Accuracy of diatom-inferred total phosphorus concentrations and the accelerated eutrophication of a lake due to reduced flushing and increased internal loading

Abstract

The sedimentary record in a small eutrophic lake (White Lough, Northern Ireland) is used to check the accuracy of reconstructing lake total phosphorus concentrations using diatoms and to propose a mechanism for the accelerated eutrophication of certain lakes. The diatom-inferred total phosphorus and sedimentary calcium, magnesium, potassium, iron, manganese, and phosphorus concentrations were measured in a dated sediment core and compared with lake monitoring results for 1978-1983. The values of and trends in diatom-inferred total phosphorus concentration closely follow the monitored concentrations. There was a period of accelerated eutrophication between 1973 and 1979 and the evidence indicates that this was due to reduced hydraulic flushing of the lake during a dry period and a sudden increase in the sediment phosphorus release rate. The results indicate that meso- to eutrophic lakes with hydraulic residence time around a year may be susceptible to this type of accelerated eutrophication.