Fish farming, metals and antibiotics in the eastern Mediterranean Sea: Is there a threat to sediment wildlife?

Antibiotic resistance and preventive strategies in foodborne pathogenic bacteria: a comprehensive review

Antibiotic resistance in foodborne bacteria poses a substantial global health challenge. Reports indicate that antibiotic overuse in middle-class and low-income countries is a significant factor in the ever-increasing resistance. Resistance mechanisms have developed through enzymatic hydrolysis, reduced membrane permeability, efflux pumps, and target site mutations. Preventive measures like proper hygiene and safe food preparation, vaccination, antibiotic stewardship and surveillance, implementing infection prevention and control (IPC) measures, good agricultural practices, and investigating novel approaches like CRISPR, NGS, nanotechnology, and bacteriophages may be employed to address this challenge. Naturally occurring preservatives (e.g., nisin) are alternatives to antibiotics for food preservation. Prebiotics, probiotics, nanobiotics, phage treatment, and antimicrobial peptides are also substitutes for antibiotics. Furthermore, plant-derived compounds, such as essential oils and plant extracts, are promising substitutes for antibiotics in animal production. This review focuses on the mechanisms of underlying antibiotic resistance in foodborne pathogens, necessary preventive measures, and the challenges associated.

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Created using BioRender https://www.biorender.com/.

Lycopene alleviates splenic injury in grass carp (Ctenopharyngodon idella) caused by endoplasmic reticulum stress-autophagy axis induced by sulfamethoxazole through regulating AKT/AMPK pathway

Sulfamethozole (SMZ), an antibiotic widely used in aquaculture, is bioaccumulating and resistant to degradation, posing ecological risks. Although environmentally relevant SMZ concentrations (0.3 μg/L) are known to impair piscine immune function, the molecular mechanisms driving its toxicity remain elusive. Lycopene (LYC) is a potent bioactive compound that alleviates SMZ-induced toxicity by regulating the endoplasmic reticulum (ER) stress autophagy axis. This experiment chooses 120 grass carps, divided into 4 groups: control group (CON), SMZ exposure group (0.3 μg/L), the LYC supplement group (10 mg/kg) and SMZ + LYC combined treatment group. The toxicity of SMZ (0.3 μg/L) to grass carp and the mitigation effect of LYC (10 mg/kg) to SMZ were studied through a 30-day experiment. Histopathological alterations were evaluated via hematoxylin-eosin (H&E) staining, ultrastructural changes were visualized by transmission electron microscopy (TEM), and key biomarkers of ER stress, autophagy, and AKT/AMPK signaling were quantified through qRT-PCR and Western blotting. Results demonstrated that SMZ exposure induced disorganization of white pulp, cellular vacuolation, and activation of melanomacrophage centers (MMCs), accompanied by significant upregulation of ER stress markers (IRE1, PERK, ATF6, GRP78, eif2α) and autophagy-related genes (LC3, P62, Beclin1, ATG5). TEM revealed nuclear pyknosis, mitochondrial swelling, and increased autophagosomes in SMZ-treated splenocytes. LYC intervention markedly attenuated these pathological injuries and suppressed ER stress and excessive autophagy by modulating the AKT/AMPK pathway. Molecular docking analysis confirmed binding affinity between LYC and AKT/AMPK proteins, with a binding energy of -8.8 kcal/mol. Our findings establish a mechanistic foundation for developing LYC-enriched functional feeds to counteract antibiotic-associated ecological risks in sustainable aquaculture.

Antibiotic Resistance in Vibrio Bacteria Associated with Red Spotting Disease in Sea Urchin Tripneustes gratilla (Echinodermata)

The red spotting disease harms sea urchins to the extent of mass mortality in the ocean and echinocultures, accompanied by environmental damage and economic losses. The current study emphasizes the antimicrobial resistance of three isolated bacteria, closely related to Vibrio harveyi, Vibrio owensii, and Vibrio fortis, associated with red spotting in the cultured sea urchin Tripneustes gratilla. In vitro trials examined the susceptibility of these bacterial isolates to various antibiotics. In addition, using an in silico examination, we revealed the arsenal of antimicrobial resistance genes in available genomes of various pathogenic Vibrio associated with diseases in sea urchins, fish, shellfish, and corals. These two approaches enabled the discussion of the similarities and differences between aquatic pathogenic Vibrio and their antibiotic resistance. Among them, we revealed a core resistance to tetracyclines and penams by the in vitro examined strains. At the same time, the in silico study also supported this core resistance by the presence of the adeF and CRP genes in the bacterial genomes. Nevertheless, variability and specific resistance were evident at the species and strain levels in the Vibrio bacteria and genomes. The in vitro trials highlighted the diverse resistance of the Vibrio harveyi-like isolate to all examined antibiotics, while the other two isolates were found susceptible to nitrofurantoin and sulfamethoxazole. The resistance of the Vibrio harveyi-like isolate could not have been obtained in the genome of the proposed relative of Vibrio harveyi VHJR7 that lacks the oqxA and oqxB genes, which enables such a resistance. A unique sensitivity of the Vibrio fortis-like isolate to erythromycin is proposed when compared to other isolated Vibrio and Vibrio genomes that seem capable of resisting this drug. According to the results, we propose nitrofurantoin or sulfamethoxazole for treating two of the red-spotting-associated isolates (Vibrio fortis and Vibrio owensii-like), but not Vibrio harveyi-like. We assume that a shared resistance to some antibiotics by Vibrios is gained by a horizontal gene transfer while previous exposures of a bacterial strain to a specific drug may induce the development of a unique resistance. Finally, we discuss the novel knowledge on antibiotic resistance in Vibrio from the current research in light of the potential risks when using drugs for disease control in aquaculture.

