USAP-DC

The Southern Ocean surrounding Antarctica is changing rapidly in response to Earth's warming climate. These changes will undoubtedly influence communities of primary producers (the organisms at the base of the food chain, particularly plant-like organisms using sunlight for energy) by altering conditions that influence their growth and composition. Because primary producers such as phytoplankton play an important role in global biogeochemical cycling, it is essential to understand how they will respond to changes in their environment. The growth of phytoplankton in certain regions of the Southern Ocean is constrained by steep gradients in chemical and physical properties that vary in both space and time. Light and iron have been identified as key variables influencing phytoplankton abundance and distribution within Antarctic waters. Microscopic algae known as diatoms are dominant members of the phytoplankton and sea ice communities, accounting for significant proportions of primary production. The overall objective of this project is to identify the molecular bases for the physiological responses of polar diatoms to varying light and iron conditions. The project should provide a means of evaluating the extent these factors regulate diatom growth and influence net community productivity in Antarctic waters. Although numerous studies have investigated how polar diatoms are affected by varying light and iron, the cellular mechanisms leading to their distinct physiological responses remain unknown. We observed several growth responses, but a majority of polar diatom growth rates and photophysiology did not appear to be co-limited by iron and light limitation. Using comparative transcriptomics, we have examined the expression patterns of key genes and metabolic pathways in several ecologically important polar diatoms isolated from Antarctic waters and grown under varying iron and irradiance conditions. In addition, molecular indicators for iron and light limitation will be developed within these polar diatoms through the identification of iron- and light-responsive genes -- the expression patterns of which can be used to determine their physiological status. Upon verification in laboratory cultures, these indicators will be utilized by way of metatranscriptomic sequencing to examine iron and light limitation in natural diatom assemblages collected along environmental gradients in Western Antarctic Peninsula waters. In order to fully understand the role phytoplankton play in Southern Ocean biogeochemical cycles, dependable methods that provide a means of elucidating the physiological status of phytoplankton at any given time and location are essential.

Person	Role
Marchetti, Adrian	Investigator and contact
Moreno, Carly	Researcher

Antarctic Organisms and Ecosystems

Award # 1341479

USAP-1341479_1

None in the Database

Repository	Title (link)	Format(s)	Status
iMicrobe	Fragilariopsis kerguelensis iron and light transcriptomes	None	exist
NCBI GenBank	Sequence data RNA-Seq of marine phytoplankton: FeB12	None	exists
NCBI GenBank	Sequence data from Ocean Station Papa seawater	None	exists
Cyverse Data Commons	Polar isolate transcriptomes	None	exist
BCO-DMO	Physiology and transcriptomes of polar isolates	None	exist
NCBI GenBank	16S and 18S Sequence data	None	exists

1. Ellis KA. et al. 2016. Cobalamin-independent methionine synthase distribution and influence on vitamin B12 growth requirements in marine diatoms. Protist.  (doi:10.1016/j.protis.2016.10.007 )
2. Lin Y. et al. (2017) Specific eukaryotic plankton are good predictors of net community production in the Western Antarctic Peninsula. Scientific Reports. 7: 14845. (doi:10.1038/s41598-017-14109-1)
3. Marchetti, A. et al. Development of a molecular-based index for assessing iron status in bloom-forming pennate diatoms. J. Phycol. (2017). (doi:10.1111/jpy.12539)
4. Moreno, C.M. et al. 2018. Examination of gene repertoires and physiological responses to iron and light limitation in Southern Ocean diatoms. Polar Biology. (doi:10.1007/s00300-017-2228-7 )
5. Moreno, C.M. et al. Interactive effects of iron and light limitation on the molecular physiology of the Southern Ocean diatom Fragilariopsis kerguelensis. in prep.
6. The molecular products and biogeochemical significance of lipid photooxidation in West Antarctic surface waters, Collins et al. Geochimica et Cosmochimica Acta, Volume 232, 1 July 2018, Pages 244-264 (doi:10.1016/j.gca.2018.04.030)
7. Brown, M. S., Bowman, J. S., Lin, Y., Feehan, C. J., Moreno, C. M., Cassar, N., … Schofield, O. M. (2021). Low diversity of a key phytoplankton group along the West Antarctic Peninsula. Limnology and Oceanography. (doi:10.1002/lno.11765)
8. Lin, Y., Moreno, C., Marchetti, A., Ducklow, H., Schofield, O., Delage, E., … Cassar, N. (2021). Decline in plankton diversity and carbon flux with reduced sea ice extent along the Western Antarctic Peninsula. Nature Communications, 12(1). (doi:10.1038/s41467-021-25235-w)
9. Lampe, R. H., Cohen, N. R., Ellis, K. A., Bruland, K. W., Maldonado, M. T., Peterson, T. D., … Marchetti, A. (2018). Divergent gene expression among phytoplankton taxa in response to upwelling. Environmental Microbiology, 20(8), 3069–3082. (doi:10.1111/1462-2920.14361)
10. Marchetti, A. (2016). Isolate information on genes found in samples collected on the Gould (LMG1411) cruise in the Western Antarctica Peninsula in 2014 (Polar Transcriptomes project). Biological and Chemical Oceanography Data Management Office. (doi:10.1575/1912/bco-dmo.665288.1)
11. Marchetti, A. (2016). Diatom growth rates from samples collected on the Gould cruise LMG1411 in the Western Antarctica Peninsula from 2014 (Polar Transcriptomes project). Biological and Chemical Oceanography Data Management Office. (doi:10.1575/1912/bco-dmo.666201.1)
12. Marchetti, A. (2016). Marine Microbial Eukaryote Transcriptome Sequencing Project (MMETSP) location information on samples obtained on Gould (LMG1411) in the Western Antarctica Peninsula during 2014 (Polar Transcriptomes project). Biological and Chemical Oceanography Data Management Office. (doi:10.1575/1912/bco-dmo.665427.1)
13. Marchetti, A. (2016). Transcriptome statistics from samples obtained on LMG1411 collected on the Gould (LMG1411) in the Western Antarctica Peninsula in 2014. (Polar Transcriptomes project). Biological and Chemical Oceanography Data Management Office. (doi:10.1575/1912/bco-dmo.665311.1)
14. Marchetti, A. (2016). Biovolume data from samples obtained on Gould cruise LMG1411 in the Western Antarctica Peninsula during 2014 (Polar Transcriptome project). Biological and Chemical Oceanography Data Management Office. (doi:10.1575/1912/bco-dmo.666234.1)
15. Marchetti, A. (2016). BLASTp homology data from genes obtained in samples collected on the Gould (LMG1411) cruise in the Western Antarctica Peninsula during 2014 (Polar Transcriptomes project). Biological and Chemical Oceanography Data Management Office. (doi:10.1575/1912/bco-dmo.665454.1)
16. Marchetti, A. (2016). Presence and absence of iron and light-related functional genes collected on the Gould (LMG1411) cruise in the Western Antarctica Peninsula during 2014 (Polar Transcriptomes project). Biological and Chemical Oceanography Data Management Office. (doi:10.1575/1912/bco-dmo.665407.1)