Effects of silt-laden water on the growth ofsubmerged plants

摘要

To investigate the impact of floods on aquatic plants, many studies have focused on water characteristics, such as the frequency and magnitude of water fluctuations and flooding duration. However, the silt, sand, and nutrients carried by floods have received less attention. In artificially fluctuating water with silted sediment, we grew three submerged species with similar canopy-forming growth habits in mixtures: rooted hydrilla (Hydrilla verticillata [L. f] Royle), rooted Eurasian watermilfoil (Myriophyllum spica-tum L.), and rootless coontail (Ceratophyllum demersum L.). We observed that silt-laden water with a higher nutrient concentration consistently enhanced the tissue nutrient concentrations of submerged plants. However, the effects of silt-laden water on plant growth differed among species and were stronger in rootless coontail than they were in rooted Eurasian watermilfoil and hydrilla. In mixed cultures, hydrilla had a competitive growth advantage over the other species because of its robust nutrient uptake and its light tolerance. Our results imply that, although turbid water significantly benefits rootless coontail, which absorbs nutrients from water, these plants cannot outcompete rooted hydrilla. To regulate the relative abundance of co-occurring, submerged species, changes in the frequency of floods carrying silt and sand, whether natural or artificial, may not be an effective strategy.