Song Yuzhi

The role of periphytes in the shift between macrophyte and phytoplankton dominated systems in a shallow, eutrophic lake (Lake Taihu, China)

Based on experiments of periphyte response to different trophic levels and their impact on macrophyte production, it was found that the periphyte biomass increased with the nutrient concentrations. Increased trophic level and periphyte biomass resulted in decreased macrophyte photosynthesis. It was suggested that the periphytes could cause resilience and hysteresis in the system shifts between macrophyte and phytoplankton domination. Other factors, such as fish farming, storm induced waves and mechanical destruction, and high water levels could be the perturbations during the system shifts, but these are not the key factors. Instead, the nutrient loading and periphyte abundance could determine the shift in lake ecosystem between macrophyte and phytoplankton domination. This finding could theoretically elucidate the mechanism of ecosystem shifts between macrophyte and phytoplankton domination.

Applicability analysis of aquatic macrophytes on controlling nitrogen and phosphorus from water in the Kangshan Bay demonstration area of Lake Taihu

In order to restore the aquatic vegetation and improve local water quality,reconstruction of two ecological types of aquatic plants were carried out in two large enclosures in the Kangshan Bay demonstration area of Lake Taihu.By annual investigation,results showed that floating-leaved aquatic plants such as Limnanthemun nymphoides and Trapa bicorni,and submerged plant such as Potamogeton macckianus grew better than other plants under controlled conditions.Their coverage was quite high during the growing season.Results also showed that,controlling wind-driven wave disturbance and improving water transparency were the prerequisite for aquatic vegetation restoration;there was no difference about N and P contents between submerged macrophyte and floating-leaved aquatic plants,but floating-leaved aquatic plants performed better than submerged macrophyte in removing water N and P content.Concerning the economic and environmental benefit,aquatic plants including L.nymphoides,T.bicorni and P.macckianus with powerful anti-wave ability could be selected as the pioneering species to rebuild the aquatic vegetation in the open area of Lake Taihu.This research provided theoretical basis for ecological restoration in the open littoral area of Lake Taihu.