Quantifying Blue Carbon Storage of the Two Dominant Temperate Seagrass Species in the Lower Chesapeake Bay

Abstract

Seagrass meadows provide key ecosystem services including storing carbon long-term by trapping and burying organic matter in the sediments. Carbon storage likely differs by dominant species within a seagrass meadow, although quantification only exists for a few key species, including those in the Zostera genus. This lack of quantification presents an important issue in the context of changing species distributions due to climate change. One such example is in the Western Mid-Atlantic, where rising summer temperatures in the lower Chesapeake Bay have shifted the dominant seagrass species from Zostera marina to Ruppia maritima, a species more tolerant to heat waves. The carbon storage potential of seagrass meadows dominated by Ruppia is unknown but thought to be lower than those of Zostera due to plant morphology and life history differences. Here, we quantify the carbon stored in Zostera and Ruppia-dominated meadows of the lower Chesapeake Bay. Forty-two sediment cores were collected from seagrass meadows of varying ages for both species and processed for percent organic matter and carbon stocks. We found that Ruppia-dominated meadows had a higher percent carbon content in the top 5 cm of their sediment compared to Zostera-dominated meadows. Aboveground biomass was positively correlated with percent carbon content in Zostera-dominated meadows but not in Ruppia-dominated meadows. Canopy height was positively correlated with percent carbon content in both Zostera and Ruppia meadows. However, aboveground biomass and canopy height were significantly higher in Zostera meadows than in Ruppia meadows despite the lower percent carbon content. Our results suggest that environmental variables may also be responsible for carbon storage in Ruppia and Zostera meadows, along with seagrass morphology. Our study quantifies the carbon stocks of an understudied seagrass species and aids in understanding the implications of species identity on the carbon storage potential of seagrass ecosystems.BiologyBachelors of Science (BS