Biases in annual density banding with implications for high-resolution growth chronologies in the massive starlet coral (Siderastrea siderea)

Abstract The aragonitic skeletons of massive corals (Scleractinia) are commonly used as biological and paleoenvironmental archives based on their annual density banding. In case of high-resolution proxy studies, however, taxon-specific biases related to the skeletal architecture of the selected coral species can occur, which may impact the resulting skeletal growth chronologies. This study focusses on the quantification of high-resolution skeletal density records in the massive starlet coral Siderastrea siderea from a nearshore reef environment at the southern coast of Belize (western Caribbean Sea) by using two-dimensional grid-scanning americium-241 ( 241 Am) gamma densitometry. Multiple linear sample pathways were systematically selected through central corallite areas (i.e., around the columella) and the corresponding walls (synapticulotheca) of contemporaneously formed corallites in S. siderea . By following this approach, annual density banding (or distortions in its formation) can be identified and related to the general architectural elements and/or to variations in the longitudinal alignment of corallites. The demarcation of high-density bands is often more clearly developed in the corallite walls than around the columella. Therefore, future high-resolution linear skeletal density chronologies should be established based on the more robust corallite walls to reduce such biases in density banding of S. siderea corals.