胶州湾大沽河潮滩营养盐在沉积物—水界面的扩散通量对盐度变化的响应

Responses of Nutrients Diffusion Fluxes Across the Sediment-Water Interface in Tidalflats to Salinity Variance:a Case Study of Daguhe Estuary,Jiaozhou Bay

2009年3、6、9和12月在胶州湾大沽河河口潮滩采集均长25cm的沉积物柱状样,利用室内培养法,培养柱状样72h。该时间段内的营养盐在水—沉积物界面的平均迁移速度视为营养盐的扩散通量。在培养中,上覆水的盐度,分别被调整到17、22和28。不同盐度水平下,氨氮和磷酸盐在沉积物—水界面的扩散通量具有明显的时空异质性;在所测试的盐度范围内,氨氮的扩散通量与盐度的相关性并不显著;而盐度对磷酸盐在沉积物—水界面的扩散具有显著的影响。在6月和9月,所有测试站位中均表现为盐度增加,磷酸盐的扩散速度下降。大沽河径流的衰减会抑制磷酸盐自沉积物向水体释放,从而导致初级生产磷的供应不足。因此,大沽河径流的降低是大沽河潮滩湿地生态功能退化的一个原因。

In March,June,September and December of 2009,sediment cores with mean depth 25 cm were sampled by box corer in the tidal flat of Daguhe Estuary.By the incubation method,these sediment cores were incubated for 72 h,and the 72 h mean transportation speed was calculated as the diffusion flux of ammonia or phosphate.Before the overlying water was added into the incubating cores,its salinity was adjusted to 17,22 and 28.There was significant spatial and temporal heterogeneity of ammonia or phosphate flux across the sediment-water interface at different salinity levels.The results indicated that there was no significant relationship between the ammonia diffusion flux and the salinity in the tested salinity range.Nevertheless,there was a significant effect of salinity on the exchange of phosphate across the interface.In June and September,the increased salinity inhibited the phosphate flux in spite of sampling stations.Furthermore,the runoff reduction of the Dagu River inhibited the phosphate release from the sediment which results in the shortage of phosphate for primary production.Thus,the reduction of river runoff should be one reason leading to the degradation of the wetland.