Occurrence and risk assessment of quinolones and sulfonamides in freshwater aquaculture ponds in Northeast Zhejiang, China

Antibiotics play an essential role in the aquaculture industry, but their overuse and weak degradability inevitably lead to light to severe residues in natural and aquaculture environments. Most studies were interested in the occurrence, distribution, and ecological risks of a limited number of antibiotics in natural environments (rivers, lakes, and coastal regions) with a minor focus on antibiotic presence in either water, sediments, or organisms in aquaculture environments located in specific regions. In this study, we conducted a comprehensive investigation into the occurrence and distribution of up to 32 antibiotics [including 15 quinolones (QNs) and 17 sulfonamides (SAs)] in organisms and their corresponding environmental matrices from 26 freshwater aquaculture ponds in Northeast Zhejiang, China. A total of 13, 9, 7, and 7 antibiotics were detected in pond water, sediments, feeds, and aquaculture organisms, respectively, with concentration ranges of 0.6-92.2 ng/L, 0.4-1169.3 ng/g dw, Collapse

Key Words

• Antibiotics
• Contamination
• Cultured ponds
• Ecological risk
• Farming
• Health risk

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MESH Headings

• Water Pollutants, Chemical/analysis
• Aquaculture
• Sulfonamides/analysis
• China
• Quinolones/analysis
• Risk Assessment
• Environmental Monitoring
• Ponds/chemistry
• Anti-Bacterial Agents/analysis
• Animals
• Fresh Water/chemistry

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Affiliation(s)

Hongmei Hu Key Laboratory of Sustainable Utilization of Technology Research for Fisheries Resources of Zhejiang Province, Zhejiang Marine Fisheries Research Institute, Zhoushan 316021, PR China
Mengyu Qi Key Laboratory of Sustainable Utilization of Technology Research for Fisheries Resources of Zhejiang Province, Zhejiang Marine Fisheries Research Institute, Zhoushan 316021, PR China
Pengfei He Key Laboratory of Sustainable Utilization of Technology Research for Fisheries Resources of Zhejiang Province, Zhejiang Marine Fisheries Research Institute, Zhoushan 316021, PR China
Xuechang Chen Key Laboratory of Sustainable Utilization of Technology Research for Fisheries Resources of Zhejiang Province, Zhejiang Marine Fisheries Research Institute, Zhoushan 316021, PR China
Zhenhua Li Key Laboratory of Sustainable Utilization of Technology Research for Fisheries Resources of Zhejiang Province, Zhejiang Marine Fisheries Research Institute, Zhoushan 316021, PR China.
Heyong Cheng College of Material Chemistry and Chemical Engineering, Key Laboratory of Organosilicon Chemistry and Material Technology, Ministry of Education, Hangzhou Normal University, Hangzhou 311121, PR China.

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How mariculture expansion is dewilding the ocean and its inhabitants

The world's oceans are largely free from intensive farming, but momentum to intensify and expand mariculture-the cultivation of aquatic organisms in the ocean-is growing. Despite optimism that mariculture will create economic and nutritional benefits for humans, it can also generate a host of risks, including environmental degradation, harms to wildlife integrity and welfare, captivity effects, and shifts in how humans view the nonhuman world. Collectively, we refer to these four types of risks as "dewilding." In this systematic review, we searched Scopus and Web of Science for recent literature documenting mariculture's dewilding impacts to organize and collate this evidence under one unified framework. We find that mariculture's dewilding impacts are consistently documented, though often in isolation, and that captivity and conceptual dewilding impacts are recognized as potential harms far less than impacts on the environment and wildlife. Future work examining mariculture's dewilding impacts will be paramount to guiding human decision-making and activity going forward.

Adsorption of metals on aged microplastics in intensive mariculture areas: Aggravating the potential ecological risks to marine organisms

Field determination of the metal adsorption capacity of microplastics (MPs) by using a passive sampler had been done in typical subtropical mariculture area in China. The adsorption of eight metals (Fe, Mn, Cu, Zn, As, Pb, Cr and Cd) by five types of MPs (low-density polyethylene, polypropylene, polystyrene, poly(ethylene terephthalate) and poly(vinyl chloride) (PVC) was compared, including metal types, mariculture types (cage and longline culture), metal residue content in ambient environment, polymer types and particle sizes of MPs. The results showed that Cu, Zn, As, Cd, Pb and Cr in the mariculture environment were contaminated compared with the quality criteria. The concentrations of these six metals adsorbed on five MPs increased linearly with those in seawater. More enriched Cu and As in MPs in marine cage culture than in longline culture, due to the obvious endogenous pollution emissions for the artificial diets, fish medicine and disinfectants. Aged PVC with more cracks and pores showed higher metal adsorption capacity than any other polymers. MPs with a smaller size range of 50-74 μm tended to accumulate higher amounts of metals than those with a larger size range of 74-178 μm, consisting with the surface characteristics of MPs. The significant positive relationship between the concentrations of nutrients in seawater and the adsorption amounts of Cu, Zn and As on MPs implies that the eutrophication would promote their pollution. Based on the ecological risk assessment, the occurrence of MPs could aggravate the potential risk of metals to marine organisms in intensive mariculture areas. This is the first time to reveal the impacts of the adsorption of metals on aged MPs on the potential ecological risks of metals to organisms under the realistic environmental condition.

