Distribution of macrozooplankton at time series station MIGZOO-1

Vertical distributions and diel migrations of the main species of micronekton, four euphausiids, one mysid, one decapod and three fishes, were described in detail in the 0-1000 m water column on a fixed station in the Northwestern Mediterranean Sea. The euphausiids Euphausia krohni and Thysanopoda aequalis, the decapod Gennadas elegans and, to a lesser extent, the fish Argyropelecus hemigymnus were shown to perform clear diel vertical migrations. Results of horizontal hauls at a given depth around sunrise and sunset showed a marked diurnal symmetry of the migratory cycles, particularly for E.krohni, T.aequalis and G.elegans. The behaviour of the euphausiid Nematoscelis megalops was more complex: it presented a repetitive bimodal day distribution and only part of its population migrated. As very weak or non-migrators we found the euphausiid Stylocheiron longicorne and the bathypelagic mysid Eucopia unguiculata, for which migration concerned only some of the older individuals. The fishes Cyclothone braueri and Cyclothone pygmaea appeared to be non-migrants. As depth increased, C.braueri was replaced by C.pygmaea, with maximum concentrations at 350-550 and 550-700 m depth, respectively.

本研究详细描述了西北地中海某固定站点0-1000米水柱中微型浮游动物（micronekton）主要种类的垂直分布与昼夜迁移特征，涉及4种磷虾（euphausiid）、1种糠虾（mysid）、1种十足目甲壳动物（decapod）及3种鱼类。研究发现，磷虾Euphausia krohni、Thysanopoda aequalis，十足目甲壳动物Gennadas elegans，以及程度较轻的鱼类Argyropelecus hemigymnus均表现出明显的昼夜垂直迁移行为。日出与日落时段特定深度的水平拖网结果显示，迁移周期具有显著的昼夜对称性，尤以E.krohni、T.aequalis和G.elegans为甚。磷虾Nematoscelis megalops的行为更为复杂：其白天呈现重复的双峰分布模式，且仅部分种群发生迁移。此外，磷虾Stylocheiron longicorne与深海层糠虾Eucopia unguiculata为弱迁移或非迁移物种，后者仅部分老年个体参与迁移。鱼类Cyclothone braueri与Cyclothone pygmaea为非迁移物种；随着深度增加，C.braueri逐渐被C.pygmaea取代，二者的最大浓度分别出现在350-550米和550-700米深度。