During a 2-year study of planktonic nitrogen (N) nutrition, temporal variability of (1) ambient nutrient concentrations; (2) uptake rates of ammonium (NH₄⁺), nitrate (NO₃⁻), nitrite (NO₂⁻), urea, and amino acids (AA) in three size fractions (> GF/F, > 5 μm, and 5–0.2 μm); (3) NH₄⁺ regeneration and NO₃⁻ regeneration (nitrification); and (4) an unexpected bloom of Alexandrium monilatum were examined. Dissolved organic N (DON) was the most abundant form of fixed N. High concentrations of NH₄⁺ and NO₂⁻ were detected during the late summer and fall, reaching maximums of 9.9 and 7.6 μmol N L⁻¹, respectively. The highest uptake rates were for NH₄⁺ at all stations, size fractions, and seasons sampled and ranged from 34 to 80% of total absolute N uptake. The magnitude of uptake rates in the > GF/F fraction generally followed the pattern of NH₄⁺ > NO₃⁻ > urea > AA > NO₂⁻ with some exceptions when urea uptake rates were higher than NO₃⁻. Rates of NH₄⁺ regeneration and nitrification often exceeded uptake rates, indicating autochthonous pathways for nutrient loading. Exceptionally high dinoflagellate biomass was found in late summer and corresponded with harmful algal blooms. Kinetic curves measured during an A. monilatum bloom showed high V_max (33.7 ± 2.7 × 10⁻³ h⁻¹) and high K_s (7.3 μmol N L⁻¹) for NH₄⁺ suggesting that it can rapidly utilize high concentrations when available but may be outcompeted by other phytoplankton when concentrations of NH₄⁺ are low. However, A. monilatum demonstrated that it is capable of using a diverse suite of N substrates, giving it a potential competitive advantage under diverse nutrient conditions.

在为期2年的浮游氮（N）营养研究中，（1）环境营养物浓度的时间变化；（2）摄取铵的速率（NH ₄ ⁺），硝酸（NO ₃ ^- ），亚硝酸根（NO ₂ ^- ），尿素，和在三个尺寸的级分的氨基酸（AA）（> GF / F，> 5微米，并5–0.2μm）；（3）NH ₄ ⁺的再生和NO ₃ ^-再生（硝化）; （4）检查了亚历山大藻的意外开花。溶解的有机N（DON）是NH的固定N.高浓度的最丰富的形式₄ ⁺和NO ₂ ^-在夏末和秋季期间检测到最大浓度分别为9.9和7.6μmolN L ^-1。NH ₄ ⁺的最高吸收速率是在所有采样站，大小分数和采样季节采集的，并且占绝对绝对N吸收总量的34％至80％。在> GF / F部分摄取速率的大小一般遵循NH的图案₄ ⁺ > NO ₃ ^- >尿素> AA> NO ₂ ^-有一些例外，当尿素吸收速率比NO较高₃ ^- 。NH ₄ ^+的比率再生和硝化作用经常超过吸收速率，这表明营养物质负载是自生途径。在夏末发现异常高的鞭毛生物量，并对应于有害的藻华。A. monilatum盛开期间测得的动力学曲线显示，NH ₄ ^+的高V _max（33.7±2.7×10 ^-3  h ^-1）和高K _s（7.3μmolN L ^-1），表明它可以在可用时快速利用高浓度但当NH ₄ ⁺浓度较低时，可能会被其他浮游植物所竞争。然而，A。monilatum 证明了它能够使用多种N底物，在多种营养条件下具有潜在的竞争优势。