ENVIRONMENTAL EFFECTS ON THE SKELETAL COMPOSITION OF DEEP-WATER GORGONIANS {KERATOISIS SPP.; ISIDIDAE)

摘要

We test for environmental effects on the elemental composition of the calcite skeleton of Keratoisis spp. by first assessing the reliability and reproducibility of on-togenetic variability as measured using electron probe microanalysis, and then by comparing this variability between specimens collected from the same and different sites off Australia and New Zealand. The data indicate good, but not perfect reprod-ucability of gross patterning at whole-of-life (centuries) and annual to decadal scales in Keratoisis (and an allied genus Lepidisis) for magnesium, strontium, and calcium, but also high levels of small-scale variability and correlation coefficients that were generally low. Poor reproducability even within specimens could reflect vital effects that vary around the perimeter of the coral, but could also reflect artifacts due to specimen preparation, uneven radial growth rates, and instrumental measurement error. Gross patterning of magnesium and, to a lesser extent, calcium is similar in specimens from the same site, but differs between those from different sites, which is consistent with an environmental effect on composition. Use of strontium as an environmental marker appears to be more problematical. Within specimens, onto-genetic variability of magnesium, strontium, and calcium correlate weakly, which probably reflects a common sensitivity to growth rates and temperatures.