Meeting Abstract

P3.123  Saturday, Jan. 5  Temperature determines plasticity in growth of the reef-building coral, Porites Lobata BARSHIS, Daniel; WATERSON, Tyler P.*; STILLMAN, Jonathon H.; Zoology, Hawai�i Institute of Marine Biology; Romberg Tiburon Center, San Francisco State University; Romberg Tiburon Center, San Francisco State University tylerwaterson@gmail.com

In the back reef lagoons of Ofu, American Samoa, corals thrive in temperatures (up to 36°C) higher than most corals can tolerate, and daily temperatures fluctuate 3-4°C. A reciprocal transplant study showed that corals from both forereef (constant temperature) and back reef environments grow more quickly in the back reef lagoon, although native back reef corals grow more quickly in all environments relative to conspecifics from the forereef. Here we examined whether these growth differences were due to temperature or other environmental factors. We collected samples of Porites lobata from forereef and back reef sites, with n=5 colonies per site and 25-30 replicates per colony. We transported the corals to our laboratory in San Francisco and split them between two tanks imitating either the forereef (29°C) or back reef (fluctuating 27-32°C). After one month, new vertical skeletal extension was measured. Both back reef and forereef corals had significantly higher skeletal extension rates in the fluctuating tank than the constant-temperature tank. In both tanks, back reef corals had significantly higher vertical extension rates than forereef corals. Our laboratory experiments yielded similar results to prior field experiments, suggesting that the major environmental factor influencing plasticity of growth rate is temperature. In future experiments, calcification and other growth factors should be considered to better characterize the physiological patterns observed. Supported by USGS BRD GCC program.