ESTABLISHING THE LIFESPAN OF ASTARTE BOREALIS (BIVALVIA) USING ISOTOPE SCLEROCHRONOLOGY

The extant genus, Astarte, exhibits decreasing size through geologic time. It is an ideal candidate for studying changes in size and lifespan through time because of its wide temporal and spatial distribution, ranging back to the Oligocene and today extending from the Arctic to the Caribbean. Our overall goal is to determine whether the observed change in size is accompanied with a change in lifespan, and if there is a relationship between lifespan and climate state. To achieve this goal, we first established a methodology to identify annual increments in shell growth and estimate age using modern shells from the White Sea, Russia. We used isotope sclerochronology to identify annual growth increments and determine that shell growth slows from late summer to winter. We hypothesize that the trigger for slowed growth is a combination of increasing freshwater input from the surrounding rivers and decreasing temperature. Ontogenetic changes were evaluated using von Bertalanffy growth equations. Previous studies have shown that modern species of Astarte live for about 20 years; however, our counts indicate they can achieve greater ages of around 30 years or more. Future work will determine if growth rates and lifespan are similar from low to high latitudes and between warm and cold climate states.