Understanding historical changes in marine communities is paramount for an accurate evaluation of their current status. Callista disrupta is the most abundant bivalve found in the subtidal soft sediments of outer Sydney Harbour, NSW. This has not always been the case, and molluscan death assemblages show the species was rare in the area during most of the last 6000 yrs. In this study we built Von Bertalanffy Growth (VBG) curves based on internal growth bands of 23 live shells (collected in 2014-2015), and excavated shells that lived between 3000 to 5000 yrs ago. The periodicity of the bands was compared across seasonal collections and validated by variations in trace element (Mg, Sr, Ba) composition using Laser Ablation ICP-MS.
Results/Conclusions
Initial results show that C. disrupta had significantly lower growth rates (VBG, Lt = 28.87 [1 – е- 0.94(t – 0.08)]), relative abundance (RA, >2%) and population density (PD, ~0.02 ind/m2), than the current living population (VBG, Lt = 46.08 [1 – е- 0.31(t – 0.44)], RA, ~65%, PD 0.5 ind/m2). Results also show significantly higher Ba concentrations in the older shells, and higher concentration of Mg and Sr in modern shells. These differences are explored as indicators of changing environmental conditions such as sea temperature, primary productivity or freshwater influx levels. We found that C. disrupta shells have the potential to save detailed information of historical environmental changes in the area and their impact on the development and survival of these individuals. Our results illustrate of how ecological community structures may respond and adapt to the changing environmental conditions of the Anthropocene.