Late Quaternary dinoflagellate cysts record abrupt climate changes along the California margin

Understanding abrupt environmental changes, including those caused by the rapidly warming oceans, requires a compilation of paleoenvironmental data obtained from marine sedimentary archives, such as Ocean Drilling Program (ODP) cores. Dinoflagellate cysts serve as sensitive and reliable indicators of past environments, and their application has gained prominence over the last decades, especially for high-resolution studies in the northeastern Pacific Ocean. Dinoflagellates are one of the most diverse and abundant groups of microalgae in coastal environments and are major primary producers. Many dinoflagellates form highly resistant organic-walled resting cysts that accumulate in sediments throughout their life cycle. The records of these microfossils provide valuable information about upper water masses at the time of cyst deposition.

In this presentation, we summarize insights gained from two high-resolution dinoflagellate cyst sedimentary records — one from the California Margin (ODP Hole 1017E) and the other one from the Santa Barbara Basin (SBB; ODP Hole 893A). Census data of cysts from the Holocene and the Last Interglacial (Over and Pospelova, 2022) enable us to identify shifts in ecosystems responding to climate change. These data were used for quantitative and qualitative reconstructions of past sea-surface temperatures, salinity, primary productivity, and potentially significant forest fires during the warm Dansgaard-Oeschger interstadial event 2 (~23,000 years ago).