Kacey L. Cope
Research Updates
Artificial Light:
Artificial Light at Night (ALAN) affects over 20% of the earth’s surface and is estimated to increase 6% per year. Most studies of ALAN have focused on a single mechanism or life-stage. We tested for indirect and direct ALAN effects that occurred by altering American toads’ (Anaxyrus americanus) ecological interactions or by altering toad development and growth, respectively. We conducted an experiment over two life-stages using outdoor mesocosms and indoor terraria. In the first phase, the presence of ALAN reduced metamorphic duration and periphyton biomass. The effects of ALAN appeared to be mediated through direct effects on toad development, and we found no evidence for indirect effects of ALAN acting through altered ecological interactions or colonization. In the second phase, post-metamorphic toad growth was reduced by 15% in the ALAN treatment. Juvenile-stage ALAN also affected toad activity: in natural light, toads retreated into leaf litter at night whereas ALAN toads did not change behaviour. Carry-over effects of ALAN were also present; juvenile toads that had been exposed to larval ALAN exhibited marginally increased activity. In this time frame and system, our experiments suggested ALAN’s effects act primarily through direct effects, rather than indirect effects, and can persist across life-stages.
(Dananay and Benard. 2018 Proc. R. Soc.)
Road Salt:
To halt the loss of biodiversity, it is important to understand the effects of anthropogenic disturbance on ecological communities. One pollutant that is increasingly recognized as a threat to the environment is road salt. Road salt is the most common de-icing agent and may contribute to some amphibian declines. Multiple studies have shown road salt decreases survival, growth and development of amphibian eggs or tadpoles. Most studies on road salt are conducted in laboratory conditions and are confined to the tadpole stage, thus potentially missing effects that are mediated through other species in the aquatic community or that are incurred after metamorphosis. We conducted two experiments to test the effect of realistic concentrations of road salt on wood frogs (Rana sylvatica) over multiple environments and life-stages. Road salt did not affect tadpole survivorship but did slow development and increased growth. Road salt also reduced zooplankton abundance, but increased algal growth. Increased algal growth may benefit tadpoles by increasing food resources and may be a result of reduced zooplankton abundance. Additionally, exposure to road salt caused tadpoles to metamorphose at a larger size. After metamorphosis, juvenile frogs were moved into outdoor terrestrial pens and were raised in high and low density treatments for approximately 18 weeks. Exposure to road salt during the tadpole stage increased mortality among terrestrial, juvenile frogs in high density treatments. These results suggest that we may be underestimating the effect of environmental pollutants when focusing only on one life stage or conducting experiments solely in laboratory settings. (Dananay et al. 2015)
Press release on this research can be found at: http://phys.org/news/2015-08-frogs-exposed-road-salt-benefit.html