engleski

Bivalve shells - Geochemistry archives of environmental variability

Due to their remarkable longevity and CaCO3 shells with distinct growth patterns, bivalve molluscs are valuable environmental archives. The majority of sclerochronological studies were conducted on one of the longest known living bivalve – Arctica islandica from the North Atlantic Ocean. However, there are still relatively small number of studies using bivalves from semi enclosed seas such as the Mediterranean and Adriatic Seas. This study analyses shell geochemistry of three species from the eastern Adriatic Sea – long-living Glycymeris pilosa, and two commercially important species Callista chione, and Venus verrucosa. Samples were collected alive by SCUBA diving from shallow (<10 m) coastal sites in the eastern part of the eastern Adriatic Sea. G. pilosa came from 6 different sampling sites, while C. chione and V. verrucosa were sampled only at the northernmost site – Barbariga (Istrian peninsula). Laser ablation– inductively coupled plasma–mass spectrometry (LA–ICP–MS ; line scan mode) was applied to determine the element chemistry along the major growth axis in the hinge. High resolution profiles of Na/Ca, Mg/Ca, Sr/Ca, and Ba/Ca were measured in 3 ontogenetically young (<12 years) specimens of C. chione and V. verrucosa from Barbariga, and 18 young (<15 years) specimens of G. pilosa from Barbariga, Pag, Pašman, Cetina, Živogošće and Pelješac. In addition, three older specimens of G. pilosa (>50 years) from Barbariga and Pelješac were analysed. Data was placed in a precise temporal context, and interannual and seasonal changes were studied. Trace elemental records were relatively synchronous between individuals from same location suggesting their potential to record marine environmental variability. Variations were observed in trace elemental records of young G. pilosa from different locations indicating different enviromental conditions. Furthermore, based on the analysis of older G. pilosa (>50 years), significant changes were observed on temporal scales. These results contribute to the understanding of shell growth dynamics.

sclerochronology, sclerochemistry, bivalve, trace elemental records

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