Department of Hydrobiology, Institute of Functional Biology and Ecology, Faculty of Biology, Biological and Chemical Research Centre, University of Warsaw, Żwirki I Wigury 101, 02-089, Warsaw, Poland.
Hydrobiological Station, Faculty of Biology, University of Warsaw, Pilchy 5, 12-200, Pisz, Poland.
Sci Rep. 2024 Apr 5;14(1):7995. doi: 10.1038/s41598-024-58406-y.
Artificial light at night (ALAN) is known to affect organisms in terrestrial ecosystems and adjacent litoral habitats. In the present study, we tested the effect of ALAN on the spatial distribution of organisms in open waters, using the insect larvae of Chaoborus flavicans as an example. During the day C. flavicans typically hide from visually hunting fish in deep, dark, anoxic waters. On safer nights, they forage in rich subsurface waters. Nighttime field tests revealed that light from an HPS street lamp mounted on a boat anchored in open water attracted planktivorous fish, but deterred planktonic Chaoborus from rich but risky surface waters. Chaoborus did not descend to the safest, anoxic hypolimnion, but remained in hypoxic mid-depth metalimnion, which does not appear to be a perfect refuge. Neither light gradient nor food distribution fully explained their mid-depth residence under ALAN conditions. A further laboratory test revealed a limited tolerance of C. flavicans to anoxia. Half of the test larvae died after 38 h at 9 °C in anoxic conditions. The trade-off between predation risk and oxygen demand may explain why Chaoborus did not hide in deep anoxic waters, but remained in the riskier metalimnion with residual oxygen under ALAN conditions.
人工夜间光照（ALAN）已知会影响陆地生态系统和相邻近岸生境中的生物。在本研究中，我们以 Chaoborus flavicans 的昆虫幼虫为例，测试了 ALAN 对开阔水域生物分布的影响。白天，Ch. flavicans 通常会躲避视觉上捕猎鱼类的深水、黑暗、缺氧水域。在更安全的夜晚，它们会在富含有机物的次表层水域觅食。夜间实地测试表明，安装在停泊在开阔水域的船只上的 HPS 路灯发出的光吸引了滤食性鱼类，但阻止了浮游性 Ch. flavicans 进入富含但有风险的表层水域。Ch. flavicans 没有下降到最安全的缺氧深层，而是留在缺氧的中层，这似乎并不是一个完美的避难所。光照梯度和食物分布都不能完全解释它们在 ALAN 条件下在中层的居留情况。进一步的实验室测试揭示了 Ch. flavicans 对缺氧的有限耐受性。在 9°C 的缺氧条件下，一半的试验幼虫在 38 小时后死亡。捕食风险和氧气需求之间的权衡可能解释了为什么 Ch. flavicans 不在深水区缺氧的水中藏身，而是在 ALAN 条件下含氧的中层风险更大的水域中。
