This study compares living and dead populations of the rare fungiid coral, Cycloseris curvata, from three locations at opposite ends of the Galápagos Archipelago. Two study sites were located at the southern-most islands (Floreana and Española Islands) and the third at the northern-most location, Darwin Island. Cycloseris is one of only two fungiid coral species in the Eastern Pacific, and occurs in isolated, patchy populations. The only known currently live population of this species in the Galápagos Islands is found at Devil’s Crown, Floreana Island. Live individuals were also observed 88 km upstream (east) of this site at Xarifa Island, Española Island in 2005 and 2007 within a robust death-assemblage of skeletons. Additionally, dead skeletons were first observed in 2012 at Darwin Island, 364 km north-northwest of the living population at Devil’s Crown. Dead skeletons were not measured at Devil’s Crown because they are more quickly covered with encrusting organisms and more difficult to locate compared to the other two sites. Skeleton size was quantified either from in situ measurements of skeletal axes with a ruler to the nearest 0.5 cm (Española), or from digital photographs using the program Coral Point Count with Excel Extensions (CPCe) (Floreana and Darwin).
Results/Conclusions
Living Cycloseris curvata individuals at Devil’s Crown were significantly larger on average than those at Xarifa (28.2 ± 11.9 cm2 vs. 13.0 ± 5.7 cm2 p < 0.001, t-Test). There were no significant differences between sizes of dead Cycloseris skeletons from Darwin and Xarifa Islands (18.4 ± 11.8 cm2 vs. 20.2 ± 9.0 cm2 p = 0.10, t-Test). This suggests that there are similar ages of mortality and taphonomic degradation in the two death assemblages. Living Cycloseris at Devil’s Crown was significantly larger than dead skeletons observed at both Xarifa Island (p < 0.001, t-Test) and Darwin Island (p < 0.001, t-Test). This suggests that Cycloseris at Devil’s Crown grows larger than individuals at either Darwin or Xarifa, and/or that larger skeletons do not maintain their epibenthic position as well as smaller skeletons. The Devil’s Crown and Xarifa sites are shallower than the site at Darwin (15m, 11m and 28m respectively), so larger coral size does not appear to be associated with increased light and consequent increased energy production by the mutualistic dinoflagellate coral symbiont (zooxanthellae). Continuing efforts seek to discover additional populations of this coral to better understand their unusual niche in benthic ecosystems.