engleski

Glycymeris pilosa - spatial and temporal insight into differences of trace element records

Investigation of the geochemical composition of bivalve shells can provide information on changes in the marine environment occurring during the organism's lifespan. High spatial and temporal resolution element records can be obtained through laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS). Glycymeris pilosa was chosen as target species as it has a lifespan exceeding 50 years and presents a potential archive of decadal climate variability. These shells contain annual growth increments which are visible in cross-sections enabling temporal positioning of geochemical data obtained from different shell portions. Bivalves were collected alive by SCUBA diving at six localities along the Eastern Adriatic coast including Barbariga, Istria in the North Adriatic Sea, Pag Island, Pašman Island, at the mouth of the river Cetina in the Central Adriatic as well as Živogošće and Drače in the Southern Adriatic. In this study we applied LA–ICP–MS in line scan mode to determine the trace element composition along the major growth axis in the hinge area of the shell to obtain high-resolution profiles of Na/Ca, Mg/Ca, Sr/Ca, and Ba/Ca. From each locality, a minimum of three similar-sized specimens were selected for the chemical analysis. To study how trace element patterns compare among individuals from the same locality and among different sites along the Eastern Adriatic coast in more recent times, three ontogenetically young (<15 years) specimens were chosen. For the more distant past, three larger, ontogenetically older (>50 years) specimens from localities near Istria and Drače were studied. Time-series of Na/Cashell, Mg/Cashell and Sr/Cashell display characteristic cyclic variations with Na/Cashell minima and Mg/Cashell and Sr/Cashell maxima occurring near annual growth lines. Ba/Cashell time-series show noncyclic sharp peaks that vary between years and among localities. Furthermore, time-series of Na/Cashell, Mg/Cashell and Sr/Cashell can be used to validate the presence of annual growth lines used to build chronologies, while Ba/Cashell time-series vary along the Eastern Adriatic coast and probably reflect local environmental changes. Research has been supported by the Croatian Science Foundation under the project SCOOL (IP2014-09-5747).

bivalve ; trace elements ; Sclerochronology ; Adriatic Sea

nije evidentirano