厦门湾水体中不同粒级颗粒物、Chl-a和234Th随潮汐的变化及其海洋学意义

在沿岸海域——厦门湾的定点观测站,研究了不同粒径悬浮颗粒物(SPM)、Chl-a和^234Th随潮汐的变化,结果表明,不管采样深度和粒级大小,Chl-a浓度的潮汐变化均为高潮大于低潮．SPM浓度的潮汐变化,表层的规律性很明显,即不管是第一天还是第二天,也不管粒径的大小,SPM浓度无例外地呈现高潮小于低潮之势．从不同粒径SPM、Chl-a的潮汐变化的比较可以看出,浮游植物等生源颗粒物在该研究水域的颗粒物中所占比例很小,颗粒物主要来自九龙江河流输入的悬浮物和表层沉积物的再悬浮．在沿岸海域,颗粒态^234Th是总^234Th的主要组成部分,^234Th各粒级的比活度均呈现高潮大于低潮的普遍趋势,基于^234Th估算的沿岸POC、PON等输出通量也存在潮汐变化的影响．文中对上述研究对象随潮汐变化的原因作了分析和讨论．

Tidal effects on size-fractioned SPM,Chl-a and 234Th in the Xiamen Bay waters and its oceanographical implications

The tidal effects on the size-fractioned SPM,Chl-a and ~(234)Th concentrations in the Xiamen Bay waters at a selected time-series station were studied.Chl-a concentrations at the high tide were higher than those at the low tide inspite of the size and sampling depth. As for the variation of SPM concentrationsin the surface waters,it exhibited an obvious trend with the tide,i.e. the concentrations at the high tide were lower than those at the low tide for all sizes and all sampling dates. The comparison between tidal effects on size-fractioned SPM and Chl-a suggested that the SPM in the Xiamen Bay waters were mostly supplied from Jiulongjiang River and the resuspended surface-sediment,while the contributionof biogenic particulate matter was smaller.In the coastal waters,most of ~(234)Thwas scavenged onto the particles and the specific activities of all size-fractionated ~(234)Th were larger at the high tide than those at the low tide.The reasons of tidal effects mentioned above were discussed.