Satellite-based indicator of zooplankton distribution for global monitoring

This study investigates the association between an index of mesozooplankton biomass, derived from the Continuous Plankton Recorder survey and satellite-derived productivity fronts in the North Atlantic. While chlorophyll-a content (CHL) is commonly described as a proxy for phytoplankton biomass, the size of productivity fronts estimated from the horizontal gradient of CHL appears to be directly linked to mesozooplankton biomass. Our results suggest that the lifespan of productivity fronts, which ranges from weeks to months, meets the time requirement of mesozooplankton to develop. The proposed indicator describes the daily distribution of mesozooplankton's suitable feeding habitat. It also provides a coherent interpretation of the productivity front development with respect to phytoplankton activity (CHL values) and potential predation by higher trophic levels. Since mesozooplankton are essential for feeding at higher trophic levels, this satellite-derived indicator delivers essential information for research and policy. An unanticipated positive trend of the indicator from 2003 to 2017 is observed at a basin scale under the current effects of climate change, with regional peaks in relatively poorly productive areas. Such monitoring indicator is potentially important to advances in marine food web modelling, fisheries science and the dynamic management of oceans towards sustainability.