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Establishing microbiome signatures is now recognized as a critical step toward identifying genetic and environmental factors shaping animal-associated microbiomes and informing the health status of a given host. In the present work, we prospectively collected 63 blood samples of the Atlantic cod population of the Southern Gulf of Saint Lawrence (GSL) and characterized their 16S rRNA circulating microbiome signature. Our results revealed that the blood microbiome signature was dominated at the phylum level by Proteobacteria , Bacteroidetes , Acidobacteria and Actinobacteria , a typical signature for fish populations inhabiting the GSL and other marine ecosystems. At the genus level, however, we identified two distinct cod groups. While the microbiome signature of the first group was dominated by Pseudoalteromonas , a genus we previously found in the microbiome signature of Greenland and Atlantic halibut populations of the GSL, the second group had a microbiome signature dominated by Nitrobacter and Sediminibacterium (approximately 75% of the circulating microbiome). Cods harboring a Nitrobacter/Sediminibacterium -rich microbiome signature were localized in the most southern part of the GSL, just along the northern coast of Cape Breton Island. Atlantic cod microbiome signatures did not correlate with the weight, length, relative condition, depth, temperature, sex, and salinity, as previously observed in the halibut populations. Our study provides, for the first time, a unique snapshot of the circulating microbiome signature of Atlantic cod populations and the potential existence of dysbiotic signatures associated with the geographical distribution of the population, probably linked with the presence of nitrite in the environment.

Climate change affects marine ecosystems by promoting pathogens that threaten key fish populations. To protect these, monitoring programs must adapt to manage threats and sustain fisheries. Here, we combined traditional PCR methods and transcriptomic analysis from a single drop of blood stored on FTA cards to determine the prevalence of erythrocytic necrosis virus (ENV) and the Ichthyophonus parasite in the Atlantic herring population. Across 2023–2024, 33% of individual blood samples tested positive for ENV and 10% for Ichthyophonus by PCR, with ENV-positive fish more frequently found in estuarine and coastal areas. Spatial analyses revealed a clustered distribution for ENV and a more sporadic occurrence of Ichthyophonus . RNA-Seq detected viral RNA fragments in ENV PCR-positive fish, revealing high levels of viral transcripts consistent with active viral replication. However, no significant changes were observed in the host blood transcriptome between infected and uninfected individuals, suggesting that ENV replication may proceed with limited systemic host transcriptional response under subclinical conditions. Overall, our study provides the first comprehensive baseline on the prevalence and molecular activity of ENV and Ichthyophonus in Atlantic herring, demonstrating the power of FTA-based RNA-Seq diagnostics to uncover hidden infections and informing future surveillance and management of wild fish populations.

Establishing long-term microbiome-based monitoring programs is critical for managing and conserving wild fish populations in response to climate change. In most cases, these studies have been conducted on gut and, to a lesser extent, skin (mucus) microbiomes. Here, we exploited the concept of liquid biopsy to study the circulating bacterial microbiome of two Northern halibut species of economic and ecological importance. Amplification and sequencing of the 16S rRNA gene were achieved using a single drop of blood fixed on FTA cards to identify the core blood microbiome of Atlantic and Greenland halibut populations inhabiting the Gulf of St. Lawrence, Canada. We provide evidence that the circulating microbiome DNA (cmDNA) is driven by genetic and environmental factors. More specifically, we found that the circulating microbiome signatures are species-specific and vary according to sex, size, temperature, condition factor, and geographical localization. Overall, our study provides a novel approach for detecting dysbiosis signatures and the risk of disease in wild fish populations for fisheries management, most notably in the context of climate change.

Carbon dioxide rebreathing (CO 2 rebreathing) significantly influences respiratory drive and the work of breathing during BiPAP ventilation. We analyzed CO 2 movement during BiPAP ventilation to find a method of real time detection of CO 2 rebreathing without the need of CO 2 concentration measurement sampled from the circuit (method expensive and not routinely used). Observational study during routine care in 15 bed university hospital ICU. At 18 patients who required BiPAP ventilation, intubated or during noninvasive ventilation, during weaning period airflow, pressure and CO 2 concentration signals were registered on both sides of venting port and 17 respiratory parameters were measured or calculated for each of 4747 respiratory cycles analyzed. Based on CO 2 movement (expiration–inspiration sequences) 3 types of cycle were identified, type I and II do not induce rebreathing but type III does. To test differences between the 3 types ANOVA, t-tests, and canonical discriminant analysis (CDA) were used. Then a multilayer perceptron (MLP) network, a type of artificial neural network, using the above parameters (excluding CO 2 concentration) was applied to automatically identify the three types of respiratory cycles. Of the 4747 respiratory cycles, 1849 were type I, 1545 type II, and 1353 type III. ANOVA and t-tests showed significant differences between the types of respiratory cycles. CDA confirmed a correct apportionment of 93.9% of the cycles; notably, of 97.9% of type III. MLP automatically classified the respiratory cycles into the three types with 98.8% accuracy. Three types of respiratory cycles could be distinguished based on CO 2 movement during BiPAP ventilation. Artificial neural networks can be used to automatically detect respiratory cycle type III, the only inducing CO 2 rebreathing.

