Effects of Heavy Metals in Lake Water and Sediments on Bottom Invertebrates Inhabiting the Brackish Coastal Lake Łebsko on the Southern Baltic Coast

Responses of diatom composition and teratological forms to environmental pollution in a post-mining lake (SW Poland)

Various types of environmental stressors, such as heavy metals, lignite residues, or extremely low water pH, cause the formation of teratological forms of diatoms during the reproductive cycle. The damage mainly includes an abnormal diatom valve outline, changes in the striation pattern, anomalies in the raphe line/sternum, reduction in the cell size, metabolism alterations, or combined deformities. Diatom remains with such morphological deformities occur in the sediments of post-mining lake ŁK-46 (SW Poland). This lake was formed by excavation after the end of lignite exploitation in the mid-1960s. The percentage of teratological valves in the studied lake ranged from 12 to 33% of the relative abundance. The majority of abnormal diatoms have been observed in species of Eunotia. The reconstruction of the diatom-inferred pH (DI-pH), together with the concentration of heavy metals in the sediments and contemporary measurements of the water pH, indicates that the lake was contaminated to varying degrees and was acidic from the beginning of lake creation until today. The lake is located in an area of acid mine drainage (AMD), and in its vicinity, there are overburden heaps containing lignite residues, which are eroded and supplied to the lake, constantly acidifying the water. In the youngest sediments, the concentration of heavy metals increased, while the percentage of abnormal diatoms decreased. Determining which factor, i.e., extremely low water pH and the presence of lignite or heavy metals, was responsible for the formation or reduction of teratogenic forms of diatoms is very difficult.

Integrative ecotoxicity evaluation of Cd, Cu, Zn and Ni in aquatic animals reveals high tolerance of Artemia franciscana

Heavy metals pose a significant threat to animals in aquatic environments due to the adverse effects they exert. Species of the genus Artemia have been described as heavy metal tolerant, but the sensitivity/tolerance range for these species has not been established. In the present study, the toxicity of Cd, Cu, Zn and Ni as reported in the ECOTOX and Web of Science databases was examined for Artemia franciscana and compared with other species and taxonomic groups using an integrative ecotoxicity evaluation. The hazard concentration for 5% of the species (HC5) of acute toxicity tests (24-96 h), obtained through a species sensitivity distribution (SSD) indicated that Cu (0.02 mg/L) and Cd (0.03 mg/L) were the metals with the highest toxicity to aquatic animals followed by Zn (0.15 mg/L) and Ni (0.23 mg/L). In addition to the higher hazard of Cu and Cd to aquatic animals, the comparison of acute LC50 values for A. franciscana indicates lower toxicity of Cd followed by Cu, Zn, and Ni (200.0, 14.5, 9.5, and 0.6 mg/L, respectively). Using the SSD and physiological sensitivity (S) approaches, it was demonstrated that A. franciscana is relatively tolerant to Cd (SSD= HC99; S = 2.21), Cu (SSD= HC97; S = 2.00), Zn (SSD= HC90; S = 1.29) and Ni (SSD= HC83; S = 0.96) compared with other species and taxonomic groups. It appears that tolerance to the metals Cd, Cu, Zn and Ni is unique to the family Artemiidae within the order Anostraca, as the families Streptocephalidae and Thamnocephalidae are not tolerant (have negative S values). Our study confirmed that as expected, A. franciscana presents higher tolerance to Cd, Cu, Zn, and Ni than other aquatic animals. Our findings confirm that A. franciscana can be used as a model organism to understand mechanisms involved in tolerance to heavy metals, mainly Cd and Cu, which are considered highly toxic to other animals.

