Glycymeris pilosa (Bivalvia) - A high-potential geochemical archive of the environmental variability in the Adriatic Sea

摘要

Due to its outstanding longevity (decades), the shallow-water bivalve Glycmeris pilosa represents a prime target for sclerochronological research in the Mediterranean Sea. In the present study, we analyzed the microgrowth patterns and the stable carbon (delta C-13(shell)) and oxygen (delta O-18(shell)) isotopes of the outer shell layer of live-collected G. pilosa specimens from four different sites along the Croatian coast, middle Adriatic Sea. Combined analysis of shell growth patterns and temporally aligned delta O-18(shell) data indicated that the main growing season lasts from April to December, with fastest growth rates occurring during July and August when seawater temperatures exceeded 22 degrees C. Slow growth in the cold season (< 12 degrees C) coincided with the formation of winter growth lines on the outer shell surface. The growth cessation occurred in winter, but on the outer shell surface the brown summer bands are more pronounced than the winter lines. Mutvei-staining of cross-sections facilitated the recognition of the growth lines. delta C-13(shell) values reflect ontogenetic changes in physiology as well as seasonal changes in primary production and salinity.