peer reviewed | We evaluated the alterations of organochlorinated compounds such as polychlorobiphenyls (PCB), dichloro-diphenyl-dichloroethylene (DDE) and dichloro-diphenyl-trichloroethane (DDT) on the thyroid in wild and cultured sea bass (Dicentrarchus labrax) at environmental concentrations. These compounds influence the endocrine system of many fish species and are qualified as endocrine disruptors. The thyroid seems to be a target organ. Two alteration endpoints: the thyroid histology and the muscular thyroid hormone concentrations, were used simultaneously. High concentrations in PCBs and DDT were detected in muscles, supporting the idea that the Mediterranean fauna could be more polluted than the Atlantic fauna. The high abundance of DDE indicates a progressive degradation of remnant DDT load and the absence of new inputs in this area. Aquaculture sea bass shows a significant higher amount of pollutants on fresh weight basis (especially PCBs) in their muscles compared to the wild sea bass. Those differences may be related mainly to the contaminations of diet. Thyroid parameters vary between wild and aquaculture sea bass, wild sea bass were characterized by higher follicle diameters, epithelial cell heights and muscular T4 concentrations. A significant relationship between persistent organic pollutants (muscular PCBs and DDT concentration) and the different thyroid parameters (diameters of follicles, epithelial cell heights and muscular T4 levels) could be observed, which support the hypothesis that these compounds have an adverse impact on thyroid morphometry and function.

Aerial and underwater imaging is being widely used for monitoring litter objects found at the sea surface, beaches and seafloor. However, litter monitoring requires a considerable amount of human effort, indicating the need for automatic and cost-effective approaches. Here we present an object detection approach that automatically detects seafloor marine litter in a real-world environment using a Region-based Convolution Neural Network. The neural network is trained on an imagery with 11 manually annotated litter categories and then evaluated on an independent part of the dataset, attaining a mean average precision score of 62%. The presence of other background features in the imagery (e.g., algae, seagrass, scattered boulders) resulted to higher number of predicted litter items compare to the observed ones. The results of the study are encouraging and suggest that deep learning has the potential to become a significant tool for automatically recognizing seafloor litter in surveys, accomplishing continuous and precise litter monitoring.

In this study bio-indicator bacteria and environmental variable parameters were investigated in the coastal areas of the Güllük Bay, Aegean Sea, Turkey. The seawater samples which were taken from surface (0–30cm) were tested regarding total and fecal coliform, streptococci and nutrients from May to February in 2012–2013. The primary hydrographic parameters were recorded using multiparameter (YSI 556) in situ at the sampling stations. The highest fecal pollution stress and indicator bacteria values were observed in the period between June and August. The finding showed that bacterial pollution sources of the study area, especially in the summer season, under the control of increasing anthropogenic activities. The finding showed that terrestrial pollution sources carry a potential risk for public and ecosystem health and the sustainable use of living sources. Precautions should be formulated and put into action immediately in order to protect the region from bacteriological risks.

Radionuclides levels were determined in indigenous and transplanted mussels (Mytilus galloprovincialis) collected from Turkish marine environment. Radioactivity concentrations of 137Cs, 40K, 226Ra, 228Ra, 210Po and 210Pb were determined in the soft tissues of the mussel samples collected in Bosphorus Strait, Coasts of Black Sea, Marmara Sea and Aegean Sea. Mussel transplantation was carried out by using mussel cages in Levantine Sea coast since M. galloprovincialis did not naturally adapt along the coast. The average activity concentrations of 137Cs, 40K, 226Ra, 228Ra, 210Po and 210Pb in the coastline of Turkey were found to be 0.7±0.1, 469±24, 0.9±0.1, 1.0±0.1, 122±4 and 10.9±0.9Bqkg−1 in dry weight (dw), respectively. The average of 210Po/210Pb ratio was found to be ∼14. Total annual effective 210Po dose was calculated to be in the range of 0.25–3.30 μSv due to mussel consumption. Radioactivity and dose levels were compared with those of similar studies carried out in Mediterranean countries.

Polar anthropogenic organic micropollutants are frequently detected in freshwater and discharged on large scale into marine systems. In this work the results of 153 samples collected from the shorelines of the Baltic Sea (Germany), Northern Adriatic Sea (Italy), Aegean Sea and Dardanelles (Greece & Turkey), San Francisco Bay (USA), Pacific Ocean (USA), Mediterranean Sea (Israel), and Balearic Sea (Spain) are presented. The samples were analyzed for various classes of micropollutants such as pharmaceuticals, corrosion inhibitors, biocides, and stimulants. Caffeine, paraxanthine, theobromine, tolyltriazole, 1H-benzotriazole, and atrazine were detected in>50% of all samples. The detection frequencies of carbamazepine, iopamidol, diuron, sulfamethoxazole, paracetamol, theophylline, and atenolol were between 20% and 32%. As caffeine is linked to untreated wastewater, the widespread occurrence of raw sewage in marine environments and thus potentially elevated nutrient concentrations and risk for the presence of wastewater-related pathogens is remarkable.

