湖泊生态系统碳汇特征及其潜在碳中和价值研究

为了应对气候挑战，达成碳达峰远景目标，需要正确评估自然资源碳中和价值。湖泊作为具有独特生态、人文价值的地理单元，因碳循环强度高、碳排放总量大，是传统意义上的碳源。通过梳理近期相关研究成果，对比不同类型湖泊碳汇/源状况，湖泊生态系统以一系列碳汇特征表现出潜在的碳中和价值。强烈的光合作用可以使水体CO₂欠饱和，但由呼吸-光合作用、碳酸盐岩溶蚀作用带来的水体碱度、CO₂分压pCO₂提高也有利于湖泊碳汇增益。CO₂在水体中大量溶解，积极参与到湖泊碳循环，将pCO₂高于40 Pa作为判断湖泊为碳源的依据可能忽视了水体碱度上升带来的碳汇。在湖泊沉积物中有机碳的累积受到生态系统光合-呼吸作用的影响，当异养微生物群落能及时分解沉入湖底的衰亡组织、有机质时，沉积物中有机碳不会大量累积，当呼吸对光合的相对滞后，有机碳才会大量累积。湖泊生态系统的生产力决定了固碳能力，是湖泊发挥碳汇效益的重要“碳库”。由水生植物固定下的CO₂总量不如浮游植物，但在过程中发挥了“压舱石”般的稳定作...

Review of lake ecosystem's characteristics of carbon sink and potential value on carbon neutrality

It is necessary to evaluate contributions of nature resources on carbon neutralization for tackling the climate change and pursuing the carbon dioxide emission peak. Lakes, which have unique contributes on ecological and humanistic services, were typically considered as carbon source due to swift carbon cycle and large carbon emission. Lakes showed great carbon sink potential with a series of carbon sink characteristics through sorting of latest related researches, comparing carbon sink/source in different types of lake. Intense photosynthesis made lake CO₂ undersaturated, but the raised CO₂ partial pressure pCO₂ and water alkalinity caused by respiration-photosynthesis and carbonate karst erosion also enhanced the lake carbon sink. As more CO₂ were in water and lake carbon cycle, judging lake as carbon source based on pCO₂ over 40 Pa might overlook carbon sink brought by raised alkalinity. The organic carbon accumulation in lake sediment was dominated by balance between respiration and photosynthesis, when heterotrophic microorganisms degraded the deposited tissues and organic matters in time, organic carbon would not accumulate significantly, when respiration was left behind photosynthesis, organic carbon would accumulate quickly. Lake ecosystem productivity determined the capability of carbon fix, constructed a carbon pool which is very important for carbon sink. The carbon fixed in macrophytes were much less than macrophytes, but macrophytes played a role of cornerstone in the progress. In the meanwhile, the latest investigations showed that carbon emission from lake are increasing. The land use issues including deforestation, farmland reclamation, urban development etc. weaken land carbon fix, this external carbon increased carbon emission from lake. Under the pressure of global warming and water eutrophication, the decomposition and mineralization of organic carbon in lake were accelerating, the capability of carbon fix in food chain were descending. To exploit potential carbon sink of lake ecosystem, the results in practice showed that there are three aspects need to be persisted and developed in the future. The first one is restoring macrophytes and improving lake water quality to escort lake carbon sink. Eco-restoration and biodiversity recovery will extend food chain, in which more carbon is transported and stored. The second one is emphasis on sediment carbon accumulation. The specie and source analysis of sediment carbon will provide a convenient way to measure carbon equilibrium instead of full carbon equilibrium analysis, the comparison with land carbon accumulation will highlight the contribution of lake to carbon sink. At last, the technological exploration to collect CH₄ from lake will deal with conflict between the low density in lake and the high density that energy industry demand and open a new filed of carbon neutralization.