Efficacy and Ecotoxicity of Novel Anti-Fouling Nanomaterials in Target and Non-Target Marine Species

Abstract

Biofouling is a global problem that affects virtually all the immersed structures. Currently, several novel environmentally friendly approaches are being tested worldwide to decrease the toxicity of biocides in non-fouling species, such as the encapsulation/immobilization of commercially available biocides, in order to achieve control over the leaching rate. The present study addresses the toxicity of two widely used booster biocides, zinc pyrithione (ZnPT) and copper pyrithione (CuPT), in its free and incorporated forms in order to assess their toxicity and anti-fouling efficacy in target and non-target species. To achieve this goal, the following marine organisms were tested; the green microalgae Tetraselmis chuii (non-target species) and both target species, the diatom Phaeodactylum tricornutum and the mussel Mytilus edulis. Organisms were exposed to both biocides, two unloaded nanostructured materials and nanomaterials loaded with biocides, from 10 μg/L to 100 mg/L total weight, following standard protocols. The most eco-friendly and simultaneously efficient anti-fouling solution against the two photosynthetic species (nanoclays loaded with ZnPT) was then tested on mussels to assess its lethal efficacy (LC = 123 μg/L) and compared with free biocide (LC = 211 μg/L) and unloaded material (LC > 1000 μg/L). A second exposure test with sub-lethal concentrations (lower than 100 μg/L), using mussels, was carried out to assess biochemical changes caused by the tested compounds. Oxidative stress, detoxification and neurotransmission markers were not responsive; however, different antioxidant patterns were found with free ZnPT and loaded nanoclay exposures. Thus, the immobilization of the biocide ZnPT into nanoclays proved to be a promising efficient and eco-friendly anti-fouling strategy.

Antimacrofouling Efficacy of Innovative Inorganic Nanomaterials Loaded with Booster Biocides

“…In the present study, the unloaded Zn-Al LDH exhibited lower mortality, which indicates it as an ideal carrier for active compounds. Similarly, Avelelas et al [25] and Martins et al [34] found that unloaded Zn-Al LDH did not cause mortality when tested on the clam Ruditapes phillipinarum and on M. edulis following 96 h of exposure. Avelelas et al [25] also demonstrated the inertness of LDH against the diatom Phaeodactylum tricornutum and the green unicellular alga Tetraselmis chuii.…”

“…Similarly, Avelelas et al [25] and Martins et al [34] found that unloaded Zn-Al LDH did not cause mortality when tested on the clam Ruditapes phillipinarum and on M. edulis following 96 h of exposure. Avelelas et al [25] also demonstrated the inertness of LDH against the diatom Phaeodactylum tricornutum and the green unicellular alga Tetraselmis chuii. In contrast, the efficacy and mortality effects of the unloaded SiNC on MED and RED mussels occurred with similar concentrations as that of the nanomaterial loaded with biocides.…”

“…Smallmatek (Aveiro, Portugal) developed and produced both the unloaded nanostructured materials (spherical mesoporous silica nanocapsules (SiNC) and Zn-Al layered double hydroxides (LDH)) and the four loaded engineered nanomaterials, corresponding to both biocides individually immobilized/encapsulated in the above nanomaterials (i.e., LDH-ZnPT, LDH-CuPT, SiNC-ZnPT and SiNC-CuPT). The tested nanomaterials were fully characterized by Avelelas et al [25]. The loading content of ZnPT is 36% in the LDH-ZnPT and 4% in SiNC-ZnPT, whereas for CuPT it is 30% in the LDH-CuPT and 5% in the SiNC-CuPT [25].…”

“…The tested nanomaterials were fully characterized by Avelelas et al [25]. The loading content of ZnPT is 36% in the LDH-ZnPT and 4% in SiNC-ZnPT, whereas for CuPT it is 30% in the LDH-CuPT and 5% in the SiNC-CuPT [25]. Stock solutions of the compounds were prepared by vigorous shaking in an ultrasonic bath for 1 h in order to achieve maximum dispersion and a homogenous dissolution.…”

“…LDH are anionic clays with a typical lateral-size ranging from 20 to 40 nm [15,23], functioning as host-guest materials [24]. Both nanomaterials have already been successfully used for corrosion protection [15,[21][22][23] and more recently for fouling control, through the immobilization of different active compounds, including the above-mentioned pyrithiones, in the scope of the BYEFOULING FP7 project [25].…”