Eco-friendly potential of a new promising antifouling synthetic compound

• ¹ Centro Interdisciplinar de Pesquisa Marine e Ambiental (CIIMAR), Portugal
• ² Faculdade de Farmácia, Universidade do Porto, Departamento de Ciências Químicas, Portugal
• ³ Faculdade de Ciências, Universidade de Lisboa, Quimica e Bioquimica, Portugal
• ⁴ Instituto Superior Técnico, Universidade de Lisboa, Engenharia Quimica, Portugal

Marine biofouling comprises a biological process resulting from accumulation of marine organisms (bacteria, fungi, sponges, algae, barnacles, and mussels) on natural and artificial surfaces submerged in water, as is the case of ship hulls, platforms, buoys, wharfs and aquaculture net cages, causing several economic, environmental and human-health impacts [1]. The development of this natural process on ships reduces their speed and manoeuvrability, resulting in increased fuel and maintenance costs. On the other hand, ships containing fouling organisms diffuse invasive species across the oceans that will end up for competing with autochthonous specie for the same habitat, being also a vector of diseases, affecting severely the human population [2]. There are several approaches to combat marine biofouling, however most of them are toxic and infective at long-term [3]. The need of “green” alternatives to combat marine biofouling has led our group to focus on the synthesis of ecological substances with antifouling (AF) properties that could be non-toxic, degradable, and that will not bioaccumulate in the environment [4]. In this work, degradation and seawater solubility, bioaccumulation, and ecotoxicity of one of the most promising AF compounds synthesized in our laboratory was evaluated. The commercial biocide Econea® was also evaluated for comparative purposes. For degradation studies, a method using solid phase extraction (SPE) followed by reverse-phase high performance liquid chromatography with diode array detector (RP-HPLC-DAD) was developed in order to quantify the synthetic compound and Econea® in artificial seawater (aSW). After 2 months in different stress conditions, full degradation of the synthetic compound was observed in almost all conditions, unlike Econea® that presented partial degradation in all tested conditions. Seawater solubility was evaluated by the shake-flask method. A solution of the shynthetic compound was analysed by HPLC leading to a solubility value of 0.0052 mg/mL, 30 times more soluble that the commercial biocide Econea® (0.00016 mg/mL) [5]. KOWWIN™ v1.68 developed by Syracuse Research Cooperation jointly with the Environmental Protection Agency (EPA) was used for in silico calculation of log Kow (octanol-water partition coefficient) in order to evaluate the bioaccumulation potential. The newly synthetic compound showed a log Kow <3, indicating a lower bioaccumulation potential when compared with the Econea biocide. The high degradation in seawater and log Kow < 3, allow us to predict that this compound will not have potential for biomagnification through the food chain. In addition, two basic level tests proposed and included in the EU hazard assessment of substances and European Eco-label were performed to assess the aquatic ecotoxicity. No toxicity was found on luminescent Vibrio fischeri bacteria test (ISO 11348-2) (EC50 30min >750 mg/L) or on Alga growth inhibition test (OECD201) (EL50 72h >100 mg/L). Taking into account these environmental fate parameters, it is possible to conclude that this compound with scale up by a suitable synthesis may be a good candidate to be incorporated in marine AF paints.