Distribution of siphonophores in the upwelling area off NW Africa

Using a Bongo-Net equipped with a multiple coded closing device, the vertical distribution of siphonophores has been observed in 100 m depth intervals at 13 stations off Cap Mirik (19°N) (from 0-500 m depth). This distributional pattern of the 15 siphonophores species found is discussed in relationship to the hydrography of this upwelling region. The following main features have been observed in comparision with the warmer oceanic water offshore: (1) a lower diversity, (2) a shallower distribution of some of the deep living species die to the lower temperature in the upper 300 m an a lower transparency, (3) no contribution to acoustic scattering by physonect siphonophores.本研究借助搭载多编码闭合装置的邦戈网（Bongo-Net），在19°N的米尔里克角外海13个站位，以100米水深为间隔开展管水母类（siphonophores）的垂直分布观测，观测水深范围为0至500米。针对本次观测发现的15种管水母类的分布格局，本研究结合该上升流区域的水文状况展开关联讨论。相较于外海暖大洋水，本次观测得到的主要特征如下：(1) 物种多样性更低；(2) 受上层300米水温偏低且透明度较差的影响，部分深水栖息物种的分布层更浅；(3) 胞管水母亚目（physonect）管水母类未对声学散射产生贡献。