Little is known about diatom parasitism in marine systems. Guinardia delicatula, a biomass‐dominant diatom on the Northeast US Shelf (NES), is regularly parasitized by the protistan nanoflagellate, Cryothecomonas aestivalis in this region. While G. delicatula is known to host other protistan parasites, direct observation of these interactions and their dynamics in nature remain elusive. Here, we integrate concurrent DNA meta‐barcoding and automated imaging‐in‐flow cytometry observations to characterize the dynamics of G. delicatula infection by a second parasite, Pirsonia (likely Pirsonia verrucosa). In contrast with C. aestivalis infections, Pirsonia infections are observed sporadically and typically only in a small fraction of the G. delicatula population on the NES. An exception was found in February 2020, when an anomalous co‐infection event was observed in G. delicatula featuring > 20% infection prevalence by Pirsonia and > 10% infection prevalence by C. aestivalis. Investigation of each parasite's infection dynamics' relationship with temperature and salinity suggested that C. aestivalis may consistently dominate G. delicatula infection dynamics due to its wider thermal tolerance range and more cosmopolitan distribution. Pirsonia only appeared capable of dominating G. delicatula infection at temperatures near or below 4°C, a known temperature threshold below which C. aestivalis infection is suppressed. Our results demonstrate the utility of integrating DNA meta‐barcoding and plankton imaging to observe the dynamics of diatom–parasite interactions in marine systems and shed light on the diversity of infection dynamics in diatom–parasite systems and the forcings governing competition among diatom parasites for a single host.

中文翻译：

---

同时进行的 DNA 元条形码和浮游生物成像揭示了硅藻中新型寄生虫感染和竞争


人们对海洋系统中硅藻的寄生知之甚少。 Guinardia delicatula 是美国东北部陆架 (NES) 上的一种以生物量为主的硅藻，经常被该地区的原生生物纳米鞭毛虫 Cryothecomonas aestivalis 寄生。虽然已知 G. delicatula 寄生有其他原生生物寄生虫，但对这些相互作用及其在自然界中的动态的直接观察仍然难以捉摸。在这里，我们整合了并发 DNA 元条形码和自动流式细胞术成像观察，以表征第二种寄生虫 Pirsonia（可能是 Pirsonia verrucosa）感染 G. delicatula 的动态。与 C. aestivalis 感染相反，Pirsonia 感染是零星发生的，通常仅在 NES 上的一小部分 G. delicatula 群体中观察到。 2020 年 2 月发现了一个例外，当时在 G. delicatula 中观察到异常双重感染事件，其中 Pirsonia 感染率 > 20%，C. aestivalis 感染率 > 10%。对每种寄生虫感染动态与温度和盐度关系的调查表明，C. aestivalis 可能始终主导 G. delicatula 感染动态，因为它具有更广泛的耐热范围和更广泛的分布。 Pirsonia 似乎只能在接近或低于 4°C 的温度下控制 G. delicatula 感染，这是一个已知的温度阈值，低于该温度阈值，C. aestivalis 感染就会受到抑制。我们的结果证明了整合DNA元条形码和浮游生物成像的实用性，可以观察海洋系统中硅藻-寄生虫相互作用的动态，并揭示硅藻-寄生虫系统中感染动态的多样性以及控制硅藻寄生虫之间竞争的力量。单一主机。