Show simple item record

dc.contributor.authorCollins, James R.  Concept link
dc.date.accessioned2017-02-16T15:52:22Z
dc.date.available2017-02-16T15:52:22Z
dc.date.issued2017-02
dc.identifier.urihttp://hdl.handle.net/1912/8721
dc.descriptionSubmitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2017en_US
dc.description.abstractWhile aerobic respiration is typically invoked as the dominant mass-balance sink for organic matter in the upper ocean, many other biological and abiotic processes can degrade particulate and dissolved substrates on globally significant scales. The relative strengths of these other remineralization processes — including mechanical mechanisms such as dissolution and disaggregation of sinking particles, and abiotic processes such as photooxidation — remain poorly constrained. In this thesis, I examine the biogeochemical significance of various alternative pathways of organic matter remineralization using a combination of field experiments, modeling approaches, geochemical analyses, and a new, high-throughput lipidomics method for identification of lipid biomarkers. I first assess the relative importance of particleattached microbial respiration compared to other processes that can degrade sinking marine particles. A hybrid methodological approach — comparison of substrate-specific respiration rates from across the North Atlantic basin with Monte Carlo-style sensitivity analyses of a simple mechanistic model — suggested sinking particle material was transferred to the water column by various biological and mechanical processes nearly 3.5 times as fast as it was directly respired, questioning the conventional assumption that direct respiration dominates remineralization. I next present and demonstrate a new lipidomics method and open-source software package for discovery and identification of molecular biomarkers for organic matter degradation in large, high-mass-accuracy HPLC-ESI-MS datasets. I use the software to unambiguously identify more than 1,100 unique lipids, oxidized lipids, and oxylipins in data from cultures of the marine diatom Phaeodactylum tricornutum that were subjected to oxidative stress. Finally, I present the results of photooxidation experiments conducted with liposomes — nonliving aggregations of lipids — in natural waters of the Southern Ocean. A broadband polychromatic apparent quantum yield (AQY) is applied to estimate rates of lipid photooxidation in surface waters of the West Antarctic Peninsula, which receive seasonally elevated doses of ultraviolet radiation as a consequence of anthropogenic ozone depletion in the stratosphere. The mean daily rate of lipid photooxidation (50 ± 11 pmol IP-DAG L−1 d−1, equivalent to 31 ± 7 𝜇g C m−3 d−1) represented between 2 and 8 % of the total bacterial production observed in surface waters immediately following the retreat of the sea ice.en_US
dc.description.sponsorshipMost of the work in this thesis was supported by awards to my advisor from the National Science Foundation (NSF OCE-1155438, OCE-1059884, and OCE-1031143), the Gordon and Betty Moore Foundation (GBMF3301), the Woods Hole Oceanographic Institution (through a Cecil and Ida Green Foundation Innovative Technology Award), and the Simons Foundation as part of the Simons Collaboration on Ocean Processes and Ecology (SCOPE). My work at Palmer Station and aboard the ARSV Laurence M. Gould was supported by the Palmer LTER study (NSF awards OPP-9011927, 9632763, 0217282, 0823101, and GEO-PLR 1440435, to H. Ducklow and others). I was personally supported in the middle years of my thesis research by a U.S. Environmental Protection Agency (EPA) STAR Graduate Fellowship (Fellowship Assistance agreement FP-91744301-0). During my fourth year, I received support from the Stanley W. Watson Student Fellowship Fund. Benefits I earned on active duty under the Post 9/11 GI Bill supported me financially in the first year of my Ph.D. studies. I received supplementary funding for my work in Antarctica through an award from the WHOI Ocean Ventures Fund.en_US
dc.language.isoen_USen_US
dc.publisherMassachusetts Institute of Technology and Woods Hole Oceanographic Institutionen_US
dc.relation.ispartofseriesWHOI Thesesen_US
dc.titleThe remineralization of marine organic matter by diverse biological and abiotic processesen_US
dc.typeThesisen_US
dc.identifier.doi10.1575/1912/8721
dc.subject.vesselKnorr (Ship : 1970-) Cruise KN207-1en_US  Concept link
dc.subject.vesselKnorr (Ship : 1970-) Cruise KN207-3en_US  Concept link


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record