Dataset gives a baseline for micro- and mesoplastic pollution distribution in 24 beaches along the Latvian coastline (Northern Europe, Baltic states), filling the existing knowledge gap and contributing to the global understanding of microplastic particles presence, transport, and the processes governing its dynamics. We also highlight citizen science as a fundamental tool to support data collection and raise awareness about microplastic pollution, as samples were collected by up to 250 volunteers during organized campaigns (Dimante-Deimantovica et al. 2023).

This work was carried out for the Danish Environment Protection Agency (EPA) targeting microplastics (MP) in Danish marine sediments. It addresses the geographical distribution of MP in sediments from 23 stations, among which, 19 were analysed in 2022 (https://www.emodnet-ingestion.eu/submissions/submissions_details.php?menu=39&tpd=1185&step=001Denmark), and four were analysed in 2023. One of these four samples were collected from Skagerrak, and three were from the North Sea. It attempts to map the level and geographical distribution of MP in sediments from the North Sea and Skagerrak. The monitoring should furthermore create a baseline for future efforts to assess temporal changes of MP in Danish marine sediments.

In relation to Danish MSFD monitoring the data maps microplastics content in sediments in Danish waters. Data covers 13 sediment samples from the Belt Sea and its fjords, Kattegat and Limfjord. The samples were taken in 2018-2021 and analyzed in 2020-2021. A study of variation of microplastics over short distances, consisting of 13 sediment samples taken in a grid in Odense Fjord in 2021. The survey showed that microplastic could be found in all sediment samples in concentrations ranging from 22 to 7402 µg kg-1 (microgram microplastic per kg sediment dry matter). As number of microplastic particles, this corresponded to between 508 and 23340 N kg-1 (number of microplastics per kg of sediment dry matter) Odense Fjord showed that the microplastic content at this locality varied greatly. The average mass concentration was 4683 µg kg-1 with a range from 250 to 24848 µg kg-1 . Measured as a number, the concentration averaged 18671 N kg-1 with a range from 7266 to 34141 N kg-1 .

Contents and composition of microplastic-like particles have been analysed in ten sediment samples from the Danish part of the open North Sea and in the Inner Danish waters in 2015. The contents of microplastic-like particles in the size range 100-5000 µm were determined to be in the range of 192-3511 particles per kg dry weight sediment, dominated by blue and black coloured particles, mainly as fibres, and particle sizes < 300 µm were dominating.

This study is a first attempt in Denmark on assessing the presence of microplastics in our open & coastal waters from Baltic to North Sea. The occurrence and impact of microplastics have in the Danish initial assessment for EU’s Marine Strategy Framework Directive (MSFD) been identified as a relevant indicator for describing “Good Environmental Status” (GES) for descriptor 10 on Marine Litter. Microplastic particles in marine waters, which consist of synthetic polymer materials, origin mainly from secondary microplastics, i.e. fragments of litter like solid waste, fishing gear, paint flakes etc. from either sea- or land based sources. Primary microplastics (engineered) are not expected to be as common as secondary microplastics. Microplastics can origin from both local sources and from long-range transport with ocean or air currents.

The dataset was collected and created through DeFishGear project from 2013 to 2017. The current dataset contains data on microplastic litter collected on the Croatian sandy beaches.