Decoding the spread of non-indigenous fishes in the Mediterranean Sea.

The ocean is dynamically changing due to the influence of climate processes and human activities. The construction of the Suez Canal in the late nineteenth century opened the Pandora's box by facilitating the dispersal of Red Sea species in the Mediterranean Sea. In this study, we developed an open-source spatio-temporal numerical analysis framework to decodify the complex spread of Mediterranean non-indigenous fish species (NIS) that entered through the Suez Canal. We utilized 772 historical detection records of 130 NIS to disentangle their dynamic spread through space and time. The results indicated that species follow a north-westward trajectory with an average expansion time step of 2.5 years. Additionally, we estimated the overall time for a NIS to reach the Central Mediterranean Sea from the Suez Canal at approximately 22 years. Based on the analysis, more than half of the introduced fishes have been established in less than 10 years. Finally, we proceeded in the cross-validation of our results using actual spread patterns of invasive fishes of the Mediterranean Sea, resulting up to 90% of temporal and spatial agreement. The methodology and the findings presented herein may contribute to management initiatives in highly invaded regions around the globe.

Assessment of Human Health Impacts from Invasive Pufferfish (Attacks, Poisonings and Fatalities) across the Eastern Mediterranean.

The silver-cheeked toadfish Lagocephalus sceleratus (Gmelin 1789), and to a lesser degree the orange spotted toadfish Torquigener hypselogeneion (Bleeker, 1852), pose threats to human health from physical attacks and poisonings in the Eastern Mediterranean Sea. This study reviewed human health-related impacts resulting from these pufferfish, compiling and assessing records from online sources, the peer-reviewed literature, medical records, personal interviews, and observations across the Eastern Mediterranean in the years 2004 to 2023. A total of 198 events impacting human health were documented: 28 records of physical attacks, at least 144 non-lethal poisoning episodes, and 27 human fatalities resulting from consumption. The majority of the reported incidences occurred in Syria, Türkiye, and Lebanon. Most physical attacks occurred in summer, while most poisoning events occurred during winter. The number of recorded incidents greatly increased after 2019, especially with regard to poisonings, yet whether this is related to greater media attention, or to increased fish abundance is unclear. This is the first comprehensive study to collate findings on attacks, poisonings and fatalities caused by these pufferfish in the Mediterranean Sea, and may help in improving national health policies. We urge the continuation of national campaigns to caution residents and tourists of these species' high toxicities and potential aggressiveness.

Can Biological Traits Serve as Predictors for Fishes' Introductions, Establishment, and Interactions? The Mediterranean Sea as a Case Study.

The Mediterranean Sea (MED) is prone to species' introductions, induced by human activities and/or climate change. Recent studies focus on the biological traits that result in such introductions, yet on a single-area-type approach. Here, we used, analyzed, and compared biological traits derived from FishBase for MED, non-indigenous (NIS) and neonative (NEO) in the Mediterranean, and adjacent Atlantic (ATL) and Red Sea (RS) species. A quantitative trait-based analysis was performed using random forest to determine the importance of traits in the successful establishment in the Mediterranean. MED fishes were mainly demersal, slow growing and small-medium sized, preferring intermediate temperatures. Conversely, ATL were mainly deep-dwelling species, preferring low temperatures. RS and NIS were predominantly reef-associated, thermophilus, and stenothermic. NEO species were stenothermic with preference to intermediate-high temperatures. Omnivores with preference to animals was the most common trophic group among regions. MED species exhibited higher phylogenetic uniqueness (PD50) compared to RS and NIS, indicating that they have long ancestral branches and few descendants. Preferred temperature, habitat type preference and maximum reported length (Lmax) and infinite length (Linf) were the most important predictors in the establishment process. Overall, the results presented here could serve as a baseline for future research, especially by using more refined and/or additional biological trail estimates.

Molecular interactions of polyvinyl chloride microplastics and beta-blockers (Diltiazem and Bisoprolol) and their effects on marine meiofauna: Combined in vivo and modeling study.

The ecotoxicological effects of beta-blockers (i.e. Diltiazem and Bisoprolol) and their interactions with the microplastic polyvinyl chloride on marine meiofauna were tested in laboratory microcosms. An experimental factorial design was applied, using meiobenthic fauna collected from the Old Harbor of Bizerte (NE Tunisia), but with a main focus on the nematode communities. The meiobenthic invertebrates were exposed to two concentrations of Diltiazem and Bisoprolol, of 1.8 µg.L-1 and 1.8 mg.L-1, respectively, and one concentration of polyvinyl chloride (i.e. 20 mg.kg-1), separately and mixed. The overall meiofauna abundance was significantly reduced in all treatments, mainly that of polychaetes and amphipods. Moreover, the juveniles-gravid female ratios of the nematode communities were the lowest in the 1.8 µg.L-1 Bisoprolol treatment and for the 1.8 mg.L-1 mixture of Diltiazem and microplastics, suggesting that different dosages influence the maturity status of the examined species. The demographic results were also supported by in silico approach. The simulation of molecular interactions revealed acceptable binding affinities (up to -8.1 kcal/mol) and interactions with key residues in the germ line development protein 3 and sex-determining protein from Coenorhabditis elegans. Overall, the experimental outcome strongly indicates synergistic interactions among the beta-blockers Diltiazem and Bisoprolol and the microplastic polyvinyl chloride on marine nematode communities.

The response of meiobenthinc sediment-dwelling nematodes to pyrene: Results from open microcosms, toxicokinetics and in silico molecular interactions.

