Vitamin and trace metal dynamics in the Southern Ocean: The Biological input vs removal processes of B-vitamins, iron, zinc and cobalt measured using a novel mass balance approach

• Applicant: Florian Koch, Ph.D.
• Subject Area: Oceanography
• Term: from 2017 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 366047219

Vast regions of the worlds ocean, including the Southern Ocean (SO) consist of high nutrient low chlorophyll (HNLC) areas. Rather than macronutrients such as nitrate, micronutrients such as trace metals (TM) and vitamins limit primary production and shape plankton community composition. While concentrations of TMs, new TM inputs and to a lesser extend TM removal processes by the plankton/particles have been extensively studied in the last three decades surprisingly little is known about the role of in situ rate processes such as recycling/grazing in replenishing the bioavailable TM pools. In addition while the importance of vitamins for SO phytoplankton communities has recently been highlighted, to date, no vitamin concentration or utilization/removal rates data exist for the SO. Also, vitamin production rates have never been assessed for any marine system. How do rates of TMs/vitamins recycling/production compare to removal processes and how important is grazing in contributing to bioavailable TMs? Will climate change, higher pCO2 and the resulting less alkaline ocean favor recycling due to changes in TM chemistry and/or biological responses? To answer these questions a novel mass balance approach to measure in situ recycling rates of the three ecological TMs iron (Fe), zinc (Zn) and cobalt (Co) as well as production/recycling rates of vitamins in different SO plankton communities will be explored. In addition, field and laboratory experiments will examine the relative importance of grazing on the pico- and nanoplankton community by higher trophic levels on these rates and investigate how ocean acidification may affect these recycling processes. Together this data will fill in a large gap in TM/vitamin research and provide vital data for global ocean models on the cycling of vitamins, iron and other ecologically relevant TMs under present and future climatic conditions.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1158: Infrastructure area - Antarctic Research with Comparative Investigations in Arctic Sea Ice Areas
• International Connection: Switzerland
• Cooperation Partners: Professorin Dr. Christel Hassler; Professor Dr. Boris Koch; Dr. Bernd Krock; Dr. Scarlett Trimborn