Zebrafish as a biological model for assessing water quality along tropical hydrographic river basins in Northeast Brazil.

Tropical rivers are the main destinations for tailings from urban, industrial and agricultural activities in the region studied. The present study aimed to investigate if early stages of zebrafish (Danio rerio) development is a viable biological model to assess the toxicity of surface waters of tropical rivers, and whether that toxicity could be correlated to standard water quality indexes. Embryos were exposed to samples from 55 sites from 10 hydrographic basins of rivers in Pernambuco State, northeastern Brazil. Lethality rates, sublethal toxicity based on the general morphology score (GMS) and frequencies of abnormalities were analyzed. Significant mortality was observed in samples of 7 basins. The GMS indicated significant delay in embryo-larval development in 50% of the samples. The highest toxicity was detected in basins within Recife metropolitan area, where 61% of the samples caused sublethal toxicity. Most frequent developmental abnormalities included non-inflation of the swim bladder, delayed hatching and blood stasis. The highest frequencies of blood stasis were detected in samples with highest NH3 concentrations, corroborated by a positive correlation suggesting the existence of a causal relationship. A significant correlation was detected between water quality indexes and GMS with a greater toxic effect being observed in samples collected in areas of greater urban density and greater contamination by domestic sewage. This study demonstrates that the early stages of the zebrafish is a viable ecotoxicological model to assess the toxicity of surface waters and can contribute to a better understanding between the chemical composition and the adverse effects suffered by fish early life stage fish in tropical rivers.

Toxicity of the oil spilled on the Brazilian coast at different degrees of natural weathering to early life stages of the zebrafish Danio rerio.

Toxicity of water accommodated fractions (WAF) from the oil spilled on the Brazilian coast at different stages of weathering were investigated using Danio rerio. Weathering stages included emulsified oil that reached the coast (OM) and oil collected 50 days later deposited on beach sand (OS) or adhered to shore rocks (OR). Parent and alkylated naphthalenes decreased whereas phenanthrenes increased from less weathered WAF-OM to more weathered WAF-OS and WAF-OR. More weathered WAF-OS and WAF-OR were more potent inducers of zebrafish developmental delay, suggesting that parent and alkylated phenanthrenes are involved. However, less weathered WAF-OM was a more potent inducer of failure in swim-bladder inflation than more weathered WAF-OS and WAF-OR, suggesting that parent and alkylated naphthalenes are involved. Decreases in heart rates and increased heart and skeletal deformities were observed in exposed larvae. Lowest observed effect concentrations for different developmental toxicity endpoints are within environmentally relevant polycyclic aromatic hydrocarbon concentrations.

Nondestructive Evaluation of Metal Bioaccumulation and Biochemical Biomarkers in Blood of Broad-Snouted Caiman (Caiman latirostris) from Northeastern Brasil.

Studies on the bioaccumulation and toxicity of contaminants in Crocodylians are scarce. We evaluated alterations in concentrations of the nondestructive biomarkers butyrylcholinesterase (BChE), glutathione-S-transferase (GST), superoxide dismutase (SOD), and reduced glutathione (GSH), together with bioaccumulation of the metals iron (Fe), copper (Cu), zinc (Zn), manganese (Mn), chronium (Cr), aluminium (Al), and lead (Pb) in Caiman latirostris captured in Tapacurá Reservoir (TR; São Lourenço da Mata, Pernambuco, Brasil), in urbanized areas of Pernambuco State (UA; Brasil) and from the AME Brasil caiman farm (AF; Marechal Deodoro, Alagoas, Brasil); the latter was used as a potential reference with low levels of contamination. For metal analysis, 500 µL of blood was digested in 65% HNO3 and 30% H2O2. The samples were analyzed by inductively coupled plasma-optical emission spectrometry. For analysis of biomarkers, an aliquot of blood was centrifuged to obtain plasma in which biochemical assays were performed. Blood concentrations of metals analyzed in animals from AF were lower compared with TR and UA, confirming that animals from the caiman farm could be used as references with low levels of contamination. Iron, Cu, Mn, Al, and Pb exceeded toxic levels for other vertebrates in animals from TR and UA. Butyrylcholinesterase activity showed significant reduction in adults from UA and TR compared with AF. An increase in the activity of GST and GSH, in adults of TR and UA in relation to AF, was verified. Superoxide dismutase activity showed a significant reduction in adults of TR in relation to AF, and the concentrations of Cu and Mn were negatively correlated with SOD activity. Animals from UA and TR showed greater concentrations of the analyzed metals compared with reference animals, and changes in biomarkers were seen, confirming the potential of these nondestructive chemical and biological parameters in blood of C. latirostris for biomonitoring of pollution. Environ Toxicol Chem 2024;43:878-895. © 2024 SETAC.

