闽江口围垦养殖对沉积物有机碳组分及其矿化的影响

研究滨海湿地围垦养殖后沉积物有机碳库的动态变化,对科学评估沿海滩涂湿地开发利用对碳库的影响具有重要意义.以闽江口鳝鱼滩湿地为研究区,采集不同围垦年限(3 a和15 a)养殖塘和短叶茳芏(Cyperus malaccensis)(养殖塘围垦前主要土著植被)湿地沉积物,测定其总有机碳(TOC)、有机碳组分(微生物生物量碳(MBC)、易氧化有机碳(EOC)、水溶性有机碳(WSOC))及有机碳矿化特征,并基于时空互代法,分析了围垦养殖对沉积物TOC、有机碳组分及矿化的影响.结果表明:围垦养殖3 a,沉积物TOC和WSOC含量总体上没有显著变化,但围垦15a,表层(0~10 cm)沉积物TOC和WSOC含量显著增加,其增加比例分别约为68.36%和68.01%;围垦养殖后,沉积物MBC没有显著变化,EOC含量则有所降低,围垦15 a后表层沉积物EOC含量约降低37.35%.围垦养殖后表层沉积物有机碳矿化速率和累积矿化量均高于短叶茳芏湿地,而亚表层(10~20 cm)沉积物矿化速率差异不显著,且表层累积矿化量高于亚表层.养殖塘沉积物TOC及有机碳组分受长期水淹和饵料添加等管理方式的影响,同时受黏粒、TN和TP等理化性质的间接影响,进一步影响沉积物矿化速率、累积矿化量和潜在矿化量(C0).上述结果预示着滨海湿地围垦养殖在一定程度上增加了沉积物有机碳的蓄积,同时也促进了有机碳矿化.

Effects of reclamation aquaculture on sediment organic carbon fractions and mineralization in the Min River Estuary

In order to assess the impact of exploitation and utilization of coastal wetland on the carbon pool, it is important to study the dynamic changes of sediment organic carbon pool in coastal wetland after reclamation and cultivation. The Min River estuary wetland was chosen as the study area, the sediment samples from the reclamation aquaculture ponds (3 years and 15 years) and the Cyperus malaccensis wetland (the main native vegetation before reclamation) were collected. The total organic carbon (TOC), organic carbon fractions (microbial biomass carbon-MBC, ease of oxidation of carbon-EOC and water soluble organic carbon-WSOC) and organic carbon mineralization characteristics of sediment were measured in laboratory. Moreover, the effects of reclamation aquaculture on the total organic carbon, organic carbon fractions and mineralization of organic carbon in sediment were also analyzed base on the space-time substitution method. The results showed that the content of TOC and WSOC in the sediment didn''t change significantly after 3 years of reclamation, but increased significantly in the sediment after 15 years of reclamation in the surface layer (0~10 cm), with increment ratios of 68.36% and 68.01%, respectively. After reclamation, the MBC of sediment was not significantly changed, while the content of EOC decreased, and the content of EOC in surface layer sediment also decreased by about 37.35% after 15 years of reclamation. After reclamation, the mineralization rate and cumulative mineralization of sediment organic carbon were higher than those of C. malaccensis wetland in the surface layer. However, the mineralization rate was not significantly changed in the sub-surface layer (10~20 cm), and the surface accumulated mineralization was higher than that of the sub-surface layer. The TOC and its fractions of sediment in the reclamation aquaculture pond were affected by the management mode such as long-term flooding and bait addition. At the same time, they also had indirect affects by the physical and chemical properties such as clay, TN and TP, which further affected the mineralization rate, accumulate mineralization, and potential mineralization (C₀). These results indicated that coastal wetland reclamation increased the carbon accumulation of sediment and promoted the mineralization of organic carbon.