Response of Vallisneria natans to Increasing Nitrogen Loading Depends on Sediment Nutrient Characteristics
Response of Vallisneria natans to Increasing Nitrogen Loading Depends on Sediment Nutrient Characteristics
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DOI：
10.3390/w8120563
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发表时间：
2016-11
期刊：
影响因子：
3.4
通讯作者：
Jiao Gu;Zenghong Xu;Hui Jin;Ning Xiaoyu;Hu He;Jinlei Yu;E. Jeppesen;Kuanyi Li
中科院分区：
文献类型：
--
作者：
Jiao Gu;Zenghong Xu;Hui Jin;Ning Xiaoyu;Hu He;Jinlei Yu;E. Jeppesen;Kuanyi Li
高氮负荷可能会导致浅水湖泊沉水植物的衰退，但其影响因环境条件而异。2013年8月，我们在太湖生态系统研究实验室(TLLER)进行了为期28天的因子设计野外中游实验，研究了在不同沉积物类型的系统中，高N负荷对苦草生长的影响。本试验采用两个营养负荷水平--当前养分负荷(Average P：5μg·L−1·day−1，N：130μg·L−1·day−1)和P：5μg·L−1·day−1，以及三倍高N负荷(N：390μg·L−1·day−1)进行试验，并采用两种不同营养水平的底泥。V.Natans的生长随着氮负荷的增加而显著下降，但这种影响取决于底泥的营养状况。在低营养底泥中，相对生长率、叶片生物量和根生物量在高氮负荷下比低氮负荷下分别下降了11.9%、18.2%和23.3%，而在高营养底泥下的降幅更大(分别为44.0%、32.7%和41.8%)。在营养丰富的沉积物中影响较大，可能反映了观察到的浮游植物更高的遮盖度和植物组织中营养物质的过度积累，尽管高营养沉积物的潜在毒性也可能起到了作用。我们的研究证实了在营养丰富的浅水湖泊中，增加氮负荷对沉水植物生长产生了负面影响，并进一步表明，当植物在营养丰富的沉积物中生长时，这种影响被放大。因此，外部氮素控制可能有助于保护或恢复沉水植物，特别是当沉积物中含有丰富的营养物质和有机物时。
High nitrogen (N) loading may contribute to recession of submerged macrophytes in shallow lakes; yet, its influences vary depending on environmental conditions. In August 2013, we conducted a 28-day factorial-designed field mesocosm experiment in Lake Taihu at the Taihu Laboratory for Lake Ecosystem Research (TLLER) to examine the effects of high N loading on the growth of Vallisneria natans in systems with contrasting sediment types. We ran the experiments with two levels of nutrient loading—present-day external nutrient loading (average P: 5 μg·L−1·day−1, N: 130 μg·L−1·day−1) and P: 5 μg·L−1·day−1, and with three times higher N loading (N: 390 μg·L−1·day−1) and used sediment with two contrasting nutrient levels. V. natans growth decreased significantly with increasing N loading, the effect being dependent, however, on the nutrient status of the sediment. In low nutrient sediment, relative growth rates, leaf biomass and root biomass decreased by 11.9%, 18.2% and 23.3%, respectively, at high rather than low N loading, while the decline was larger (44.0%, 32.7% and 41.8%, respectively) when using high nutrient sediment. The larger effect in the nutrient-rich sediment may reflect an observed higher shading of phytoplankton and excess nutrient accumulation in plant tissue, though potential toxic effects of the high-nutrient sediment may also have contributed. Our study confirms the occurrence of a negative effect of increasing N loading on submerged plant growth in shallow nutrient-enriched lakes and further shows that this effect is augmented when the plants grow in nutrient-rich sediment. External N control may, therefore, help to protect or restore submerged macrophytes, especially when the sediment is enriched with nutrients and organic matter.