engleski

Bivalve Glycymeris pilosa as Data Archive of the Global Atmospheric 14C Change and the Suess Effect

Investigation of geochemical composition of bivalve shells can provide information on the changes in marine environment occurring during the organism's life span. Glycymeris pilosa is a relatively large (>8 cm) and a long-lived bivalve (>60 years) that is locally abundant in the Adriatic Sea. Its growth increments are annual and clearly visible in shell cross sections, which enable correct temporal positioning of geochemical data obtained from different shell parts. In this study we present results of 14C and 13C analyses in carbonates of five individual shells that grew in period 1948-2015 in the north Adriatic Sea. Samples were collected by SCUBA diving from ~10 m depth near Barbariga, Istria. In laboratory, shells were measured, area of the hinge of one shell valve was cut, acetate peel replicas of shell cross section were prepared following procedure from Peharda et al. (2016) and longevity of shells was estimated. Carbonate samples were drilled from the external surface of the second valve, each sample covering between one and five growth increments depending on the width of the increment. Four live collected and one fossil individual were analyzed. 14C analyses of shell carbonates from all individual shells revealed 14C increase characteristic for a reflection of atmospheric 14C bomb peak. Calendar years corresponding to growth increments of the fossil shell from which carbonate samples were collected were determined by using the trend of 14C increase along its growth line compared to a temporal 14C curve obtained from live samples. The comparison was made by means of finding the best fit between two curves by implementing the least square method. This was also verified by the schlerochronological fit. The intensity of the 14C peak observed in the shells is damped and delayed compared to the atmospheric bomb peak in the northern hemisphere. Suess effect is indicated in a temporal decrease of δ13C values in the umbo of the shells. Results of this study clearly illustrate the potential of G. pilosa as geochemical data archive.

Glycymeris pilosa ; 14C bomb peak ; Suess effect ; north Adriatic

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