Abstract This study evaluates the spatial and historical patterns of primary productivity proxies and trace elements in core and surface sediments from the southern Marmara Sea following the 2020 mucilage event, with emphasis on the Erdek and Bandırma Gulfs. Stratigraphic records reveal a sustained rise in eutrophication indicators and metal enrichment over the last ~ 200 years, coinciding with accelerated industrialization and urban expansion in the region. Surface sediments from the southern Erdek Gulf display pronounced accumulation of nitrogen, phosphorus, biogenic silica, organic carbon, and trace metals (As, Cd, Cr, Ni, Zn, Hg), primarily driven by terrestrial inputs associated with the Gönen River catchment. In the Bandırma Gulf, elevated contamination levels are attributed to maritime traffic, port operations, and industrial discharge, with the western shoreline representing the most impacted sector while northern coastal areas remain comparatively less contaminated. Anthropogenic enrichment of Cu, Cd, Zn, Ni, As, Cr, and Hg underscores the dual vulnerability of these systems to eutrophication and chemical pollution. Furthermore, this work provides the first characterization of dinoflagellate cyst assemblages during a mucilage episode in the area, identifying 15 taxa including harmful species ( Alexandrium sp. , Operculodinium centrocarpum, Lingulodinium machaerophorum) . Their presence indicates elevated ecological risk and potential for future harmful algal bloom development, particularly in the Bandırma Gulf.
Kükrer et al. (Mon,) studied this question.