Abstract
Heavy metal pollution is still present in the Danube River basin, due to intensive naval and agricultural activities conducted in the area. Therefore, continuous monitoring of this pivotal aquatic macro-system is necessary, through the development and optimization of monitoring methodologies. The main objective of the present study was to develop a prediction model for heavy metals accumulation in biological tissues, based on field gathered data which uses bioindicators (fish) and oxidative stress (OS) biomarkers. Samples of water and fish were collected from the lower sector of Danube River (DR), Danube Delta (DD) and Black Sea (BS). The following indicators were analyzed in samples: cadmium (Cd), lead (Pb), iron (Fe), zinc (Zn), copper (Cu) (in water and fish tissues), respectively, catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), malondialdehyde (MDA) (in fish tissues). The pollution index (PI) was calculated to identify the most polluted studied ecosystem, which revealed that Danube River is seriously affected by the presence of Fe (IP = 4887) and strongly affected by the presence of Zn (IP = 4.49). The concentration of Cd in fish muscle tissue was above the maximum permitted level (0.05 µg/g) by the EU regulation. From all analyzed OS biomarkers, MDA registered the highest median values in fish muscle (145.7 nmol/mg protein in DR, 201.03 nmol/mg protein in DD, 148.58 nmol/mg protein in BS) and fish liver (200.28 nmol/mg protein in DR, 163.67 nmol/mg protein, 158.51 nmol/mg protein), compared to CAT, SOD and GPx. The prediction of Cd, Pb, Zn, Fe and Cu in fish hepatic and muscle tissue was determined based on CAT, SOD, GPx and MDA, by using non-linear tree-based RF prediction models. The analysis emphasizes that MDA in hepatic tissue is the most important independent variable for predicting heavy metals in fish muscle and tissues at BS coast, followed by GPx in both hepatic and muscle tissues. The RF analytical framework revealed that CAT in muscle tissue, respectively, MDA and GPx in hepatic tissues are most common predictors for determining the heavy metals concentration in both muscle and hepatic tissues in DD area. For DR, the MDA in muscle, followed by MDA in hepatic tissue are the main predictors in RF analysis.
Highlights
The Romanian Danube River basin, especially the lower sector, represents the basis for developing the country’s blue growth potential, to align to the European Union average performance registered by the blue economy sector
The lower sector of the Romanian Danube River (LRDR) connects to the Black Sea through the Danube Delta and if pollution occurs upstream of the river, the negative effects of this phenomenon can extend on the Romanian Black Sea and Danube Delta coastal areas as well
The LRDR could be considered the basis for improving Romanian blue growth in the context of European Union intention for developing a more sustainable blue economy, due to large diversity of fish stocks and aquaculture fish farm facilities connected to the Danube River for assuring their inlet water
Summary
The Romanian Danube River basin, especially the lower sector, represents the basis for developing the country’s blue growth potential, to align to the European Union average performance registered by the blue economy sector. The living resources subsector must be developed, while assuring both the safety and security of aquatic food products. This objective can pose a real challenge to achieve since in the lower sector of the Romanian Danube River (LRDR) basin several important economic/anthropogenic activities related to shipyard industry (in the area of Brăila, Galat, i and Tulcea city), steel industry (Galat, i county), alumina industry (Tulcea county) and intensive agricultural activity (especially in Brăila and Tulcea county) are present. According to [1], the coastal area accumulates large quantities of metals from agricultural and industrial activities.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
