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The uptake rates of NH 4 + , NO 3 − , and urea‐N were determined for Lake Kinneret microplankton over a 2‐year period. NO 3 − was usually the most abundant (0.2–19.3 µ g‐atoms N·liter −1 ), NH 4 + occasionally reached similar concentrations (<0.05–16.4 µ g‐atoms N·liter −1 ), and urea‐N was always present in low concentrations (<0.5–1.5 µ g‐atoms N·liter− 1 ). NO 3 − dominated the total nitrogenous nutrient pool during spring (>90% ∑N as NO 3 − ) when Peridinium cinctum was dominant, but at all times phytoplankton showed preferential NH 4 + uptake. The Peridinium bloom periods were characterized by the highest specific uptake and transport rates for NH 4 + . Turnover times throughout the study ranged from 21‐>7,000 h for NO 3 − , I‐630 h for NH 4 + , and 5‐>560 h for urea‐N. Patterns of preferential utilization for NO 3 − , NH 4 + , and urea‐N were similar to those reported for Chesapeake Bay plankton. Midday uptake rates for NO 3 − , NH 4 + , and urea‐N were all higher under natural light than in darkness.