Discipline: Ecology Environmental and Earth Sciences
Subcategory: Ecology
Session: 4
Room: Private Dining
Ignacio Rueda - Texas A&M University-Corpus Christi
Co-Author(s): Maile Coberly, The University of Hawai’i at Manoa, HI; Skye Inn, The University of Hawai’i at Manoa, HI; Eleanor Tenbrink, Texas A&M University-Corpus Christi, TX
Corals are an ecologically important keystone species that build complex habitats supporting 25% of all known marine organisms. Human carbon dioxide (CO2) emissions are decreasing pH and will reach 0.2 units lower by the year 2100, termed ocean acidification (OA). Coral calcification is mediated by seawater chemistry, however, there is conflicting research on how variable seawater chemistry such as OA impacts coral growth. Resistance to OA may be found in some species of coral that are located on reefs that already experience low pH, such as in Kaneohe Bay, Hawai’i. Therefore, coral colonies from two sites (leeward and windward) around Coconut Island, Hawai’i, representing differences in water chemistry, were exposed to experimental treatments (high total alkalinity, low pH, total alkalinity + low pH, control) for one month at the Hawai’i Institute of Marine Biology (HIMB) to fill the knowledge gap regarding variable water chemistry impact on coral growth. The fluctuations in seawater chemistry between Coconut Island’s leeward and windward sides created an opportunity to analyze the resistance and adaptability of corals from distinct environments in response to future OA conditions. Analysis of individual calcification growth rates (n=3) was assessed using the buoyant weight weekly and total alkalinity technique to capture peak calcification at mid-day and low calcification at night. A pulse amplitude modulated fluorometry device was used to measure weekly photosynthetic responses of the coral individuals. Calcification rates did not differ between sites when comparing the two control groups. After 4 weeks of exposure, there were no differences in calcification rates to any of the treatment conditions. However, during the first week, there was a 57% increase in calcification for colonies from the leeward site when exposed to high CO2 but no change for colonies from the windward site. Interestingly, this increase was not sustained over time, and by week 4, calcification rates were equal to the control. Understanding the impact of changing ocean chemistry on coral growth is essential for determining tolerance thresholds that may inhibit calcification and photosynthesis. This study revealed coral resistance and distinct temporal responses to future OA conditions that highlight important factors to consider in the experimental design of OA studies.References: Bahr, K.D., Rodgers, K.S., & Jokiel, P.L. (2018). Ocean warming drives decline in coral metabolism while acidification highlights species-specific responses. Mar Biol Res, 14(9-10), 924-935. Jokiel, P.L. (2011). Ocean Acidification and Control of Reef Coral Calcification by Boundary Layer Limitation of Proton Flux. Bull Mar Sci, 87(3), 639-657. Shamberger, K. E. F., Feely, R. A., Sabine, C. L., Atkinson, M. J., DeCarlo, E. H., Mackenzie, F. T., Drupp, P. S., & Butterfield, D. A. (2011). Calcification and organic production on a Hawaiian coral reef. Mar Chem, 127 (1-4), 64-75.
Funder Acknowledgement(s): I thank Dr. Ku’ulei Rodgers for providing guidance. Funding was provided by an NSF grant (NSF BIO-OCE #2049406).
Faculty Advisor: Dr. Keisha Bahr, Keisha.Bahr@tamucc.edu
Role: I was fully integrated with every step of the experimental design. I worked as a unit to perform weekly calcification measurements by using the incubation technique to evaluate growth during mid-day and night. I conducted site characterization, field measurements of water chemistry, and seawater analysis of the mesocosm setup. In addition, I used the buoyant weight and total alkalinity technique to quantify the metabolic growth of the individual coral specimens. Lastly, I used Pulse Amplitude Modulated Fluorometry to measure the photosynthetic efficiency of PSII.