Phosphorus stoichiometric homeostasis of submerged macrophytes and associations with interspecific interactions and community stability in Erhai Lake, China

Abstract

According to stoichiometric homeostasis theory, eutrophication is expected to increase the dominance of submerged macrophytes with low homeostatic regulation coefficients (H) relative to those with high H values, ultimately reducing macrophyte community stability. However, empirical evidence supporting this hypothesis is limited. In this study, we conducted a three-year tracking survey (seven sampling events) at 81 locations across three regions of Erhai Lake. We assessed the H values of submerged macrophyte species, revealing significant H values for phosphorus (P) and strong associations of H_P values (range: 1.58-2.94) with species and community stability. Moreover, in plots simultaneously containing the dominant high-H_P species, Potamogeton maackianus, and its low-H_P counterpart, Ceratophyllum demersum, we explored the relationships among eutrophication, interspecific interaction shifts, and community dynamics. As the environmental P concentration increased, the dominance of P. maackianus decreased, while that of C. demersum increased. This shift coincided with reductions in community H_P and stability. Our study underpins the effectiveness of H values for forecasting interspecific interactions among submerged macrophytes, thereby clarifying how eutrophication contributes to the decline in stability of the submerged macrophyte community.

Keywords: Ecological stoichiometry; Eutrophication; Regime shift; Relative dominance; Species dominance; Species stability.