# Possible Missing Sources of Atmospheric Glyoxal Part I: Phospholipid Oxidation from Marine Algae
## 3 Results and Discussion
### Verification of IMPACTS at a Microcosm Scale  
To validate that the presence of marine glyoxal is indeed linked to the microbiological activity of the seawater and was not an artifact of the wave channel, a subsequent culture flask experiment was conducted in a fume hood using 1.5 L of SIO pier seawater (collected 8 August 2014) spiked with excess nutrients to aid in a quick bloom cycle. Again, utilizing _o_-PDA derivatization within an impinger and GC/MS analysis, glyoxal was detected on Days 3-4 of the collection period (Figure 2a). Together, these findings definitively demonstrate that the ocean can contribute to the levels of glyoxal found in the atmosphere. Moreover, these data suggest that glyoxal formation is directly linked to the life-cycle of the phytoplankton.  
In addition to the SSA collection via impinger, the SSA and headspace of the culture flask experiment were also sampled using a variety of SPME fibers (Figure 2b). The chromatograms for each fiber type used per day were overlayed to provide an aggregated view of the molecules captured. Primarily fatty acid methyl esters (FAMEs) [palmitic (C16:0, RT 47.6 min), stearic (C18:0, RT 53.9 min), oleic (C18:1, RT 53.2 min), and anradichic (C20:0, RT 59.9 min)] were detected during Day 1 and Day 5. Due to the toxic nature of free fatty acids to both eukaryotic and prokaryotic cells [57], fatty acids chains are predominately foundin the form of ester- and ether-linkages in cell membrane components such as glycolipids, triacylglycerlycerides, and phospholipids. In the same vein, FAMEs are not typically occurring cellular molecules, although 3-hydroxy C16:0 FAME has been identified as an endogenous volatile extracellular factor in cell density-associated regulation of virulence genes in the plant pathogenic bacteria _Ralstonia solanacearum_[58]. As such, the presence of FAMEs likely indicates the death and cellular decomposition of the phytoplankton, followed by the transesterification of fatty acid containing molecules to yield FAMEs. The presence of FAME implies that methanol is present. The oxidation of methanol produces formaldehyde, although it is possible that formaldehyde is produced in another way. Although it was not directly observed, benzimidazole, the reaction product of \(o\)-PDA and formaldehyde was detected (Figure 2c), which implies methanol may have undergone oxidation.  
Figure 2: GC/MS temporal chromatograms of glyoxal transported by SSA and collected within an impinger of \(o\)-PDA where it was derivatized to quinoxaline (RT 12.1; SIC \(m/z\) 130) **(a)**; and gas-phase molecules captured by an array of SPME fibers (traces are superimposed) highlighting the primary presence of unsaturated FAMEs **(b)** during the microcosm culture flask experiment. Formaldehyde was also characterized in the impinger of \(o\)-PDA where it was derivatized to benzimidazole (RT 30.1 min, SIC \(m/z\) 118) during the microcosm experiment. Labeled peaks were verified by retention time and MS spectrum using standards (Figures S3–S5). **(c)** the reaction product of \(o\)-PDA and formaldehyde was detected, which implies methanol may have undergone oxidation.