In addition to macronutrients (fixed nitrogen (NO 3 + NO 2 ), phosphate (PO 4 ), and silicic acid), trace metals (TMs) including iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), manganese (Mn), and cadmium (Cd) have attracted research interest due to their roles in marine primary productivity (Morel & Price, 2003;Twining & Baines, 2013). Because the supply of bio-essential TMs is in large parts of the global ocean insufficient to fully meet phytoplankton growth requirements (C. M. Moore et al., 2013), short-term growth of phytoplankton communities is often TM limited or co-limited (e.g.,