Dupont Nicolas, Aksnes Dag L
Department of biology , University of Bergen , PO Box 7803, N-5020 Bergen , Norway.
J Plankton Res. 2010 Jun;32(6):773-783. doi: 10.1093/plankt/fbq015. Epub 2010 Feb 19.
Jellyfish blooms are of increasing concern in many parts of the world, and in Norwegian fjords an apparent increase in mass occurrences of the deep water jellyfish Periphylla periphylla has attracted attention. Here we investigate the hypothesis that changes in the water column light attenuation might cause local retention and thereby facilitate mass occurrences. We use a previously tested individual-based model of light-mediated vertical migration in P. periphylla to simulate how retention is affected by changes in light attenuation. Our results suggest that light attenuation, in combination with advection, has a two-sided effect on retention and that three fjord categories can be defined. In category 1, increased light attenuation turns fjords into dark "deep-sea" environments which increase the habitat and retention of P. periphylla. In category 2, an optimal light attenuation facilitates the maximum retention and likelihood for mass occurrences. In category 3, further increase in light attenuation, however, shoals the habitat so that individuals are increasingly exposed to advection and this results in loss of individuals and decreased retention. This classification requires accurate determinations of the organism's light preference, the water column light attenuation and topographical characteristics affecting advection.
水母大量繁殖在世界许多地区日益受到关注，在挪威峡湾，深水水母珀氏拟海蜇大量出现的明显增加引起了人们的注意。在此，我们研究水柱光衰减变化可能导致局部滞留从而促进大量出现这一假说。我们使用先前测试过的基于个体的珀氏拟海蜇光介导垂直迁移模型，来模拟光衰减变化如何影响滞留。我们的结果表明，光衰减与平流相结合，对滞留具有双面影响，并且可以定义三种峡湾类别。在第1类中，光衰减增加会使峡湾变成黑暗的“深海”环境，这会增加珀氏拟海蜇的栖息地和滞留率。在第2类中，最佳光衰减有利于最大滞留率和大量出现的可能性。然而，在第3类中，光衰减的进一步增加会使栖息地变浅，从而使个体越来越多地受到平流影响，这导致个体损失和滞留率降低。这种分类需要准确测定生物体的光偏好、水柱光衰减以及影响平流的地形特征。
