Constantine Parinos

Coccolithophores are important components of marine phytoplankton and are found to be useful indicators of the environmental conditions of the upper water column. In this study, we investigate coccolithophore abundance and composition in the Cretan Sea and South Cretan area (Eastern Mediterranean), and their relation to prevailing hydrodynamic conditions during late February/early March 2019. Results showed that total coccolithophore abundance ranged from 26.3 × 10² to 258.8 × 10² coccospheres L⁻¹, averaging at 135.8 × 10² coccospheres L⁻¹. Among the 45 identified species, the opportunistic Emiliania huxleyi was the most dominant, representing 89% of the coccolithophore assemblage. In the Cretan Sea, this species showed relatively homogeneous abundances throughout the upper 100 m depth of the water column; however, towards the Rhodes Cyclone, where a weak stratification had started, and the mixed layer was relatively shallow, higher abundances were found at depths shallower than 50 m. Syracosphaera molischii co-occurred with Emiliania huxleyi, whereas Rhabdosphaera clavigera, Syracosphaera pulchra, and Syracosphaera mediterranea were also present but in lower abundances, reflecting the influence of warm, salty Levantine Surface Water. Based on the morphological analysis, Emiliania huxleyi was mostly represented by heavily calcified forms consistent with winter-spring patterns in the Aegean Sea. The observation of signs of dissolution with high relative abundances of etched/corroded coccospheres indicates the sensitivity of Emiliania huxleyi to the prevailing circulation pattern during the 2019 mixing event within the Rhodes gyre.

The pollution status of Saronikos Gulf was studied via target and suspect screening, with WWTPs identified as the main sources. PFAS concentrations exceeded AA-EQS values in 92% of seawater samples. Circulation/precipitation patterns are discussed.

This work concisely presents findings and insight on the impact of shipping on pollution of an eastern Mediterranean coastal marine ecosystem - Saronikos Gulf, Greece. Advanced modelling tools (STEAM, SILAM, Delft3D) were employed to assess shipping-related pollution from direct discharges and atmospheric emissions of heavy metals, PAHs and Elemental (black) Carbon (EC). Simulations for 2018 revealed that shipping contributed < 1% to total pollutant loads. Projections for 2050 under various traffic and fuel scenarios indicated that open-loop scrubber discharges could increase concentrations locally. The fate of fine EC particles was also investigated, showing that EC from shipping represents a small fraction of total atmospheric deposition, though some accumulation in marine sediments occurs. High-resolution Delft3D simulations, forced by seasonal EC deposition data accounting for all sources from the WRF-CAMx modelling system, were used to evaluate EC transport and distribution in the Gulf. Results showed increased EC levels in Elefsis Bay for January and July 2019 and decreasing gradients offshore, in agreement with field observations, reflecting source importance and seasonal variation. Findings highlight the limited yet important role of shipping in localized marine pollution.

This study presents the living coccolithophore communities and the morphological variability of Emiliania huxleyi in the South Aegean Sea from three sampling regions during winter-early spring (March 2017, March 2019) and summer (August 2019). Emphasis is given to March 2017 to monitor the variations in coccolithophore assemblages after an exceptionally cold event in December 2016, which resulted in newly produced dense waters that ventilated the Aegean deep basins. The assemblages displayed distinct seasonality with the predominance of E. huxleyi and Syracosphaera molischii during winter-early spring, associated with the water column mixing. By contrast, summer assemblages were featured by holococcolithophores and typical taxa of warm, oligotrophic upper waters. It seems that the phytoplanktonic succession as well as the nutrient supply to the upper euphotic layers were affected by the water column perturbation during the extreme winter of 2016–2017, which led to strong convective mixing and dense water formation. The decreased coccosphere densities during March 2017, accompanied by the notable presence of diatoms, were most probably associated with a prolonged diatom bloom, causing delay in the development of the coccolithophore community and resulting in a nitrogen-limited setting. Emiliania huxleyi morphometry showed the characteristic seasonal calcification trend of the Aegean, with the dominance of smaller coccoliths in the summer and increased coccolith length and width during the cold season. The intense cold conditions and wind-induced mixing during the winter of 2016–2017 possibly increased the absorption of atmospheric CO₂ in surface waters, causing increased acidity and the subsequent presence of etched/undercalcified E. huxleyi coccoliths and other taxa, most probably implying in situ calcite dissolution.

In this study, we investigate the pollution status in impacted seawaters and sediments of coastal areas in the region of Thessaly, central Greece, following the Storm Daniel extreme flood event in September 2023, a phenomenon classified as the deadliest Mediterranean tropical-like cyclone in recorded history and one of the costliest cyclones beyond the North Atlantic. For this, an ultra high-performance liquid-chromatography-based wide-scope target screening of more than 2300 LC-amenable emerging contaminants (ECs) was carried out utilizing the technique of TIMS-QTOF-MS. Our results highlight the fact that the extreme floodwater runoff resulted in an extensive transportation of terrestrial derived material from the impacted areas and a major transport of plant protection products, pharmaceuticals, including even illicit drugs, surfactants, industrial chemicals, and per- and polyfluorinated alkyl compounds (PFAS) at sea, as a result of the overflowing of local wastewater treatment plants and the destruction of agricultural, industrial, and port facilities. Overall, the phenomenon resulted in a major alteration of the classification of the determined ECs in seawaters and most importantly in sediments of the study area, with potential implications for their environmental quality status.

