In 2016, a massive harmful algal bloom (HAB) of Alexandrium catenella around Chiloe island caused one of the major socio-ecological crisis in Chilean history. This red tide occurred in two distinct pulses, the second, most anomalous, bursting with extreme toxicity on the Pacific coast, weeks after the highly controversial dumping off Chiloe of 4,700 t of rotting salmons, killed by a previous HAB of Pseudochattonella verruculosa. We study the transport of this pollution, analyzing the physical oceanographic conditions during and after the dumping. We find that a cyclonic gyre was present between the dumping site and the coast, visible in satellite altimetry and sea surface temperature data. Using Lagrangian simulations, we confirm that near-surface currents could have brought part of the pollution to the coast, and fueled the bloom. This scenario explains also the anomalous later finding of ammonium near Chiloe. Finally we discuss the mismanagement of risk throughout the events. | Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 3150587

Pangasius production in Vietnam is widely known as a success story in aquaculture, the fastest growing global food system because of its tremendous expansion by volume, value and the number of international markets to which Pangasius has been exported in recent years. While certification schemes are becoming significant features of international fish trade and marketing, an increasing number of Pangasius producers have followed at least one of the certification schemes recognised by international markets to incorporate environmental and social sustainability practices in aquaculture, typically the Pangasius Aquaculture Dialogue (PAD) scheme certified by the Aquaculture Stewardship Council (ASC). An assessment of the environmental benefit of applying certification schemes on Pangasius production, however, is still needed. This article compared the environmental impact of ASC-certified versus non-ASC certified intensive Pangasius aquaculture, using a statistically supported Life Cycle Assessment (LCA). We focused on both resource-related (water, land and total resources) and emissions-related (global warming, acidification, freshwater and marine eutrophication) categories.

International audience | <div><p>Aquaculture is crucial in meeting global seafood demand; however, intensification often leads to bacterial diseases that threaten productivity. Dicentrarchus labrax, a key species in European aquaculture, is highly vulnerable to vibriosis, primarily caused by Vibrio harveyi. This study investigates genetic profiles associated with vibriosis by analyzing V. harveyi strains from a seabass farm during 2022 vibriosis outbreaks. Sampling from biofilm and water environments yielded 946 bacterial isolates, of which 56 were identified as V. harveyi using MALDI-TOF MS. ERIC-PCR genotyping revealed four distinct profiles. Despite observing variability in the presence of the 80 tested virulence genes, the overall genetic variation among these profiles was not pronounced. Notably, no single genotypic profile was linked to vibriosis. These findings suggest that the presence of virulence genes alone may not predict disease outbreaks, thus highlighting the need for future research on environmental and transcriptional factors to improve disease control in aquaculture systems.</p></div>

This study focused on the impacts of aged aquaculture microplastics (MPs) on oysters (Crassostrea gigas). Adult oysters were exposed for two months to a cocktail of MPs representative of the contamination of the Pertuis Charentais area (Bay of Biscay, France) and issuing from oyster framing material. The MPs mixture included 28% of polyethylene, 40% of polypropylene and 32% of PVC (polyvinyl chloride). During the exposure, tissues were sampled for various analyzes (MP quantification, toxicity biomarkers). Although no effect on the growth of adult oysters was noted, the mortality rate of bivalves exposed to MPs (0.1 and 10 mg. L⁻¹ MP) increased significantly (respectively 13.3 and 23.3% of mortalities cumulative). On the one hand, the responses of biomarkers revealed impacts on oxidative stress, lipid peroxidation and environmental stress. At 56 days of exposure, significant increases were noted for Glutathione S-Transferase (GST, 10 mg. L⁻¹ MP), Malondialdehyde (MDA, 10 mg. L⁻¹ MP) and Laccase (LAC, 0.1 and 10 mg. L⁻¹ MP). No variations were observed for Superoxyde Dismutase (SOD). Besides, ingestion of MPs in oyster tissues and the presence in biodeposits was highlighted. In addition, in vitro fertilisations were performed to characterize MPs effects on the offspring. Swimming behavior, development and growth of D-larvae were analysed at 24-, 48- and 72-h after fertilisation. D-larvae, from exposed parents, demonstrated reduced locomotor activity. Developmental abnormalities and arrest as well as growth retardation were also noted. This study highlighted direct and intergenerational effects of MPs from aged plastic materials on Pacific oysters.

