The toxigenic diatom Pseudo-nitzschia multiseries Hasle, isolated from the U.S. Pacific Northwest, was examined in unialgal laboratory cultures and in natural assemblages during shipboard experiments, to examine cellular growth and domoic acid (DA) production as a function of nitrogen (N) substrate and availability expected during bloom development and decline. Laboratory experiments utilizing batch cultures conducted at saturating (120 μmol photons m⁻² s⁻¹) photosynthetic photon flux density (PPFD), demonstrated that P. multiseries (strain NWFSC-245) grows equally well on the three N substrates tested (nitrate [NO₃⁻], ammonium [NH₄⁺] and urea), and achieved an average specific growth rate of 0.83 d⁻¹. Despite equivalent growth rates, cellular toxicity (particulate DA concentration normalized to cell abundance) varied as a function of N substrate, with urea-grown cells demonstrating 1.3- and 3.4-fold more toxicity than both NH₄⁺- and NO₃⁻-grown cells. Cellular toxicity of the N-limited chemostat cultures, grown at a dilution rate of 0.48 d⁻¹, were less than the cellular toxicity measured for the N-replete batch cultures for all three N substrates, but again cellular toxicity varied as a function of N substrate and the urea-supported cells were 3.5- and 4.3-fold more toxic than the respective NH₄⁺- and NO₃⁻-supported cells. Starved cultures of P. multiseries showed no decline in cellular toxicity or change in the order of toxicity as a function of N substrate, and cells previously supported by urea were 13- and 5-fold more toxic than NH₄⁺- and NO₃⁻-supported cells. At all three levels of N-sufficiency, the urea-grown cells consistently produced the highest concentration of particulate DA per cell compared to cells grown on either NO₃⁻ or NH₄⁺.

Shipboard N enrichment experiments using natural phytoplankton assemblages were conducted off the west coast of Washington in an area characterized by elevated concentrations of macronutrients and iron. All N (NO₃⁻, NH₄⁺ and urea) treatments showed significant increases in biomass (as measured by total and size-fractionated chlorophyll a) and the abundance of Pseudo-nitzschia species over the 6-d experiment. As with the unialgal laboratory experiments, cellular toxicity varied as a function of the N source supporting growth, and the planktonic assemblages enriched with either NH₄⁺ or urea demonstrated greater cellular toxicity than the assemblages supported solely by NO₃⁻. These laboratory and field results demonstrate that N substrate can regulate the toxicity of Pseudo-nitzschia species, and that N source should be considered when evaluating the potential effects of cultural eutrophication on the growth of toxigenic diatoms.

的产毒硅藻拟菱形藻multiseries Hasle城，从美国太平洋西北分离，在unialgal实验室培养物和天然组合时船上实验检查，以检查细胞生长和软骨藻酸（DA）生产为氮气的功能（N）基板和在花期发展和衰退期间预期的可用性。利用在饱和（120μmol光子m ^-2  s ^-1）光合光子通量密度（PPFD）下进行的分批培养进行的实验室实验表明，多系列疟原虫（菌株NWFSC-245）在测试的三种N底物（硝酸盐[硝酸盐[ NO ₃ ⁻ ]，铵[NH ₄ ⁺]和尿素），平均比增长率为0.83 d ^-1。比两者NH尽管等效的增长率，细胞毒性（微粒DA浓度归一化至细胞丰度）改变为N衬底的功能，与脲生长的细胞显示出1.3倍和3.4倍的毒性₄ ⁺和NO - ₃ ^- -grown细胞。以0.48 d ^-1的稀释率生长的N限制性化学稳定培养物的细胞毒性小于所有三种N底物的N批量培养物中测得的细胞毒性，但细胞毒性又随N的变化而变化。 N底物和尿素支持的细胞比各自的NH ₄ ⁺毒性高3.5倍和4.3倍-和NO ₃ ^- -支持细胞。饥饿的多系疟原虫培养物未显示细胞毒性下降或毒性顺序随N底物的变化而变化，先前由尿素支持的细胞的毒性比NH ₄ ⁺ -和NO _3-高13倍和5倍^。支持的细胞。在所有三个层次的N-自给自足的，尿素生长的细胞始终产生每个细胞相比生长在任一没有细胞的微粒DA的最高浓度₃ ^-或NH ₄ ⁺。

使用天然浮游植物组合进行船上N富集实验是在华盛顿西海岸以外的地区进行的，该地区以大量营养素和铁的浓度升高为特征。所有N（NO ₃ ^-，NH ₄ ⁺和尿素）处理显示出生物量显著增加（如由总和大小分级叶绿素测量一个）和的丰度拟菱形藻物种在6-d的实验。与单宁实验室实验一样，细胞毒性随支持生长的氮源的变化而变化，并且富含NH ₄ ⁺或尿素的浮游生物组合物显示出比仅由NO支撑的组合物更大的细胞毒性。₃ ^- 。这些实验室和现场结果表明，N底物可以调节拟南芥属物种的毒性，并且在评估文化富营养化对产毒硅藻生长的潜在影响时应考虑N来源。