Ecological indicators for qualitative assessment of Ojarud River: A case study

Today, the application of ecological indicators based on organisms has replaced traditional saprobic approaches for assessment of the quality of rivers impaired due to organic pollution and some other environmental disturbances. This study aimed to weigh the quality of the Ojarud River in Ardabil, Iran, applying biological and physiological indices of macro-invertebrates. A total of 12,524 samplings were fulfilled at four stations (S1, S2, S3, S4) from the headstream to downstream by a Surber sampler (30 × 30 cm²) from June/2020 to April/2021. All year round, the highest frequent families were Chironomidae (2658), Simuliidae (1025) from Diptera and Caenidae (1855), and Baetidae (724) from Ephemeroptera. The diversity pattern was analyzed by PAST software, and Primer 7 (BIO-ENV analysis) was utilized to understand what factor has the most impact on the distribution of macro-invertebrates. The least similarity of S4 to other stations was recognized by Cluster analysis. As per the ANOSIM (analysis of similarities), a statistically significant difference in the macroinvertebrates' frequency was established between S3 and other stations (p = .0001, r = .63). Moreover, the relationship between heavy metals and macro-invertebrate showed that the three families of Simuliidae, Gomphidae, and Caenidae had a positive correlation with the concentrations of heavy metals in the sediment. As per the Ephemeroptera, Plecoptera and Trichoptera index, the water quality was placed in the "excellent" class, but the Biological Monitoring Working Party and Hilsenhoff Family Biotic Index indices scored the water quality "good" class at S1 and the "poor" class at S3. Based on the results of this study, the use of physicochemical and hydro-morphological indicators can support the biological indicators but cannot replace them. In addition, careful evaluation of biological indicators is required to develop conservation strategies.

Toxic Metals, Non-Metals and Metalloids in Bottom Sediments as a Geoecological Indicator of a Water Body's Suitability for Recreational Use

The study of bottom sediments was conducted within the basins of water bodies used for recreational purposes (e.g., bathing, fishing and diving) in the Silesian Upland and its periphery in southern Poland. Various concentrations of trace elements were found in bottom sediments, reflected by the following levels: Pb (30-3020 mg/kg), Zn (142-35,300 mg/kg), Cd (0.7-286 mg/kg), Ni (10-115 mg/kg), Cu (11-298 mg/kg), Co (3-40 mg/kg), Cr (22-203 mg/kg), As (8-178 mg/kg), Ba (263-19,300 mg/kg), Sb (0.9-52.5 mg/kg), Br (1-31 mg/kg), Sr (63-510 mg/kg) and S (0.001-4.590%). These trace elements are present in amounts that usually exceed those found in other bodies of water or are sometimes even unprecedented among bodies of water in the world (e.g., cadmium-286 mg/kg, zinc-35,300 mg/kg, lead-3020 mg/kg, arsenic-178 mg/kg). It was found that bottom sediments were contaminated to varying degrees with toxic metals, metalloids and non-metals, as evidenced by the values of geoecological indicators, i.e., the geoaccumulation index (-6.31 < I_geo < 10.90), the sediment contamination factor (0.0 ≤ Cfi < 286.0), the sediment contamination degree (4.6 < C_d < 513.1) and the ratios of the concentrations found to the regional geochemical background (0.5 < I_RE < 196.9). It was concluded that the presence of toxic elements (e.g., lead, zinc, cadmium, chromium, strontium and arsenic) in bottom sediments should be taken into account when classifying water bodies as suitable for recreational use. A maximum ratio of the concentrations found to the regional geochemical background of I_RE ≤ 5.0 was proposed as the threshold for the permissibility of recreational use of water bodies. The water bodies used for recreational purposes in the Silesian Upland and its periphery do not meet the geoecological conditions for safe use in terms of recreation and leisure activities. Forms of their recreational use that directly affect the participants' health (e.g., fishing and the consumption of fish and other aquatic organisms) should be abandoned.

