A manipulative field experiment was designed to investigate the effects of sediment-nutrients and sediment-organic matters on seagrasses, Zostera japonica, using individual and population indicators. The results showed that seagrasses quickly responded to sediment-nutrient and organic matter loading. That is, sediment-nutrients positively impacted on seagrasses by increasing N content of leaves and roots, leaf length and belowground biomass. Sediment-organic matter loading lowered N content of seagrass leaves and belowground biomass. Negative effects of organic matter loading were aggravated during nutrient loading, by decreasing N content of leaves, P content of roots, leaf width, shoot number in the middle period of the experiment, increasing C/N ratio of leaves, C/P and N/P ratio of roots and above to belowground biomass ratio of seagrasses. Consequently, Z. japonica could be considered as a fast indicator to monitor seagrass ecosystem status in the eutrophic areas and facilitate to interpreting the response of seagrasses to multiple stressors.
Keywords: Indicators; Nutrient; Organic matter; Seagrass; Sediment dynamics.
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