Geology

Daytime

Biology

Atmospheric sciences

Oceanography

Photosynthetically active radiation

Photosynthesis

Diel vertical migration

Predation

Zooplankton

Ecology

Botany

Shoaling and schooling

Dusk

Environmental science

Proceedings of the National Academy of Sciences

Significance Our study provides evidence that, in addition to diel vertical migration, zooplankton residing at &gt;300-m depth during the day perform high-frequency, vertical migrations due to light modulation by clouds. Using a water-following framework and measurements and modeling of the twilight zone light field, we isolated the detailed phototactic response and show that some twilight zone animals are considerably more active than previously thought, with a cumulative distance traveled of more than one-third of that for diel migration. The increased movement increases predation risk and has implications for the metabolic requirements of these animals in the food-limited deep sea.

Cloud shadows drive vertical migrations of deep-dwelling marine life