Print PageMost of the research on artificial light has focused on one group of organisms (such as sea turtles or insects), however, artificial light might also influence entire ecosystems and how they function. We aimed to test a series of hypotheses about how artificial light might change stream ecosystem processes. Specifically, we predicted that invertebrate drift, fish presence and condition, and leaf litter decomposition would all decrease under artificial light. We tested this by setting up ~40 m long paired reaches on each of 4 small streams, one with light and one control, in the Malcolm Knapp Research Forest, 60 km east of Vancouver, Canada. Three high-pressure sodium streetlights were placed along the banks of each experimental reach and were lit for 8-9 hours every night during the entire month of June 2011.
Results/Conclusions
Preliminary results show that responses to artificial light are variable. For instance, fish body condition was higher in the experimental reach relative to the control reach of one stream (p = 0.01), but the other streams did not exhibit a difference between experimental and control reaches. Similarly, leaf litter decomposition rates were not significantly different between experimental and control reaches. On the other hand, we did find the predicted decrease in invertebrate drift in the experimental reaches. These results suggest that while the effects of artificial light at night on stream ecosystem functioning are variable, important ecosystem functioning is altered by the presence of artificial lights. City and conservation planners should take this into account when designing appropriate lighting installations near stream and riparian habitats.
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