Metal-free single heteroatom (N, O, and B)-doped coconut-shell biochar (denoted as N-CSBC, O-CSBC, and B-CSBC, respectively) were fabricated in a one-step pyrolysis process to promote peroxymonosulfate (PMS) activation for the elimination of sulfathiazole (STZ) from aquaculture water. B-CSBC exhibited remarkably high catalytic activity with 92% of STZ degradation in 30 min attributed to the presence of meso-/micro-pores and B-containing functional groups (including B–N, B–C, and B₂O₃ species). Radical quenching tests revealed SO₄•⁻, HO•, and ¹O₂ being the major electron acceptors contributing to STZ removal by PMS over B-CSBC catalyst. The B-CSBC catalyst has demonstrated high sustainability in multiple consecutive treatment cycles. High salinity and the presence of inorganic ions such as chloride, enhanced the performance of the sulfate radical-carbon-driven advanced oxidation processes (SR–CAOPs) as pretreatment strategy that significantly facilitated the removal of STZ from aquaculture water. Furthermore, a potential sulfonamide-degrading microorganism, Cylindrospermum_stagnale, belonging to the phylum Cyanobacteria, was the dominant functional bacteria according to the results of high-throughput 16S rRNA gene sequencing conducted after the B-CSBC/PMS treatment. This study provides new insights into the SR–CAOP combined with bioprocesses for removing STZ from aqueous environments.

Rising of temperature in conjunction with acidification due to the anthropogenic climates has tremendously affected all aquatic life. Small changes in the surrounding environment could lead to physiological constraint in the individual. Therefore, this study was designed to investigate the effects of warm water temperature (32 °C) and low pH (pH 6) on physiological responses and growth of hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂) juveniles for 25 days. Growth performance was significantly affected under warm water temperature and low-pH conditions. Surprisingly, the positive effect on growth was observed under the interactive effects of warm water and low pH exposure. Hybrid grouper exposed to the interactive stressor of warm temperature and low pH exhibited higher living cost, where HSI content was greatly depleted to about 2.3-folds than in normal circumstances. Overall, challenge to warm temperature and low pH induced protein mobilization as an energy source followed by glycogen and lipid to support basal metabolic needs.

Hydrogen peroxide (H₂O₂), as a common disinfectant, has been extensively used in aquaculture. The toxicity of high ambient H₂O₂ for gills and liver of fish has received attention from many researchers. However, whether H₂O₂ exposure induced brain injury and neurotoxicity has not been reported in fish. Therefore, this study aimed to explore the potential mechanism of H₂O₂ toxicity in brain of common carp via transcriptome analysis and biochemical parameter detection. The fish were exposed to 0 (control) and 1 mM of H₂O₂ for 1 h per day lasting 14 days. The results showed that H₂O₂ exposure caused oxidative damage in brain evidenced by decreased glutathione (GSH), total antioxidant capacity (T-AOC) and nicotinamide adenine dinucleotide (NAD⁺) levels, and increased formation of malondialdehyde (MDA) and 8-hydroxy-2′-deoxyguanosine (8-OHdG). Meanwhile, H₂O₂ exposure reduced 5-hydroxytryptamine (5-HT) level, and down-regulated tryptophan hydroxylase 1 (tph1a), tph2, 5-hydroxytryptamine receptor 1A-beta (htr1ab) and htr2b expression in brain. Transcriptome analysis showed that H₂O₂ exposure up-regulated 604 genes and down-regulated 1209 genes in brain. Go enrichment displayed that the differently expressed genes (DEGs) were enriched mainly in cellular process, single-organism process, metabolic process, and biological regulation in the biological process category. Further, KEGG enrichment indicated that H₂O₂ exposure led to dysregulation of neurotransmitter signals including depression of glutamatergic synapse, GABAergic synapse and endocannabinoid signaling. Also, we found the alteration of three key pathways including calcium, cAMP and HIF-1 in brain after H₂O₂ exposure. In conclusion, our data indicated that H₂O₂ exposure induced oxidative damage and neurotoxicity, possibly related to dysregulation of neurotransmitters and calcium, cAMP and HIF-1 signaling pathways, which may adversely affect learning, memory and social responses of common carp. This study provided novel insight into biological effects and underlying mechanism of H₂O₂ toxicity in aquatic animal, and contributed to proper application of H₂O₂ in aquaculture.

