Ulva sensu lato associated bacterial communities across the Atlantic-Baltic Sea gradient

481 Microbiome samples of 15 Ulva sensu lato species (Blidingia minima, Kornmannia leptoderma, Ulva australis, Ulva compressa, Ulva fenestrata, Ulva intestinalis, Ulva lacinulata, Ulva linza, Ulva prolifera, Ulva torta, and 5 unresolved Ulva species). Samples were distributed across the Atlantic-Baltic Sea salinity gradient (3.5-36 PSU).