The dark ocean and the underlying deep seafloor together represent the largest environment on this planet, comprising about 80% of the oceanic volume and covering more than two-thirds of the Earth's surface, as well as hosting a major part of the total biosphere. Emerging evidence suggests that these vast pelagic and benthic habitats play a major role in ocean biogeochemistry and represent an “untapped reservoir” of high genetic and metabolic microbial diversity. Due to its huge volume, the water column of the dark ocean is the largest reservoir of organic carbon in the biosphere and likely plays a major role in the global carbon budget. The dark ocean and the seafloor beneath it are also home to a largely enigmatic food web comprising little-known and sometimes spectacular organisms, mainly prokaryotes and protists. This review considers the globally important role of pelagic and benthic protists across all protistan size classes in the deep-sea realm, with a focus on their taxonomy, diversity, and physiological properties, including their role in deep microbial food webs. We argue that, given the important contribution that protists must make to deep-sea biodiversity and ecosystem processes, they should not be overlooked in biological studies of the deep ocean.

暗海和下面的深海底面共同构成了这个星球上最大的环境，约占海洋总量的80％，覆盖了地球表面的三分之二以上，并且拥有整个生物圈的大部分。越来越多的证据表明，这些广阔的中上层和底栖生境在海洋生物地球化学中起着重要作用，并代表了高遗传和代谢微生物多样性的“未开发储量”。由于其巨大的容量，暗海的水柱是生物圈中最大的有机碳库，可能在全球碳预算中发挥重要作用。黑暗的海洋和它下面的海底也是一个巨大的神秘食物网的所在地，其中包含鲜为人知的生物，有时甚至是壮观的生物，主要是原核生物和原生生物。这篇综述考虑了深海领域中所有原生动物大小级别的浮游和底栖生物的全球重要性，重点是它们的分类学，多样性和生理特性，包括它们在深层微生物食物网中的作用。我们认为，鉴于生物学家必须对深海生物多样性和生态系统过程做出重要贡献，因此在深海生物学研究中不应忽视它们。