The Effects of Hypersalinity on Aiptasia Polyps Final Presentation Group 1: Valeria Dias, Barbara Kiersz, Caitlin Liston, Isaac Markus, Amy Muehlmatt, Yamily Musa.

Questions Discussed How does water salinity affect the symbiosis of polyps and zooxanthellae? After initial bleaching has occurred from shock, do the polyps continue to bleach over time?

Null Hypotheses An increase in salinity will have no effect on density of zooxanthellae in the polyps. After the polyps have been partially shocked at 45 ppt, the bleaching will come to a halt and zooxanthellae density will remain constant.

Experimental Design The polyps were shocked by increasing the salinity of the tank to 45 ppt. The polyps were kept at a steady salinity – 45 ppt – for remaining time, while we monitored for bleaching. Zooxanthellae density, protein concentration and chlorophyll concentration were measured for a total of four weeks.

Alternate Hypotheses An increase in salinity will cause zooxanthellae to die or separate from coral polyps, lowering their density in the polyps. After they have been shocked, polyps will continue to slowly lose zooxanthellae when kept at a constant salinity of 45ppt.

*Data* Week 1 Week 2 Week 3 Week 4 8.9 x 108 1.7 x 108 8.0 x 107 Zooxanthellae Density (per gram of polyp) 8.9 x 108 1.7 x 108 8.0 x 107 1.4 x 108 Chlorophyll (ng/ 106 cells) 0.24 3.28 8.26 3.79 Protein (mg/g solution) 45.0 25.6 23.8 21.40 Week 1: Salinity was increased from 35 ppt to 37 ppt. Week 2: Found salinity at 40 ppt, raised it to 43 ppt. Week 3: Found salinity at 45 ppt, kept it constant at 45 ppt. Week 4: Found salinity at 45 ppt - Final measurements of variables

Background Info Polar ice sheets and global warming: ~“Over the last 15 years, the Northern Hemisphere tropical temperatures have gone up by one half degree (Fahrenheit)," says Alan Strong of NESDIS (qtd. in “NOAA…”) Possible melting from Greenland, Antarctica, ice sheets, and ice caps (van deer Veen). This melting leads to cooler deep waters with a lower salinity, HOWEVER…. *chart taken from (van der Veen).

Continued… ….As the cold water is added to the equator the warm water rises. As the warmer water evaporates from the surface of the ocean the salinity level increases. Corals are found in the tropical and subtropical regions around the equator, therefore global warming causes a fluctuation of salinity levels in their environment.

Conclusion Weeks 1-3: Our hypothesis was supported by the results obtained during the first three weeks; the polyps did bleach. Week 4: The zooxanthellae density increased, suggesting the polyps adapted to the new salinity level (osmoconformation) or an error in the experiment.

So What? With the rapid increase in temperature, the water around the equator is getting saltier and saltier, and if the hyper saline shock is large enough, coral bleaching occurs. While these corals may adapt to their new environment, if the shock is too great, there will be mass bleaching of the corals and eventually their death.

Sources “NOAA delivers early warning of coral bleaching.” Cable News Network, 2001. 14 Nov 2006. <http://archives.cnn.com/2000/NATURE/10/05/coral.bleaching.enn/> van der Veen, C. J. “Polar ice sheets and global sea level: how well can we predict the future?” Global and Planetary Change. Vol. 32, 2-3. 15 April 2002. 165-94. Dr. Dan DiResta

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