Effects of nutrient enrichment and Bellamya aeruginosa (Reeve) presence on three submerged macrophytes

Freshwater snails and submerged macrophytes are both important aquatic biological groups. The presence of freshwater snails might affect the growth of submerged macrophytes in term of their feeding behavior and metabolism. Bellamya aeruginosa (Reeve) is an important freshwater snail for most of Chinese waters and rarely grazes submerged macrophytes. We expected this snail species would benefit the growth of submerged macrophytes. We conducted a control experiment to study effects of nutrient enrichment in the water column and B. aeruginosa absence/presence on growth and carbon (C), nitrogen (N) and phosphorus (P) stoichiometric characteristics of three submerged macrophytes, Ceratophyllum demersum (L.), Hydrilla verticillata (L. f.) Royle, and Vallisneria natans (Lour.) Hara. The results indicated that both nutrient enrichment and B. aeruginosa presence affected the biomass and C, N, and P stoichiometric characteristics of submerged macrophytes. However, the effects of nutrient enrichment were relative larger than those of B. aeruginosa presence. B. aeruginosa could promote the biomass of V. natans in low nutrient levels but did not significantly affect the biomass of the other two macrophytes. B. aeruginosa presence increased the N contents of H. verticillata and V. natans, decreased the P contents of V. natans, and had negligible effects on C. demersum. Our study highlights that the effects of B. aeruginosa on submerged macrophytes were very complicated. More studies still should be done in order to give a scientific advice on how these two biological groups are combined used in the restoration of degraded aquatic ecosystems.