Diel vertical migration (DVM) is the process of pelagic organisms vertically moving in the water column on a daily basis, often traveling dozens to hundreds of meters . DVM is a wide spread phenomenon that occurs across many taxa and has large consequences in ocean ecosystems.  It is particularly notable in zooplankton communities, whose migrations contribute substantially to biogeochemical cycles. Mesozooplankton communities, largely dominated by copepods, will feed in surface layers of the ocean at night and migrate into deeper waters during daytime. Through this movement, copepods actively transport carbon to depth. While some studies have hypothesized that DVM provides a physiological advantage such as a reduction in UV damage or metabolic and demongraphic benefits, the predator-avoidance hypothesis has received the most support to explain what causes DVM. According to this hypothesis, zooplankton evacuate the sunlit surface to evade visual predators before ascending at night to feed. DVM may thus be a function of an individual copepod's detection risk by a visual predator, which can depend on the copepod's morphological features such as size and transparency.

In their new study titled "Size and transparency influence diel vertical migration patterns in copepods", graduate student Alex Barth, his mentor Dr. Josh Stone, and their collaborator Dr. Rod Johnson used in situ imaging to evaluate how copepod morphological traits influence DVM patterns. They specifically test whether increases in body size and in transparency  increase and reduce DVM magnitude, respectively. They found that larger copepods have a larger DVM signal, and that darker copepods also have a larger DVM signal, but only among the largest group of copepods and not smaller ones. These results reveal a complex dynamic between copepod traits and DVM behavior and provide new insight into the DVM dynamics in oligotrophic gyres.