Department of Mathematics and Statistics, University of Strathclyde, Glasgow G1 1XH, UK.
Scottish Association for Marine Science, Oban, Argyll PA37 1QA, UK.
Biol Lett. 2021 Feb;17(2):20200810. doi: 10.1098/rsbl.2020.0810. Epub 2021 Feb 24.
The predation risk of many aquatic taxa is dominated by visually searching predators, commonly a function of ambient light. Several studies propose that changes in visual predation will become a major climate-change impact on polar marine ecosystems. The High Arctic experiences extreme seasonality in the light environment, from 24 h light to 24 h darkness, and therefore provides a natural laboratory for studying light and predation risk over diel to seasonal timescales. Here, we show that zooplankton (observed using acoustics) in an Arctic fjord position themselves vertically in relation to light. A single isolume (depth-varying line of constant light intensity, the value of which is set at the lower limit of photobehaviour reponses of spp. and krill) forms a ceiling on zooplankton distribution. The vertical distribution is structured by light across timescales, from the deepening of zooplankton populations at midday as the sun rises in spring, to the depth to which zooplankton ascend to feed during diel vertical migration. These results suggest that zooplankton might already follow a foraging strategy that will keep visual predation risk roughly constant under changing light conditions, such as those caused by the reduction of sea ice, but likely with energetic costs such as lost feeding opportunities as a result of altered habitat use.
许多水生类群的捕食风险主要由视觉捕食者主导，通常与环境光有关。一些研究提出，视觉捕食的变化将成为对极地海洋生态系统的主要气候变化影响。高北极地区的光照环境经历着极端的季节性变化，从 24 小时光照到 24 小时黑暗，因此为研究昼夜到季节性时间尺度的光照和捕食风险提供了一个自然实验室。在这里，我们表明，北极峡湾中的浮游动物（通过声学观测）在垂直方向上与光照有关。单一等照度线（光照强度随深度变化的线，其值设定为 spp.和磷虾的光行为反应下限）在浮游动物分布上限处形成一个天花板。垂直分布受到光照的时间尺度的影响，从春季太阳升起时浮游动物种群在中午加深，到浮游动物在昼夜垂直迁移期间上升觅食的深度。这些结果表明，浮游动物可能已经遵循了一种觅食策略，即在光照条件变化（例如海冰减少引起的变化）下，使视觉捕食风险大致保持不变，但可能会产生能量成本，例如由于栖息地使用的改变而失去觅食机会。
