Coastal marine sediments receive intensive stress from urbanization and industrialization, which is manifested by increased contents of heavy metals and organic pollutants. Saronikos Gulf and the small embayment of Elefsis, stretch along the coast of the greater Athens and Pireaus port, the most urbanized and industrialized areas in Greece. Here we present the data of a 20-years geochemical record on grain-size, organic carbon, and major and trace elements contents of the Saronikos Gulf sediments. A total of 216 sediment samples were collected within the period of 1999 to 2018 from the four sub-sectors of the gulf, namely, the Elefsis Bay, the Inner, Outer, and Western (Megara and Epidavros basin) Saronikos Gulf. Additionally, at least one core was obtained from each sub-sector. Sediments deposited at pre-industrial periods were recognized by 14C and 210Pb datings, and served for establishing regionalized, background levels of metals. Factor analysis was conducted to reveal the inter-parametric relationships, thus their common sources, as well as transport and deposition pathways. Then, Enrichment Factors and the multi-elemental Modified Pollution Index (MPI) were calculated to assess the current environmental status of the sediments. Data of sampling sites with at least a five-year record, were assessed for temporal trends, to explore whether sustained, increasing or decreasing trends of the MPI are observed. The dataset and analyses presented here support the research article entitled Geochemistry of major and trace elements in surface sediments of the Saronikos Gulf (Greece): assessment of contamination between 1999 and 2018 by Karageorgis A.P., Botsou F., Kaberi H., and Iliakis S., https://doi.org/10.1016/j.scitotenv.2020.137046

Data were collected in the southern Western Black Sea (Bulgarian and Romanian territorial waters) for the Eurofleets+ PHYCOB cruise. This submission contains CTD and nutrient data. The main scientific objectives of the research cruise are: 1) To assess the presence of toxic microalgae in the plankton assemblage of the Western Black Sea. 2) To quantitatively determine the spatial distribution of toxic phytoplankton species and their corresponding toxins in the plankton. 3) To quantitatively describe the spatial distribution of toxic phytoplankton resting stages in surface sediments and determine hotspots of recruitment and bloom initiation. 4) To define correlations among hydrographic and/or meteorological conditions and occurrence of HAB species. 5) To characterize the plankton communities accompanying HAB species together with toxin analysis of size fractionated samples. 6) To identify heterotrophic dinoflagellates, ciliates, or other small zooplankton as possible toxin vectors. 7) To isolate toxic Black Sea microalgal species and establish monoclonal cultures for characterization of Black Sea strains. 8) To perform an interseasonal comparison of toxigenic plankton species by combining the data sets collected during the R/V Akademik cruise that was performed in May/June 2019 with our data from summer. 9) To compare the data set from the Western Black Sea to the Southern (North-) Western North Sea, Baltic Sea and West Greenland obtained during earlier expeditions for site comparisons.

During the 2007 MEDECO cruise of RV Pourquoi Pas ? (Sarrazin & Pierre, 2007), http://www.iso-analytical.co.uk/index.html). This data underlies the following paper: Carlier A., Ritt B., Rodrigues C.F., Sarrazin J., Olu K., Grall J. & Clavier J. (2010): Heterogeneous energetic pathways and carbon sources on deep eastern Mediterranean cold seep communities. Marine Biology 157 (11), 2545–2565 (2010), https://archimer.ifremer.fr/doc/00016/12684/ The dataset consists of two files: one containing the data itself, and one describing all used terms (measurements or metadata). Important Note: This submission has been initially submitted to SEA scieNtific Open data Edition (SEANOE) publication service and received the recorded DOI. The metadata elements have been further processed (refined) in EMODnet Ingestion Service in order to conform with the Data Submission Service specifications.

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.