Toxicities of the degraded mixture of Irgarol 1051 to marine organisms

The inhibitory effects of the antifouling compound Irgarol 1051 on the marine diatom Skeletonema sp. across a broad range of photosynthetically active radiation

The release of anthropogenic organic pollutants has resulted in extensive environmental risks to coastal waters. Among pollutants released, the most common antifoulant, Irgarol 1051, is an effective inhibitor of photosystem II of photoautotrophs; thus, the continuous release of this compound into surrounding seawater would potentially threaten marine algae. To investigate this, we grew the model marine diatom Skeletonema sp. at different concentrations of Irgarol 1051 and levels of photosynthetically active radiation (PAR). Irgarol did not affect the photochemical capacity when cells were incubated in the dark, but photochemical yields all significantly decreased, and relative inhibition by Irgarol increased once cells were exposed to even the lowest PAR, with lower photochemical yields observed under increased level of Irgarol. In addition, the rate of decrease in yield increased with Irgarol concentration but was unchanged among PAR treatments. The growth rates showed a similar pattern to photochemical yields, with lower values under higher Irgarol concentrations, but with no significant differences in the effect of Irgarol observed between the light levels employed. The ratio of repair to damage rates of PSII clearly shows that this ratio decreased with light intensity, largely due to increases in damage rates and that the PAR level at which repair balanced damage decreased under a high level of Irgarol. Our results suggest that the inhibitory effects of Irgarol become obvious after PAR exposure even at a relatively low light level, suggesting that Irgarol would affect phytoplankton throughout the daytime, and may therefore have a broad environmental risk, potentially limiting coastal primary production.

Pollutants from shipping - new environmental challenges in the subarctic and the Arctic Ocean

Maritime activities in the subarctic and Arctic Ocean are predicted to substantially increase in the future due to climate change and declining sea ice cover. Inevitably, the consequences will be seen in impacts on marine ecosystems in this region at many different levels, such as increased pollution load due to antifouling biocides, polycyclic aromatic hydrocarbons, metals and pharmaceuticals. Here we discuss the current situation and evaluate the effect of increased shipping on the environmental status of subarctic and Arctic waters, in relation to elevated loads of both legacy and emerging pollutants in the region. It is of high importance to evaluate the current levels of selected pollutants, which will most likely rise in near future. Furthermore, it is important to improve our understanding of the effects of these pollutants on marine organisms at high latitudes, as the pollutants may behave differently in cold environments compared to organisms at lower latitudes, due to dissimilar physiological responses and adaptations of the cold-water organisms. Integrative studies are needed to better understand the impact of pollutants on the marine fauna while monitoring programmes and research should be continued, with an increased capacity for emerging pollutants of concern.

Microfluidic Encapsulation of Hydrophobic Antifouling Biocides in Calcium Alginate Hydrogels for Controllable Release

Microencapsulation of biocides is used in long-life antifouling coating paints for marine applications and building materials. Here, we report the microfluidic production of calcium alginate (Ca-alginate) hydrogel particles to modulate the release of the encapsulated drug Irgarol (N-cyclopropyl-N'-(1,1-dimethylethyl)-6-(methylthio)-1,3,5-triazine-2,4-diamine), which is a hydrophobic and specifically phytotoxic antifoulant that inhibits photosystem II in aquatic plant species. We first encapsulated the drug inside the highly spherical Ca-alginate hydrogels of an average diameter ∼160 μm with a coefficient of variation of less than 4% and an average roundness of more than 0.96. The release speeds of the encapsulated and nonencapsulated drugs in pure water were measured separately by ultraviolet-visible spectroscopy. A stable and controllable release rate of the loaded drug was achieved by hydrophilic encapsulation. In addition, cellulose fibers were incorporated to enhance the mechanical strength of the hydrogels. Finally, the antifouling effect of the encapsulated drug was demonstrated using water grass (Bacopa monnieri).

Antifouling biocides as a continuous threat to the aquatic environment: Sources, temporal trends and ecological risk assessment in an impacted region of Brazil

Antifouling biocides, such as irgarol and diuron, are commonly used in antifouling paints. Recently, studies carried out in a Brazilian region of ecological concern have warned for extremely high levels of these biocides. So, this work focused on a 4-year (2015-2018) evaluation considering the occurrence, environmental fate, seasonal variations and ecological risk assessment of irgarol and diuron in water and sediment from São Marcos Bay, Brazil, which is an area of international relevance located in the Amazon region. The results showed the ubiquitous presence of antifouling biocides, as well as their wide distribution along the bay. The concentration range of irgarol was between <0.8 and 89.4 ng L^-1 in water and between <0.5 and 9.2 ng g^-1dw in sediments, whereas diuron showed a range between <1.4 and 22.0 ng L^-1 in water and between <2.0 and 15.0 ng g^-1dw in sediments. The distribution of the biocides was mainly related to the intense Bay hydrodynamics. The environmental risk assessment showed that irgarol and diuron posed "high risk" to the aquatic biota of São Marcos Bay, exceeding international Environmental Quality Guidelines. The results represent a robust study on the environmental fate of such biocides and intend to be a useful data source for eventual legislation since regulation concerning antifouling substances is necessary for Brazil.

