ABSTRACT: Impacts on growth rates from exposure to ammonium (NH₄⁺) and nitrate (NO₃^-), at non-limiting concentrations, in combination with irradiances varying from 25 to 600 µmol photons m^-2 s^-1 were investigated in the pelagic diatom Thalassiosira weisflogii and the benthic diatom Entomoneis paludosa recently isolated from Suisun Bay in northern San Francisco Bay. Growth rates were higher in T. weisflogii (0.76 ± 0.3 d^-1) compared with E. paludosa (0.58 ± 0.2 d^-1) across all irradiances and nitrogen (N) treatments. Differences in growth rates with N source were regulated by irradiance in both diatoms and were greatest at the intermediate irradiance due to saturation of rates at 85 µmol photons m^-2 s^-1 when growing on NH₄⁺ and at 200 µmol photons m^-2 s^-1 when growing on NO₃^-. Notable physiological differences between these 2 diatoms included a larger range in the quantum yield of photosystem II (F_v/F_m) and in chlorophyll a per cell as a function of irradiance in T. weissflogii compared with E. paludosa. In addition, a negative interaction of high NH₄⁺ concentration (1000 µmol l^-1) and irradiance (≥200 µmol photons m^-2 s^-1) was observed on growth rates in E. paludosa that was not evident in T. weissflogii. Differences in physiological parameters of these diatoms are discussed in relation to their distributions and frequency of occurrence in Suisun Bay.

中文翻译：

---

氮源，浓度和辐照度对旧金山湾北部特有的两个硅藻生长速率的影响

摘要：对暴露于铵生长速率的影响（NH ₄ ⁺）和硝酸盐（NO ₃ ^- ），在非限制性的浓度，与辐照度为25至600微摩尔光子不同组合中号^-2小号^-1在进行了研究远洋硅藻Thalassiosira weisflogii和底栖硅藻Entomoneis paludos最近从旧金山湾北部的Suisun湾分离出来。生长速率在较高T. weisflogii（0.76±0.3 d ^-1相比）E.蚊（0.58±0.2 d ^-1）在所有辐照度和氮（N）处理中。N源生长速率的差异受两个硅藻的辐照度的影响，并且在中等辐照度时最大，这是因为在NH ₄ ⁺和200 µmol光子m ^-2上生长时，在85 µmol光子m ^-2 s ^-1处的速率饱和S ^ ^-1的NO生长时₃ ^- 。这两个硅藻之间显着的生理差异包括光系统II（F _v / F _m）和每个细胞中叶绿素a的量子产率的较大范围，这取决于魏氏拟南芥中的辐照度。与E. paludosa相比。此外，高NH的负相互作用₄ ⁺浓度（1000微摩尔升^-1）和光照（≥200微摩尔光子米^-2小号^-1）中观察到对生长速率E.蚊，这不是显而易见的在T. weissflogii。讨论了这些硅藻在生理参数上的差异，以及它们在遂顺湾的分布和发生频率。