Meiofauna higher taxa abundance data from a monitoring study of sandy beach meiofauna before and after sand nourishment (Ahrenshoop, Baltic Sea)

We provide abundance data for meiofauna taxa determined from 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 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 (situated 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. The organisms were extracted by decantation over a 32-μm sieve. The total number of individuals per taxon was counted and is presented as individuals per 10 cm2. In the framework of our monitoring, samples were primarily taken for a large-scale metabarcoding study on meiofauna communities. One core per station and sampling date was reserved for morphology-based community analyses. Here we present the results for the stations AH01, AH03, AH05, and PAP. We selected these stations because of their location at both ends and in the center of the impacted zone (AH01, AH03, AH05) and at the control site (PAP). The meiofauna (32–1000 µm) was mostly represented by Copepoda, Nematoda, Platyhelminthes, Gastrotricha, and some Annelida. We counted 27445 individuals in total, encompassing 10 higher taxa. We counted copepod nauplii separately due to their small body size. We defined the combined group “Plathyhelminthes+Diurodrilus sp.” because members of the annelid genus Diurodrilus sp. are not distinguishable from Platyhelminthes under the stereomicroscope. Here we present a Table on meiofauna higher taxa counts per 10cm2 (as xlsx and tab-delimited file; including metadata for each sample: event; date; latitude; longitude; station, core and sample ID; sediment depth). The meiofauna abundance data are part of a larger ecological study on the influence of sand nourishment on meiofauna communities, which included grain-size 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-kuestenforschung.de/ecas-baltic.html本数据集提供了采自阿尔内斯霍普（波罗的海）沙岸潮间带沉积物样本中的小型底栖动物（meiofauna）类群丰度数据。5个采样站位位于受养滩工程影响的区域内，该区域介于东北部自然保护区边界与防波堤北侧附近区域之间（站位编号AH01–AH05）。另设1个未受扰动的对照站位，位于阿尔内斯霍普以南（靠近尼哈根）的帕佩拉勒路尽头（PAP）。本次采样共开展4次：首次采样于养滩工程实施前完成（T0：2021年9月14日）；其余3次采样于工程扰动后开展，分别为T1（2022年3月23日）、T2（2022年9月27日）及T3（2023年3月28日）。每次采样时，使用手机上的手持全球定位系统（GPS）应用记录每个站位采样点的经纬度。各站位的采样点位置随时间发生变化：养滩工程前，由于多年来的沙质侵蚀，海滩较为狭窄；养滩工程后，在T1采样时海滩新增范围约40米；随后，持续的沙质侵蚀使得位于潮间带的采样点在T2和T3阶段向内陆迁移。 采样点设置于两座丁坝之间区域中部的滩水界面（潮间带水位线）。使用内径5.4厘米的有机玻璃柱样管垂直插入沉积物中，采集深度达15厘米。每份柱样被切割为3段5厘米的沉积层（0–5 cm、5–10 cm及10–15 cm）。沉积层样品保存在96%–99%的乙醇溶液中。通过32μm孔径筛网淘洗法分离沉积物中的生物个体，统计得到的各类群个体总数以每10平方厘米的个体数表示。 本监测项目的采样主要服务于一项针对小型底栖动物群落的大规模元条形码测序（metabarcoding）研究。每个站位每次采样的柱样中，预留1份用于开展基于形态学的群落分析。本次公开的结果对应站位AH01、AH03、AH05及PAP。选取上述站位的依据为：AH01、AH03、AH05分别位于受影响区域的两端及中部，PAP则为对照站位。本次研究涉及的小型底栖动物体长范围为32–1000 μm，主要类群包括桡足类（Copepoda）、线虫动物门（Nematoda）、扁形动物门（Platyhelminthes）、腹毛动物门（Gastrotricha）及部分环节动物门（Annelida）类群。本次研究共统计个体总数27445只，涵盖10个高级类群。由于桡足类无节幼体体型极小，我们将其单独计数。我们将“扁形动物门+Diurodrilus属（Diurodrilus sp.）”合并为一个类群，因为在实体显微镜下无法区分环节动物门Diurodrilus属物种与扁形动物门物种。 本数据集附带一份小型底栖动物高级类群每10平方厘米个体数统计表（文件格式为Excel（xlsx）及制表符分隔文本文件；包含每份样本的元数据：事件、采样日期、纬度、经度、站位、柱样及样本编号、沉积层深度）。 本小型底栖动物丰度数据隶属于一项探究养滩工程对小型底栖动物群落影响的大型生态学研究，该研究同时包含沉积物粒度分析与元条形码测序分析（详见"related works"）。 备注：本研究与ECAS Baltic项目相关，但未获得该项目资助。ECAS Baltic项目全称为“德国波罗的海海岸生态友好型海岸防护与支持生态系统的海岸适应策略”，项目网址：https://deutsche-kuestenforschung.de/ecas-baltic.html