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Inicio  /  Water  /  Vol: 8 Núm: 12 Par: 0 (2016)  /  Artículo
ARTÍCULO
TITULO

Response of Vallisneria natans to Increasing Nitrogen Loading Depends on Sediment Nutrient Characteristics

Jiao Gu    
Zenghong Xu    
Hui Jin    
Xiaoyu Ning    
Hu He    
Jinlei Yu    
Erik Jeppesen    
Kuanyi Li    

Resumen

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.

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