Metals Bioaccumulation in Important Marine Species of the Bulgarian Black Sea and Screening-Level Human Health and Ecological Risk Assessment

Fish and seafood make up a large proportion of the Bulgarian diet, but there are no country-specific fish consumption advisories to offer consumer advice on serving size and frequency, particularly for some native species. I evaluated the levels of select metals and non-metals (arsenic, mercury, lead, cadmium, and chromium) in two highly consumed marine organisms of the Black Sea along the Bulgarian coastline, the Round Goby (Neogobius melanostomus) and Mediterranean Mussel (Mytilus galloprovincialis). Plankton was also evaluated, as an indicator of contaminant bioaccumulation in the food web. By using the angling removal technique and purchase at fish markets for the fish and mussels, respectively, collected were 110 fish (= 7 composite samples of 10, 1 composite of 13, and 37 individual Goby samples) and > 270 mussels (= 9 composite Mussel samples) over the course of two field seasons (Summer 2016 and Summer 2017). Also collected were 6 composite plankton samples via vertical sampling. Upon collection, the samples were processed before delivery to a laboratory for metals analysis. Contaminant levels were compared between composite samples using Kolmogorov-Smirnov tests and Kruskal-Wallis tests, and Spearman correlation was used to evaluate the relationship between contaminant levels and distance from locations exhibiting intense industrial activity. The results indicated that elevated levels of arsenic and chromium were detected in nearly all fish, mussel, and plankton samples. Mercury, lead, and cadmium levels were below the Level of Quantification (LOQ) for all samples. Multiple fish and mussel composite samples differed in their distributions, while an inverse relationship was established for Contaminants of Concern (COC) levels and distance from industrial “hot spots” for most locations. A positive correlation was found regarding COC levels and some industrial hubs. Hazard Quotients (HQs) were developed as part of a screening-level human health and ecological risk assessment, but insufficient data did not permit the development of Protective Concentration Levels (PCLs). HQs for arsenic often exceeded 1 for both fish and mussels, but chromium HQs were below 1 for both fish and plankton samples. This research will provide the Bulgarian population with a better understanding of current contaminant levels in seafood species and the potential health risks associated with fish and mussel consumption. It will also illustrate needs for future research and help marine resource managers and specialists with a broader assessment of ecosystem health.