The concentrations of metals were measured in macroalgae species seasonally at eight coastal stations along the eastern Aegean coast. Sediment and seawater samples were also collected to detect their metal contents in order to gain more information on the environmental conditions of the area and possible bioaccumulation patterns. The aim of this study is, to gather more information on the use of selected species as cosmopolitan biomonitors for the eastern Aegean; to provide information on the marine environmental quality by the use of macroalgae and to determine which algae species are suitable as biomonitoring species for the study area. The relative abundance of metals in macroalgae decreases in the order: Fe–Zn–Cu–Cr–Cd–Hg–Pb and seawater: Fe–Zn–Pb–Cu–Cr–Cd–Hg. In sediment the distribution order from higher to lower was Fe–Cr–Zn–Pb–Cu–Hg–Cd. The brown algae Cystoseira sp., the green algae Ulva sp. and Enteromorpha sp. possess high potential as cosmopolitan biomonitors for trace metals in the Aegean Sea.

Trace elements have the potential to bioaccumulate in marine organisms and to biomagnify towards the upper levels of marine trophic webs, resulting in a range of negative effects on organisms. Elasmobranchs are highly susceptible to bioaccumulation of trace metals, while their consumption by humans is increasing worldwide. Therefore, it is important to monitor the trace metal content in the edible tissues of elasmobranchs. This work reveals the content of 12 trace metals in the edible tissues of 10 elasmobranch species caught in Greek waters. Levels above the permissible limits for Hg and Pb were found in some species, while analysis of the lifetime consumption risk for adults and children using the Target Hazard Quotient (THQ), revealed a high risk for two of the most toxic substances on the priority list for substances, namely As and Hg. These are preliminary results, and further research is required to understand better the issue.

The faunistic analysis of soft bottom benthic materials collected from the Aegean and Levantine coasts of Turkey in August 2016 and 2017 revealed a total of 7 sipuncula species and 975 individuals belonging to 6 genera. The maximum population density of sipunculans was found to be 1790 ind.m⁻² in the Aegean Sea and 730 ind.m⁻² in the Levantine Sea. Onchnesoma steenstrupii steenstrupii was the most dominant species, comprising 83.1–92.8% of the total number of specimens in the Aegean Sea and 87.2–96.2% of the total number of specimens in the Levantine Sea. Four major sipunculan assemblages were found in the regions, and the main environmental factors controlling these assemblages were depth, temperature, salinity, the sediment grain size, nutrients and total organic carbon. Different abiotic factors affected the distribution of different sipunculan species in the regions. The present study included two cryptogenic sipunculan species; Apionsoma (Apionsoma) misakianum and Aspidosiphon (Aspidosiphon) mexicanus.

In this study, we provide baseline data on the composition, major sources and mechanisms driving the distribution of polycyclic aromatic hydrocarbons (PAHs) mixtures in surficial sediments collected from 43 offshore and open/deep sea locations across the north, central and south Aegean Sea. The determined total concentrations of the considered PAH compounds were generally low, comparable to those reported in relatively non-polluted coastal and open/deep Mediterranean marine sites. Their molecular profile and diagnostic indices reveal mixed contributions from both pyrolytic and petrogenic sources across the study area. Organic carbon exerts an important control on the transport and ultimate accumulation of PAHs, however, the presented results highlight a significant variability in sedimentary PAHs concentrations and compositional patterns within the studied Aegean Sea sub-regions. This could be likely attributed to a combination of distinct hydrological and biogeochemical characteristics, surface and near bottom water mass circulation patterns and the relative importance of PAH sources.

Bryozoans are the major component of marine macro-fouling communities. In the study, the relations between bryozoan species and environmental variables were investigated at seven stations along the Aegean coast in August and December 2015. Constant bryozoan species in both sampling periods were Bugula neritina, Amathia verticillata, Shizoporella errata, Cryptosula pallasiana and Celleporaria brunnea. Their relationship with physico-chemical variables (Temperature, salinity, pH, dissolved oxygen, ammonium, nitrite and nitrate nitrogen, orthophosphate phosphorous, total phosphate, chlorophyll-a) were analysed by means of logistic regression analysis. The result showed that temperature with B. neritina; NH4-N, oPO4-P and TPO4-P with A verticillata; dissolved oxygen concentrations with S. errata and C. brunnea were positively related (p < 0.05).