Grain size distribution in sediment samples from a monitoring study of sandy beach meiofauna before and after sand nourishment (Ahrenshoop, Baltic Sea)

We provide grain size data for sediment samples collected on the sandy-beach water line of Ahrenshoop (Baltic Sea). Five sampling stations lay within the zone impacted by the sand nourishment between the boundary of the nature reserve in the north east and a site just north of the breakwater (AH01–AH05). An unaffected reference station was located south of Ahrenshoop (close to Niehagen) at the end of the road Pappelallee (PAP). Samples were collected at four dates. The first sampling was carried out before the sand nourishment took place (T0: 14 and 16 September 2021). Three samplings were realised after the impact: T1 (23 March 2022), T2 (27 September 2022), and T3 (28 March 2023). Latitude and longitude of each sampling location per station were recorded at each sampling date using a hand-held GPS application on a mobile phone. At the stations sampling locations varied over time. Prior to the sand nourishment the beach was narrow due to sand erosion in previous years. After the nourishment the additional extent of the beach was approximately 40 m at sampling date T1. Subsequently, progressive sand erosion forced the sampling locations (at the water line) further inland at T2 and T3. Samples were taken from the beach-water interface (water line) in the middle of the area between two groynes. Plexiglass cores (inner core diameter 5.4 cm) were inserted vertically into the sediment down to 15 cm depth. Each core was sliced in 5 cm-layers (0–5, 5–10 and 10–15 cm). Sediment horizons were preserved in 96–99% ethanol. After the organisms were extracted by decantation (32-μm sieve) the remaining sediment was dried at 80 °C. No remarkable amount of silt and clay was observed in the samples. The dried sediment was mechanically sieved over a column of stacked sieves with decreasing mesh sizes representing different grain size fractions: very fine Sand % (63-125 µm), fine Sand % (125-250 µm), medium Sand % (250-500 µm), Coarse Sand % (500-1000 µm), very Coarse Sand % (1000-2000 µm), Granule % (2000-4000 µm), large Granule % (>4000 µm). The grain size data are part of a larger ecological study on the influence of sand nourishment on meiofauna communities, which included meiofauna abundances and metabarcoding analyses (see "related works"). Comment: Our study is related to but not funded by the project ECAS Baltic: Strategies of ecosystem-friendly coastal protection and ecosystem-supporting coastal adaptation for the German Baltic Sea Coast https://deutsche-kuestenfors