October 10, 2023 10:05 to October 12, 2023 17:30
Head Quarters, Goa
online
Title of Talk: Vertically migrating phytoplankton fuel high oceanic primary production
Speaker: Prof Kai Wirtz
Professor, University Kiel
Department Head at Hereon
Geesthacht/Hamburg
Date & Time: 12th October 2023, 1600 hrs
Venue: Webinar
About the Speaker
Kai Wirtz is professor at Unuversity Kiel and department head at Hereon Geesthacht/Hamburg, with expertise in trait-based ecology, social dynamics, marine ecosystem modelling, benthic-pelagic coupling and plankton. He is a member of the German coordination board for coastal research and leads a large joint German project on multiple stressors on the North Sea ecosystem &40;MuSSeL&41;.
Abstract
Marine net primary production (NPP) is remarkably high given the typical vertical separation of 50–150 m between the depth zones of light and nutrient sufficiency, respectively. Here I present evidence that many autotrophs bridge this gap through downward and upward migration, thereby facilitating biological nutrient pumping and high rates of oceanic NPP. A Lagrangian model suggests that phytoplankton vertical
migration (PVM) fuels up to 40% (>28 tg yr−1 N) of new production and directly contributes 25% of total oceanic NPP (herein estimated at 56 PgC yr−1). Confidence in these estimates is supported by good reproduction of seasonal, vertical and geographic variations in NPP. In contrast to common predictions, the PVM model predicts higher NPP under global warming when enhanced stratification reduces physical nutrient transport into the surface ocean. These findings suggest that PVM is a
key mechanism driving marine biogeochemistry and therefore requires consideration in global carbon budgets and modeling.