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Methodology

Background and Purpose

References

Lipid Regulation Table

Figure 1. PCA Scores Plot for PC1 (56.70%) and PC2 (19.32%) comparing the lipid composition between two calcified strains E. huxleyi 607 and E. huxleyi 624 before grazing (control) and after grazing. There are clear differences in lipid regulation between the control and grazing treatments within each strain. Each treatment includes three replicates as shown in the data points.

Figure 2. PLS-DA Scores Plot for LV1 (55.91%) and LV2 (7.74%) comparing the lipid composition between two calcified strains E. huxleyi 607 and E. huxleyi 624 before grazing (control) and after grazing. The differences in lipid regulation between the control and grazing treatments are more prominent in the PLS-DA than PCA for each strain. Each treatment includes three replicates as shown in the data points.

Figure 4. PLS-DA Scores Plot for LV1 (56.93%) and LV2 (21.93%) comparing the lipid composition between two naked strains E. huxleyi 374 and E. huxleyi 379 before grazing (control) and after grazing. The differences in lipid regulation between the control and grazing treatments are more prominent in the PLS-DA than PCA for each strain. Each treatment includes three replicates as shown in the data points.

Figure 3. PCA Scores Plot for PC1 (60.71%) and PC4 (4.86%) comparing the lipid composition between two naked strains E. huxleyi 374 and E. huxleyi 379 before grazing (control) and after grazing. There are clear differences in lipid regulation between the control and grazing treatments within each strain. Each treatment includes three replicates as shown in the data points.

1. Monteiro, F. M., Bach, L. T., Brownlee, C., Bown, P., Rickaby, R. E., Poulton, A. J., Tyrrell, T., Beaufort, L., Dutkiewicz, S., Gibbs, S., Gutowska, M. A., Lee, R., Riebesell, U., Young, J., & Ridgwell, A. (2016). Why marine phytoplankton calcify. Science advances, 2(7), e1501822.

2. Harvey, E.L. and others. 2015. Consequences of strain variability and calcification in Emiliania huxleyi on microzooplankton grazing. Journal of plankton Research 37(6), 1137-1148.

3. Field, C.B., and others. 1998. Primary production of the biosphere: Integrating terrestrial and oceanic components. Science 281, 237-240.

4. Calbet, A. and Landry, M.R. 2004. Phytoplankton growth, microzooplankton grazing, and carbon cycling in marine systems. Limnology and Oceanography 49, 51-57.

5. Guschina I.A., Harwood J.L. (2009) Algal lipids and effect of the environment on their biochemistry. In: Kainz M., Brett M., Arts M. (eds) Lipids in Aquatic Ecosystems. Springer, New York, NY

6. Collins, J.R., and others. 2016. LOBSTAHS: an adduct-based lipidomics strategy for discovery and identification of oxidative stress biomarkers. Analytical Chemistry 88, 7154-7162.

7. Hunter, J.E., and others. 2015. Targeted and untargeted lipidomics of Emiliania huxleyi viral infection and life cycle phases highlights molecular biomarkers of infection, susceptibility, and ploidy. Frontiers in Marine Science 2, 81.

8. Poulin, R.X., and others. 2018. Chemical encoding of risk perception and predator detection among marine estuarine invertebrates. PNAS 115(4), 662-667.

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Table 1. The lipid composition of each strain of E. huxleyi was analyzed via PCA and PLS-DA, and the lipids that held prominent weight in the PLS-DA quantitatively compared treatments of each individual strain before and after grazing. The colored boxes show that there were many unique changes in lipid composition within each individual strain. The orange boxes represent the presence of more lipids before grazing and the blue boxes represent the presence of more lipids after grazing. The symbols beside the lipid types represent the chemical background of each lipid, whether they are a polar (shaded circle), nonpolar (unshaded square), or pigment (unshaded diamond) lipid.

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Acknowledgments

Conclusions and Future Work

A tremendous thank you to Dr. Kelsey Poulson-Ellestad for mentoring me through my first independent research project at Roosevelt University with relentless enthusiasm and support, and for supplying cultures of E. huxleyi and O. marina along with all the necessary equipment to finish each experiment. Also, thank you to Elizabeth L. Harvey and Kyle M. J. Mayers for organizing the data that I used to analyze via Eigenvector Research Inc.

• PCA and PLS-DA data showed that grazing stress influences E. huxleyi lipid composition between all four strains.
• Each strain contained a unique lipidomic profile before and after grazing, but there was no strong evidence showing that lipid profiles were dependent on calcification.
• Each strain varied in polar, nonpolar, and pigment lipids before and after grazing. Future experiments will evaluate how specific lipids influence O. marina’s palatability towards E. huxleyi.
• Polar lipids tend to provide structure to the cell membrane, serve as intermediates in metabolic pathways, and/or play a role in responding to change in their environment; whereas nonpolar lipids tend to function as energy storage until metabolically needed; and pigment lipids serve photosynthetic purposes such as absorbing energy⁵.

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Impacts of Oxyrrhis marina Grazing on Emiliania huxleyi and the Changes in Lipid Composition between Calcified and Naked Strains

Sarah Chavez¹, Kelsey Poulson-Ellestad², Kyle Mayers³, Helen Fredricks⁴, Benjamin Van Mooy⁵, and Elizabeth Harvey⁶

¹Roosevelt University, Chicago, IL, USA; ²NORCE Norwegian Research Centre, Bergen, Norway; ³Woods Hole Oceanographic Institution, Woods Hole, MA USA ; ⁴University of Georgia, Savannah, GA, USA

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• Marine phytoplankton are the fabric of the oceanic food web and play a vital role in biogeochemical cycling².
• Only contributing to about 1% of global plant biomass, phytoplankton are responsible for 50% of the global primary productivity³.
• Emiliania huxleyi, a cosmopolitan, bloom-forming species of phytoplankton, produces coccoliths to form a shell, protecting itself from photodamage, viral/bacterial attack, and predators, such as Oxyrrhis marina¹.
• This microzooplankton protist, O. marina, can reduce daily phytoplankton productivity up to 70%⁴.
• It is important to investigate why O. marina chooses its prey and how grazing stress impacts E. huxleyi lipids, further gaining insight into O. marina’s palatability towards E. huxleyi.
• Lipid compositions of four different strains of E. huxleyi (2 calcified, 2 naked) were evaluated before and during grazing using principal component analysis (PCA) and partial least squared discriminant analysis (PLS-DA) using Solo software by Eigenvector Research Inc.

Calcified Strains Reveal Grazing Stress and Lipid Change

Naked Strains Reveal Grazing Stress and Lipid Change