A Long Term Study of the Phosphorus Cycle in Lough Neagh,Northern Ireland

Eleven years of weekly observations on the phosphorus cycle in Lough Neagh are analysed. The data comprised inputs, outputs and lake concentrations of the soluble and particulate phosphorus fractions. It is shown that the particulate phosphorus input quickly sediments to the bottom and the particulate phosphorus in the lake is largely made up of phytoplankton. The average phosphorus retention in the lake was 34 %, similar to the particulate phosphorus input. Climate has a big influence on the phosphorus input and sediment release, both of which varied two-fold. A simulation model suggested that suppression of sediment P release would reduce lake winter phosphorus concentrations by an average of 29 %.