High-resolution geochemical record of Petaluma Marsh from the San Francisco bay area
Abstract
The San Francisco Bay has the largest concentration of salt marshes in the state of California, representing a diversity of marsh habitat. Protecting these environments is critical, as salt marshes provide refuge to endangered species, absorb carbon from the atmosphere, and preserve detailed evidence of past climatic, hydrologic, geomorphic, and ecologic conditions. However, much of the marshes have been impacted by pollutants, altered or lost entirely due to human activity over the past 150 years, making their prehistoric conditions, ecological trajectories and resilience to disturbance uncertain. In this study, we collected data from Petaluma Marsh, one of the oldest marshes in the Bay Area, to document the sedimentological and accretionary history, geochemical changes including heavy metal concentrations, and patterns and shifts in productivity and C sequestration as a response to climatic and anthropogenic changes since the mid-Holocene. Loss-on ignition, pXRF, and magnetic susceptibility data were collected at high resolution from a 12-meter, 6000 year old, sedimentary core recovered from this tidal marsh located along the Petaluma river in the northern Bay region. Average rate of sediment accretion was 3.6 ± 0.8 mm/yr. Preliminary results confirm dramatic anthropogenic impacts on the Petaluma watershed, particularly over the last 150-200 years. However, based on statistical time-series analysis of long-core elemental concentrations, results show that modern conditions are not so far removed compared to prehistoric conditions, as often suggested by century-scale analyses. Modern heavy metal concentrations (e.g., Cr, Fe, Sr, Ba, Zr, Rb and Ni) match concentration levels from 4000-5000 yr BP. However, Pb levels in the marsh post-European land use are higher now than ever before. Average carbon content, as determined from LOI (Craft, 1991), is 22.3 ± 7.5 % over the length of the core, but decreased with European land modification and increased in recent years. Our results show the effects of anthropogenic changes on this ancient and ecologically important marsh in the north San Francisco Bay area that can help better inform restoration ecologists and policy makers, specifically in terms of marsh accretion, C sequestration and heavy-metal pollutants.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFMGC23B1046F
- Keywords:
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- 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGE;
- 1824 Geomorphology: general;
- HYDROLOGY;
- 1895 Instruments and techniques: monitoring;
- HYDROLOGY;
- 4217 Coastal processes;
- OCEANOGRAPHY: GENERAL