Running the gauntlet: potential threats to vertical migrators of Monterey Bay

The diel vertical migrations by zooplankton and nekton occur throughout the world-ocean and facilitate the export of carbon from surface waters into the mesopelagic ocean. Driven by the selective advantage of avoiding visual predators near the surface during the day, there are a host of non-visual predators, like siphonophores and medusae that migrating prey must avoid if they are to be successful. Here we examine these migrations from the perspective of the migrators in order to illustrate the kinds of predatory threats they face, and we begin to quantify the threat potential of these non-visual predators based on their size and predation strategies. Our data come from MBARI’s ROV-based, mesopelagic time series which has quantified the abundance and distribution of the midwater community of Monterey Bay for over two decades.