QUATERNARY HISTORIES OF SALT MARSHES IN CALIFORNIA PROVIDE ENVIRONMENTAL BASELINES

Coastal ecosystems are of great concern under global climate change scenarios due in part to the rapidity of projected changes as well as the difficulty of understanding long-term histories of these environments because of that rapid change. Coastal salt marshes, like lacustrine or inland freshwater marshes, preserve very detailed information about the ecosystem and surrounding environment. These brief, local records may not always be suitable for broad-scale or regional, paleoclimate reconstructions, but they are an unrivaled resource for stakeholders and policy managers looking to better understand the history of their coastal region. We have gathered an archive of over 100 sediment cores from 12 salt marshes in California, ranging from Humboldt Bay to Tijuana River Estuary. Broadly, our goals for the project include estimating local and regional sediment accretion rates to compare to current and projected rates of sea-level rise (SLR), quantifying carbon stock and sequestration rates, and estimating the relative age of these salt marshes in their current position. We have found that average accretion in CA salt marshes is 3.5 ± 0.9 mm yr^-1, compared to current SLR of ~3mm yr^-1 and projected rates from 17 to 21 mm yr^-1 (IPCC 2013). Average carbon sequestration to 1 m depth is 98.86 g C m^-2 yr^-1, compared to global estimates from 50 to 250 g C m^-2 yr^-1 (Chmura et al. 2003; Hopkinson, Cai, and Hu 2012; Ouyang and Lee 2014). Ages of basal salt marsh or core bases vary anywhere from 300 – 3000 YBP, demonstrating the irregularity and transience of these environments. These results, as well as current collaborative efforts using these data for vulnerability assessments and carbon storage models in the works, demonstrate the applicability of quaternary studies to our current and future environmental challenges.