Plastic debris provides a stable substrate and novel ecological niche for microorganisms in the aquatic environment, which was referred to as “Plastisphere”. Little is known about distribution patterns and responses of ecological function and structure of microbial communities in the plastisphere along rivers which usually have antibiotics pollution gradient. In this study, the differences in the community structure between the plastisphere and the planktonic bacteria, and their spatial variation of the community structure and function along a river with increased antibiotics pollution gradient was investigated at the watershed scale. The diversity of bacteria colonized on most plastic debris was higher than in surrounding water. Plastic debris could accumulate a higher abundance of some potential pathogens than surrounding water even at high antibiotics concentrations. The source tracking results showed that downstream plastisphere inherited much higher proportions of bacterial taxa from upstream than planktonic bacteria. About 92.3–99.7% of bacteria communities in downstream water were not from upstream but from the input of downstream human activities. On the contrary, high proportions of bacterial taxa in downstream plastisphere were closely connected to upstream. The plastisphere possesses higher ecological functional diversity than the planktonic bacteria. Seventy nine functional groups across plastisphere were predicted using functional annotation of prokaryotic taxa and only 65 functional groups were found in the planktonic bacteria. Plastisphere also acts as hotspot for biogeochemical cycling of nutrients such as N and S. Intensive human activities of urban and downstream agriculture and aquaculture had great effects on microbial community structure and functional groups of the Urumqi River. Pastisphere communities are much more resistant to human disturbance than planktonic bacteria. Compared to surrounding water, plastisphere increased inheritance from upstream microbial structure and function and also increased survival and propagation of pathogens in the downstream water with high concentrations of antibiotics.

The strict environmental management has been implemented in Taihu Basin to reduce the surface water contamination; however, the effectiveness of the management actions has not been comprehensively evaluated. In the present study, 364 samples were collected during four campaigns over a span of one year from surface water, municipal wastewater treatment plants (MWWTPs), industrial wastewater treatment plants (IWWTPs), industrial enterprises, and aquaculture in a typical region in the Upper Taihu Basin. Overall concentration, temporal variation and spatial distribution of 16 PAHs in surface water and various pollution sources were evaluated and the potential pollution sources were identified. Results showed that concentrations of individual PAHs in the surface water ranged from less than the limit of quantification (LOQ) to 949 ng L⁻¹, indicating a reduction of PAH contamination level after the implementation of environmental management actions. Influent of MWWTPs and wastewater from industrial enterprises exhibited relatively high ∑PAHs concentrations (mean: 880 ng L⁻¹ and 642 ng L⁻¹, respectively); these samples also exhibited a similar seasonal variation as well as composition of PAH congeners to those found in surface water, and therefore were designated as the main emission sources of PAHs in the studied region. Additional source apportionment using principal component analysis was also conducted to verify the proposed sources and diagnose other pollution sources. The findings provided a thorough understanding of PAH pollution, especially its major emission sources, in a typical region with pollution-intensive industries after the implementation of strict environmental management.

Trichlorfon is an organic phosphorus pesticide used to control different parasitic infections in aquaculture. The repeated, excessive use of trichlorfon can result in environmental pollution, thus affecting human health. This study aimed to determine the effects of different concentrations of trichlorfon (0, 0.1, 0.5 and 1.0 mg/L) on the intestinal barrier, oxidative stress, inflammatory response and intestinal microbiome of common carp. Trichlorfon exposure significantly reduced the height of intestinal villus and decreased the expression levels of tight junction genes, such as claudin-2, occludin and ZO-1, in common carp. Moreover, the activities of antioxidant enzymes, such as CAT, SOD and GSH-Px, exhibited a decreasing trend with increasing trichlorfon concentrations, while the contents of MDA and ROS elevated in the intestinal tissues of common carp. The mRNA and protein levels of pro-inflammatory cytokines TNF-α and IL-1β were significantly upregulated by trichlorfon exposure. The level of anti-inflammatory cytokine TGF-β was remarkably higher in 1.0 mg/L trichlorfon treatment group compared to control group. In addition, the results demonstrated that trichlorfon exposure could affect the microbiota community composition and decreased the community diversity in the gut of common carp. Notably, the proportions of some probiotic bacteria, namely, Lactobacillus, Bifidobacterium and Akkermansia, were observed to be reduced after trichlorfon exposure. In summary, the findings of this study indicate that exposure to different concentrations of trichlorfon can damage intestinal barrier, induce intestinal oxidative damage, trigger inflammatory reaction and alter gut microbiota structure in common carp.