Pollution with copper (Cu), lead (Pb), zinc (Zn), chromium (Cr), and nickel (Ni) heavy metals of the surface sediments collected from three semi-closed East Mediterranean Gulfs, namely Kavala, Strymonikos, and Ierissos Gulfs, North Aegean Sea, Greece, was investigated to evaluate potential benthic ecological risks. The mean concentrations of the studied metals decrease according to the order: Zn > Pb > Cr > Ni > Cu (176.50, 166.23, 127.41, 43.12, and 33.64 mg kg−1 dry weight). Quality indicators and possible ecological risks for metals in surface sediments were evaluated at 60 sampling sites of these three gulfs using the contamination factor (CF), the contamination degree (CD), the pollution load index (PLI), the geoaccumulation index (Igeo), the potential risk factor (PRFi), and the potential ecological risk index (PERI). Based on Igeo, the Ierissos Gulf sampling sites IER 2, 3, 7, and 9 exhibit moderate Pb pollution, whereas the sampling sites IER 6 and 8 show moderate to strong and strong Pb pollution, respectively. Based on the PRFi and PERI, the studied heavy metals did not pose any significant environmental risks for most of the investigated sites except IER 6 and 8 sampling sites, which may pose considerable environmental risk for Pb. To evaluate potential sources for each metal, multivariate techniques including hierarchical cluster analysis and ANOVA were used.

Aegean Sea albacore (T. alalunga), fresh or processed, is marketed locally in Greece or exported, mainly to Japan, Italy, Spain, and France. To provide information for consumers and biomonitoring programs and assess the potential human health risks, concentrations of mercury (Hg), cadmium (Cd) and lead (Pb) were determined in albacore edible muscle samples from two fishing grounds of the Aegean Sea, Greece via graphite furnace atomic absorption spectrometry (GF-AAS). Of the 82 individuals, 28 contained Cd and three contained Pb above the permissible limits set by the European Union (0.1 mg kg−1 wet wt and 0.3 mg kg−1 wet wt, respectively). None of the samples contained mercury above the limit (1.0 mg kg−1 wet wt). Potential health risks to human via dietary intake of albacore were estimated by the total target hazard quotients (TTHQs), which indicated that the consumers could acquire health problems due to consumption of Aegean Sea albacore. Thus consequently, concentrations of toxic heavy metals in albacore, especially mercury, must be monitored regularly and comprehensively with respect to consumer health.

Management of nutrient inputs and usage of nuisance biomass as feedstock for bioenergy may be the solution of coastal lagoons eutrophication. We studied the species composition, photosynthetic pigments (Chl-a and Chl-c) and performance (OJIP-kinetics and JIP-test parameters), biochemistry (lipids and carbohydrates composition), and hydrogen production potential of Limnoraphis (Lyngbya) nuisance biomass collected from Lafri lagoon (1.24 km2) in Greece. The results showed that the removal of algal biomass from Lafri lagoon before its sedimentation, characterized by low Fν/Fm (0.42) and PItotal (2.67) values, and transfer of this in a simple, closed bioreactor, has the potential to produce hydrogen (H2), a renewable CO2-neutral energy that can directly be converted into electricity. The free carbohydrates of the lagoon water and that from the algal cells (42g glucose analogs per m3) could be also transferred to alcohols (biofuels), while the rest of the biomass could be used as organic fertilizer. The total lipid content (2.51%) of dry biomass composed primarily by palmitic acid was low. However, the presence of eicosapentaenoic (3.5%), and docosahexaenoic (1.7%), polyunsaturated fatty acids is worth mentioning. By harvesting and conversion of this coastal lagoon nuisance algal biomass to energy or other products, one could improve its water quality and, therefore, biodiversity and fish production; that is a sustainable solution of eutrophication necessary for the ongoing climatic change.