Biomimetic Approaches for the Development of New Antifouling Solutions: Study of Incorporation of Macroalgae and Sponge Extracts for the Development of New Environmentally-Friendly Coatings

Abstract

Biofouling causes major economic losses in the maritime industry. In our site study, the Bay of La Paz (Gulf of California), biofouling on immersed structures is a major problem and is treated mostly with copper-based antifouling paints. Due to the known environmental effect of such treatments, the search for environmentally friendly alternatives in this zone of high biodiversity is a priority to ensure the conservation and protection of species. The aim of this work was to link chemical ecology to marine biotechnology: indeed, the natural defense of macroalgae and sponge was evaluated against biofoulers (biofilm and macrofoulers) from the same geographical zone, and some coatings formulation was done for field assays. Our approach combines in vitro and field bioassays to ensure the selection of the best AF agent prospects. The 1st step consisted of the selection of macroalgae (5 species) and sponges (2 species) with surfaces harboring a low level of colonizers; then extracts were prepared and assayed for toxicity against Artemia, activity towards key marine bacteria involved in biofilm formation in the Bay of La Paz, and the potency to inhibit adhesion of macroorganisms (phenoloxidase assays). The most active and non-toxic extracts were further studied for biofouling activity in the adhesion of the bacteria involved in biofilm formation and through incorporation in marine coatings which were immersed in La Paz Bay during 40 days. In vitro assays demonstrated that extracts of Laurencia gardneri, Sargassum horridum (macroalgae), Haliclona caerulea and Ircinia sp. (sponges) were the most promising. The field test results were of high interest as the best formulation were composed of extracts of H. caerulea and S. horridum and led to a reduction of 32% of biofouling compared with the control.

Keywords: Haliclona caerulea; Ircinia sp.; Laurencia gardneri; Sargassum horridum; adhesion; algae; antifouling; biofilm; extracts; field assays; sponges.

Figure 1

Effect of algae and sponge extracts (LgEt (Laurencia gardneri ethanol), LgDC (Laurencia gardneri CH₂Cl₂), UlEt (Ulva lactuca ethanol), UlDC (Ulva lactuca CH₂Cl₂), CfEt (Codium fragile ethanol), CfDC (Codium fragile CH₂Cl₂), ShEt (Sargassum horridum ethanol), ShDC (Sargassum horridum CH₂Cl₂), GvEt (Gracilaria vermiculophylla ethanol), GvDC (Gracilaria vermiculophylla CH₂Cl₂), Hc (Haliclona caerulea) and Isp (Ircinia sp.) and Ka (Kojic acid, used as a control) on the phenoloxidase inhibition.

Figure 2

Potency of macroalgae and sponge extracts in the inhibition of bacterial adhesion (a) Sargassum horridum EtOH extract, (b) Laurencia gardneri CH₂Cl₂ extract, (c) Haliclona caerulea MeOH extract, and (d) Ircinia sp. MeOH extract.

Figure 3

Epibiont percentage coverage of plates containing extracts after 40 days of exposure in the field (Marina La Paz). Antifouling Paint (AFP), Control plate without paint (CP), Formulated Paint (FP), L. garneri extract (PLg), S. horridum extract (PSh), H. caerulea extract (PHc), Ircinia sp. extract (PIsp).

Figure 4

Pictures of plates (control, coated with commercial paint or extracts) after 40 days of immersion in the field (Marina La Paz). (a) Antifouling Paint (AFP), (b) Control plate without paint (CP), (c) Formulated Paint (FP), (d) L. garneri extract (PLg), (e) S. horridum extract (PSh), (f) H. caerulea extract (PHc) and (g) Ircinia sp. extract (PIsp) (Scale bar: 1 cm).