Falcão M, Gaspar M B, Caetano M, Santos M N, Vale C
Instituto Nacional de Investigação Agrária e das Pescas (INIAP/IPIMAR), Centro Regional de Investigação Pesqueira do Sul (CRIPSul), Av 5 de Outubro s/n, 8700-305 Olhão, Portugal.
Mar Environ Res. 2003 Dec;56(5):649-64. doi: 10.1016/S0141-1136(03)00069-2.
The physical and chemical changes in sediment and near bottom water caused by clam dredging were examined during July and September 1999, at two locations Vilamoura (VL) and Armona (AR), south coast of Portugal. Sediment cores and near bottom water were collected simultaneously before dredging (control samples) and within short time intervals (min-h) after dredging. After dredging operations, microphytobenthos coming from the path were accumulated in the re-worked sediment (ridge). Chlorophyll a in superficial sediment increased from 1.2 microg x g(-1) before dredging to 1.7 microg x g(-1) after dredging and these higher values remained for a few hours. However, the expected increase of chlorophyll a in near bottom water due to re-suspension was not observed. After sediment disturbance an instantaneous sorption of phosphorus onto iron oxides occurred in the upper sediment layers (from 2 to 3 micromol x g(-1) before dredging to 4-5 micromol x g(-1) after dredging). A microcosm experiment showed that after sediment disturbance HPO(4)(2-) dissolved in pore water decreased from 40 to 10 microM being simultaneously sorbed onto iron oxides formed in the top layer of sediment. The ammonium, nitrates, organic nitrogen, phosphate and silicate dissolved in pore water decreased immediately after dredging activity and simultaneously an increase in near bottom water was sporadically observed. Generally, the re-establishment of seabed was reached within a short time (min-h), at both stations (VL and AR).
1999年7月和9月，在葡萄牙南海岸的两个地点维拉莫拉（VL）和阿尔莫纳（AR），研究了蛤类捕捞对沉积物和近底层水造成的物理和化学变化。在捕捞前（对照样本）以及捕捞后的短时间间隔（分钟至小时）内，同时采集沉积物岩心和近底层水样本。捕捞作业后，来自捕捞路径的微型底栖植物在重新扰动的沉积物（脊）中积累。表层沉积物中的叶绿素a含量从捕捞前的1.2微克×克-1增加到捕捞后的1.7微克×克-1，且这些较高值持续了几个小时。然而，未观察到因再悬浮导致近底层水中叶绿素a预期的增加。沉积物扰动后，上层沉积物中瞬间发生了磷在铁氧化物上的吸附（从捕捞前的2至3微摩尔×克-1增加到捕捞后的4至5微摩尔×克-1）。一项微观实验表明，沉积物扰动后，孔隙水中溶解的HPO4(2-)从40微摩尔降至10微摩尔，同时被吸附到沉积物顶层形成的铁氧化物上。疏浚活动后，孔隙水中溶解的铵、硝酸盐、有机氮、磷酸盐和硅酸盐立即减少，同时偶尔观察到近底层水中有所增加。总体而言，两个站点（VL和AR）的海床在短时间（分钟至小时）内就恢复了原状。
