Evaluation of cycle and effect of phosphorus in plankton ecosystem in the waters of the Pearl River Estuary
珠江口水域浮游生态系统中磷的循环及其效应评估

Available water volume for phytoplankton photosynthesis, effect of zooplankton grazing on the regeneration of phosphorus and bio-utilization of phosphorus in the waters of the Pearl River Estuary were studied by both field and laboratory experiments. Analysis of the data between 2002 and 2003 indicated that the available water volume for phytoplankton photo-synthesis changed seasonally, with about 9.7×104m3 in dry season and 6.6×104m3 in wet season. The same trend was also found in primary productivity, with approximate 36kg.d-1 in dry season and 31kg.d-1 in wet season, respectively. Phosphorus regen-eration could be accelerated by zooplankton grazing and could meet 1.5%-15.6% of phosphorus required by phytoplankton growth seasonally. Amount of phosphorus that directly released from zooplankton grazing was much higher than that from zooplankton biological turnover.