The collective motion of small shrimp as they migrate up and down each day generates downward jets of water that could have a substantial effect on ocean mixing. That’s according to a team from Stanford University, US.
The centimetre-scale brine shrimp are too small to create enough turbulence to alter ocean mixing as an individual. But they migrate vertically over hundreds of metres each day in dense groups, with the aggregation spanning tens of metres vertically.
John Dabiri of Stanford University, US, and colleagues put Artemia salina shrimp in two stably stratified tanks, one to measure irreversible mixing of the density stratification and one to perform flow visualization.
As the shrimp, encouraged to migrate with a light source, swam upwards, the flow in the wakes of the individual shrimp coalesced to form a large-scale downward jet, even in densely stratified water.
Dabiri and colleagues published their findings in Nature.