| Popis: |
Bivalve growth chronologies have shown great potential as proxies of environmental variability, but they are still limited to a relatively small number of taxa and certain geographic regions. The smooth clam Callista chione is a commercially important venerid bivalve which inhabits sandy sediments in coastal waters of the eastern Atlantic Ocean and the Mediterranean Sea. With clearly visible growth lines and life span that can reach more than four decades, C. chione shell represents an interesting sclerochronological archive. Callista chione shells were collected alive at three locations in the Adriatic Sea: (1) Gulf of Venice, Italy, (2) Pag Bay, and (3) Pašman Channel, Croatia. In the laboratory, shells were embedded in epoxy resin and cut along the axis of maximum growth, ground, polished and etched in acid. Acetate peel replicas were prepared and photographed with Zeiss microscope and camera while Image Pro Primer program was used to measure increment widths. Visual cross dating of images was done by list-year method while R package dplR was used to construct the chronologies. The maximal estimated age of the analysed specimen was 46 years. Increment widths were measured in samples that had clear boundaries in acetate peels. Constructed growth chronologies ranged from 1999 to 2018 at Gulf of Venice, 2002 to 2019 at Pag Bay, and 1996 to 2015 at Pašman Channel. Finally, chronologies were compared with each other and with available environmental data, evaluating their potential as proxies of environmental change in the Mediterranean. Research was supported by the Croatian Science Foundation, research project BivACME. |
