Zooplankton Diel Vertical Migration impact on particulate matter flux in the Atlantic

Abstract

The transfer of organic particles to midwater depth is an important factor that supplies organisms at depth with food and for the functioning of the entire marine ecosystem. Zooplankton are key species to contribute to this transfer. Many stay during the night at surface waters where they feed, and migrate during daytime to bellow the euphotic zone to hide from sunlight and predators – a process called Diel Vertical Migration (DVM). This DVM creates an active export of organic and inorganic matter to depths, as the organisms excrete, defecate, respire and die. An Intermediate Particle Maximum (IPM) at midwater depth has been found at similar depth as the DVM at several locations, but it is unclear if this is a more general phenomenon. We here provide the first geographical map of the IPM depths and integrated area for almost the entire tropical Atlantic. We also check if zooplankton DVM is the main mechanism that can generate it, and the relation with primary productivity. The IPM was found in almost all the sampling sites. The IPM occurs at shallower depths in the eastern tropical Atlantic compared to western regions. Zooplankton DVM shows a similar pattern. The IPM depth is overall located at or below the zooplankton migration depths which makes it likely that the IPM is fueled by particles carried to depth by the migrators.