An experiment conducted with 'open microcosm' made by connected sedimentary compartments with different qualities was for 30 days to evaluate the migratory behaviour of nematodes as induced by exposure to pyrene. The nematofauna was collected along with sediment from a reference site in Bizerte lagoon. Following one week acclimatization period, the populated sediments were topped with azoic sediments, with a pyrene concentration of 150 µg kg-1. The concentration of pyrene from sediments was measured on a weekly basis. A stable status of nematode assemblages was reached between the upper and lower compartments in each microcosm, whatever the treatment type. An upward exploratory phase was observed during the first two weeks within the assemblages, possibly induced by the repellent chemodetection of pyrene. This observation was confirmed by the toxicokinetic properties and molecular interactions of pyrene with the germ-line development Protein 3 and sex-determining protein of Caenorhabditis elegans as nematode model.

Toxicity of hydroxychloroquine, a potential treatment for COVID-19, on free-living marine nematodes.

On March 2020, hydroxychloroquine (HCQ) was recommended as a treatment for COVID-19 high risk patients. Following the massive and widespread use of HCQ worldwide, a discernible high quantity is anticipated to end-up through the sewage systems in marine coastal areas. A closed microcosm study was undertaken herein for 30 days where meiobenthic nematodes were exposed to a range of HCQ concentrations (3.162, 31.62 and 63.24 µg.ml-1). After one month of exposure in HCQ, the total abundances and Shannon-Wiener index of the assemblages decreased, whereas the individual mass and the Trophic Diversity Index increased at the highest concentrations. Overall, a numerical negative impact was observed for the epistrate feeders and non-selective deposit feeders, however, this benefited to the omnivores-carnivores, and particularly to the Oncholaimids. Such responses of the nematodes 2B and the corresponding taxa are bioindicative of current- or post-COVID-19 crisis risks in relation with the bioaccumulation of HCQ in seafood.

Multi-biomarker approach in Mytilus galloprovincialis and Ruditapes decussatus as a predictor of pelago-benthic responses after exposure to Benzo[a]Pyrene.

This study evaluated the biomarker responses indicative of exposure to Benzo[a] Pyrene (B[a]P) in Mytilus galloprovincialis and Ruditapes decussatus. A significant increase of the total oxyradical scavenging capacity (TOSC) was observed after seven days of exposure to two concentrations of B[a]P (100 and 300 µg.L-1), in the digestive gland with the lowest concentration tested. The TOSC in the gills increased notably only after the exposure to 300 µg.L-1 of B[a]P. Interestingly, the superoxide dismutase (SOD) and catalase (CAT) activities in gills and digestive gland on one hand and glutathione S-transferase (GST) in gills in the other, were positively correlated with the concentration of B[a]P with a significant induction noticed at the highest concentration. In contrast, a significant increase of the GST activity was observed in the digestive gland following the exposure of bivalves to 100 µg.L-1. In pelagic (M. galloprovincialis) or benthic (R. decussatus) bivalves, the AChE activity decreased discernibly in digestive glands and gills with the increase of B[a]P concentrations as evidence of neurotoxic effects. In clams, the exposure to B[a]P was followed by a significant increase of Malondialdehyde level (MDA) in gills and digestive gland, this does not occur in gills of Mytilus galloprovincialis at the concentration of 100 µg.L-1. Overall, the results found seems to indicate that the mussel was more suitable as a predictor tool of toxicity of B[a]P.

Nematode traits after separate and simultaneous exposure to Polycyclic Aromatic Hydrocarbons (anthracene, pyrene and benzo[a]pyrene) in closed and open microcosms.

The majority of experimental studies carried out to date, regarding the effects of pollutants on meiofauna have been conducted by means of closed systems, and rarely using open ones. The current work explored the impact of three Polycyclic Aromatic Hydrocarbons (PAHs), anthracene, pyrene and benzo[a]pyrene, applied alone or combined, on meiobenthic nematodes using both systems. The results revealed that single PAHs impacted the nematofauna similarly in closed or open systems with a higher toxicity observed for benzo[a]pyrene. However, the closed microcosms contaminated with PAHs became organically enriched, resulting in more non-selective deposit feeders and omnivores-carnivores. Taxonomic and functional effects related to combinations of PAHs were close to those of individual treatments in closed systems, however, for open ones, the outcomes were different. The caudal morphology influenced the response of taxa during their avoidance/endurance of hydrocarbons in open systems where the effects of PAHs mixtures appeared not only additive but also synergetic. Based on the results of the study, the use of open systems is preferred to closed ones as the research outcomes were more accurate and representing better conditions prevailing in nature.

Spatial fishing restrictions benefit demersal stocks in the northeastern Mediterranean Sea.

The multi-level benefits that marine organisms gain when protected from fishing are well acknowledged. Here, we investigated the effects of a 40-year trawling ban on the status of targeted and non-targeted marine species within a major fishing ground in the northeastern Mediterranean Sea (Thermaikos Gulf, Aegean Sea). Biomass and somatic length of fish and invertebrates (six commercial and three non-commercial demersal species) were measured in three areas of varying fishing pressure, depending on the temporal and spatial operational regimes of fishing vessels. The positive effects of fishing restrictions on the studied demersal stocks were clearly revealed, as the commercial fish species exhibited higher biomass in the intermediate and low pressure areas, as well as increasing maximum and mean total length (and other length indicators) with decreasing fishing effort. The mean total length of non-commercial species generally did not differ among areas, except for species caught and discarded at high rates. The present study shows that fishing does alter the population structure and biomass of commercial demersal species, and that fishing restrictions greatly contribute to improving the status of demersal populations within the restricted areas by providing a refuge for large individuals and their important contribution to the gene pool.