Corresponding author: Albena Alexandrova (
Academic editor: Michaela Beltcheva
The aim of the present study was to perform a pilot assessment and analysis of the oxidative stress (
Citation: Alexandrova A, Raev Y, Dimitrov D, Chipev N, Tsvetanova E, Georgieva A, Raykov V (2022) Comparative study on the oxidative stress of commercially important fish species from localities with different ecological conditions along the Bulgarian Black Sea coast. In: Chankova S, Peneva V, Metcheva R, Beltcheva M, Vassilev K, Radeva G, Danova K (Eds) Current trends of ecology. BioRisk 17: 117–126.
Fish are a major component of aquatic ecosystems and the good state and health of their populations is crucial for ecosystem stability. Marine fish populations are subjected to increasing environmental pollution and also to overfishing pressure (
The sustainable management of marine fish stocks requires not only regulation of the fish populations, but also knowledge regarding the ability of the fish to respond and adapt to multiple environmental stressors (
The aim of the present study was to provide a pilot assessment and analysis of the oxidative stress level of four commercially important fish species from representative localities of the Bulgarian Black Sea coastal area.
The fish species selected for this study were: the demersal round goby (
Trawling localities along the Bulgarian Black Sea coast with depth and bottom temperature.
Code | Trawling locality | Trawling start point | Trawling end point | Depth | Tbottom |
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N, E | N, E | [m] | [°C] | ||
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Maslen Nos |
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37 | 7.7 |
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St. Oryahovo |
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23 | 7.9 |
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Nessebar |
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20 | 7.4 |
In the laboratory, fish individuals were measured with a caliper and weighed on scales with an accuracy of 0.01 g. The Fulton’s condition factor (K) of the fish individuals was computed according to
The fish were dissected and their liver and gills were extracted. The organs were homogenized in 0.1 M potassium phosphate buffer (pH 7.4) and centrifuged at 3000 g for 10 min to obtain a post-nuclear fraction, used for determination of lipid peroxidation and glutathione levels. A portion of post-nuclear fraction was re-centrifuged at 12000 g for 20 min at 4 °C for obtaining a post-mitochondrial supernatant, used for measurement of the antioxidant enzymes activities.
The OS biomarkers were measured spectrophotometrically using commercially available kits: Lipid Peroxidation (MDA) Assay Kit MAK085, Glutathione Assay Kit CS0260, SOD Assay Kit-WST 19160, Catalase Assay Kit CAT100, Glutathione Peroxidase Cellular Activity Assay CGP1, and Glutathione-S-Transferase Assay Kit CS0410 (Sigma-Aldrich Co. LLC, USA). The manufacturer’s working instructions were strictly followed.
Acetylcholinesterase (AChE) activity was assayed by the method of Ellman (
For statistical analyses the software package STATISTICA 10 (StatSoft Inc.) was used. The Kruskal–Wallis test was used to assess the significance of differences among the values of the OS biomarkers. Post hock comparisons between variables were made using Mann-Whitney test. Multidimensional Scaling (
Data from the measurements of the OS biomarkers in the liver and gills of the studied fish species from the selected localities of the Bulgarian Black sea coast are presented in Table
Values (ME±SD) of the measured OS biomarkers in gills and liver of the studied fish species from the different localities of the Black Sea coast (*statistical significance of differences at p<0.05: Sn indicate significant differences of the OS indicator in fish species between sites; letters (G, L) indicate significance of differences of the OS indicator between organs – G = gills and L = liver).
Site | Liver | Gills | ||||||||||||
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*LPO | GSH | SOD | CAT | GPx | GST | AChE | LPO | GSH | SOD | CAT | GPx | GST | AChE | |
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S1 |
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±1.42 *s2,3 | ±134 *s2,3 | ±4.85 *s2,3 | ±0.02 | ±3.22 | ±12.1 *s3 | ±0.64 *s2,3L | ±0.18 *s2,3 | ±99 | ±2.8 *s2,3 | ±0.02 *s3 | ±1.43 *s3 | ±0.87 *s2,3 | ±1.43 *s2,3G | |
S2 |
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±2.01 *s1 | ±7 *s1 | ±0.26 *s1 | ±0.08 | ±2.86 | ±1.8 *s3 | ±0.59 *s1L | ±1.68 *s1 | ±39 | ±0.16 *s1 | ±0.15 *s3 | ±1.21 | ±1.22 *s1,3 | ±0.33 *s1G | |
S3 |
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±0.65 *s1 | ±23 *s1 | ±1.05 *s1 | ±0.03 | ±10.7 | ±40.6 *s1,2L | ±1.06 *s1L | ±0.04 *s1 | ±33 | ±0.38 *s1 | ±0.04 *s1,2 | ±1.84 *s1 | ±4.14 *s1,2 | ±0.85 *s1G | |
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±1.36 | ±54 | ±2.05 | ±0.04 *G | ±5.59 | ±18.2 *G | ±0.76 *G | ±0.63 | ±57 | ±1.13 | ±0.07 *L | ±1.49 | ±2.08 *L | ±0.87 *L | |
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S1 |
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±0.12 *s3G | ±217 *G | ±3.75 *s3G | ±2.12 *s3G | ±3.24 *s3 | ±7.3 *s3G | ±12.0 *s3G | ±0.86 *s3L | ±51 *L | ±5.18 *L | ±0.33 *L | ±5.07 | ±1.08 *s3L | ±7.60 *L | |