Oil spill impact on Brazilian coral reefs based on seawater polycyclic aromatic hydrocarbon contamination, biliary fluorescence and enzymatic biomarkers in damselfish Stegastes fuscus (Teleostei, Pomacentridae).

The crude oil contamination along the Brazilian Northeast coast significantly impacted reef ecosystems. This study assessed polycyclic aromatic hydrocarbons (PAHs) in seawater, fluorescence of bile PAHs, and biochemical biomarkers in damselfish Stegastes fuscus across four coral reef areas pre- and post-oil contamination. Serrambi (SE) and Japaratinga (JP1) were identified as suitable reference areas. PAH concentrations significantly increased in water post-contamination, predominantly 2 to 3 ring parent and alkylated PAHs. Biliary PAHs naphthalene, phenanthrene, chrysene, pyrene and benzo(a)pyrene increased on Paiva post-spill versus pre-spill to 173 %, 449 %, 334 %, 331 % and 131 %, respectively. Significant increases in ethoxy-resorufin-O-deethylase (EROD) (852 %), catalase (CAT) (139 %) and decrease in lipid peroxidation (LPO) (40 %) and acetylcholinesterase (AChE) (75 %) were verified in Paiva samples. Biliary PAHs and biochemical biomarkers were altered in S. fuscus after exposure to PAHs dissolved from the oil. Stegastes fuscus emerges as a promising sentinel organism for coastal reef oil pollution monitoring.

Lethal and Sublethal Toxicity of Un-Ionized Ammonia to Early-Life Stages of Danio rerio.

Un-ionized ammonia (NH3) is a prevalent contaminant found in aquatic ecosystems, frequently associated with complex mixtures of other toxic contaminants. Early embryo-larval stages of zebrafish Danio rerio became an important model for water quality monitoring, and it is necessary to characterize its susceptibility to NH3 exposure. Fertilized eggs were exposed to NH3 concentrations ranging from 0.02 to 5.23 mg NH3 L-1 until 168 h postfertilization (hpf). The lethal concentration to 50% of exposed zebrafish during 96 h was 2.07 mg NH3 L-1, 25% above the median value reported values for early developmental stages of fishes. Sublethal toxicity endpoints indicated the lowest observed effect concentrations for slow blood circulation at 24 hpf, decreased heart ventricular contractions at 72 hpf, incomplete yolk sac absorption at 96 hpf, failure in swim bladder inflation at 96 hpf, developmental retardation at 96 hpf, decreased total length, decreased swimming speed, altered trajectories, and acetylcholinesterase inhibition at 168 hpf of 0.85, 0.06, 0.15, 0.06, 0.15, 0.61, 1.35, 0.35, and 0.85 mg NH3 L-1, respectively. Environmentally relevant NH3 concentrations can affect zebrafish's early development and larval viability, and our results help discriminate NH3 contribution to the toxicity of complex environmental mixtures when zebrafish is used in water quality monitoring.

Biliary polycyclic aromatic hydrocarbons and enzymatic biomarkers in Eugerres brasilianus along four tropical estuaries.

Polycyclic aromatic hydrocarbons (PAH) in bile and biochemical biomarkers were evaluated in Brazilian mojarra Eugerres brasilianus along four estuaries in northeastern Brazil. Bile PAHs naphthalene, phenanthrene chrysene, pyrene and benzo[a]pyrene were lowest at Formoso River Estuarine System (FRES), an area with low population density focused on tourism. Fish sampled in Suape Estuarine Complex (SEC), where a growing industrial port complex is established indicated higher naphthalene and pyrene concentrations compared with FRES. Fish sampled in highly urbanized and populated Bacia do Pina Estuarine Complex (BPEC) and Barra de Jangada Estuarine System (BJES) indicated an increase in all PAHs compared to FRES. Activities of phase 1 Ethoxyresorufin-O-deethylase, phase 2 glutathione-S-transferase and antioxidant defense catalase were induced up to 20, 2 and 2-fold in BJES and BPEC compared to FRES. This study confirms E. brasilianus as an important sentinel species, providing baseline information for these tropical estuaries with different degrees of anthropogenic pressure.

Contamination and Toxicity of Surface Waters Along Rural and Urban Regions of the Capibaribe River in Tropical Northeastern Brazil.

