Vertical distribution of epipelagic siphonophores at the confluence between Benguela waters and the Angola Current over 48 hours
Vertical distribution of epipelagic siphonophores at the confluence between Benguela waters and the Angola Current over 48 hours
复制标题
48小时内本格拉水域与安哥拉海流交汇处表层管水母的垂直分布
作者：
F. Pagés;J. Gili
本文研究了纳米比亚北部（18°00′S 10°30′E）海域上浮游虹吸管的昼夜分布。该地区的特点是安哥拉海流的地表水与本格拉最北端地区的水混合在一起。在采样期间，安哥拉海流的持续流动在约30 m深度产生了一个明显的温跃层。为了研究这些水文条件下上层海洋物种的垂直分布格局，在48 h的时间内，在水柱顶部200 m的窄深度层反复取样。共收集到34种。股薄球藻和尾尾螯藻占主导地位。在采样的第二天，特别是在温跃层以上的层中，观察到物种和个体的数量增加。只有少数种类表现出夜间向上迁移，越过两个水团之间的边界。各物种深度分布的差异与3个明显的现象有关：在2个水体中分别存在2个独立的虹吸管种群；垂直迁移的种类最为丰富，它们能够跨越温跃层；以及大多数上层物种斑块大小的差异。
The diel distribution of epipelagic siphonophores at a station off northern Namibia (18°00′ S 10°30′ E) was studied. This area is characterized by the mixing of surface waters of the Angola Current with the waters of the northernmost Benguela region. During the sampling period, the continuous flow of the Angola Current gave rise to a marked thermocline at ca 30 m depth. In order to study the diel vertical distribution patterns of epipelagic species under these hydrographic conditions, narrow depth horizons in the top 200 m of the water column were sampled repeatedly over a 48 h period. Thirty-four species were collected. Sphaeronectes gracilis and Chelophyes appendiculata predominated. Increasing numbers of species and individuals were observed on the second day of sampling, particularly in the layers above the thermocline. Only a few species showed an upward nocturnal migration that crossed the boundary between 2 water masses. The differences in the depth distributions of the various species were related to 3 distinct phenomena: the existence of 2 separate siphonophore populations associated with each of the 2 water masses; vertical migration by the most abundant species, which were able to cross the thermocline; and differences in patch size for the most epipelagic species.