Abstract
Pteropods are considered the "canaries of the ocean" due to their sensitivity to environmental changes. Understanding the dynamics of aragonite calcification and fluxes through the ocean is a particularly important issue in carbonate chemistry and key to assessing the impacts of ocean acidification regionally and globally. Using δ18O and δ 13C isotope data, pteropod shell size and density data from analyses of shell flux in the Oceanic Flux Program sediment traps offshore Bermuda, and Bermuda Atlantic Time-Series hydrographic data, we can learn much regarding how variable water column temperature and chemical composition conditions impact the distribution, calcification depth and aragonite flux provided by the two most commonly found species in the region, Heliconoides inflatus (formerly known as Limacina inflata) and Styliola subula. This study examines the impact of two specific hydrographic events-the passage of a mesoscale cyclonic eddy in spring 2007 and the occurrence of an extreme deep-convective mixing event in spring 2010-on the flux and calcification depths of H. inflatus and S. subula in the Sargasso Sea region. δ 18O-determined calcification depths for both species were found to be deeper than those reported by a few previous studies, and are substantially impacted by physical environmental forcing. During the 2007 mesoscale eddy event, both species' calcification depths deepened by 50-75 m. In 2010, the extreme mixed layer event coincided with calcification depths of >400-500 m for S. subula and H. inflatus. The study also reveals the importance of juvenile pteropods, ultimately finding that they contribute quantitatively more to the aragonite flux than adults during certain time periods. This suggests that juveniles likely play a significant role in buffering ocean acidification through their dissolution.