Structural diagnosis of benthic invertebrate communities in relation to salinity gradient in Baltic coastal lake ecosystems using biological trait analysis

This study is based on biological trait analysis (BTA), which provides a link between the distribution and biological characteristics of species. The paper investigates differences in the structure and functional diversity of benthic fauna in terms of seven biological traits (mobility, habitat, feeding type, habitat modification, body form, body size and feeding apparatus) in nine Baltic coastal lakes whose salinity ranged from 0.1 to 7.3 PSU. Mobile organisms were more common in lakes with higher salinity, while sessile and semi-mobile species preferred low-salinity or freshwater environments. There were also noticeable differences connected with feeding type: collectors and scrapers were more common in brackish lakes, and collectors were significantly dominant in freshwater and transitional ones. This indicates that Baltic coastal lakes are inhabited by similar species of benthic fauna, but that certain biological traits occur with different frequencies. We therefore identified features that may affect the functioning of coastal lakes with a relatively narrow salinity gradient (0.1–7.3 PSU). It seems to confirm the possibility of using BTA methods to determine key characteristics that are helpful for understanding the differences between aquatic ecosystems. The results may provide a basis for further research on changes in the functional diversity of lakes along the southern coast of the Baltic Sea, particularly in view of climate change, given their being small, shallow and less resilient lakes.

Microplastics- and copper-induced changes in neurogenesis and DNA methyltransferases in the early life stages of zebrafish

In this study, zebrafish embryos were exposed to microplastics (MPs, 2 mg/L) and copper (Cu, 60 and 125 μg/L), alone or combined, for 14 days, and the development of motor neurons was assessed through gene expression and immunohistochemistry. DNA methyltransferases (DNMTs) genes expression was also evaluated. The results showed a downregulation of neuronal proliferation (sox2, pcna), neurogenesis (neuroD, olig2), and motor neurons development (islet) related genes, implying potential deficits in the neurogenesis of the exposed zebrafish early life stages. Downregulation of the maintenance and de novo DNMTs expression was also found, indicating that the DNA methylation patterns could be modulated by MPs and Cu. A high relative volume of proliferating cell nuclear antigen (PCNA)-positive cells was found in the fish retina from the MPs exposed group, suggesting that MPs increased the rate of cellular division. In contrast, a significant decrease of PCNA-positive cells, and therefore a lower cell proliferation, was found in the retina and brain of zebrafish exposed to Cu and Cu + MPs, which could lead to cognitive and behavioral functions impairment. No alterations were found in the relative volume of ISL1&2-positive cells. This study contributes to the knowledge of the mechanisms by which MPs and Cu cause neurotoxicity, fundamental for a comprehensive and realistic ecological risk assessment in aquatic populations.

Toxicity of microplastics and copper, alone or combined, in blackspot seabream (Pagellus bogaraveo) larvae

Plastics pose serious risks for fish productivity and a potential constraint for food security. Newly hatched blackspot seabream larvae were exposed to microplastics (MPs), copper (Cu, 10-810 µg/L) and their mixtures (Cu+MPs), during 3 and 9 days. Biochemical biomarkers and the expression of antioxidant and neurotoxicity-related genes were evaluated. In the 3-day exposure, catalase and glutathione-S-transferase activities decreased in MPs, Cu and Cu+MPs groups, followed by an increase of lipid peroxidation in the Cu270 and Cu270 +MPs exposed larvae. In the 9-day exposure, ROS levels increased in MPs and Cu30 groups, but no significant oxidative damage was observed, suggesting that the antioxidant system overcome the induced oxidative stress. However, the acetylcholinesterase transcript was downregulated in MPs, Cu and Cu10+MPs groups, indicating that MPs effects in cholinergic neurotransmission may arise after longer exposures. Overall, MPs and Cu can reduce survival, induce oxidative stress, lipid peroxidation, neurotoxicity, and impact negatively fish larvae fitness.

