Evidence for the Production of Copper-complexing Ligands by Marine Phytoplankton in the Canadian Arctic and Subarctic NE Pacific

Organic complexation affects the uptake of copper and other bioactive metals by phytoplankton, with important implications for marine productivity and climate change. However, relatively little is known about the origin and identity of marine copper-complexing ligands. We used immobilized copper(II)-ion affinity chromatography (IMAC) to isolate dissolved (< 0.2 µm) copper ligands from seawater samples collected during the 2015 Canadian Arctic GEOTRACES expedition and recent Line P cruises. UV detection at 254 nm was employed to monitor elution of the compounds retained by IMAC. The areas of the resulting peaks were used to generate depth profiles showing the distribution of marine copper ligands in the Canadian Arctic and alone Line P. The depth of highest ligand concentration was generally found to coincide with the chlorophyll maximum depth. Correlations between ligand concentration and in situ chlorophyll-a fluorescence further suggest that marine phytoplankton or cyanobacteria could be an important source of copper ligands. Spectroscopic analysis of fractions collected during IMAC provides additional information about the composition and structure of these ligands. Use of this information to better understand and predict how copper complexation and bioavailability might affect or be influenced by plankton ecology and climate change will be discussed.