Meeting Abstract
37.3 Friday, Jan. 4 Flexibility of coral response to diel thermal fluctuations PUTNAM, H.M.*; EDMUNDS, P.J.; California State University Northridge; California State University Northridge hollieputnam@gmail.com
The effects of high temperature on corals have been studied extensively, but little is known of the response to frequent thermal fluctuations that are common on shallow reefs. In the lagoon of Moorea, French Polynesia, daily variations of ~3�C create a potentially challenging environment for corals, yet coral communities are extensive and largely healthy. Using the lagoon corals Pocillopora meandrina and Porites rus as model systems, this study explored the extent to which fluctuating temperatures affect the physiology of symbiotic corals. Indoor microcosms under ambient light levels were used to create ecologically relevant conditions consisting of three treatments of 30�C, 28�C, 26�C, and a fourth oscillating from 26� to 30�C on a diel cycle. Corals were incubated in these treatments for 12 d, and their response assessed from changes in dark-adapted yield (FV/FM), chlorophyll-a content, Symbiodinium density (considered �symbiont traits�), and skeletal growth (a holobiont trait). A multivariate approach identified one principle component (PC) that accounted for much of the variance (40%) in all four physiological traits, and this PC was significantly affected by the treatments. Univariate analyses revealed that the multivariate effect was driven primarily by large declines (17-45%) in Symbiodinium density in the oscillating temperature treatment for both species, but in contrast, growth did not vary among treatments. These results are interesting because they show for two coral species that variable lagoon environments can have negative effects on symbiont traits, yet a fitness-related trait of the holobiont is unaffected. It is possible that the fitness of corals may be conserved in a thermally heterogeneous environment through plastic responses of their symbionts.
