Dredging can cause high suspended sediment concentrations (SSC) in the water column, posing a hazard to filter feeding organisms like sponges as sediment may clog their aquiferous systems and reduce feeding. In order to provide pressure−response values for sponges to SSC and tease apart the cause:effect pathways of dredging pressures, five heterotrophic and phototrophic species were experimentally exposed to a range of dredging-relevant SSC of up to 100 mg L−1, with light compensation across treatments to ensure that SSC was the primary physical parameter. This study shows that some sponge species exposed to high SSC (≥23 mg L−1) for extended periods (28 d) have lower survival, increased necrosis and depletion of energy reserves. In contrast, SSC of ≤10 mg L−1 caused few, if any, negative effects and is thus suggested as a prudent sub-lethal threshold for sponges. Microbial communities did not change significantly among SSC treatments, although a nutritional shift from mixotrophy towards increased phototrophy was detected for some sponge species exposed to high SSC. Importantly however, it is expected that the combined effect of SSC with low light availability and sediment smothering as occurs during dredging operations will increase the negative effects on sponges.
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机译:疏can会导致水柱中的悬浮沉淀物浓度高(SSC),对过滤诸如海绵之类的进食生物具有危害,因为沉淀物可能会堵塞其含水系统并减少进食。为了提供海绵对SSC的压力响应值并弄清疏pressure压力的成因途径,将五种异养和光养物种实验性地暴露于与疏ging相关的SSC范围高达100 mg L - 1 sup>,并在各个治疗过程中进行光补偿,以确保SSC是主要的物理参数。这项研究表明,某些海绵物种长时间(28 d)暴露于高SSC(≥23mg L −1 sup>)时,存活率较低,坏死增加,能量储备减少。相反,SSC≤10≤mgL -1 sup>几乎不会产生负面影响,因此建议作为谨慎的海绵亚致命阈值。在SSC处理中,微生物群落没有显着变化,尽管对于某些暴露于高SSC的海绵物种,其营养从混合营养转向向光营养增加。然而,重要的是,预计在疏dr操作期间,SSC的光利用率低和沉积物窒息的综合作用将增加对海绵的负面影响。
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