Physical and chemical food safety hazards and associated health risks in seafood: A Mediterranean perspective (Part 1)

Several risks to food safety are associated with seafood. The marine environment is heavily affected by various materials, both of physical and chemical nature, which have significant impact on the safety of seafood. Recently, there has been a concerning discovery regarding seafood contamination. As it appears, there are physical hazards present, specifically in the form of nano- and micro-plastic materials. Additionally, chemicals from various sources have been detected. These chemicals are commonly used in the production of convenience goods, antimicrobials, antibiotics, heavy metals and industrial effluents. This chapter has focused on the various hazards that can influence the safety of seafood in the marine environment. It covers both physical and chemical sources of these hazards, ensuring a comprehensive understanding of the potential risks involved. There are indications that the consumption of polluted seafood in the Mediterranean region can have negative impact on human health.

Seasonal Variability in the Influence of Coastal Aquaculture Operation on Benthic–Pelagic Coupling Processes in Shallow Aquatic Ecosystems

Coastal shellfish aquaculture can influence benthic–pelagic-coupled systems because cultured species consume phytoplankton in the water column and return the captured organic matter and nutrients to the environment as biodeposits, which fall to the seafloor, affecting local sediment characteristics and the benthic community. In 2023, we conducted monthly field surveys to characterize the relationships between shellfish aquaculture and the surrounding environment by examining a range of physical and biological variables along the benthic–pelagic gradient at multiple sampling locations in relation to their distances from the aquaculture facilities in Onagawa Bay, Japan. The abundances of benthic macrofauna were dominated by polychaetes (86.3%), followed by gastropods (4.7%), malacostracans (2.7%), ophiuroids (2.1%), and bivalves (1.5%). Both benthic biomass and biodiversity were markedly higher, but the chlorophyll-a concentration of the water column and the sediment organic matter content were significantly lower at the closest proximity to the aquaculture facilities. Although the physical presence of shellfish aquaculture may effectively enhance pelagic–benthic energy fluxes, such processes may also pose a new challenge under the influence of recent global warming, causing widespread hypoxic conditions due to increased stratification in the water column accompanied by excess organic inputs from the aquaculture.

Trajectories of trace element accumulation in seagrass (Posidonia oceanica) over a decade reveal the footprint of fish farming

To evaluate the effect of trace element (TE) release from fish farms on seagrass Posidonia oceanica, we compared TE concentrations (As, Cd, Co, Cu, Mn, Mo, Ni, Pb, V, Zn) in shoots near fish cages (Station 'Cage') with those away from them (Station 'Control') in two fish farm facilities (Site 1 and Site 2, North Aegean Sea, Greece). We assessed the present (i.e., 2021, year of sampling) and past (reconstructed period 2012-2020) accumulation of TEs using the living compartments (leaf blades, sheaths, rhizomes, roots, epiphytes) and the dead sheaths, respectively. We also assessed possible seagrass degradation by reconstructing past rhizome production. P. oceanica rhizome production at the 'Cage' stations was up to 50% lower than at the 'Control' stations. Most TE concentrations were higher at 'Cage' stations, but the differences often depended on the seagrass living compartment. Significant differentiation between 'Cage' and 'Control' stations was observed based on the TE concentrations of the dead sheaths during 2012-2020. The contamination level at the 'Cage' stations was mostly moderate in Site 1 and low in Site 2, during the reconstructed period, while an increasing contamination trend was found for certain potential phytotoxic TEs (As, Cu, Cd, Mo, V). Our results emphasize the need for the aquaculture industry to work towards a more ecologically aware approach.

Metal bioaccumulation and genotoxicity in Oreochromis niloticus reared in farming pools influenced by mining activities in Napo, in the Ecuadorian Amazon

Mining areas may suffer long-term metal contamination and represent harmful remnants of former mining activities. In the northern Amazon of Ecuador, former mining waste pits are used in Oreochromis niloticus (Nile tilapia) fish farming. Given the high consumption of this species by the local population, we aimed to estimate human consumption risks by determining Cd, Cu, Cr, Pb, and Zn tissue bioaccumulation (liver, gills, and muscle) and genotoxicity (micronucleus essay) in tilapia cultivated in one former mining waste pit (S3) and compare the findings to tilapias reared in two non-mining areas (S1 and S2); 15 fish total. Tissue metal content was not significantly higher in S3 than in non-mining areas. Cu and Cd were higher in the gills of tilapias from S1 compared to the other study sites. Higher Cd and Zn were detected in the liver of tilapias from S1 compared to the other sampling sites. Cu was higher in the liver of fish from S1 and S2, and Cr, in the gills of fish from S1. The highest frequency of nuclear abnormalities was observed in fish from S3, indicating chronic exposure to metals at this sampling site. The consumption of fish reared at the three sampling sites results in a 200-fold higher Pb and Cd ingestion than their maximum tolerable intake thresholds. Calculated estimated weekly intakes (EWI), hazard quotients (THQ), and Carcinogenic Slope Factors (CSF_ing) denote potential human health risks, indicating the need for continuous monitoring in this area to ensure food safety not only in areas affected by mining, but in general farms in the region.

