蟹类底栖动物对河口潮滩无机氮界面交换的影响

Impacts of burrowing crab on the dissolved inorganic nitrogen exchange at the sediment-water interface in the intertidal flat of the Yangtze estuary

以长江河口的沿岸及岛屿潮滩高潮滩湿地为研究区域，结合现场调查和实验室模拟分析，初步研究了大型穴居底栖动物无齿相手蟹（Sesarma denaan）活动对长江口潮滩沉积物一水界面无机氮交换以及界面处氮的生物地球化学循环的影响。结果表明，高潮滩蟹类底栖动物活动对潮滩滩面地貌施加了显著的改造作用，蟹类活动较集中的地段，蟹洞覆盖率达到2％～3％，滩面掘出沉积物高达1～1．5kg／m^2。潮水淹没情况下，小范围内高密度的蟹类活动能通过机体排泄、加强沉积物再悬浮及促进沉积物一水界面溶质交换等方式致使沉积物出现三态无机氮的巨大释放。蟹类活动造成的洞穴结构及对沉积物的翻动混合能增加沉积物中的氧气含量，促进沉积物中有机氮的矿化和NH4^＋的释放，造成无机氮在沉积物中的剖面分布特征发生较大变化．

The burrowing crabs are important bioturbators of intertidal flats. Selecting the Yangtze estuary coastal and island high tidal flat wetland as a study area, based on the integrated method of field investigation and experimental simulation, the impacts of macrobenthos crab Sesarma denaan sp. activities on the DIN exchange in the sediment-water interface and nitrogen biogeochemical cycling of tidal flat are analyzed and discussed simply in this paper. It is revealed that the burrowing benthos crab activities exert an outstanding reconstruction on tidal flat morphology. For example, in high crab dense zone the cave area accounts for 2%-3% of flat and the dry weight of burrowing mound can reach 1 to 1.5 kg per square meter. When high tidal flat is submerged, intensive crab Sesarma denaan sp. activities can cause a very large release of DIN by virtue of excretion, burrowing, bioturbation and sediment resuspension. Developed cave in sediment and continual turnover of sediment by crab can improve an organic matter remineralization and ammonification, consequently reworking the DIN vertical profile in sediment.