中国海藻养殖的碳汇及环境效益分析

Carbon sink and environmental benefit analysis of seaweed cultivation in China

在全球气候变化加剧的背景下,充分利用海藻养殖碳汇功能是实现中国“双碳”目标的重要途径,其关键在于科学、精准和系统地测算海藻养殖碳汇能力。以往关于海藻养殖碳汇的研究大多忽视了海藻养殖过程中丢失的颗粒有机碳(POC)和释放的惰性溶解有机碳(RDOC)在固碳中的作用。本文基于2000—2022年中国9个沿海省份海藻养殖产量数据,考虑海藻养殖过程中通过释放POC和RDOC形成的碳汇,对我国海藻养殖长期碳汇和短期碳汇进行评估。此外,本研究还分析了中国9个沿海省份海藻养殖去除氮磷水平及其效益。评估结果表明:2000—2022年中国9个沿海省市海藻养殖平均产量为18.2×10^(5)t·a^(−1),平均种植面积为11.1×10^(4) hm^(2)·a^(−1);中国海藻养殖平均长期碳汇为2.70×10^(5)t(C)·a^(−1),平均短期碳汇为4.75×10^(5)t(C)·a^(−1),平均总碳汇(长期碳汇和短期碳汇之和)为7.45×10^(5)t(C)·a^(−1),且中国海藻碳汇将呈逐年增加趋势,预计2030年中国9个沿海省份海藻养殖总碳汇将达14.22×10^(5)t(C)。从总碳汇、长期碳汇和短期碳汇三方面来看,福建、山东和辽宁3省贡献了约91.5%的碳汇量,南部海洋经济圈碳汇增加最多。中国9个沿海省份海藻养殖碳汇量由于养殖种类和产量等原因差异较大,海带具有最高的固碳能力,与其他海藻相比,实现我国“碳中和”目标所需的养殖面积最小。从长期碳汇、短期碳汇和总碳汇三个方面分别估算实现我国“碳中和”目标所需海带养殖面积依次为1.14×10^(7) hm^(2)、0.65×10^(7) hm^(2)和0.41×10^(7) hm^(2)。根据中国9个沿海省份海藻养殖产量估算,2000—2022年其海藻养殖对氮磷的年平均去除量分别为5.44×10^(4) t(N)·a^(−1)和0.66×10^(4) t(P)·a^(−1),释放氧气1.99×10^(6) t(O2)·a^(−1),2022年其海藻养殖总环境效益达173.03亿元。本研究结果可以为“碳中和、减缓海水脱氧和富营养化”背景下发展海藻养殖提供重要数据支撑。

Against the background of intensifying global climate change,fully utilizing the efficient carbon sink function of seaweed cultivation is an important way to achieve China’s“double carbon”goal.To maximize the potential of seaweed cultivation as a carbon sink,it is essential to scientifically,accurately,and systematically calculate its carbon sequestration capacity.Most of the previous studies on the carbon sink of seaweed cultivation have overlooked the critical contributions of lost particulate organic carbon(POC)and released refractory dissolved organic carbon(RDOC)during the cultivation process.Based on the production data of seaweed cultivation from nine coastal provinces in China from 2000 to 2022 and considering the carbon sequestration formed by the release of POC and RDOC during seaweed cultivation,the long-term and short-term carbon sinks of seaweed cultivation in China were evaluated in this study.In addition,we have further analyzed the removal of nitrogen and phosphorus and the related economic benefits of the seaweed cultivation.The results showed that the average production of seaweed cultivation in the nine coastal provinces in China from 2000 to 2022 was 18.2×10^(5)t·a^(−1),with an average cultivation area of 11.1×10^(4) hm^(2)·a^(−1).The average long-term carbon sink of seaweed cultivation in China was 2.70×10^(5)t(C)·a^(−1),while the average short-term carbon sink was 4.75×10^(5)t(C)·a^(−1).The average total carbon sink(long-term carbon sink+short-term carbon sink)was 7.45×10^(5)t(C)·a^(−1),and the carbon sink of seaweed cultivation in China was expected to increase annually.Approximately,the total carbon sink of seaweed cultivation in China will reach 14.22×10^(5)t(C)by 2030.Fujian,Shandong,and Liaoning contributed approximately 91.5%of the total carbon sink,long-term carbon sink,and short-term carbon sink,with the greatest increase observed in the southern marine economic circle.The carbon sinks of seaweed cultivation in nine coastal provinces in China showed large differences owing to cultivation variety,aquaculture production,etc.Saccharina japonica had the highest carbon sequestration capacity among the seaweed species,and compared to other seaweeds,it required the smallest cultivation area to achieve China’s“carbon neutrality”goals.For long-term carbon sink,short-term carbon sink,and total carbon sink,the required cultivation area for Saccharina japonica to achieve China’s“carbon neutrality”goal was estimated to be 1.14×10^(7) hm^(2),0.65×10^(7) hm^(2),and 0.41×10^(7) hm^(2),respectively.According to the coastal seaweed production,the annual average removal of nitrogen and phosphorus by seaweed cultivation from 2000 to 2022 was estimated at 5.44×10^(4) t(N)·a^(−1)and 0.66×10^(4) t(P)·a^(−1),respectively.Furthermore,the release of oxygen was estimated at 1.99×10^(6) t(O2)·a^(−1),and the total environmental benefits of coastal seaweed cultivation in China reached 17.30 billion¥in 2022.The results of this study provide important insights into the development of seaweed cultivation in the context of achieving“carbon neutrality”and mitigating seawater deoxygenation and eutrophication.