统地开展普里兹湾、阿蒙森海、宇航员海、白令海、楚科奇海和加拿大海盆等南北极海域生物泵运转规律及维系机制的研究,探究了生物固碳、颗粒有机碳输出、有机物降解、营养盐再生和有机物埋藏等过程的动力学特征及空间变化规律,揭示了淡水组分、颗粒物浓度和痕量营养盐Fe等环境因子对生物泵的影响。研究发现,海冰融水、冰川融水/河水等淡水组分通过改变水体层化、光可获得性和营养盐供给等影响了生物固碳速率、Fe吸收速率和颗粒有机碳(POC)输出通量的空间变化;有机物降解及硝化作用主导着营养盐再生过程;南极底层水形成和颗粒物跨陆架输送影响生物泵的表-底耦合状况。同时,面对未来气候变化和人类活动的双重压力,亟待加强生物泵与食物网相互作用的研究,以准确掌握极区海洋生态系统变化的规律及机制。

The biological pump is one of the important pathways for the net absorption of atmospheric CO2 and is also a key linkage between the upper ocean and benthic ecosystems in the polar oceans.This article summa-rizes the research on biological pumps carried out systematically in the Prydz Bay,Amundsen Sea,Cosmo-naut Sea,Bering Sea,Chukchi Sea,Canada Basin,and other Arctic and Antarctic seas in the past 10 years by utilizing the unique functions of radionuclides and stable isotopes.These studies depicted the dynamic characteristics and spatial variation of processes such as biological uptake of carbon,export of particulate organic carbon,degradation of organic matter,regeneration of nutrients,and burial of sedimentary organic matter.In addition,the effects of environmental factors such as freshwater components,particle concentra-tion,and trace Fe on the biological pump were also explored.Our study found that freshwater components,such as sea ice meltwater,glacier meltwater/river water,etc.,affect the spatial variation of carbon fixation rate,Fe uptake rate,and POC export flux by changing water stratification,light availability,and nutrient supply;organic matter degradation and nitrification dominate the nutrient regeneration;and the formation of Antarctic bottom water and the cross-shelf transport of particulate matter affect the surface-bottom coupling of biological pumps.Facing the dual pressures of future climate change and human activities,it is urgent to strengthen research on the interaction between biological pumps and food webs to accurately grasp the laws and mechanisms of changes in polar marine ecosystems.