Erftemeijer Paul L A, Lewis Roy R Robin
WL/Delft Hydraulics, P.O. Box 177, 2600 MH Delft, The Netherlands.
Mar Pollut Bull. 2006 Dec;52(12):1553-72. doi: 10.1016/j.marpolbul.2006.09.006. Epub 2006 Oct 31.
Main potential impacts on seagrasses from dredging and sand mining include physical removal and/or burial of vegetation and effects of increased turbidity and sedimentation. For seagrasses, the critical threshold for turbidity and sedimentation, as well as the duration that seagrasses can survive periods of high turbidity or excessive sedimentation vary greatly among species. Larger, slow-growing climax species with substantial carbohydrate reserves show greater resilience to such events than smaller opportunistic species, but the latter display much faster post-dredging recovery when water quality conditions return to their original state. A review of 45 case studies worldwide, accounting for a total loss of 21,023 ha of seagrass vegetation due to dredging, is indicative of the scale of the impact of dredging on seagrasses. In recent years, tighter control in the form of strict regulations, proper enforcement and monitoring, and mitigating measures together with proper impact assessment and development of new environmental dredging techniques help to prevent or minimize adverse impacts on seagrasses. Costs of such measures are difficult to estimate, but seem negligible in comparison with costs of seagrass restoration programmes, which are typically small-scale in approach and often have limited success. Copying of dredging criteria used in one geographic area to a dredging operation in another may in some cases lead to exaggerated limitations resulting in unnecessary costs and delays in dredging operations, or in other cases could prove damaging to seagrass ecosystems. Meaningful criteria to limit the extent and turbidity of dredging plumes and their effects will always require site-specific evaluations and should take into account the natural variability of local background turbidity.
疏浚和采砂对海草的主要潜在影响包括植被的物理清除和/或掩埋，以及浊度和沉积物增加的影响。对于海草来说，浊度和沉积物的临界阈值，以及海草在高浊度或过多沉积物时期能够存活的持续时间，因物种而异。具有大量碳水化合物储备的较大、生长缓慢的顶极物种比小型机会主义物种对这类事件表现出更大的恢复力，但当水质条件恢复到原始状态时，后者在疏浚后的恢复速度要快得多。对全球45个案例研究的综述表明，疏浚导致海草植被总共损失21,023公顷，这表明了疏浚对海草的影响规模。近年来，通过严格的法规、适当的执法和监测、缓解措施以及适当的影响评估和新环境疏浚技术的开发等形式进行更严格的控制，有助于防止或尽量减少对海草的不利影响。这些措施的成本难以估计，但与海草恢复计划的成本相比似乎微不足道，海草恢复计划通常规模较小且往往成效有限。将一个地理区域使用的疏浚标准复制到另一个区域的疏浚作业中，在某些情况下可能会导致限制过度，从而导致疏浚作业产生不必要的成本和延误，或者在其他情况下可能对海草生态系统造成破坏。限制疏浚羽状流的范围和浊度及其影响的有意义的标准总是需要针对具体地点进行评估，并应考虑当地背景浊度的自然变异性。
