Comparative Sedimentology Between Caribbean and North Pacific Seagrass Beds

A suite of short push cores were collected in and around seagrass meadows located within Tomales Bay, CA and Coral Bay, St. John, U.S. Virgin Islands to determine regional differences in sedimentology between sediments in seagrass and sediment outside seagrass beds. Seagrasses are the least studied type of blue carbon, however preliminary results already indicate large carbon reservoirs below the beds in both the northern California estuary and Coral Bay. Push cores were analyzed for grain size, carbonate content, total organic matter, and microfossil assemblages. Microfossil assemblages were examined in order to determine changes in biological communities over time. Distinguishable patterns in sedimentology between seagrass and non-seagrass sediments may provide indications about surrounding water chemistry. Due to upwelling off the coast of California, the water of Tomales Bay is highly acidic. For this reason, it is expected that carbonate content will be higher in sediment from seagrass beds compared to outside the beds in Tomales Bay. In Coral Bay, however, there should be no difference in carbonate content between sites within seagrass beds and adjacent sediment because the water in that region has a higher pH and therefore will not be as highly impacted by the presence of seagrass beds.