Maternal transfer of florfenicol impacts development and disrupts metabolic pathways in F1 offspring zebrafish by destroying mitochondria

Maternal exposure to antibiotics existing in the environment is a predisposing factor for developmental malformation with metabolic disorders in offspring. In this study, female zebrafish (3 months) were exposed to 0.05 mg/L and 0.5 mg/L florfenicol (FF) for 28 days. After pairing and spawning with healthy male fish, F1 embryos were collected and developed to 5 d post-fertilization (dpf) in clear water. And the adverse effects on the F1 generation were examined thoroughly. The fecundity of F0 female fish and the hatchability, mortality, and body length of F1 larvae significantly decreased in the treatment group. Meanwhile, multi-malformation types were found in the exposure group, including delayed yolk sac absorption, lack of swim bladder, and spinal curvature. Metabolomic and transcriptomic results revealed alterations in metabolism with dysregulation in tricarboxylase acid cycle, amino acid metabolism, and disordered lipid metabolism with elevated levels of glycerophospholipid and sphingolipid. Accompanying these metabolic derangements, decreased levels of ATP and disordered oxidative-redox state were observed. These results were consistent with the damaged mitochondrial membrane potential and respiratory chain function, suggesting that the developmental toxicity and perturbed metabolic signaling in the F1 generation were related to the mitochondrial injury after exposing F0 female zebrafish to FF. Our findings highlighted the potential toxicity of FF to offspring generations even though they were not directly exposed to environmental contaminants.

Significant contribution of coastal fish-farm activities to the inventory of trace elements in coastal waters: Traced by ammonia and rare earth elements

In this study, we investigated the influence of fish-farm activities on the inventory of trace elements (Mn, Fe, Co, Ni, and Cu) in the coastal waters off the fish-farm plants on Jeju Island, Korea. NH₄⁺ and rare earth elements (REEs) were used as tracers to examine the production and removal processes. Relatively higher concentrations of trace elements were observed in the coastal waters and significantly correlated with NH₄⁺. Our results suggest that the excess dissolved trace elements in the coastal waters could be mainly produced inside fish farms, together with the production of NH₄⁺ and light-REEs (La to Nd). Although dissolved trace elements were found to be partially scavenged onto particles in the fish-farm rearing waters, indicated by the significant removal of particle-reactive Ce, these particles would be eventually discharged into the coastal ocean and release the dissolved trace elements back into the water columns.

Exploring the variation of bacterial community and nitrogen transformation functional genes under the pressure of heavy metals in different coastal mariculture patterns

Equilibrium in microbial dynamics and nitrogen transformation in the sediment is critical for maintaining healthy mariculture environment. However, our understanding about the impact of heavy metals on the bacterial community and nitrogen transformation functional genes in different mariculture patterns is still limited. Here, we analyzed 30 sediment samples in the vertical distribution from three different mariculture patterns mainly include open mariculture zone (K), closed mariculture pond (F) and pristine marine area (Q). Illumina MiSeq Sequencing was applied to investigate the bacterial community and structure in the sediment. Quantitative polymerase chain reaction (qPCR) was used to determine the effect of heavy metals on nitrogen transformation functional genes. Results showed that bacterial community and structure varied greatly in different mariculture patterns. Chloroflexi, Proteobacteria and Desulfobacterota were predominant phyla in the coastal mariculture area. High concentrations of heavy metals mainly enriched in the up layer (5-40 cm) of the sediment in the mariculture zone. The abundance of functional genes in the closed mariculture pond was much higher than the open mariculture zone and pristine marine area. And the high abundance of nitrification and denitrification functional genes mainly accumulated at the depth from 5 cm to 40 cm. Heavy metals content such as Fe, Cr, Mn, Ni, As, Cd, Pb and nutrient content NH₄⁺-N, NO₃^--N and NO₂^--N were highly associated with bacterial community and nitrogen transformation functional genes. This study comprehensively elaborated the effect of heavy metals on the bacterial community and nitrogen transformation functional genes in different coastal mariculture patterns, indicating the possible role of closed mariculture pond in reducing nitrogen transformation efficiency, which will provide useful information for preventing pollution risk in the mariculture area.

Damage and elimination of soil and water antibiotic and heavy metal pollution caused by livestock husbandry

The combination of antibiotics and heavy metals (HMs) increases the toxicity range of influence and requires additional research attention. This article analyzed the toxicity mechanisms and damage of combined pollution. Cross-resistance, co-resistance, and co-regulation are the primary toxicity mechanisms. Combined pollution increases antibiotic resistance genes (ARGs), increases bacterial resistance, and promotes the horizontal transfer of ARGs, affecting the types and distribution of microorganisms. The hazard of combined pollution varies with concentration and composition. The physicochemical and biological technologies for eliminating combined pollution are primarily elaborated. Adsorption, photocatalytic degradation, and microbial treatment show high removal rates and good recyclability, indicating good application potential. This review provides a basis and reference for the further study the elimination of combined antibiotic and HM pollution.

