Biological Sciences Department, Binghamton University (SUNY), Binghamton, NY 13902, USA.
Biological Sciences Department, Binghamton University (SUNY), Binghamton, NY 13902, USA.
Environ Pollut. 2019 Aug;251:600-608. doi: 10.1016/j.envpol.2019.05.016. Epub 2019 May 8.
Changing light conditions due to human activities represents an important emerging environmental concern. Although changes to natural light conditions can be independently detrimental, in nature, organisms commonly face multiple stressors. To understand the consequences of altered light conditions, we exposed a model amphibian (wood frog; Lithobates sylvaticus) to a control and two anthropogenic light conditions: intensified daytime illuminance and artificial light at night - ALAN (intensified daytime illuminance + extended photoperiod). We measured (1) metrics of fitness (hatching success as well as survival to, size at, and time to metamorphosis) (2) susceptibility (time to death) to a commonly co-occurring anthropogenic stressor, road salt (NaCl) and (3) susceptibility (infection load) to a common parasite (trematode). We also explored behavioral (swimming activity) and physiological (baseline corticosterone (CORT) release rates) changes induced by these light conditions, which may mediate changes in the other measured parameters. We found that both intensified daytime illuminance and ALAN reduced hatching success. In contrast, for amphibians that successfully hatched, neither treatment affected amphibian survival or time to metamorphosis but individuals exposed to ALAN were larger at metamorphosis. The light treatments also had marginal effects; individuals in ALAN treatments were more susceptible to NaCl and trematodes. Finally, tadpoles exposed to ALAN moved significantly less than tadpoles in the control and intensified daytime illuminance treatments, while light had no effect on CORT release rate. Overall, changes in light conditions, in particular ALAN, significantly impacted an amphibian model in laboratory conditions. This work underscores the importance of considering not only the direct effects of light on fitness metrics but also the indirect effects of light with other abiotic and biotic stressors. Anthropogenic-induced changes to light conditions are expected to continue increasing over time so understanding the diverse consequences of shifting light conditions will be paramount to protecting wildlife populations.
由于人类活动导致的光照条件变化是一个重要的新兴环境问题。尽管自然光照条件的变化可能会独立地产生不利影响，但在自然界中，生物通常会面临多种压力源。为了了解光照条件变化的后果，我们将一种模式两栖动物（林蛙； Lithobates sylvaticus）暴露于对照和两种人为光照条件下：白天光照强度增强和夜间人工光照（白天光照强度增强+光照周期延长）。我们测量了（1）适应度指标（孵化成功率以及存活到、达到和变态时间的大小）（2）对一种常见共同人为压力源（道路盐（NaCl））的易感性（死亡时间）和（3）对一种常见寄生虫（吸虫）的易感性（感染负荷）。我们还探索了这些光照条件引起的行为（游泳活动）和生理（皮质酮（CORT）基础释放率）变化，这些变化可能会调节其他测量参数的变化。我们发现，白天光照强度增强和夜间人工光照都降低了孵化成功率。相比之下，对于成功孵化的两栖动物，两种处理都没有影响两栖动物的存活率或变态时间，但暴露于夜间人工光照的个体在变态时更大。光照处理也有轻微的影响；夜间人工光照处理的个体对 NaCl 和吸虫更敏感。最后，暴露于夜间人工光照的蝌蚪的移动明显少于对照和白天光照强度增强处理的蝌蚪，而光照对 CORT 释放率没有影响。总体而言，光照条件的变化，特别是夜间人工光照，在实验室条件下显著影响了一种两栖动物模型。这项工作强调了不仅要考虑光照对适应度指标的直接影响，还要考虑光照与其他非生物和生物压力源的间接影响的重要性。随着时间的推移，预计人为引起的光照条件变化将继续增加，因此了解光照条件变化的多种后果对于保护野生动物种群至关重要。
