Caspian microplastic evidence dataset

This dataset compiles quantitative and methodological evidence on microplastic occurrence in the Caspian Sea Basin. It includes structured data extracted from ten peer-reviewed studies published between 2020 and 2026 and one visual-microscopic pilot dataset from Azerbaijan. The records cover coastal and offshore waters, beach and bottom sediments, river estuaries, wetlands, fish and Caspian seals. The dataset contains information on study location, environmental matrix, sample size, reported abundance, measurement unit, particle morphology, colour, size, dominant polymers and analytical confirmation methods. Original measurement units are retained because sediment, water and biota data are not directly comparable. The Azerbaijan pilot observations are identified as microplastic-like anthropogenic particles because FTIR or Raman confirmation was not conducted. The dataset is intended to support systematic review, secondary-data analysis, identification of geographical and methodological research gaps, and sustainable coastal management research in the Caspian Sea Basin.