Arctic cod (Boreogadus saida) is the most abundant forage fish in the Arctic Ocean. Here we review Arctic cod habitats, distribution, ecology, and physiology to assess how climate change and other anthropogenic stressors are affecting this key species. This review identifies vulnerabilities for different life stages across the entire distribution range of Arctic cod. We explore the impact of environmental (abiotic and biotic) and anthropogenic stressors on Arctic cod with a regional perspective in a scenario up to the year 2050 and identify knowledge gaps constraining predictions. Epipelagic eggs and larvae are more vulnerable to climate change and stressors than adults. Increased water temperatures, sea-ice decline, altered freshwater input, acidification, changing prey field, increased interspecific competition, new predators, and pollution are the principal stressors that will affect Arctic cod populations. Detrimental effects are likely to be greater in regions characterized by the advection of warmer Atlantic and Pacific waters. In contrast, Arctic cod may benefit from ocean warming in colder areas of the High Arctic. The risk from fisheries is moderate and primarily limited to bycatch. Overall, a decrease in suitable habitat and an associated decline in total Arctic cod biomass are predicted. In most Arctic seas, the relative abundance of Arctic cod within the fish community will likely fluctuate in accordance with cold and warm periods. A reduced abundance of Arctic cod will negatively affect the abundance, distribution, and physiological condition of certain predators, whereas some predators will successfully adapt to a more boreal diet. Regional management measures that recognize the critical role of Arctic cod are required to ensure that increased anthropogenic activities do not exacerbate the impacts of climate change on Arctic marine ecosystems. Ultimately, the mitigation of habitat loss for Arctic cod will only be achieved through a global reduction in carbon emissions.

An increasing number of boreal marine species are expected to invade the warming Arctic Ocean with the potential to displace endemic species. We provide first evidence that Pacific sand lance ( Ammodytes hexapterus ) is expanding its range in the Canadian Arctic Archipelago, a region far outside the species temperate-boreal traditional range south of the Bering Strait. To the best of our knowledge, supported by local Inuit knowledge, the species was not present in the area until the present decade. We observed an increasing density of larval Pacific sand lance with time over the 2011–2016 period, suggesting that environmental conditions are becoming increasingly favorable for the species to reproduce in the Central Canadian Arctic. The northward distribution change of Pacific sand lance is occurring earlier than predicted by current models and could trigger abrupt shifts in Arctic marine food webs if the boreal invader displaces polar cod, a key prey species for top predators in Arctic marine ecosystems.

The study of microbiomes in fish populations offers vital insights for ecological and fisheries management, particularly in responses to environmental changes. Although traditional studies have concentrated on the gut microbiome, the emerging concept of a circulating blood microbiome suggests it may act as an early indicator of dysbiosis and various health conditions by reflecting transient bacterial DNA presence. In this study, we examined the gut and blood microbiomes of Sebastes fasciatus (Storer, 1854), a species of redfish of significant economic and ecological importance in the Gulf of St. Lawrence, to obtain critical information for health monitoring, pathogen detection, and ecological management in fisheries. Our results revealed that the gut and blood microbiomes of S. fasciatus have distinct bacterial DNA signatures, with significant differences in microbial diversity. Notably, although both microbiomes exhibited similar dominant genera, specific amplicon sequence variants varied significantly. Through a controlled experimental design, we found that the dietary impacts on microbiome composition were statistically significant yet minimal, suggesting that environmental factors play a more substantial role in shaping microbial communities. Finally, we report the presence of potential pathogens and opportunistic bacteria found exclusively in the blood microbiome. Our results highlight the blood microbiome's value as a sensitive health and environmental stress indicator, essential for sustainable fish population management. Integrating microbiome indicators can improve fisheries management and ecosystem sustainability, offering a model applicable to various marine species and environments.

Metformin-associated lactic acidosis (MALA) is a severe metabolic failure with high related mortality. Although its use is controversial, intermittent hemodialysis is reported to be the most frequently used treatment in conjunction with nonspecific supportive measures. Our aim was to report the evolution and outcome of cases managed by continuous renal replacement therapy (CRRT). Over a 3-year period, we retrospectively identified patients admitted to the intensive care unit for severe lactic acidosis caused by metformin. We included patients in our study who were treated with CRRT because of shock. We describe their clinical and biological features at admission and during renal support, as well as their evolution. We enrolled six patients with severe lactic acidosis; the mean pH and mean lactate was 6.92±0.20 and 14.4±5.1 mmol/l, respectively. Patients had high illness severity scores, including the Simplified Acute Physiology Score II (SAPS II) (average score 63±12 points). Early CRRT comprised either venovenous hemofiltration (n = 3) or hemodiafiltration (n = 3) with a mean effluent flow rate of 34±6 ml/kg/h. Metabolic acidosis control and metformin elimination was rapid and there was no rebound. Outcome was favorable in all cases. Standard use of CRRT efficiently treated MALA in association with symptomatic organ supportive therapies.

The polar cod, Boreogadus saida, is an abundant and ubiquitous forage fish and a crucial link in Arctic marine trophic dynamics. Our objective was to unravel layers of genomic structure in B. saida from Canadian waters, specifically screening for potential hybridization with the Arctic cod, Arctogadus glacialis, large chromosomal inversions, and sex-linked regions, prior to interpreting population structure. Our analysis of 53,384 SNPs in 522 individuals revealed hybridization and introgression between A. glacialis and B. saida. Subsequent population level analyses of B. saida using 12,305 SNPs in 511 individuals revealed three large (ca. 7.4–16.1 Mbp) chromosomal inversions, and a 2 Mbp region featuring sex-linked loci. We showcase population structuring across the Western and Eastern North American Arctic, and subarctic regions ranging from the Hudson Bay to the Canadian Atlantic maritime provinces. Genomic signal for the inferred population structure was highly aggregated into a handful of SNPs (13.8%), pointing to potentially important adaptive evolution across the Canadian range. Our study provides a high-resolution perspective on the genomic structure of B. saida, providing a foundation for work that could be expanded to the entire circumpolar range for the species.