Occurrences, transport drivers, and risk assessments of antibiotics in typical oasis surface and groundwater

Intensive use of antibiotics affects biogeochemical cycles and stimulates the evolution of antibiotic resistance, thus threatening global health and social development. The spatiotemporal distributions of antibiotics in single aqueous matrices have been widely documented; however, their occurrence in surface-groundwater systems has received less attention, especially in arid regions that usually have fragile ecosystems. Therefore, we investigated the occurrence of thirty-one antibiotics in the surface water and adjacent groundwater in the Xinjiang Uygur Autonomous Region, China. The results showed that the total concentrations of detected antibiotics varied from 17.37 to 84.09 ng L^-1 and from 16.38 to 277.41 ng L^-1 in surface and groundwater, respectively. The median concentration of antibiotics showed the pattern of norfloxacin (4.86 ng L^-1) > ciprofloxacin (3.93 ng L^-1) > pefloxacin (3.39 ng L^-1) in surface water; whereas in groundwater, this was in the order of pefloxacin (6.30 ng L^-1) > norfloxacin (4.33 ng L^-1) > ciprofloxacin (2.68 ng L^-1). Heatmap analysis indicated that vertical infiltration had limited effects on antibiotic exchange in surface-ground water systems because of the high potential evaporation and low water storage. Redundancy analysis suggested that the oxidation-reduction potential (p < 0.01) and dissolved oxygen (p < 0.05) jointly affected the distribution of antibiotics in surface water. Ecological risk assessment showed that antibiotics in 98.9% of surface water and 99.1% of groundwater did not pose significant risks to aquatic species. The findings of this study will help develop effective mitigation strategies for antibiotics in aquatic environments.

Intensive marine finfish aquaculture impacts community structure and metal bioaccumulation in meso-zooplankton

Commercial aquaculture has a profound impact on coastal marine environments. Here, we investigate the spatial impact of intensive commercial finfish aquaculture on local meso-zooplankton communities and the bioaccumulation of aquaculturally-derived metals (and other elements) within zooplankton samples in the Vourlias Bay, Greece. The results indicate alterations to zooplankton community composition correlate with increased eutrophic compound concentrations in the water column in closer proximity to aquaculture stations (100-300 m from fish cages). During the summer sampling, higher concentrations of accumulated metals within zooplankton samples were found at reference stations furthest from fish cages (>1000 m). During the winter sampling, however, spatial differences in accumulated metal concentrations were limited. We suggest metals are rapidly accumulated at lower trophic levels near aquaculture stations and are then dispersed to greater distances while ascending the trophic chain. This research provides good evidence for future investigations into zooplankton as an environmental impact bioindicator for aquaculture.

Identifying pollution sources of sediment in Lake Jangseong, Republic of Korea, through an extensive survey: Internal disturbances of past aquaculture sedimentation

Lake sediments are important sinks of various pollutants and preserve historical pollution records caused by anthropogenic activities. Recently, the sediments of Lake Jangseong, South Korea were first detected with high concentrations of organic matter (ignition loss [IL]; total organic carbon [TOC]), nutrients (total nitrogen [TN]; total phosphorus [TP]), and some heavy metals (Zn, Cu, Cd, and Hg). Here, we identified the origins of these concentrations accumulated in the sediments using extensive surveys and various assessments. Sediment pollution assessed by sediment quality guidelines, pollution load index, and potential ecological risk index was found to be of serious concern for IL, TN, TP, and Cd. Thus, we assessed pollution sources through spatial, grid, and vertical distributions and found that the high pollutant concentrations detected in 2020 were confirmed only at a certain location in the lake. Additionally, similar results were detected in the sedimentary layer below a sediment core at a depth of 15.0 cm. The high pollutant concentrations locally occurred around a "hotspot" site that was previously frequently used for aquaculture activities, indicating that the pollutants were accumulated in sediments owing to past cage fish farming rather than from influx of externally sourced pollution. Furthermore, chemical fractionation of phosphorus and heavy metals and assessment of stable isotopes (¹³C and ¹⁵N) of organic matter suggested that the pollutants in the sediments at the "hotspot" sites had different origins than those found at other sites. Accordingly, the by-products discharged after cage fish farming, such as residual feed, fish meal, and waste, accumulated in the sediments and were then exposed to natural internal disturbances caused by the effects of climate change-induced drought. This local distribution and the phosphorus and heavy metal chemical fraction results with low elution potential indicated that the pollutants in the sediments of Lake Jangseong had negligible impact on water quality.

