A multi-species modelling approach to select appropriate submerged macrophyte species for ecological restoration in Gonghu Bay, Lake Taihu, China

- A submerged macrophyte model that can simulate several submerged macrophytes species simultaneously was constructed.
- The model was calibrated and validated with pilot-scale experimental data, and used to choose the appropriate species and initial plant biomass for submerged macrophyte recovery.
- The critical water transparency thresholds for macrophytes in Gonghu Bay was also determined by the model.

In this study, we built a submerged macrophyte model (GBAEDM) that could simulate several macrophyte species simultaneously. The model was calibrated and validated using pilot-scale experimental data, with satisfactory results. The coefficient of determination (R2) and root-mean-square error (RMSE) values were 0.86 and 0.03 for TP, 0.71 and 0.38 for TN, 0.93 and 6.78 for Chl a, and 0.99 and 27.61 for submerged macrophyte biomass. The GBAEDM was then used to choose appropriate species and suitable initial plant biomass submerged macrophyte recovery in Gonghu Bay. The appropriate species at 1 m depth were Vallisneria spinulosa (1150 g/m2), Myriophyllum spicatum (525 g/m2), and V. spinulosa-M. spicatum mixed (600 g/m2; 3:1) communities. At 2 m depth, the appropriate species were M. spicatum (1450 g/m2) and V. spinulosa-M. spicatum mixed (1950 g/m2; 12:1) communities. Only M. spicatum (1608 g/m2) was recommended at 3 m depth. Finally, the GBAEDM was used to determine the critical water transparency thresholds for submerged macrophytes in Gonghu Bay. A transparency value of 0.62 m at 2 m (the WT/H value of 0.31) was determined as the critical underwater light threshold for the recovery of submerged macrophytes in Gonghu Bay.