S2 |
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±0.05 *s3G | ±118 | ±8.27 *G | ±3.65 *s3G | ±1.51 *s3G | ±10.4 *s3G | ±10.9 *s3G | ±0.19 *s3L | ±27 *s3 | ±3.59 *L | ±0.11 *L | ±4.73 *L | ±2.62 *s3L | ±75.3 *s3L | |
S3 |
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±0.60 *s2,3G | ±75 G | ±12.4 *s1 | ±1.64 *s1,2 | ±3.08 *s1,2G | ±4.72 *s1,2G | ±3.40 *s1,2G | ±1.25 *s1,2L | ±12 *s2L | ±7.16 | ±0.31 | ±0.07 *L | ±1.91 *s1,2L | ±1.9 *s2L | |
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±0.26 *G | ±136 *G | ±8.14 *G | ±2.47 *G | ±2.61 | ±7.49 *G | ±8.79 *G | ±0.77 *L | ±30 *L | ±5.31 *L | ±0.25 *L | ±3.29 | ±1.87 *L | ±28.3 *L | |
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S1 |
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±1.48 *L | ±68 | ±3.08 | ±0.72 | ±16.3 | ±18.2 *s3G | ±20.3 *G | ±0.39 *L | ±21 *s3 | ±5.16 | ±0.27 | ±9.08 | ±10.5 *L | ±60.4 *L | |
S2 |
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±0.58 *L | ±8 | ±7.73 | ±0.17 *s3 | ±14.6 | ±11.0 *G | ±13.5 *s3G | ±0.43 *L | ±49 | ±6.38 | ±0.33 | ±8.80 | ±1.55 *L | ±28.7 *L | |
S3 |
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±1.25 *L | ±18 | ±0.86 *G | ±0.20 *s2 | ±5.42 | ±3.49 *s1G | ±3.68 *s2G | ±0.96 *L | ±19 *s1 | ±0.95 *L | ±0.24 | ±3.12 | ±0.89 *L | ±7.81 L | |
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±1.10 *L | ±31 | ±3.89 | ±0.36 | ±12.1 | ±10.9 | ±12.5 *G | ±0.59 *L | ±30 | ±4.16 | ±0.28 | ±7.00 | ±4.31 *L | ±32.3 *L | |
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S1 |
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±8.22 | ±8.63 *G | ±3.28 *G | ±1.97 *G | ±11.2 *s3 | ±11.5 *s3G | ±59.1 *s2G | ±0.57 | ±343 *L | ±1.18 *L | ±0.44 *L | ±17.8 *s3 | ±5.16 *s3L | ±26.9 *L | |
S2 |
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±4.15 | ±63 *G | ±0.72 *G | ±0.72+= *G | ±11.6 *s3 | ±6.73 *s3G | ±6.03 *s1G | ±0.80 | ±41 *L | ±1.0 *L8 | ±0.58 *L | ±23.6 | ±2.45 *s3L | ±28.0 *L | |
S3 |
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±2.78 *G | ±100 | ±3.61 | ±1.23 *G | ±0.26 *s1,2G | ±3.02 *s1,2 | ±6.20 *G | ±0.8 *L2 | ±49 | ±0.90 | ±0.06 *L | ±6.74 *s1L | ±1.80 *s1,2 | ±41.9 *L | |
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±5.05 | ±57 *G | ±2.54 *G | ±1.3 *G1 | ±7.73 | ±7.09 *G | ±23.8 *G | ±0.73 | ±145 *L | ±1.05 *L | ±0.36 *L | ±16.1 | ±3.14 *L | ±32.3 *L |
*LPO was expressed as nmoles MDA/mg protein; GSH was expressed as ng/mg protein, all enzymes were expressed as U/mg protei
Significantly higher LPO and GST activities were established, together with the lowest AChE activity in both liver and gills of round gobies and mullets from Nessebar Bay, compared to those from Maslen Nos and Staro Oryahovo (Table
In order to identify significant similarities (dissimilarities) between the values of the measured OS biomarkers MDS was applied (Fig.
The activity of the pro/antioxidative processes in the studied fish species showed some indicative similarities (and dissimilarities) (Fig.
As a general measure of fish condition and health, we used Fulton’s condition factor (K) (Fig.
Multidimentional scaling of similarity (dissimilarity) between the studied fish species in their level of OS (
Fulton’s condition factor (K) of studied fish species from the sampled localities of the Black Sea coastal zone (Mean±SD).
Changes in the balance of cell oxidative processes are a basic reaction of marine organisms to the impact of environmental pressure. The increasing contamination of the sea with metals, polycyclic aromatic carbohydrates and eutrophication leads to increase of LPO and alters the activity of antioxidant protection in the tissues of marine fish and other organisms (
In this study, we reported preliminary data on the OS level in the liver and gills of four commercially important fish species (sprat, horse mackerel, round goby and red mullet) from the Bulgarian Black Sea region. The first overall finding of our study was that in the gills and liver of fish different oxidative changes were present, most probably due to their unique composition and metabolic profile. Secondly, the studied fish species differed in the level of their OS and antioxidant systems activation, which depended on their life style and habitat (food preferences and habits, mobility and hence metabolism levels). The round goby and red mullet are classified as slow-swimming and carnivorous, while horse mackerel and sprat are fast-swimming and plankton feeders (
Our findings on the specific pro/antioxidative processes in the studied fish species were confirmed by values of the Fulton’s condition factor (K). This biometric tool is used to indicate the general health and wellbeing of the fishes (
It can be concluded that round goby and red mullet are more vulnerable to OS induced by marine environmental factors than the horse mackerel and sprat. However, their antioxidant defense system allows them to tolerate and adapt to the environmental conditions of their habitats. Therefore, it could be assumed that demersal fish species are more convenient for monitoring the state of the marine environment and the risk for impairing the fitness of fish. Obviously, further studies are needed for more comprehensive assessment of OS in fish of economic importance in the Bulgarian part of the Black Sea.
This work was supported by grant KП-06-H41/7/2020 of National Science Fund, Bulgaria.