Internal phosphorus loading from bottom sediments of a shallow preliminary reservoir

The aim of the studies done in a shallow preliminary reservoir (western Poland) was to determine the intensity and seasonal variability of phosphorus release from bottom sediments. Ex situ studies were done using intact sediment cores taken in succeeding seasons at 3 research stations. The highest phosphorus loading was observed in spring (May and April), both in 2005 and 2006. The range of loading was between 23.7 and 66.6 mgP m-2 d-1. More intensive phosphorus release during warmer months was caused by microbiological decomposition of fresh organic matter, comprised of decaying filamentous algae from the previous vegetation season. Spatial variability resulted from differences in water depth between stations and in the biomass of filamentous green algae in 2005.