The organic carbon resulting from photosynthesis in the upper ocean is transferred downward through the passive sinking of organic particles, physical mixing of particulate and dissolved organic carbon as well as active flux transported by zooplanktonic and micronektonic migrants. Several meso- and bathypelagic organisms feed in shallower layers during the nighttime and respire, defecate, excrete and die at depth. Recent studies suggest that migrant micronekton transport similar amounts of carbon to migrant zooplankton. However, there is scarce information about biomass and carbon flux by non-migratory species in the mesopelagic and bathypelagic zones. The non-migratory bristlemouth fishes (Cyclothone spp.) and partial migrator (A. hemigymnus) remineralise organic carbon at depth, and knowledge about this process by this fauna is lacking despite them having been referred to as the most abundant vertebrates on Earth. Here we show the vertical distribution of biomass and respiration of non-migratory mesopelagic fishes, during day and night, using the enzymatic activity of the electron transfer system (ETS) as a proxy for respiration rates. The study is focused on five Cyclothone species (C. braueri, C. pseudopallida, C. pallida, C. livida and C. microdon) and Argyropelecus hemigymnus. The samples were taken on a transect from the oceanic upwelling off Northwest Africa (20° N, 20° W) to the south of Iceland (60° N, 20° W). Cyclothone spp. showed, by far, the largest biomass (126.90 ± 86.20 mg C·m⁻²) compared to A. hemigymnus (0.54 ± 0.44 mg C·m⁻²). The highest concentrations of Cyclothone spp. in the water column were observed between 400 and 600 m and from 1000 to 1500 m depths, both during day and night. For the different species analysed, ETS activity did not show significant differences between diurnal and nocturnal periods. The total average specific respiration of Cyclothone spp. (0.02 ± 0.01 d^-1) was lower than that observed for A. hemigymnus (0.05 ± 0.02 d^-1). The average carbon respiration of Cyclothone spp. was 2.22 ± 0.81 mg C·m⁻²·d^-1, while it was much lower for A. hemigymnus (0.04 ± 0.03 mg C·m⁻²·d^-1). The respiration of Cyclothone spp. was lower in the bathypelagic than in the mesopelagic zone (0.84 ± 0.48 vs 1.36 ± 1.01 mg C·m⁻²·d^-1, respectively). These results, to our knowledge, provide the first account of remineralisation by this community in the meso and bathypelagic zones of the ocean.

上层海洋光合作用产生的有机碳通过有机颗粒的被动下沉、颗粒和溶解的有机碳的物理混合以及浮游动物和微运动迁移的主动通量向下转移。一些中层和深海生物在夜间以较浅的层为食，并在深处呼吸、排便、排泄和死亡。最近的研究表明，迁移的微游动物与迁移的浮游动物运输相似数量的碳。然而，关于中层和深海区非洄游物种的生物量和碳通量的信息很少。非洄游性刚毛鱼 ( Cyclothone spp.) 和部分洄游者 ( A. hemigymnus) 在深度再矿化有机碳，尽管它们被称为地球上最丰富的脊椎动物，但对这种动物群的这一过程的了解仍然缺乏。在这里，我们使用电子转移系统 (ETS) 的酶活性作为呼吸速率的代表，显示了生物量的垂直分布和非洄游中层鱼类在白天和晚上的呼吸。该研究的重点是五种Cyclothone物种（C. braueri、C. pseudopallida、C. pallida、C. livida和C. microdon）和Argyropelecus hemigymnus. 这些样本取自西北非洲（20° N，20° W）到冰岛南部（60° N，20° W）的海洋上升流的横断面。Cyclothone spp。到目前为止，与A. hemigymnus (0.54 ± 0.44 mg C· m ^-2 ) 相比，显示出最大的生物量 (126.90 ± 86.20 mg C· m ^-2 )。Cyclothone spp的最高浓度。在 400 至 600 m 和 1000 至 1500 m 深度之间观察到水柱，无论是白天还是晚上。对于所分析的不同物种，ETS 活动在昼夜时段之间没有显示出显着差异。Cyclothone spp的总平均比呼吸。(0.02 ± 0.01 d ^-1 ) 低于观察到的A. hemigymnus (0.05 ± 0.02 d ^-1 )。Cyclothone spp的平均碳呼吸。为 2.22 ± 0.81 mg C·m ^-2 ·d ^-1，而A. hemigymnus低得多（0.04 ± 0.03 mg C·m ^-2 ·d ^-1）。Cyclothone spp的呼吸作用。深海层低于中层层（分别为 0.84 ± 0.48 对 1.36 ± 1.01 mg C·m ^-2 ·d ^-1）。据我们所知，这些结果首次说明了该群落在海洋中部和深海带的再矿化。