Stoichiometric characteristics of four submersed macrophytes in three plateau lakes with contrasting trophic statuses

Plant nutrient concentrations and their stoichiometric characteristics are often used to predict nutrient availability and nutrient limitation. However, there is still debate because plants, especially submersed macrophytes, can store excess nutrients and exhibit different survival strategies. To determine the extent to which the trophic status of lakes affect nutrient concentrations of submersed macrophytes and to estimate the relative contribution of lake and interspecific differences to variation of plant nutrient concentrations, we investigated four common submersed macrophytes, Potamogeton maackianus, Potamogeton pectinatus, Potamogeton malaianus and Myriophyllum spicatum, in three plateau lakes with contrasting trophic statuses (i.e. oligotrophic: Fuxian Lake; mesotrophic: Erhai Lake; eutrophic: Dianchi Lake) in Yungui Plateau in southwest China. The results indicated that the average C: N ratios were not different among the three lakes. However, the C: P and N: P ratios in Erhai Lake and Dianchi Lake were significantly lower than those in Fuxian Lake. The N: P ratios of P. maackianus and P. pectinatus did not significantly differ among the lakes. By contrast, the N: P ratios of P. malaianus and M. spicatum indicated different levels of interspecific stoichiometric homeostasis. The C and N concentrations and C: N ratios were mainly determined by the species, while the P concentrations and C: P ratios were mainly determined by the trophic status of lakes. Our study suggested that the C: N: P stoichiometric characteristics of submersed macrophytes exhibit high interspecific differences but substantial homoeostasis in response to different trophic conditions in plateau lakes.