Factors Influencing Orthophosphate Turnover Times: a Comparison of Canadian and New Zealand Lakes

Fifty-five samples of lakewater from 21 New Zealand and 9 Canadian lakes were analyzed for dissolved phosphate, particulate phosphorus, and particulate nitrogen. The particulate N was used as an estimate of phytoplankton biomass and the ratio of particulate N to particulate P was used as an indicator of phosphorus sufficiency or deficiency within the biota. 32 P-PO 4 -derived turnover times were found to be positively related to the size of the dissolved phosphate pool, negatively related to biomass, and were short where phosphorus deficiency existed. The amount of particulate nitrogen in the Canadian lake samples probably indicates an abundance of this nutrient in Canadian waters relative to that found in New Zealand. High seston N/P ratios in Canadian samples indicate a degree of phosphorus shortage in biota which is seen in few New Zealand waters.