[This dataset is embargoed until September 30, 2027]. The dataset includes concentrations of a range of metal(loid)s in seawater, marine sediment, plankton and fish samples collected in East Scotland between 2020 and 2023. The data was collected as part of the project "Uptake of chemicals from legacy waste sites in coastal food webs and effects on higher predators" ("CLEWS"). The samples were collected during a monitoring field campaign to determine spatial and temporal differences in concentrations of metal(loid)s in sediment and water and to characterise the uptake of these contaminants into planktonic and fish species which are the major food source of shags. The field campaign was carried out within shag population foraging ranges and focused on the Firth of Forth area, with additional water, sediment and fish samples collected off North Aberdeenshire coast where some shags from Firth of Forth colonies spent time outside of the breeding season. Full details about this dataset can be found at https://doi.org/10.5285/839ca281-01b1-4bb8-8f54-92e6c59d7e3c
