State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, PR China.
State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, PR China.
Mar Pollut Bull. 2018 Sep;134:5-13. doi: 10.1016/j.marpolbul.2018.02.043. Epub 2018 Mar 10.
Trace element accumulation is an anthropogenic threat to seagrass ecosystems, which in turn may affect the health of humans who depend on these ecosystems. Trace element accumulation in seagrass meadows may vary temporally due to, e.g., seasonal patterns in sediment discharge from upstream areas. In addition, when several trace elements are present in sufficiently high concentrations, the risk of seagrass loss due to the cumulative impact of these trace elements is increased. To assess the seasonal variation and cumulative risk of trace element contamination to seagrass meadows, trace element (As, Cd, Cr, Cu, Pb, Hg, Mn and Zn) levels in surface sediment and seagrass tissues were measured in the largest Chinese Zostera japonica habitat, located in the Yellow River Estuary, at three sites and three seasons (fall, spring and summer) in 2014-2015. In all three seasons, trace element accumulation in the sediment exceeded background levels for Cd and Hg. Cumulative risk to Z. japonica habitat in the Yellow River Estuary, from all trace elements together, was assessed as "moderate" in all three seasons examined. Bioaccumulation of trace elements by seagrass tissues was highly variable between seasons and between above-ground and below-ground biomass. The variation in trace element concentration of seagrass tissues was much higher than the variation in trace element concentration of the sediment. In addition, for trace elements which tended to accumulate more in above-ground biomass than below-ground biomass (Cd and Mn), the ratio of above-ground to below-ground trace element concentration peaked at times corresponding to high water discharge and high sediment loads in the Yellow River Estuary. Overall, our results suggest that trace element accumulation in the sediment may not vary between seasons, but bioaccumulation in seagrass tissues is highly variable and may respond directly to trace elements in the water column.
微量元素积累是人为对海草生态系统的威胁，这反过来又可能影响到依赖这些生态系统的人类的健康。由于来自上游地区的沉积物季节性排放等原因，海草草甸中的微量元素积累可能会随时间而变化。此外，当几种微量元素以足够高的浓度存在时，由于这些微量元素的累积影响，海草丧失的风险就会增加。为了评估海草草甸中微量元素污染的季节性变化和累积风险，2014 年至 2015 年，在黄河口中国最大的 Zostera japonica 栖息地的三个地点和三个季节（秋季、春季和夏季）测量了表层沉积物和海草组织中的微量元素（As、Cd、Cr、Cu、Pb、Hg、Mn 和 Zn）水平。在所有三个季节中，沉积物中 Cd 和 Hg 的微量元素积累都超过了背景水平。在所有三个季节中，对黄河口 Z. japonica 栖息地的所有微量元素的累积风险评估为“中等”。海草组织对微量元素的生物积累在季节之间和地上与地下生物量之间差异很大。海草组织中微量元素浓度的变化比沉积物中微量元素浓度的变化大得多。此外，对于倾向于在上地生物量中积累多于地下生物量的微量元素（Cd 和 Mn），地上与地下微量元素浓度的比值在与黄河口高水流量和高泥沙负荷相对应的时间达到峰值。总的来说，我们的研究结果表明，沉积物中的微量元素积累可能不会随季节变化，但海草组织中的生物积累变化很大，可能直接响应水柱中的微量元素。
