文蛤的生物沉积和呼吸排泄过程及其在双台子河口水层-底栖系统中的耦合作用

为揭示河口埋栖性双壳贝类优势种类在水层——底栖系统中的生态耦合作用,利用生物沉积物捕集器和封闭式代谢瓶,于双台子河口现场研究了文蛤主要生理生态过程如生物沉积速率、耗氧率、排氨率和排磷率的季节变化。结果表明,文蛤的生物沉积速率、耗氧率、排氨率及排磷率均具有明显的季节变化:夏季最高,冬季最低。二龄及三龄文蛤个体的生物沉积速率周年变化分别为0.02—0.30 g-1个-1d-1、0.06—0.60 g-1个-1d-1;耗氧率变化分别为0.45—16.64 mg-1个-1d-1、1.03—30.51 mg-1个-1d-1;排氨率季节变化分别为0.001—0.14 mg-1个-1d-1、0.002—0.28 mg-1个-1d-1;排磷率季节变化分别为0.002—0.069 mg-1个-1d-1、0.003—0.16 mg-1个-1d-1。文蛤的生物沉积速率及呼吸排泄速率均受龄期制约:在同一季节,文蛤的单位个体生物沉积速率及呼吸和排泄速率均表现为二龄三龄。方差分析显示,季节、龄期及两者交互作用对文蛤生物沉积速率、耗氧率、排氨率及排磷率均有显著影响。基于不同季节双台子河口文蛤生物量(0.67个/m2、2.4 g/m2),估算出文蛤种群每年向该河口排放大约5321.90 t生物沉积物(干重)、1.43 t NH+4-N和0.93 t PO3-4-P,并且消耗大约221.59 t O2。研究结果表明,文蛤通过生物沉积及呼吸排泄作用,大大加强了双台子河口沉积物-水界面的物质交换通量,在双台子河口水层-底栖系统耦合作用中扮演着重要生态角色。

Influence of biodeposition, respiration, and excretion of the buried clam Meretrix meretrix on the pelagic-benthic coupling in Shuangtaizi Estuary

In order to evaluate the effect of the dominant buried clam on pelagic-benthic coupling in an estuary ecosystem, the field experiments on biodeposition, respiration and excretion of Meretrix meretrix were conducted from July 2010 to April 2011 in the Shuangtaizi Estuary, Bohai Sea of P. R. China. Different sizes of clams, namely 2-yr old clams ((36.36 ± 0.23) mm, SH) and 3-yr old clams ((46.60 ± 0.23) mm, SH) were collected respectively. The results showed that there were significant seasonal changes on biodeposition, oxygen consumption and excretion rates of the hard clams among four seasons, with the maximum rates in summer and minimum rates in winter. The seasonal variation of biodeposition rates for 2 and 3-year-old M. meretrix were 0.02-0.30 g^-1 ind^-1 d^-1 and 0.06-0.60 g^-1 ind^-1 d^-1, respectively, among seasons. The hard clams consumed considerable amount of oxygen, ranging from 0.45-16.64 mg^-1 ind^-1 d^-1 and 1.03- 30.51 mg^-1 ind^-1 d^-1 for 2 and 3-year-old species, respectively. Ammonium excretion rates respectively ranged from 0.001-0.14 mg^-1 ind^-1 d^-1 and 0.002-0.28 mg^-1 ind^-1 d^-1 for 2 and 3-year-old clams. The hard clam M. meretrix released 0.002-0.069 mg^-1 ind^-1 d^-1 and 0.003-0.16 mg^-1 ind^-1 d^-1 PO₄^3--P in the 2 and 3-year-old clams. All the physiological rates of the tested clams at the same season showed a similar tendency of 2-year-old < 3-year-old among the four seasons. One-way ANOVA showed that there were significant effects of seasonality, clam age and their interactions on biodeposition, respiration and excretion rates of the clam. A density of 0.67ind/m² of and a biomass of 2.4 g/m² were previously observed in spring, summer and autumn in twelve sampling sites of the Shuangtaizi Estuary. Based on the above data, it is estimated that the hard clams may produce 1.43 tons of NH₄⁺-N, 0.93 tons of PO₄^3--P and discharge as much as 5321.90 tons of deposit to the estuary waterbody, and consume 221.59 tons of O₂ annually. Our study indicates that M. meretrix populations greatly enhanced material exchange fluxes across the water-sediment interface through its biodeposition, respiration and excretion process, and plays an important role in pelagic-benthic coupling in Shuangtaizi Estuary.