Meeting Abstract

21.3  Friday, Jan. 4  The effect of temperature on the growth rates and oxygen consumption of 6 cnidarian algal symbionts MCGINTY, E.S.*; MCMAHON, R.F.; MYDLARZ, L.D.; Univ. of Texas at Arlington mcginty@uta.edu

Algal symbionts in the genus Symbiodinium that form mutualistic relationships with many cnidarians are critical to coral reef maintenance, growth and persistence, but little is known about their physiology, especially in how it relates to genetic diversity that exists within the genus. In particular, gaps surround our understanding of variation among different symbionts, and how that physiology changes during exposure to stressors associated with climate change, such as elevated temperatures. To investigate this, 6 different Symbiodinium cultures (types A1, A2, B1, B2, E1 and F2) were exposed to a range of temperatures and the resulting oxygen consumption rates and growth rates were compared. Cultures were acutely exposed to temperatures ranging from 25°C to 37°C (42°C for F2) and dark oxygen consumption rates were measured, allowing determination of maximum oxygen consumption rates and Q10 rates. Differences existed among algal types for the maximum rate, temperature where maximum rates were reached, which ranged from 31°C (B1) to 41°C (F2), and Q10 rates, with the lowest at 2.804 (E1) and the highest at 5.880 (B2). Growth rates at 26°, 30°, and 34°C were also measured and differences among Symbiodinium types were again observed. Preliminary analysis suggests that in some Symbiodinium types, oxygen consumption continued beyond temperatures where positive growth rates were maintained, indicating that algal cells are still alive at these temperatures but unlikely able to support their own growth. These findings, and the potential implications on the algal-cnidarian symbioses, will be applied to elucidate the physiological responses of Symbiodinium to stressors associated with climate change and address their role in coral decline.