Sunscreens containing zinc oxide nanoparticles can trigger oxidative stress and toxicity to the marine copepod Tigriopus japonicus

The study, for the first time, evaluated the leaching rate of zinc oxide nanoparticles (nZnO) from human skins which were applied with three commercial sunscreens containing nZnO as an active ingredient. The leaching rate of nZnO varied greatly among the sunscreens, with a range of 8-72% (mean ± SD: 45% ± 33%). We further investigated their toxicities to the marine copepod Tigriopus japonicus. We found that 96-h median lethal concentrations of the three sunscreens to T. japonicus were > 5000, 230.6, and 43.0 mg chemical L^-1, respectively, equivalent to Zn²⁺ concentrations at >82.5, 3.2, and 1.2 mg Zn L^-1, respectively. Exposure to the individual sunscreens at environmentally realistic concentrations for 96 h led to up-regulation of antioxidant genes in T. japonicus, while they triggered the release of reactive oxygen species based on the results of in vivo assays. Evidently, these nZnO-included sunscreens can cause oxidative stress and hence pose risk to marine organisms.

In vivo toxicities of nine engineered nano metal oxides to the marine diatom Skeletonema costatum and rotifer Brachionus koreanus

This study compared in vivo acute toxicities of nine engineered nano metal oxides to the marine diatom Skeletonema costatum and rotifer Brachionus koreanus. The sequence of their toxicities to S. costatum, based on growth inhibition, was: nano zinc oxide (nZnO) > nTiO₂ (rutile) > nMgO > Annealed nMgO > nTiO₂ (anatase) > γ-nAl₂O₃ > nIn₂O₃ > α-nAl₂O₃ > nSnO₂. Similarly, nZnO was also the most toxic to B. koreanus, but the other nano metal oxides were non-lethal. nMgO and nZnO were confirmed to trigger reactive oxygen species (ROS) mediated toxicity to the two marine organisms, while nTiO₂ (both anatase and rutile forms) likely induced oxidative stress as shown by their acellular ROS production. nZnO may also cause damage in the endocrine system of B. koreanus, as indicated by the increased transcription of retinoid X receptor. Annealed nMgO reduces its toxicity via removal of O₂^- and impurities from its surface.

Occurrence and partitioning of antifouling booster biocides in sediments and porewaters from Brazilian Northeast

Fouling organisms attach and grow on submerged surfaces causing several economic losses. Thus, biocides have been introduced in antifouling paints in order to avoid this phenomenon, but their widespread use became a global problem, mainly in ports, leisure and fishing boat harbors, since these substances can be highly toxic to non-target organisms. The occurrence and environmental behavior of antifouling biocides are especially unknown in some peculiar regions, such as Amazon areas. Thus, the aim of this work was to evaluate, for the first time, levels and the partitioning behavior of the antifouling organic biocides irgarol, diuron and also stable degradation products of dichlofluanid and diuron (DMSA and DCPMU, respectively) in sediments and porewaters from a high boat traffic area located in the Northeast of Brazil, a pre-Amazon region. Our results showed high concentrations of irgarol (<1.0-89.7 μg kg^-1) and diuron (<5.0-55.2 μg kg^-1) in sediments. In porewater, DCPMU (<0.03-0.67 μg L^-1) and DMSA (<0.008-0.263 μg L^-1) were the mainly substances detected. High K_d and K_oc obtained for both irgarol and diuron showed a partitioning preference in the solid phase. This work represents one of the few registers of contamination by antifouling substances in Amazonian areas, despite their environmental relevance.

Toxicities of Irgarol 1051 derivatives, M2 and M3, to two marine diatom species

Irgarol 1051 is highly toxic to marine autotrophs and has been widely used as an antifouling booster biocide. This study tested the toxicities of two s-triazine derivatives of Irgarol, namely M2 (3-[4-tert-butylamino-6-methylthiol-s-triazin-2-ylamino]propionaldehyde) and M3 (2-methylthio-4,6-bis-tert-butylamino-s-triazine) to two marine diatom species, Skeletonema costatum and Thalassiosira pseudonana through standard acute (96h) and chronic (7d) growth inhibition tests. Results showed that both of the two chemicals significantly inhibited the growth of S. costatum (M2: 96h-EC50 = 6789.7 μg L^-1, 7d-EC50 = 3503.7 μg L^-1; M3: 96h-EC50 = 45193.9 μg L^-1, 7d-EC50 = 5330.0 μg L^-1) and T. pseudonana (M2: 96h-EC50 = 366.2 μg L^-1, 7d-EC50 = 312.5 μg L^-1; M3: 96h-EC50 = 2633.4 μg L^-1, 7d-EC50 = 710.5 μg L^-1), while their toxicity effects were much milder than Irgarol and its major degradation product M1. By comparing with previous findings, the susceptibilities of these s-triazine compounds to two tested species were ranked as: Irgarol > M1 ≫ M2 > M3. This study promotes future research efforts on better understanding of the ecotoxicities of M2 and M3, and incorporating such information to improve the current monitoring, risk assessment and regulation of the use of Irgarol.