中国长足摇蚊幼虫和霍普水丝蚓扰动下沉积物氧气特征分析

BIOTURBATION EFFECTS OF TANYPUS CHINENSIS AND LIMNODRILUS HOFFMEISTERI ON PENETRATION AND DISTRIBUTION OF SEDIMENT OXYGEN

为研究中国长足摇蚊幼虫(Tanypus chinensis)和霍普水丝蚓(Limnodrilus hoffmeisteri)扰动对表层沉积物氧气渗透及空间分布的影响,采集梅梁湾表层沉积物,借助高精度溶氧微电极,研究两种生物扰动作用下,太湖梅梁湾表层沉积物氧气渗透深度和空间分布的变化,并根据氧气在流动培养体系中浓度的变化和在扩散边界层中的扩散过程这两种方法计算界面氧气交换速率。结果表明,中国长足摇蚊幼虫和霍普水丝蚓两种底栖生物扰动均能提高沉积物界面氧气交换速率,且微电极法的计算值要低于流动培养法。通过溶氧微电极剖面能够准确的获得氧气渗透深度的信息。结果发现:长足摇蚊幼虫的扰动能提高沉积物氧气渗透深度并造成氧气在沉积物内空间分布的差异,长足摇蚊幼虫扰动后沉积物氧气渗透深度由无扰动的6 mm增至10 mm。与长足摇蚊幼虫相比,霍普水丝蚓扰动没有增加沉积物氧气渗透深度及造成空间分布差异。对比两种计算方法发现,在生物扰动作用下,由于生物作用的影响,根据氧气在扩散边界层的扩散得到的值可能会低估氧气的界面交换速率。

Bioturbation effects of Tanypus chinensis and Limnodrilus hoffmeisteri,on sediment oxygen penetration depth and distribution,were investigated in this research.Surface sediments were collected from Meiliang Bay,in Lake Taihu.Oxygen penetration depth and distribution in sediment were measured by the use of microelectrodes,and then Tanypus chinensis and Limnodrilus hoffmeisteri were added into the sediment.Oxygen exchange rates across the sedi-ment-water interface were calculated by two different methods： oxygen concentration decreased in the flow-through system and oxygen profiles obtained by the microelectrode.Results showed that Tanypus chinensis and Limnodrilus hoffmeisteri could enhance the oxygen exchange rates between sediment-water interface,while the second method could underestimated the exchange rates.The oxygen penetration depth could be inferred directly from the microprofiles,which demonstrated that oxygen penetration into sediment were greatly enhanced by Tanypus chinensis.Sediment oxygen penetration depth increased from 6 mm to 10 mm,while Limnodrilus hoffmeisteri showed no significantly effects on sediment oxygen penetration depth and distribution.Results of oxygen exchange rates demonstrated that oxygen exchange rates calculated with the second method could be underestimated,because the activity of Bottom fauna in sediment could consumed oxygen thus decreased calculation accuracy.