The dataset contains sedimentation velocity measurements for 22 morphologically diverse macroalgae species (n = 49), the seagrass Zostera marina (n = 3), and plastic particles of four distinct shapes (n = 16). Each sample was measured at least five times, with some measured up to seven times. Detailed morphological descriptions and images are available in the corresponding paper. Samples with a SampleID starting with "K" were collected in January 2023 from the Kiel Fjord, Germany (between Strande and Bülk light house, 54°26'57.4N 10°11'37.6E). U. gigantea was collected in June 2024 in Yerseke, Netherlands (51°30'09.0N, 4°02'39.7E). All other samples were collected in June 2024 at the same site from the Kiel Fjord as in 2023, as well as two additional locations (Schilksee, 54°25'16.3N 10°10'43.1E and Mönkeberg, 54°21'20.92N 10°10'41.97E). Sedimentation velocity measurements were conducted in plastic cylinders, allowing particles to sink 15 cm to reach their terminal sinking velocity before starting the measurements. The sinking time was recorded using a stopwatch, and sedimentation velocity was calculated by dividing the sinking distance by the elapsed time. Test with varying cylinder heights showed no significant differences in results.
Macrophyte species measured: Fucus vesiculosus, Fucus serratus, Saccharina latissima, Gracilaria vermiculophylla, Ceramium virgatum, Vertebrata fucoides, Polysiphonia stricta, Spermothamnion repens, Ahnfeltia plicata, Furcellaria lumbricalis, Coccotylus truncatus, Delesseria sanguinea, Cladophora flexuosa, Cladophora sp., Rhodomela confervoides, Pyropia leucosticta, Ulva clathrata, Ulva linza, Kornmannia leptoderma, Bryopsis hypnoides, Acrosiphonia centralis, Ulva gigantea, and Zostera marina.
The plastic particles include eight circular pieces of foil (disks), three table tennis balls, two plastic nets, and three rubber bands. The foil disks were cut to different diameters and some were punched with different numbers of small holes. The name of the foil circles indicates both their diameter and perforation level. For example, "Disk 40-1" had a diameter of 40 mm and was unpunched, where "1" denotes unpunched, "2" partially punched, and "3" heavily punched, "4" extremely heavily punched. The three tennis balls shared identical dimensions but had different mass densities due to the different level of replacement of air with seawater and glass beads in the tennis ball.