Extending international toxicity testing guidance to middle eastern test species

A broad-taxa approach as an important concept in ecotoxicological studies and pollution monitoring

Aquatic invertebrates play a pivotal role in (eco)toxicological assessments because they offer ethical, cost-effective and repeatable testing options. Additionally, their significance in the food chain and their ability to represent diverse aquatic ecosystems make them valuable subjects for (eco)toxicological studies. To ensure consistency and comparability across studies, international (eco)toxicology guidelines have been used to establish standardised methods and protocols for data collection, analysis and interpretation. However, the current standardised protocols primarily focus on a limited number of aquatic invertebrate species, mainly from Arthropoda, Mollusca and Annelida. These protocols are suitable for basic toxicity screening, effectively assessing the immediate and severe effects of toxic substances on organisms. For more comprehensive and ecologically relevant assessments, particularly those addressing long-term effects and ecosystem-wide impacts, we recommended the use of a broader diversity of species, since the present choice of taxa exacerbates the limited scope of basic ecotoxicological studies. This review provides a comprehensive overview of (eco)toxicological studies, focusing on major aquatic invertebrate taxa and how they are used to assess the impact of chemicals in diverse aquatic environments. The present work supports the use of a broad-taxa approach in basic environmental assessments, as it better represents the natural populations inhabiting various ecosystems. Advances in omics and other biochemical and computational techniques make the broad-taxa approach more feasible, enabling mechanistic studies on non-model organisms. By combining these approaches with in vitro techniques together with the broad-taxa approach, researchers can gain insights into less-explored impacts of pollution, such as changes in population diversity, the development of tolerance and transgenerational inheritance of pollution responses, the impact on organism phenotypic plasticity, biological invasion outcomes, social behaviour changes, metabolome changes, regeneration phenomena, disease susceptibility and tissue pathologies. This review also emphasises the need for harmonised data-reporting standards and minimum annotation checklists to ensure that research results are findable, accessible, interoperable and reusable (FAIR), maximising the use and reusability of data. The ultimate goal is to encourage integrated and holistic problem-focused collaboration between diverse scientific disciplines, international standardisation organisations and decision-making bodies, with a focus on transdisciplinary knowledge co-production for the One-Health approach.

Inhibition of algal blooms by residual antibiotics in aquatic environments: Design, screening, and validation of antibiotic alternatives

Water blooms frequently appear in the aquatic environment with global warming. However, traditional methods for treating water bloom usually require the addition of algaecides, which may lead to secondary environmental pollution problems in the water environment. To solve this problem, researchers have initiated efforts to harness pre-existing chemical substances within aquatic environments to regulate algal blooms, thereby pioneering novel avenues for water body management. Therefore, an integrated approach involving molecular docking, molecular dynamics simulations, three-dimensional quantitative structure-activity relationship (3D-QSAR), and toxicokinetics methods were utilized for the molecular modification of fluoroquinolone antibiotics, to design and screen fluoroquinolone substitutes with improved toxicity of cyanobacteria and green algae, functionality, and environmental friendliness. A total of 143 fluoroquinolone alternatives were designed in this study, and lomefloxacin-6 (LOM6) was found as the optimum alternative to lomefloxacin (LOM), with increased toxicity to cyanobacteria and green algae by 31 % and 72 %. Molecular docking of LOM before and after modification with seven other cyanobacterial and green algal photosynthetic proteins revealed that LOM6 exhibited varying degrees of increased toxicity towards 6 of these photosynthetic proteins, of which 2J96 protein increased the most (136.25 %). It shows that the residual LOM6 in the water environment has a certain inhibitory effect on the algae bloom. In addition, results showed that LOM6 had synergistic toxic effects on cyanobacteria and green algae with other pollutants residual in the aqueous environment, such as trichloroethyl phosphate, triethyl phosphate, perfluorononanoic acid, perfluorooctanoic acid. This indicates that LOM6 has better algal removal effectiveness in aqueous environments where organophosphate flame retardants and perfluorinated compounds exist together. In this paper, a novel method was developed to remove cyanobacteria and green algae in water environment and reduce the secondary pollution through theoretical simulation, which provides theoretical support for the control of water blooms.

Biphasic effects of typical chlorinated organophosphorus flame retardants on Microcystis aeruginosa

The potential accumulation of chlorinated organophosphorus flame retardants (Cl-OPFRs) in aquatic environments sparked interest in studying the effects of Cl-OPFRs on cyanobacterial blooms. In this work, two common Cl-OPFRs, tris(1,3-dichloro-2-propyl) phosphate (TDCPP) and tris(2-chloroethyl) phosphate (TCEP), induced dose-dependent biphasic effect on bloom-forming M. aeruginosa. The hormetic response to low-dose Cl-OPFRs was associated with the upregulation of the type I NADH dehydrogenase (NDH-1) complex and its mediated cyclic electron transfer (CET) pathway, as reflected by a transient post-illumination increase in chlorophyll fluorescence, the dark reduction of P700⁺ and the change of NDH-1-related gene expression. The increased CET activity and carotenoid content jointly reduced the intracellular ROS production, facilitating cyanobacterial growth. Conversely, a higher concentration of both Cl-OPFRs induced severe inhibition of growth and photosynthetic oxygen-evolving activity through an imbalance between PSII and PSI. Toxic-dose Cl-OPFRs inhibited state transition and fixed cells into the State I with a higher PSII/PSI ratio, as indicated by chlorophyll fluorescence induction, 77 K fluorescence emission spectra and photosystem stoichiometry. The elevated PSII/PSI ratio created an imbalance between the two photosystems and eventually lead to ROS overproduction, which generate adverse effects on cell growth. This work provides important insights into the hormetic mechanism of Cl-OPFRs on Microcystis aeruginosa and their potential roles in harmful cyanobacteria blooms.

Spatial and temporal analysis of the risks posed by metal contamination in coastal and marine sediments of Bahrain

Nine metals including Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn were analysed from sediment samples collected from 29 stations since 2007 from Bahraini waters. Within this study, it was investigated whether concentrations of these determinants are at concentrations above internationally established Assessment Criteria (AC). The majority of sites were considered not to pose a toxicological risk in terms of metal contamination. Where breaches occurred, they were mainly from historic samples related to Cr, Cu and Ni contamination. A trend assessment revealed that out of 59 significant trends, 36 were downwards and 23 upwards, indicating that some determinants like Al, Zn and Ni are improving strongly across some sites, whilst areas associated with industrial activity still see some increasing trends for Al, Cd, Pb and Zn.

Baseline survey of marine sediments collected from the Kingdom of Bahrain: PAHs, PCBs, organochlorine pesticides, perfluoroalkyl substances, dioxins, brominated flame retardants and metal contamination

A baseline survey of sediment contamination was undertaken at 14 locations around the coastline of Bahrain in May 2017, followed by a focused survey of 20 sites, in November 2019. Samples were assessed for industrial pollutants, including metals, PAHs and a suite of organohalogen compounds. The data generated indicated that levels of chemical contaminants were generally low and did not pose a toxicological risk when assessed against commonly applied sediment quality guidelines (SQG). The highest concentrations of PAHs and PCBs were identified in samples collected at coastal sites adjacent to a refinery area known to contain a diverse mix of industry. Tubli Bay, a heavily stressed small bay receiving high loads of sewage effluent, was also identified as an area warranting further investigation with elevated concentrations of BDE209, PFOS and metal contamination. Such data provides a useful baseline assessment of sediment contamination, against which management control measures can be assessed.