Assessing Multiple Carbon Fluxes in a Temperate, Pacific Seagrass Meadow

Melissa Ward1, Tessa M Hill2, Aurora M Ricart3, Brian Gaylord4, Brady Charles O'Donnell5, Lena R Capece6, Priya Shukla7, Kristy Kroeker8, Eric Sanford4 and Walter C Oechel9, (1)Bodega Marine Laboratory, University of California Davis, Davis, CA, United States, (2)University California Davis, Earth and Planetary Sciences and Bodega Marine Laboratory, Davis, CA, United States, (3)Bodega Marine Laboratory, University of California Davis & Bigelow Laboratory for Ocean Sciences, Bodega Bay, CA, United States, (4)Department of Evolution and Ecology, University of California Davis and Bodega Marine Laboratory, Bodega Bay, CA, United States, (5)Bodega Marine Laboratory, University of California Davis, CA, United States, (6)Bodega Marine Laboratory, University of California Davis, Goleta, United States, (7)Bodega Marine Laboratory, University of California Davis, Bodega Bay, CA, United States, (8)University of California Santa Cruz, Ecology and Evolutionary Biology, Santa Cruz, CA, United States, (9)San Diego State University, Global Change Research Group, Dept. of Biology, San Diego, CA, United States
Abstract:
Conservation and restoration of submerged aquatic vegetation have been proposed as strategies for combatting the effects of increases in oceanic and atmospheric carbon dioxide (CO2) concentrations. Seagrass meadows can act as carbon sinks by (1) drawing down atmospheric CO2; (2) absorbing aqueous carbon in seawater; and (3) sequestering organic carbon in sediment. However, few studies consider multiple carbon fluxes or how they interact with one another within a given seagrass meadow, often leading to apparent discrepancies in the net carbon values assigned to meadows.Here, we analyzed three key carbon cycle components in a temperate seagrass meadow (Zostera marina). We specifically focused on atmospheric CO2exchange, seawater carbonate chemistry, and carbon burial. Atmospheric exchange over the meadow, despite high temporal variability, served as a significant net annual sink for atmospheric CO2, absorbing 491.47 ± 46.63 g C m-2 y-1. A first order estimate of seagrass metabolism indicated net absorption of 227 g C m-2yr-1in summer and 746 g C m-2yr-1in winter. Seagrass metabolism also increased temporal variability in pH and DO (dissolved oxygen). Variability in DO concentration correlated with overlying air-sea fluxes, suggesting that seagrass photosynthetic activity can influence atmospheric CO2drawdown. Lastly, a substantial amount of carbon is buried and stored annually in meadow sediments, with a burial rate of 12.74 – 16.99 g Corgm-2yr-1producingorganic carbon stocks of 4.1 ± 0.37 mg cm-3. Together these data help elucidate the interdependencies of carbon fluxes in seagrass meadows and their role in climate change and OA mitigation.