This study investigates the composition, abundance, and vertical export of polycyclic aromatic hydrocarbons (PAHs) across three deep basins of the northeastern Mediterranean Sea (NEMS) over one year. Sinking particles were collected using sediment traps, and PAH analysis was conducted via gas chromatography-mass spectrometry. PAH fluxes varied significantly, peaking in the north Aegean Sea due to mesotrophic conditions, nutrient-rich riverine and Black Sea water inflows, and maritime anthropogenic inputs. The fluxes were highest in winter and lowest in fall. In the Cretan Sea, petrogenic sources (~70%) dominated, driven by currents, with fluxes highest in spring and lowest in winter. The Ionian Sea exhibited lower fluxes, peaking in summer and decreasing in fall. Atmospheric deposition seems to be the main transport pathway of pyrolytic PAHs in this site, while its high-water column depth (4300 m) compared to the other sites presumably enables extended degradation of organic constituents during particle settling. The positive matrix factorization (PMF) and principal component analysis (PCA) results reveal complementary insights into PAH sources and transport mechanisms. PMF analysis identified combustion (61%) and petrogenic (22%) sources, while PCA highlighted biogenic fluxes (57.7%) and atmospheric deposition. Seasonal productivity, riverine inputs, and water circulation shaped PAH variability, linking combustion-related PAHs to atmospheric soot and petrogenic PAHs to organic-rich particles.

This study investigates the intricate dynamics of siliceous plankton species within the open marine regions of the Greek Seas, focusing on their seasonal and spatial variability. For this purpose, vertical export fluxes of diatoms (DtF), silicoflagellates (SF), and radiolaria (RF) were analyzed in three sediment trap time series obtained from the North Aegean, Cretan, and Ionian Seas. Special attention was given to diatom assemblages, resulting in the estimation of the DtF community structure and diversity for each studied site. Diatom flux values reached 353.9 × 10³ valves m⁻² day⁻¹, 77.7 × 10³ valves m⁻² day⁻¹, and 42.4 × 10³ valves m⁻² day⁻¹ in the North Aegean, Ionian, and Cretan Seas, respectively. SF maxima were 1309.8 × 10³ skeletons m⁻² day⁻¹ in the North Aegean Sea, 35.2 × 10³ skeletons m⁻² day⁻¹ in the Ionian Sea, and 11.9 × 10³ skeletons m⁻² day⁻¹ in the Cretan Sea (South Aegean Sea). RF values reached 13.9 × 10³ radiolaria m⁻² day⁻¹, 11.9 × 10³ radiolaria m⁻² day⁻¹, and 5.4 × 10³ radiolaria m⁻² day⁻¹ in the North Aegean, Ionian, and Cretan Seas, respectively. The North Aegean Sea exhibited significantly higher mean total fluxes, particularly for diatoms, driven by the north-to-south oligotrophy gradient, which was influenced by riverine inflows and the nutrient-rich Black Sea water. In the Cretan and Ionian Seas, convective mixing and atmospheric deposition, especially during increased rainfall (precipitation) events, were identified as primary drivers for the increased siliceous plankton fluxes recorded in the late winter–spring months. Diatom communities were dominated by Naviculales and Fragilariales; the prevalence of the former in the North Aegean Sea is likely linked to the higher nutrient levels in its upper photic zone, as Naviculales includes species with a high affiliation to nutrient enrichment.

To study the spatiotemporal variability of particle-bound polycyclic aromatic hydrocarbons (PAHs) and assess their carcinogenic potential in six contrasting urban environments in Greece, a total of 305 filter samples were collected and analyzed. Sampling sites included a variety of urban background, traffic (Athens, Ioannina and Heraklion), rural (Xanthi) and near-port locations (Piraeus and Volos). When considering the sum of 16 U.S. EPA priority PAHs, as well as that of the six EU-proposed members, average concentrations observed across locations during summer varied moderately (0.4–2.2 ng m⁻³) and independently of the population of each site, with the highest values observed in the areas of Piraeus and Volos that are affected by port and industrial activities. Winter levels were significantly higher and more spatially variable compared to summer, with the seasonal enhancement ranging from 7 times in Piraeus to 98 times in Ioannina, indicating the large impact of PAH emissions from residential wood burning. Regarding benzo(a)pyrene (BaP), an IARC Group 1 carcinogen and the only EU-regulated PAH, the winter/summer ratios were 24–33 in Athens, Volos, Heraklion and Xanthi; 60 in Piraeus; and 480 in Ioannina, which is afflicted by severe wood-burning pollution events. An excellent correlation was observed between organic carbon (OC) and benzo(a)pyrene (BaP) during the cold period at all urban sites (r² > 0.8) with stable BaP/OC slopes (0.09–0.14 × 10⁻³), highlighting the potential use of OC as a proxy for the estimation of BaP in winter conditions. The identified spatiotemporal contrasts, which were explored for the first time for PAHs at such a scale in the Eastern Mediterranean, provide important insights into sources and controlling atmospheric conditions and reveal large deviations in exposure risks among cities that raise the issue of environmental injustice on a national level.