Assessment of toxic metal contamination, distribution and risk in the sediments from lagoons used for fish farming in the central region of Peru

Toxic metal contamination, distribution and risk were evaluated in the sediments of three lagoons used for fish farming in the central region of Peru. The distribution of toxic metals in the sediment was in the following descending order of Zn > V > Ni > Cu > Pb > As > Cr > Co > Cd > Sb. Contamination factor (Cf) and geoaccumulation index (I_geo) values for Co, Cr, Cu, Ni, Pb, Sb, V and Zn indicated low contamination and for Cd moderate contamination. The pollution load index (PLI) ranged from 0.3856 to 0.5622; indicating no appreciable contamination and the modified degree of contamination (mCd) corroborated this result. The potential ecological risk (R_i) in the Tranca Grande and Pomacocha lagoons revealed a low potential ecological risk and in Tipicocha a moderate potential ecological risk. HI values < 1 indicated that non-carcinogenic adverse effects were negligible. In adults, the Total carcinogenic risk (TCR) values for As, Cd, Cr, Ni and Pb were less than 1.00E-04, indicating no significant carcinogenic risk. In children, TCR values showed similar behavior with the exception of As. Therefore, considering that fish production for domestic consumption and export is carried out in these lagoons, it is important to continue monitoring toxic metals to protect the health of these ecosystems and human health.

An IMTA in Greece: Co-Culture of Fish, Bivalves, and Holothurians

Integrated multitrophic aquaculture (IMTA) is an innovative mariculture methodology that reduces the environmental footprint and increases the profitability of the farm. It combines the cultivation of species belonging to different trophic levels, simulating a natural food web. In this study, five Mediterranean species were co-cultured in three operating fish farms in the Aegean (E. Mediterranean) Sea with different trophic conditions. The co-cultivated species were sea bream (Sparus aurata), European sea bass (Dicentrarchus labrax), Mediterranean mussel (Mytilus galloprovincialis), rayed pearl oyster (Pinctada imbricata radiata), and sea cucumber (Holothuria polii). Bream, bass, and mussels were cultivated according to the traditional on-growing methods (fish cages and longlines), whereas the pearl oysters and sea cucumbers were cultivated in baskets designed specifically for oyster farms. To estimate the growth of the co-cultivated species, growth indicators were calculated using length and weight measurements. Furthermore, the growth measurements from co-cultivated species were compared to the respective ones from natural populations. All the species showed high survival rates in the integrated multitrophic aquaculture (IMTA) conditions. Pearl oysters and Mediterranean mussels had positive growth in fish farms with high concentrations of nutrients. Mussel condition index (CI) was 42% in Aquaculture 1 (Aq1) and 33% in Aquaculture 2 (Aq2), compared to 35% in a typical Mediterranean mussel farm. Pearl oysters CI in Aq1 was 53%, in Aq2 56%, in Aquaculture 3 (Aq3) 19%, and in natural populations ranging from 30% to 45%. In contrast, holothurians did not gain weight under the fish cage regime despite the high survival rate. Their final total weight was 17.3 g in Ag1, 8.3 g in Aq2, and 18.3 g in Aq3, but in the natural population, the mean weight was 80 g.

Flumequine-loaded titanate nanotubes as antibacterial agents for aquaculture farms

Flumequine (FLUM), a quinolone-derived antibiotic is one of the most prescribed drugs in aquaculture farms. However, its intensive use becomes worrisome because of its environmental risks and the emergence of FLUM-resistant bacteria. To overcome these problems we propose in this study the encapsulation and the delivery of FLUM by titanate nanotubes (TiNTs). Optimal FLUM loading was reached by suspending the dehydrated powder nanomaterials (FLUM : TiNTs ratio = 1 : 5) in ethanol. The drug entrapment efficiency was calculated to be 80% approximately with a sustained release in PBS at 37 °C up to 5 days. Then FLUM@TiNTs was evaluated for both its in vitro drug release and antimicrobial activity against Escherichia coli (E. coli). Spectacularly high antibacterial activity compared to those of free FLUM antibiotic was obtained confirming the efficiency of TiNTs to protect FLUM from rapid degradation and transformation within bacteria improving thereby its antibacterial effect. Indeed FLUM@TiNTs was efficient to decrease gradually the bacterial viability to reach ≈5% after 5 days versus ≈75% with free FLUM. Finally, the ex vivo permeation experiments on sea bass (Dicentrachus labrax) intestine shows that TiNTs act to increase the intestinal permeation of FLUM during the experiment. Indeed the encapsulated FLUM flux increased 12 fold (1.46 μg cm² h⁻¹) compared to the free antibiotic (0.18 μg cm² h⁻¹). Thanks to its physical properties (diameter 10 nm, tubular shape…) and its high stability in the simulated intestinal medium, TiNTs are easy internalized by enterocytes, thus involving an endocytosis mechanism, and then improve intestinal permeation of FLUM. Taken together, FLUM@TiNTs hold potential as an effective approach for enhancing the antimicrobial activity of FLUM and pave the way not only for future pharmacokinetic studies in the treatment and targeting of fish infections but also for instating of novel strategies that overcome the challenges associated with the abusive use of antibiotics in fish farming.

Flumequine (FLUM), a quinolone-derived antibiotic is one of the most prescribed drugs in aquaculture farms.

