From Thoreau's woods to the Canary Islands: exploring ocean biogeochemistry through enzymology

Abstract

This essay relates my odyssey in exploring enzyme reactions as oceanographic rate proxies and describes my scientific contributions since 1963. To elucidate biogeochemical processes in marine ecosystems I explored calculating respiratory oxygen utilization (OUR) and nitrate respiration from activities of the respiratory electron transport system (ETS), assimilatory phytoplankton nitrate uptake from nitrate reductase activity, and respiratory CO2 production from isocitrate dehydrogenase. This exploration began at Woods Hole Oceanographic Institute doing a thesis on Krebs-Cycle-based respiration in the quahog, Venus mercenaria, for my B. Sc. at the Massachusetts Institute of Technology (MIT). It continued at the Friday Harbor Marine Laboratory (FHL) of the University of Washington (UW) developing a biological oceanography MS thesis testing succinate dehydrogenase activity as a respiration proxy in Artemia salina. Upon realizing that the ETS, not the Krebs-Cycle, controlled the electron flux to O2, I developed the ETS idea to determine seawater OUR for a Ph. D. thesis at UW. The resulting assay led to the first direct measurements of deep-sea metabolism and allowed biochemical calculations of OUR profiles in the Costa Rica Dome, in the Peru upwelling, and in other ocean water columns. I continued this research at Maine's Bigelow Laboratory for Ocean Science (BLOS), and at Quebec's Institute Maurice Lamontagne (IML). Then, after moving to Spain, I used the stability of my pension to continue this research at the University of Las Palmas de Gran Canaria (ULPGC) where I am catalysing new thinking about ocean metabolism. Here, these topics are integrated into an autobiographic history of this science.