Artificial light and nocturnal activity in gammarids

Area of Science:

• Aquatic Ecology
• Environmental Science
• Ecotoxicology

Background:

• Artificial light at night (ALAN) is an emerging stressor in aquatic ecosystems.
• Stream invertebrates are exposed to increased light levels from nearby artificial lights.
• Previous research suggests light may impact nocturnal behaviors like drift.

Purpose of the Study:

• To investigate the impact of artificial light on the nocturnal drift rates of stream invertebrates.
• To test the hypothesis that light exposure depresses drift and that invertebrates acclimate to light over time.
• To compare invertebrate activity and drift patterns under varying light conditions.

Main Methods:

• Eight artificial flumes (75m x 1m) were used to simulate stream conditions.
• One flume received strong nighttime light (416 lx), creating a light gradient across others.
• A control flume was kept in complete darkness; light levels mimicked urban areas.

Main Results:

• Contrary to hypotheses, no tested light treatment significantly affected gammarid drift rates.
• In situ activity measurements showed increased activity in darkness and decreased activity under bright light.
• Both nocturnal and diurnal drift increased, with unexpectedly higher drift rates during the day.

Conclusions:

• Artificial light pollution may not directly impact invertebrate drift rates as hypothesized.
• Invertebrate activity patterns are sensitive to light, with a preference for darker conditions.
• Further research is needed to understand the complex responses of aquatic invertebrates to light pollution, including diurnal drift patterns.