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Copper nutrition and transport mechanisms in plankton communities in the northeast Pacific Ocean

University of British Columbia

Copper (Cu) is an essential micronutrient for phytoplankton, particularly during iron limitation, but can also be toxic at relatively low concentrations. While Cu stoichiometry and metabolic functions in marine phytoplankton have been studied, little is known about the substrates for Cu transport and the Cu nutritional state of indigenous phytoplankton communities. The aim of my thesis was two-fold: investigate the bioavailability of organically bound Cu to laboratory and indigenous phytoplankton, and evaluate Cu nutrition of phytoplankton along Line P, a coastal- open ocean transect in the northeast subarctic Pacific Ocean. Organically complexed Cu was bioavailable to four laboratory phytoplankton strains and an Fe-limited phytoplankton community. A laboratory investigation of the substrates for the high-affinity Cu transport system in the model diatom Thalassiosira pseudonana confirmed that organically complexed Cu(II) can be acquired, and likely via extracellular reduction and internalization of Cu(I). Cellular uptake rates of the laboratory strains were similar to those estimated for the natural phytoplankton assemblage, and provide additional evidence that some in situ Cu ligand complexes are likely bioavailable. Using bottle incubations, I investigated the potential for Cu limitation and toxicity in open ocean Fe-limited phytoplankton communities. In 2010, I provided physiological evidence for an interaction between Fe and Cu metabolisms in an Fe-limited phytoplankton community. In 2011, Cu availability to an Fe-limited community was reduced, using a strong Cu(II)-specific ligand, resulting in slower Cu uptake rates, faster growth rates, and increased cyanobacteria abundance. Despite large variations in macronutrient, light, and iron along Line P in 2011, net primary productivity was negatively correlated with inorganic Cu concentrations, and positively correlated with the strength of the in situ ligands. The potential roles of Cu ligands in the sea are discussed, highlighting that the bioavailability of in situ organic Cu complexes is a key determinant for marine primary productivity.

Text

2014-10-22

Attribution-NonCommercial-NoDerivs 2.5 Canada

http://hdl.handle.net/2429/50840

Oceanography

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/2.5/ca/