Variation in Sediment Available-Phosphorus in Dianchi Lake and Its Impacts on Algal Growth

Sediment phosphorus (P) is an active component of the P cycle in lakes and its availability and movement could play an important role in eutrophication. Sediments from different depths in five representative sites of Dianchi Lake China, i.e., Haigeng, Dounan, Luojiacun, Xinjie, and Kunyang, were studied from January to December to evaluate the spatial and temporal dynamics in available-P and soluble-P and their impacts on algal growth. The results showed that the average sediment available-P and soluble-P were 41.2 mg kg(−1) and 0.27 mg kg(−1), respectively. Sediment available-P and soluble-P concentrations varied significantly among seasons, sites, and layers, with the following order: surface (0–5 cm) > middle (5–10 cm) > bottom (10–20 cm). The release and transformation characteristics of available-P and soluble-P at the sediment–water interface varied among sites. The Haigeng site, with the most severe algae blooms, had significantly higher average available-P and soluble-P in sediment than other sites. This indicated that phosphorus release and availability were associated with algal growth, and that the sediment surface (0–5 cm) is an important internal source that supports algal growth in Dianchi Lake.