Effects of aquaculture waste feeds and antibiotics on marine benthic ecosystems in the Mediterranean Sea

Intensive aquaculture is an important source of organic waste and antibiotics into the marine environment. Yet, their impacts on benthic marine ecosystems are poorly understood. Here, we investigated the ecological impacts of fish feed waste alone and in combination with three different antibiotics (i.e., oxytetracycline, florfenicol and flumequine) in benthic ecosystems of the Mediterranean Sea by performing a field experiment. We assessed the fate of the antibiotics in the sediment and their accumulation in wild fauna after two weeks of exposure. Moreover, we investigated the impact of the feed waste alone and in combination with the antibiotics on sediment physico-chemical properties, on benthic invertebrates, as well as on the microbiota and resistome of the sampled sediments. One week after the last antibiotic application, average oxytetracycline and flumequine concentrations in the sediment were <1% and 15% of the applied dose, respectively, while florfenicol was not detected. Flumequine concentrations in wild invertebrates reached 3 μg g^-1, while concentrations of oxytetracycline were about an order of magnitude lower, and florfenicol was not detected. Feed waste, with and without antibiotics, increased the concentration of fine particulate matter, affected the pH and redox conditions, and significantly reduced the biodiversity and abundance of benthic invertebrates. Feed waste also had a significant influence on the structure of sediment microbial communities, while specific effects related to the different antibiotics ranged from insignificant to mild. The presence of antibiotics significantly influenced the normalized abundance of the measured antibiotic resistance genes. Florfenicol and oxytetracycline contributed to an increase of genes conferring resistance to macrolides, tetracyclines, aminoglycosides and chloramphenicol, while flumequine had a less clear impact on the sediment resistome. This study demonstrates that feed waste from aquaculture farms can rapidly alter the habitat and biodiversity of Mediterranean benthic ecosystems, while antibiotic residual concentrations can contribute to the enrichment of bacterial genes resistant to antibiotic classes that are of high relevance for human medicine.

Microbial diversity in intensively farmed lake sediment contaminated by heavy metals and identification of microbial taxa bioindicators of environmental quality

The cumulative effects of anthropogenic stress on freshwater ecosystems are becoming increasingly evident and worrisome. In lake sediments contaminated by heavy metals, the composition and structure of microbial communities can change and affect nutrient transformation and biogeochemical cycling of sediments. In this study, bacterial and archaeal communities of lake sediments under fish pressure contaminated with heavy metals were investigated by the Illumina MiSeq platform. Despite the similar content of most of the heavy metals in the lagoon sediments, we found that their microbial communities were different in diversity and composition. This difference would be determined by the resilience or tolerance of the microbial communities to the heavy metal enrichment gradient. Thirty-two different phyla and 66 different microbial classes were identified in sediment from the three lagoons studied. The highest percentages of contribution in the differentiation of microbial communities were presented by the classes Alphaproteobacteria (19.08%), Cyanophyceae (14.96%), Betaproteobacteria (9.01%) y Actinobacteria (7.55%). The bacteria that predominated in sediments with high levels of Cd and As were Deltaproteobacteria, Actinobacteria, Coriobacteriia, Nitrososphaeria and Acidobacteria (Pomacocha), Alphaproteobacteria, Chitinophagia, Nitrospira and Clostridia (Tipicocha) and Betaproteobacteria (Tranca Grande). Finally, the results allow us to expand the current knowledge of microbial diversity in lake sediments contaminated with heavy metals and to identify bioindicators taxa of environmental quality that can be used in the monitoring and control of heavy metal contamination.

Effects of four different adjuvants separately combined with Aeromonas veronii inactivated vaccine on haematoimmunological state, enzymatic activity, inflammatory response and disease resistance in crucian carp

The purpose of the current study was to explore the immunomodulatory effects of different adjuvants combined with inactivated vaccines under Aeromonas veronii TH0426 infection in crucian carp. This study explored the best conditions for A. veronii as an inactivated vaccine, and included an animal safety test. Furthermore, we expressed the flagellin FlaA of the A. veronii TH0426 strain for use as an adjuvant supplemented in the diet. Crucian carp were fed 12 different experimental diets for 35 days, including the administration of 10 different adjuvants and inactivated vaccine combinations (50% aluminum hydroxide gel and inactivated vaccine combination, and inactivated vaccine with 20%, 30%, or 50% glucan, astragalus polysaccharide or flagellin), inactivated vaccine alone, and PBS control without adjuvant and inactivated vaccine. After the 42 day feeding trials, the fish were challenged with A. veronii TH0426, and the survival rate over 14 days was recorded. In addition, flagellin FlaA can be expressed normally in large amounts. All experimental groups produced higher levels of IgM serum titres than the control group in the different feeding cycles. Moreover, the activity of serum ACP, AKP, SOD, and LZM, and the expression of inflammatory factors were significantly increased in the experimental groups compared with the control group. The results of qRT-PCR analysis showed that the transcription levels of the IL-10, IL-1β, IFN-γ and TNF-α genes in heart, liver, spleen and kidney tissues were significantly enhanced by adjuvant treatment, indicating that the addition of adjuvants can significantly promote the body's inflammatory response. In addition, the phagocytic activity of leukocytes in each adjuvant treated group was significantly enhanced compared to that in the groups without adjuvant. After the A. veronii challenge, the survival rate of all adjuvant-treated groups was significantly higher than that of the control group, and the 50% flagellin adjuvant group had the highest rate of 78.37%. Overall, our findings strongly indicate that adjuvants not only significantly improve the body's immunity, but also exhibit a strong anti-infection ability. Importantly, this work provides a new perspective for the prevention and control of aquaculture diseases.

