Problems in estimating phytoplankton nitrogen limitation in Shallow Eutrophic Lakes
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In three shallow eutrophic lakes, phytoplankton nutrient limitation was investigated. Special emphasis was laid on nitrogen limitation. Two different methods were applied: growth response after nutrient supply (enrichment response) and ammonium enhancement response. In two of the three lakes, nitrogen limitation occurred, but the two methods led to different results. The enrichment response was related to the ambient nitrogen concentrations whereas the ammonium enhancement response corresponded more closely with the phytoplankton C:N ratios. Thus, it is difficult to estimate nitrogen limitation in systems with rapid changing nutrient conditions.
Key wordsgrowth bioassay dark carbon fixation mixing nutrient ratio
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