Meeting Abstract

109-2  Thursday, Jan. 7 08:15  Anemones on acid: The effects of increased pCO₂ on carbonic anhydrase activity in the symbiotic sea anemone Anthopleura elegantissima KOCH, J.C.*; CONTOLINI, G.M.; University of Washington Friday Harbor Laboratories and Oregon State University, Corvallis; University of Washington Friday Harbor Laboratories and University of California, Santa Cruz kochja@science.oregonstate.edu

Anthopleura elegantissima participates in a facultative symbiosis with two genera of microalgae, the dinoflagellate Symbiodinium spp. and the chlorophyte Elliptochloris marina. The symbiosis is centered around nutrient exchange including reduced organic carbon, inorganic nitrogen and carbon dioxide (CO₂). The CO₂ is used in algal photosynthesis and is produced in part by anemone carbonic anhydrase (CA) which catalyzes the reversible reaction of sodium bicarbonate to CO₂. Under ocean acidification conditions, algal symbiont densities in A. elegantissima have been shown to increase, thereby increasing the demand for CO₂ by the symbionts. Additionally, ocean acidification causes an increase in the abundance of bicarbonate and CO₂ in seawater. Therefore, we predicted that an increase in algal symbiont density under acidifying conditions would trigger an increase in anemone CA activity to meet the need for increased CO₂. Aposymbiotic, Symbiodinium-, and Elliptochloris-containing A. elegantissima were collected from four locations around San Juan Island, and placed into ambient and high pCO₂ conditions for 10 days. Anemone CA activity was only measured after the experiment and algal densities were measured before and after the experiment. There was no significant effect of pCO₂ or symbiotic state on the CA or density of algal symbionts after ten days of treatment. Our findings suggest that A. elegantissima may have internal homeostatic mechanisms to respond to increased pCO₂ levels and concomitant increased algal densities.