Removal of levofloxacin from aqueous solution by green synthesized magnetite (Fe3O4) nanoparticles using Moringa olifera: Kinetics and reaction mechanism analysis

Levofloxacin antibiotic is frequently being detected in the environment and regarded as an emerging contaminant. The present study was focused on the green synthesis of magnetite (Fe₃O₄ - gINPs) nanoparticles from Moringa olifera and its efficiency for removal of levofloxacin from aqueous solution. The adsorbent magnetite nanoparticles (Fe₃O₄) were prepared by green synthesis using Moringa olifera and coprecipitation method. Characterizations analyses of both chemically and green synthesized nanoparticles were performed by SEM, XRD, and FTIR. The average crystallite size of gINPs was 14.34 nm and chemically synthesized was 18.93 nm. The performance of the synthesized product was evaluated by adsorption capacity and removal efficiency. The parameters considered included adsorbent (gINPs) dosage, initial concentration of adsorbate, pH, contact time, and temperature. The obtained data were fitted to kinetic and isotherm models to determine the mechanism. Adsorption batch experiments were conducted to determine the reaction mechanism by studying kinetics while fitting isotherm models for samples analyzed using HPLC at 280 nm. Results showed that 86.15% removal efficiency of 4 mg L^-1 levofloxacin was achieved by 100 mg L^-1 gINPs in 24 h contact time when all other parameters (pH 7, temperature 25 °C) were kept constant. The maximum adsorption capacity achieved at equilibrium was 22.47 mg/g. Further, it was identified as a pseudo-second-order model with R² = 0.965 for adsorption kinetics while isotherm data better fitted to the Freundlich model compared to Langmuir isotherm with R² = 0.994. The potential pathway determined for levofloxacin removal was chemisorption with minor diffusion, multilayer, spontaneous and exothermic processes on the gINPs (Fe₃O₄). Reusability experiments were conducted in four cycles and removal efficiency varied from 85.35% to 80.47%, indicating very high potential of the adsorbent for re-use.

Antibiotic-Resistant Bacteria in Aquaculture and Climate Change: A Challenge for Health in the Mediterranean Area

Aquaculture is the productive activity that will play a crucial role in the challenges of the millennium, such as the need for proteins that support humans and the respect for the environment. Aquaculture is an important economic activity in the Mediterranean basin. A great impact is presented, however, by aquaculture practices as they involve the use of antibiotics for treatment and prophylaxis. As a consequence of the use of antibiotics in aquaculture, antibiotic resistance is induced in the surrounding bacteria in the column water, sediment, and fish-associated bacterial strains. Through horizontal gene transfer, bacteria can diffuse antibiotic-resistance genes and mobile resistance genes further spreading genetic determinants. Once triggered, antibiotic resistance easily spreads among aquatic microbial communities and, from there, can reach human pathogenic bacteria, making vain the use of antibiotics for human health. Climate change claims a significant role in this context, as rising temperatures can affect cell physiology in bacteria in the same way as antibiotics, causing antibiotic resistance to begin with. The Mediterranean Sea represents a 'hot spot' in terms of climate change and aspects of antibiotic resistance in aquaculture in this area can be significantly amplified, thus increasing threats to human health. Practices must be adopted to counteract negative impacts on human health, with a reduction in the use of antibiotics as a pivotal point. In the meantime, it is necessary to act against climate change by reducing anthropogenic impacts, for example by reducing CO2 emissions into the atmosphere. The One Health type approach, which involves the intervention of different skills, such as veterinary, ecology, and medicine in compliance with the principles of sustainability, is necessary and strongly recommended to face these important challenges for human and animal health, and for environmental safety in the Mediterranean area.

Impact of Marine Aquaculture on the Microbiome Associated with Nearby Holobionts: The Case of Patella caerulea Living in Proximity of Sea Bream Aquaculture Cages

Aquaculture plays a major role in the coastal economy of the Mediterranean Sea. This raises the issue of the impact of fish cages on the surrounding environment. Here, we explore the impact of aquaculture on the composition of the digestive gland microbiome of a representative locally dwelling wild holobiont, the grazer gastropod Patella caerulea, at an aquaculture facility located in Southern Sicily, Italy. The microbiome was assessed in individuals collected on sea bream aquaculture cages and on a rocky coastal tract located about 1.2 km from the cages, as the control site. Patella caerulea microbiome variations were explained in the broad marine metacommunity context, assessing the water and sediment microbiome composition at both sites, and characterizing the microbiome associated with the farmed sea bream. The P. caerulea digestive gland microbiome at the aquaculture site was characterized by a lower diversity, the loss of microorganisms sensitive to heavy metal contamination, and by the acquisition of fish pathogens and parasites. However, we also observed possible adaptive responses of the P. caerulea digestive gland microbiome at the aquaculture site, including the acquisition of putative bacteria able to deal with metal and sulfide accumulation, highlighting the inherent microbiome potential to drive the host acclimation to stressful conditions.