AN ANALYSIS OF THE TOTAL PHOSPHORUS CYCLE IN SOME TEMPERATE LAKES - THE RESPONSE TO ENRICHMENT

1. Total phosphorus (TP) cycles were examined in seventeen lakes from the Scottish lowlands and Northern Ireland, which varied in annual mea n TP from 17 to 192 mu g P l(-1). 2. It is clear from the data that th e annual range of TP concentrations increases as the annual maximum TP increases. Although the annual minimum TP increases somewhat with inc reasing annual maxima, even enriched lakes show a pronounced TP minimu m. As a result, the annual maximum values are highly correlated with t he ranges and means, but less so with the annual minima. 3. The data a re discussed in relation to a conceptual sine wave model and it is sug gested that enrichment modulates the amplitude of the sine wave. 4. Me chanisms conditioning the maximum and minimum values are reviewed.