Publication Date:
2022-05-25
Description:
Submitted 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 2016
Description:
The role of oxylipins in ocean biogeochemistry was investigated using microcosm amendment experiments, environmental lipidomics, and culture based studies. Oxylipins are a bioactive class of secondary metabolites produced by diatoms and other eukaryotic phytoplankton. Previous research has focused mainly on one class of oxylipins, polyunsaturated aldehydes (PUAs), and their impacts on copepods. And few studies have looked at the
impacts of oxylipins in situ. Here I show that oxylipins have the potential to impact carbon flux attenuation, oxylipin production in situ is linked to diatom bloom decline and viruses, and oxylipins deter microzooplankton grazing. Sinking particles collected in the North Atlantic were determined to be hot spots for PUAs with concentrations in the micromolar range. Natural particle associated microbial communities exhibited a dose dependent response to PUAs. Stimulatory PUA concentrations ranged from 1-10 μM, resulting in enhanced remineralization of organic
matter by particle associated microbes. Thus, PUAs produced during bloom decline may lead to greater flux attenuation and nutrient recycling. A novel lipidomics approach was applied along a cruise track in the California Coastal System revealing that
canonical diatom free fatty acids and oxylipins dominated the dissolved lipidome and oxylipin abundance was
correlated with diatom bloom demise as assessed by phaeophytin and biogenic Si. RNA viruses were likely the
cause of diatom bloom demise and may have induced oxylipin production. The link between viruses and oxylipins represents a new infochemical signaling pathway in the ocean. Many oxylipins that are novel to the marine
environment were also identified. The dissolved lipidome was sampled during grazing experiments with the microzooplankton grazer Oxyrrhis marina and both wild type Phaeodactylum tricornutum and a chronically stressed, transgenic strain (PtNOA). Grazing was suppressed in the PtNOA treatments compared to the WT, likely due to upregulation of small unknown lipophilic molecules. This suggests that cellular stress and oxylipin production may deter microzooplankton grazing in the
environment potentially altering the transfer of energy through the microbial food web. By employing interdisciplinary approaches, we have learned that oxylipins production in situ is linked to bloom decline and the bioactivity of these compounds has significant implications for ocean biogeochemical cycles.
Description:
This research was supported by a National Science Foundation Graduate Research Fellowship
and grants from the U.S. National Science Foundation (OCE-1061883, OCE-1031143, and OCE
1155663), the Gordon and Betty Moore Foundation (GBMF3301), the U.S. Office of Naval
Research (N000140910091), and the Simons Collaboration on Ocean Processes and Ecology
(SCOPE).
Keywords:
Knorr (Ship : 1970-) Cruise KN207-1
;
Knorr (Ship : 1970-) Cruise KN207-3
;
Point Sur (Ship) Cruise PS1312
;
Atlantic Exploer (Ship) Cruise AE1103
;
Biogeochemistry
Repository Name:
Woods Hole Open Access Server
Type:
Thesis
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