Title: Lessons from Ancient Seas: What Fossil Mollusks Teach Us about the Future of Our Oceans
Abstract:
The fossil record provides abundant information on past extinctions that can help predict biotic response to environmental change and offer a baseline for restoration. This approach, known as conservation paleobiology, makes it possible to gain a long-term perspective on modern ecosystems.
In the first case study, my collaborators and I established a baseline for oysters using the fossil record from the Chesapeake Bay region. By examining the age distribution, growth rates, population densities, and paleoenvironment of Pleistocene fossil oysters, a clearer picture of oyster reefs before human disturbance can be established. Shell height and longevity in Chesapeake Bay oysters declined significantly from the Pleistocene to today, while growth rates have increased. This is driven by age truncation, in which both harvesting and disease preferentially remove the larger, reproductively more active, and primarily female members of the population. Although oyster management in the Chesapeake Bay has historically focused on protecting and supplementing early life stages, this study argues for a shift to support later life stages.
The second case study focuses on how mollusks responded to an interval of warming that occurred approximately three million years ago. During the mid-Piacenzian Warm Period (MPWP), sea surface temperatures rose approximately 3°C, and atmospheric CO2 concentrations were higher than pre-industrial levels. We compiled data on fossil bivalve and gastropod assemblages from time intervals before, during, and after the MPWP from museum and field collections. Molluscan diversity doubles during the MPWP and does not immediately return to pre-event levels. Similarly, community structure differs significantly between each time interval; species composition and abundance do not return to pre-event conditions after the MPWP. As climate change intensifies, implications for modern molluscan fauna include long-term shifts in both diversity and community structure, which may have implications for ecosystem services.