Phytoplankton Sensitivity to Heavy Metals in Baltic Coastal Lakes

This study aimed to compare concentrations of chlorophyll-a between individual phytoplankton groups for four shallow Baltic coastal lakes, varying in type of connection with the sea. For two years, the research focused on quantifying the effects of abiotic factors—concentrations of heavy metals (Ba, Bi, Cr, Cu, Mn, Fe, Ni, Pb, and Zn) and hydrological connectivity—on phytoplankton composition, biomass, and photosynthetic activity. Our results show that hydrological factors are the main predictors of phytoplankton structure. The lakes differed in salinity: freshwater vs. brackish vs. transitional lakes. Irrespective of lake type, the dominant group was that of Cyanobacteria (~80%), but their percentage contribution was lower in the brackish lake. Baltic seawater intrusion resulted in a decrease in heavy-metal concentrations in lake water for Fe, Zn, Pb, and Bi. Redundancy analysis (RDA) suggested positive effects of some heavy metals on the biomass of the Chlorophyta and Bacillariophyta. For the Cryptophyta only, a slight decrease in biomass was linked with increased metal concentrations in open water.

Salinity as a Key Factor on the Benthic Fauna Diversity in the Coastal Lakes

Benthic communities were studied in nine Polish coastal lakes of the Baltic Sea; representing three levels of hydrological connection with the sea (isolated, periodically connected, and permanently connected), with resultant differences in salinity (freshwater, transitional, and brackish). The lakes classified in this way allowed us to investigate biodiversity in relation to the degree of environmental pressure. Stress intensity in coastal water bodies, resulting from contrasting marine and terrestrial influences, varied from mild to severe. Spatial variation in environmental predictors affected species richness more strongly than seasonal fluctuations. The broader the spatial salinity gradient, the smaller the species number recorded. Differences in the intensity of natural instability only slightly affected species number and α-diversity. In Baltic coastal lakes, characterized by low salinity (max. 7.5 PSU), benthic faunal communities were dominated by large populations of opportunistic species. This applied primarily to closed systems and those periodically influenced by seawater intrusion. The marine component of fauna played a more important role in increasing the diversity of benthos in permanently open water bodies (brackish). The highest density of benthic fauna was recorded in them, whereas low values were associated with the strongest instability, observed in lakes periodically linked with the sea (transitional).

Study on the Evaluation of (Heavy) Metals in Water and Sediment of Skadar Lake (Montenegro), with BCF Assessment and Translocation Ability (TA) by Trapa natans and a Review of SDGs

Skadar Lake is a crypto-depression, a shallow lake, near to the Adriatic coast; the largest in the Balkan Peninsula and in southeastern Europe. The Lake is a very complex aquatic ecosystem in which anthropogenic activities have a long history in terms of the impact on wildlife and the overexploitation of natural resources. Such consequences related to heavy metals represent a global problem. Heavy metal pollution can cause severe ecological consequences in aquatic ecosystems. These pollutants accumulate in the aquatic biota from water, sediment and through the food chain, the impact can magnify. Aquatic macrophytes are good indicators of the health of a water body. This research was carried out to evaluate heavy metals concentration in water, sediment and in the aquatic macrophyte Trapa natans (water chestnut), with BCF (bio-concentration factor), BSAF (biota sediment accumulation factor) and TA (translocation ability), in order to determine the water quality of this specific part of the aquatic ecosystem of Skadar Lake near to the settlement of Vranjina, a fishing village. The determination of heavy metals was carried out by ICP-OES. (Inductively coupled plasma-optical emission spectrometry). Statistical analysis was established by R statistical computing software, version 3.5.3. The metal concentration in the water decreases in the following sequential order: As > Pb > Zn > Cu = Al = Cr > Cd = Hg. Meanwhile in the sediment, the descending sequence is as follows: Cr > Zn > Cu > Pb > As > Cd > Hg. The ability of plants to absorb and accumulate metals from the aqueous growth medium was assessed using a bio-concentration factor. The BCF in the stem, leaf and fruit has high values, mainly, of Al, Cr, Cu and Zn, while for the biota sediment accumulation factor, the highest values were recorded for the following elements: Hg, Cd, Cu and Zn. Analysis of the translocation ability of TA shows the dominance of four metals: Pb, Cd, Hg and As. A significant positive Kendall’s correlation coefficient between sediment and stem (R = 0.73, p < 0.05), stem and leaf (R = 0.87, p < 0.05) and leaf and fruit (R = 1, p < 0.05) was established.