The Capibaribe River provides water to a population of 1.7 million people in the Brazilian northeast, while receiving agricultural runoff and industrial and domestic effluents along its 280 km. The present study evaluated the ecotoxicity of surface waters along ten sites in rural and urban areas using zebrafish (Danio rerio) early-life stages and related it to water quality indices and chemical abiotic variables. Lethality rates, delays in embryo-larval development quantified by the general morphology score (GMS), and frequencies of developmental abnormalities were analyzed. A correlation was detected between zebrafish GMS and water quality index (WQI), sensitivity to domestic sewage contamination, and trophic state index, focused on eutrophication. These indices agreed in identifying a spatial pattern of smaller impact in terms of ecotoxicity, domestic sewage contamination, and eutrophication risk at three sites in rural areas (mean GMS 16.9), an intermediate impact at four sites with urban and agricultural influence (mean GMS 16.4), and greatest impacts at three more urbanized sites (mean GMS 14.9). Most frequent developmental abnormalities included noninflation of the swim bladder, delayed hatching, nonprotrusion of the mouth, blood stasis, and nondevelopment of pectoral fins. Toxic NH3 concentrations varied spatially, with higher concentrations in urban sites; and blood stasis correlated positively with NH3 , suggesting a causal relationship. Polycyclic aromatic hydrocarbons were detected in both rural and urbanized sites, contributing to detected toxicity. The present study demonstrates the potential of zebrafish early-life stages as an ecotoxicological model that may contribute to a better understanding of surface water quality and ecotoxicity in tropical river systems. Environ Toxicol Chem 2021;40:3063-3077. © 2021 SETAC.

Histological and Behavioral Toxicity of Tributyltin in the Tropical Guppy Poecilia vivipara.

The tropical estuarine guppy Poecilia vivipara was used to address fish early life stage toxicity caused by the antifouling contaminant tributyltin. Six-day-old P. vivipara were exposed for 7 d to control water and waterborne tributyltin at 15.8, 83.8, 716, and 818 ng tin (Sn) L-1 . After exposure, swimming, feeding, growth, and eye histological endpoints were evaluated. Histopathological analysis of the retinal pigment epithelium (RPE) indicated alterations in pigment positioning at all tributyltin concentrations. A dose-dependent increase in photoreceptor layer disorganization and iris melanin hyperpigmentation was verified, and high frequencies of RPE invaginations and iris epithelial cell atrophy were observed even at the lowest exposure concentration of 15.8 ng Sn L-1 . At the highest exposure level (818 ng Sn L-1 ) fish also presented reductions in swimming speed, swimming resistance, daily capture of Artemia nauplii, and growth in weight of 85, 60, 33, and 56% relative to controls, respectively. This association between retinal histopathology and reduced swimming and foraging behavior can reduce recruitment to the adult population. Environ Toxicol Chem 2020;39:1953-1963. © 2020 SETAC.

Toxicity of effluents from gasoline stations oil-water separators to early life stages of zebrafish Danio rerio.

Used petroleum hydrocarbons and gasoline stations runoff are significant sources of polycyclic aromatic hydrocarbons (PAHs) to aquatic ecosystems. Samples of the final effluent of oil-water-separators were collected at gasoline stations in the metropolitan region of Recife, Brazil, before release to sewage or rainwater systems. Effluent soluble fractions (ESF) were prepared and bioassays were performed according to the Fish Embryo Toxicity Test. The test involved exposing zebrafish Danio rerio embryos to dilutions of the ESFs for 96 h, with daily examination of lethality and sublethal morphological effects integrated through the General Morphology Score (GMS), based on the achievement of developmental hallmarks. Frequencies of abnormalities were recorded after exposures. ESF LC50-96h (lethal concentration to 50% of exposed embryos) in the most toxic effluent achieved 8.9% (v/v), equivalent to 11 µg phenanthrene equivalents L-1. GMS scores indicated significantly delayed embryo-larval development at ESF dilutions of 10% and 20% from effluents of all gas stations. Major abnormalities detected after the 96 h exposure included the presence of a yolk sac not fully absorbed coupled with the lack of an inflated swim bladder, lack of both pectoral fins, and the failure to develop a protruding mouth. Effective equivalent PAH concentrations that induce a 50% frequency of larvae without an inflated swim bladder (EC50) were 4.9 µg phenanthrene L-1, 21.8 µg naphthalene L-1, and 34.1 µg chrysene L-1. This study shows that PAHs in ESFs from gas stations oil water separators are toxic to zebrafish, contributing to the toxicity of urban storm waters.