When you’re the size of plankton, water may as well be molasses. Viscosity rules at these scales, and swimming plankton leave distinctive wakes that are slow to dissipate. Fish that feed on plankton use these trails to find their prey. But this microscopic world is changing as the ocean warms.
At higher temperatures, water is less viscous, and plankton wakes don’t last as long. To make matters worse for hungry fish, warmer waters have led to an explosion in a species of faster plankton, capable of moving hundreds of body lengths a second. This species is far more difficult to catch, which may explain some of the collapses we’re observing in populations of fish like cod and haddock. (Video and image credit: BBC Earth Lab)