Geochemical parameters were measured at two CO2 sites and one non-CO2-impacted site near the island of Panarea (Italy). All sites were located between ~15 and 20 m water depth at a temperature of 19°C. Water samples were obtained above and within sandy sediments as well as around seagrass bushes. pos1 = ca.1 m above sediment (30 cm above seagrass leaves)pos2 = ca. 40 cm above sediment (between seagrass leaves)pos3 = ca. 20 cm above sediment (at the beginning of the leaves)pos4 = ca. 10 cm above sediment (10 cm beneath rhizome; directly within seagrass mat)positive sediment depth values: below sediment surface; negative sediment depth values: in the water column above sedimentAll values are mean values.