基于生态能质理论的大型底栖生物碳与有机碎屑碳间量化关系研究——以南海北部近岸海域为例

The benthic ecosystem has played an important role in the global biogeochemical cycles and energy exchange. The research process is in dire need of highly comprehensive and accurate methods. However, there is still limited research into the evaluation of structure and function of the regional benthic community, its role in the carbon energy flow as well as the quantitative relationship between the benthic carbon and the organic detrital carbon in the surrounding environment. As an overall index, the eco-exergy has been widely applied to evaluating the structure and function of the ecosystem and thus can reflect the energy flow among components of the system. This project chooses the northern coastal area of South China Sea with abundant benthos as the study area. The research materials include the historical materials of the surveys conducted in the study area, the benthic samples collected from 2016 to 2017 as well as the environmental physicochemical parameters. The qualitative and quantitative description of the temporal and spatial distribution characteristics of the macrobenthic carbon has been conducted at the levels of community structure, eco-exergy and species. From the angle of thermodynamic equilibrium, the minimum flux of the organic detrital carbon necessary for maintaining the energy balance of macrobenthic community has been quantified. The quantitative relationship between benthic carbon and organic detrital carbon in the environment has also been established. Besides innovating in the research methods, this research can provide new ideas for evaluating the structure and function of the ecosystem as well as researching the carbon sequestration potential of the macrobenthic community.

底栖生态系统在全球生物地球化学循环与能量交换中占有重要位置，研究过程亟需综合性强、准确性高的方法，但目前对于底栖生物群落的结构功能评估及其在碳能量流动中的作用研究仍缺乏了解，包括底栖生物碳的定量及其与周围环境中有机碎屑碳之间的量化关系。生态能质作为整体性指标已广泛用于生态系统结构功能评估，能反映系统各组分间的能量流动。本项目拟选择底栖动物丰富的南海北部近岸海域为研究区，以研究海域航次调查的历史资料、2016-2017年航次采样的底栖生物样品和环境理化数据为研究材料，对研究区大型底栖动物群落的结构功能、生态能质等级以及物种水平上的底栖生物碳的时空分布特征进行定性定量描述，拟从热力学平衡的角度，定量维持底栖生态系统能量平衡时所需的有机碎屑碳的最小通量，构建底栖生物碳与水柱环境中有机碎屑碳间的量化关系，在研究方法上有创新性，也为生态系统结构功能评估和大型底栖动物群落固碳潜力研究提供新思路。

大型底栖动物在海洋生态系统的能量流动和物质循环中起着关键作用。本课题通过对南海北部近岸海域大型底栖生物样品的生物多样性指标、生态能质指标（Ex和Exst）以及碳氮指标（包括TOC, TN, δ13C和δ15N）分析，结合沉积物及水质参数测试的结果，揭示了南海北部大型底栖生物碳与有机碎屑碳间量化关系。研究表明：（1）沉积有机碳在大陆架底栖营养网的碳循环过程中起着重要作用。基于生态能质理论相同的β值进行大型底栖生物分类，β功能分组下，大多数底栖动物的δ13C值（-16.68‰～-21.85‰）和营养级（2.0-3.4）变化区间小，说明其食物来源、组成和生活习性相近，研究区内的底栖动物群落存在生态位重叠现象；（2）从北到南的调查断面，生物多样性指数值呈增大趋势，生态能质（Ex）也呈增加趋势，而结构能质（Exst）却呈现减少趋势，结合研究区水体和沉积环境特征，建立生态系统整体性评价指标体系，通过多边形面积计算法得出整体性评价结果并发现，生态系统中高生态能质等级群落的结构与功能现状对综合评价结果的区域变化有很大影响，底栖生物多样性和生态能质含量呈正相关关系；（3）南海陆架北部大型底栖动物中TOC含量（1.05%–71.08%，平均值为27.01%）远高于沉积物中的TOC含量（0.11%–0.84%，平均值为0.30%），以大型底栖动物的平均TOC含量为基础，通过线性回归模型建立生态能质、沉积物重量和生物有机碳之间的关系方程：y=49.714x+476.06，R2=0.9687，得到大型底栖生态系统生态能质值与支撑底栖生态系统能量维持所需沉积物重量之间的数量关系。.总之，这项工作的结果将为进一步研究近岸生态系统的碳能流和平衡提供新的思路和有益的补充。