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Effects of Ocean Acidification on Antarctic Algal Species

This study examines the impact of ocean acidification on dominant Antarctic algal species and their physiological responses. The effects of increasing CO2 levels on cell growth and photosynthetic efficiency are investigated. The results will contribute to understanding the consequences of ocean acidification on the Antarctic marine ecosystem.

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Effects of Ocean Acidification on Antarctic Algal Species

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  1. The Effects of Ocean Acidification on the Physiology of Dominant Antarctic Algal Species Amelia Snow Dr. Oscar Schofield and Dr. Grace Saba

  2. The CO2 Problem • Since 1800s 40% increase • Preindustrial= 280 ppm • Current= 385ppm • 0.5% increase per year • Ocean absorbs 1/3 CO2 in atmosphere • Temperature increases CO2 solubility

  3. Carbonate chemistry controls pH of seawater • atmCO2 = CO32- and pH • Decrease by 0.12 pH units and 28% increase in ocean acidity • CO2 projected to double by 2100 • Decrease by 0.2-0.3 pH units • 100-150% increase in acidity since before the industrial revolution

  4. Warming in the West Antarctic Peninsula • Fastest warming location on Earth (winter) • Increase of 6oC in past 50 years (>5x the global average) • Increase in ocean heat content • 87% of glaciers in retreat • Sea ice duration decreased by ~90 days

  5. Changes in West Antarctic Peninsula Phytoplankton 1970s-1980s 1995-2005 Montes-Hugo et al. 2009 • Changes in climate=changes in phytoplankton • Warming =chl a by 12% • Shift from large to small cells • Increase in diatom-driven primary productivity in the Southern region • Shift to cryptophytes in Northern region

  6. Phytoplankton Ocean Acidification Tortell et al. 2008 • Few studies in Ross Sea, Antarctica • CO2= relative growth rate and primary productivity • Low CO2-small pennate diatoms • Higher CO2-large chain forming diatoms • Difference in CO2 acquisition due to size of phytoplankton

  7. Diatoms v. Cryptophytes Chaetocerosatlanticus Geminigeracyrophila Fragilariopsiscylindrus http://www.biol.tsukuba.ac.jp http://www.jgi.doe.gov http://tolweb.org • <10 μm • Single-celled • Flagellates • Correlate with warmer temperatures and lower salinity • Increase trend seen in last few years • Related to gelatinous salp feeding efficiency • Krill cannot feed efficiently on cryptophytes (too small) • Decrease in carbon transport to higher trophic levels • 15-270 μm • Single-celled • Chain-forming • Cell wall made of silica • Responsible for 20% of global photosynthesis • Responsible for most carbon sequestration • Most trophic carbon transfer

  8. Objectives and Hypothesis • Objectives: • Compare cell growth and photosynthetic performance of three species of dominant Antarctic algae • Cryptophyte-Geminigeracryophila • Pennate diatom-Fragilariopsiscylindrus • Chain-forming diatom-Chaetocerosatlanticus

  9. Objectives and Hypothesis • Objectives: • Compare cell growth and photosynthetic performance of three species of dominant Antarctic algae • Cryptophyte-Geminigeracryophila • Pennate diatom-Fragilariopsiscylindrus • Chain-forming diatom-Chaetocerosatlanticus • Hypothesis: • pH will decrease as CO2 increases • Diatom abundance and photosynthetic efficiency will increase as CO2 increases • Cryptophyte abundance and photosynthetic efficiency will decrease as CO2 increases

  10. Significance • Phytoplankton are link between lower and higher trophic levels in food web • Drastic changes in phytoplankton result in extreme changes in higher trophic levels • Ultimately could affect carbon cycle

  11. Experimental Design • CO2 bubbling setup • 27 1L bottles • 3 replicates of each species • 3 treatments • 180 ppm • 385 ppm • 750 ppm • Dilution 180 ppm 385 ppm 750 ppm Geminigeracryophila Fragilariopsiscylindrus Chaetocerosatlanticus

  12. Experimental Design • Measurements • pH (pH probe) • Cell count (coulter counter) • fv/fm (FIRe)

  13. Results-pH pH Geminigeracryophila Fragilariopsiscylindrus Chaetocerosatlanticus

  14. Growth Curve-Geminigeracryophila Cells/mL Time (Days)

  15. Growth Curves-Fragilariopsiscylindrus Cells/mL Time (Days)

  16. Growth Curves -Chaetocerosatlanticus Cells/mL Time (Days)

  17. Results-Growth Rates k 385 750 180

  18. Results-Photosynthetic Efficiency fv/fm 180 385 750

  19. Conclusions • Geminigerabest under ambient conditions and did not survive 750 ppm • Fragilariopsisdoes not vary between pCO2 • Chaetocerosmore successful under higher CO2 • Community structure unknown future

  20. Further Investigation • 1000 ppm • Fe Limitation • Low vs. High Light • Time

  21. Acknowledgements • Dr. Oscar Schofield • Dr. Grace Saba • Emily Pirl • Dr. Josh Kohut • Dr. Scott Glenn • Dr. John Reinfelder • George H. Cook Honors Program • Rutgers Coastal Ocean Observation Lab • Institute of Marine and Coastal Sciences • Kyle Richter • Shannon Harrison • Amanda Jones • Dave Kaminsky

  22. Questions?

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