中国长足摇蚊(Tanypus chinensis)幼虫底栖扰动对沉积物溶解氧特征及反硝化的影响

Bioturbation effect of Tanypus chinensis larvae on denitrification rate and process in sediments

以中国长足摇蚊(Tanypus chinensis)幼虫对沉积物的生物扰动过程为研究对象,运用稳定同位素示踪及同位素配对技术,深入探讨长足摇蚊幼虫扰动对太湖梅梁湾沉积物硝酸盐界面迁移、溶解氧侵蚀深度及沉积物反硝化速率及两种不同反硝化过程(非耦合反硝化(DW)和耦合反硝化(DN))的影响.摇蚊幼虫扰动后,添加15N两种处理沉积物氧气消耗速率由355.49±131.49μmol/(m2.h)变化为546.39±261.41μmol/(m2.h),而未添加15N两种处理由313.57±61.63μmol/(m2.h)变化为554.17±184.36μmol/(m2.h),硝酸盐界面迁移结果表明:扰动显著加强了水体硝酸盐向沉积物迁移的速率,加强沉积物作为上覆水中NO3-N汇的作用,摇蚊幼虫扰动组的硝酸盐迁移速率从-33.75±29.25μmol/(m2.h)提高到-210.14±117.25μmol/(m2.h).同位素添加实验发现,摇蚊幼虫底栖扰动能显著提高沉积物总反硝化速率,与对照组相比,总反硝化速率从31.83±8.79μmol/(m2.h)上升到228.98±54.09μmol/(m2.h),增加了约6倍左右.利用同位素配对法计算对两种不同反硝化过程进行区分,发现非耦合反硝化速率从15.78±8.51μmol/(m2.h)上升到182.96±45.22μmol/(m2.h),耦合反硝化速率从16.04±5.63μmol/(m2.h)增加到46.01±8.97μmol/(m2.h),预示着底栖生物扰动能同时增加耦合和非耦合两种反硝化过程,而非耦合反硝化过程的增加强度远大于耦合反硝化.

Stable isotope tracing and Isotope Pairing Technique（IPT） were used to investigate the effects of bioturbation of Tanypus chinensis larvae in Meiliang Bay,Lake Taihu.The effects included nitrate flux at the sediment-water surface,dissolve oxygen penetration depth,denitrification rate,and the two different pathways,denitrification coupled to nitrification（DN） and denitrification from overlying water（DW）.Compared to the control,the SOD after Tanypus chinensis added increased from 355.49±131.49μmol/（m^2·h） to 546.39±261.41μmol/（m^2·h ）and from 313.57±61.63μmol/（m^2·h ）to 554.17±184.36μmol/（m^2·h） with and without Na15NO3 ammended,respectively.The results of nitrate diffusion experiment showed that bioturbation stimulated nitrate diffusion from water to sediment and increase total nitrification rate compared with the non-bioturbated sediment.Total denitrification rate was significantly increased from 31.83±8.79μmol/（m^2·h） to 228.98±54.09μmol/（m^2·h）.DW was stimulated from 15.78±8.51μmol/（m^2·h） to 182.96±45.22μmol/（m^2·h）,and DN from 16.04±5.63μmol/（m^2·h to 46.01±8.97μmol/（m^2·h）.This result showed that zoobenthos bioturbation can stimulate both DW and DN,and the DW was more stimulated than DN.