大型底栖动物对长江口潮滩沉积物-水界面无机氮交换的影响

基于实验模拟,通过对比分析潮滩无机氮长短期通量交换、循环规律及沉积物中无机氮的剖面特征在有/无底栖动物活动背景下的差异,探讨了双壳类底栖动物河蚬对长江口潮滩沉积物-水界面无机氮交换的影响及其机制.研究发现:潮滩无机氮界面交换中,河蚬的钻穴活动能增加向上覆水方向氨氮和硝氮的通量值;河蚬长期栖息对界面的生物扰动和代谢物排放能促进氨氮向上覆水的释放并逐渐加强沉积物氧化层中的硝化活动;界面附近河蚬的扰动和喷灌活动改变了沉积物中无机氮的垂直剖面特征,加速了沉积物中有机质的矿化分解和两相界面间氨氮的离子交换,促进沉积物氮库向滨岸水体的释放输出.

Impact of Macrofaunal Activities on the DIN Exchange at the Sediment-Water Interface Along the Tidal Flat of Yangtze River Estuary

The macrofaunal activities exert intensive and extensive influences on the accumulation,transportation,exchange and geochemistry processes of pollutants and redox sensitive elements around the sediment-water interface.Based on the simulated and contrastive analysis method,effects of bivalve Corbicula fluminea activities on dissolved inorganic nitrogen(DIN) exchange between sedimentwater interface in different experimental conditions and nitrogen biogeochemical cycling along the tidal flats of Yangtze River estuary are discussed.In short time experiment,Corbicula fluminea burrowing activities increased NH₄⁺ release from sediments,and NO₃^- efflux to overlying water was much more in Corbicula fluminea inhabiting core.During long time incubation,NH₄⁺ and NO₃^- released in turn from the sediments,bioturbation can facilitate NH₄⁺ release from the sediments at the beginning of incubation,and stronger nitrification derived from bioturbation within the sediments enlarge NO₃^- concentration.Disturbance and bioirrigation of Corbicula fluminea can accelerate organic matter mineralization and NH₄⁺ exchange between overlying water and pore water,result in a larger release from NH₄⁺ pool in top-sediment to overlying water.In conclusion,by means of excretion,burrowing,bioirrigation and bioturbation,Corbicula fluminea activities can evidently modify the nitrogen dynamics in sediment-water system.