Comparison of the Level and Mechanisms of Toxicity of Nanoparticles of Underwater Welding in Bioassay with Three Marine Microalgae

In this work, the toxicity level of nano- and microparticles obtained by underwater welding was assessed. The toxicity of nano- and microparticles obtained by underwater welding was evaluated on three types of marine microalgae: <i>Heterosigma akashiwo</i> (Ochrophyta), <i>Porphyridium purpureum</i> (Rhodophyta), and <i>Attheya ussuriensis</i> (Bacillariophyta). The aim was to study the environmental risks associated with the ingress of micro- and nanoparticles of metal oxides into the marine environment. Water samples containing suspensions from wet welding and cutting processes were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) to determine heavy metal concentrations. Biotesting included evaluation of growth inhibition, cell size change, and membrane potential of microalgae using flow cytometry. The results showed that samples APL-1 and APL-2 (flux-cored wire) were the most toxic, causing concentration-dependent growth inhibition of <i>H. akashiwo</i> and <i>A. ussuriensis</i> (<i>p</i> < 0.0001) as well as membrane depolarization. For <i>P. purpureum</i>, ELc and ELw (coated electrodes) samples stimulated growth, indicating species-specific responses. The stability of the nanoparticles and their bioavailability were found to play a key role in the mechanisms of toxicity. The study highlights the need to control the composition of materials for underwater welding and to develop environmentally friendly technologies. The data obtained are important for predicting the long-term effects of pollution of marine ecosystems by substances formed during underwater welding.