高压下深海碳循环的过程及其对生命活动的影响

Deep-sea carbon cycle under high pressure and its impacts on life activities

目前约25%化石燃料来源的CO_(2)被海洋吸收,缓解了人类活动对气候变化的影响。海洋通过多个概念的碳泵将大气中的CO_(2)输送到深海。深海高压和低温的特点有利于CO_(2)溶解,目前已经储存了相当于大气含量50倍的无机碳,另外,深海沉积物中还储存有大量甲烷水合物。认识深海中的碳循环过程,对于保护海洋固碳能力、开发固碳潜力有重要意义。总结了国内外在海洋碳库、碳输送研究方面的进展,重点讨论了深海C元素转化循环的过程以及高压对生命活动的影响。微生物驱动了深海碳循环,大部分浮游植物所包含的有机碳在沉降过程中被微生物矿化成CO_(2)以及转化为难降解的有机碳,使深海成为巨大的、长周转时间的有机碳库;高压能提高古菌甲烷厌氧氧化的活性,提升屏蔽海底甲烷释放的能力,同时,高压下氧化甲烷的过程中不仅产生碳酸氢盐,还产生可支持异养生物的乙酸,因此,全球甲烷厌氧氧化的通量可能被低估;高压下细胞代谢额外产生的氨,可作为氨氧化古菌固定无机碳的潜在能量来源。总之,研究现在以及未来的人类活动对深海碳循环过程的影响以及环境效应,评估应用深海作为地球工程技术平台封存CO_(2)的可能性,都迫切需要加深对碳循环在内的深海元素循环的认识。

Currently,about 25%of CO_(2)from fossil fuel sources has been absorbed by the oceans,which mitigated the impact of human activities on climate change.The oceans transported CO_(2)from the atmosphere to the deep sea through several conceptual carbon pumps.The high pressure and low temperatures of the deep sea could facilitate the dissolution of CO_(2),and the oceans have stored inorganic carbon equivalent to 50 times of that in the atmosphere currently.Besides,the large amounts of methane hydrates have been stored in deep-sea sediments.Understanding the carbon cycle process in the deep sea is important to protect the carbon sequestration capacity and develop the carbon sequestration potential of the ocean.The authors have summarized the domestic and international researches on ocean carbon reservoirs and carbon deliveries,focusing on the process of the carbon cycle in the deep sea and the impacts of high pressure on life activities.The microorganisms drive the deep-sea carbon cycle,and the most of the organic carbon containing in phytoplankton is mineralized to CO_(2)by microorganisms during sedimentation or converted to refractory organic carbon,which makes the deep sea to be a vast and long-turnover time reservoir of organic carbon.The high pressure could increase the activity of archaeal methane anaerobic oxidation and enhance the ability to shield methane release from the seafloor.Besides,the process of methane oxidation under high pressure produces bicarbonate,and acetic acid which can support heterotrophs,so the global budget of methane anaerobic oxidation may be underestimated.The additional production of ammonia from cellular metabolism under high pressure could serve as a potential energy source for inorganic carbon fixation by ammonia-oxidizing archaea.Therefore,it is urgent for deepening our understanding of the deep-sea carbon cycle and other elemental cycles to investigate the impact of present and future human activities on deep-sea carbon cycle processes and environmental effects,and to assess the possibility of applying the deep sea as a geoengineering technology platform to sequester CO_(2).