Seagrass Beds: Can Zostera marina provide refuge for calcifiers in the face of ocean acidification?

Bonnie WangUniversity of California, Davis, 95616

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METHODS

RESULTS CONCLUSION

• 6, 14-18cm, sediment ‘push cores’ collected along a transect

• 4 cores inside the bed and 6 cores outside the bed

• Cores subsampled at 4 cm resolutions

• Percent carbonate measured

• Microfossils quantified

Figure 1. Study Site: Chicken Ranch Beach, Tomales Bay, CA. Yellow line represents transect inside seagrass bed and red line represents the transect outside.

Figure 2. Numerous calcareous foraminifera.

• The variability in percent carbonate inside the seagrass bed is less than the variability outside the bed

• The difference in percent carbonate between the inside and outside the bed is statistically insignificant

• Average abundance of calcareous foraminifera and ostracods greater outside the bed than inside the bed

• Average abundance of gastropods and bivalves were statistically insignificant

• Seagrass beds do affect calcification as percent carbonate and calcifier abundance is lower inside the bed

• Calcareous foraminifera do not make up for the high percent of carbonate seen outside the bed – may be explained by fragmented shells that were unaccounted for

• Nelson (2015) suggests that results could be due to seagrass beds having lowest pH and Ω aragonite measurements when comparing these measurements inside and outside the bed

• Outside the bed, there is a negative linear relationship between percent carbonate and percent calcareous foraminifera

Figure 3. The average percent carbonate for inside and outside samples at different depths is shown along with the standard deviation.

Figure 4. The average abundance of foraminifera, agglutinated and calcareous, at different depths. The two different color represents whether the values observed were from outside the seagrass bed or inside the seagrass bed.

Figure 5. Percent of carbonate compared to the percent of calcareous foraminifera in each sample.

ACKNOWLEDGEMENTSSpecial thanks to Dr. Tessa Hill for providing this wonderful opportunity and for supporting and guiding me throughout this research. I would also like to thank Aaron Ninokawa for helping me with the data collection. Last but not least, a huge thank you to my collaborator, Mackenzie Nelson, for always listening and providing feedback.

INTRODUCTIONAn increase in anthropogenic CO2 is disrupting the equilibrium of ions in the ocean, causing ocean acidification. This negatively impacts calcareous organisms by disfavoring the production of carbonate ions, a main component in shells and skeletons.

However, the utilization of CO2 through photosynthesis in the seagrass beds (Zostera marina) may create a localized buffer zone from acidification.