Skip to content

The Remineralization of Marine Organic Matter by Diverse Biological and Abiotic Processes

James Collins, Ph.D., 2017
Benjamin Van Mooy, Advisor

Aerobic respiration is typically invoked as the dominant mass-balance sink for organic matter in the upper ocean, yet many other biological and abiotic processes can degrade particulate and dissolved substrates on globally significant scales. In this thesis, I query some of these alternative pathways of remineralization. I first assess the relative importance of particle-attached microbial respiration compared to other processes that degrade sinking marine particles. I found that sinking particle material was transferred to the water column 3.5 times as fast as it was directly respired, questioning the assumption that direct respiration dominates remineralization. I next present a new lipidomics method and open-source software package for identification of molecular biomarkers in large, high-mass-accuracy HPLC-ESI-MS datasets. I use the software to identify > 1,100 unique lipids and oxylipins in a marine diatom. Finally, I present the results of photooxidation experiments conducted in waters of the West Antarctic Peninsula, which receive elevated doses of ultraviolet radiation as a consequence of anthropogenic ozone depletion. The mean daily rate of lipid photooxidation in the water column (equivalent to 32 ± 7 µg C m-3d-1) represented between 2 and 8 % of the total bacterial production observed in surface waters following sea ice retreat.