Multi-seasonal barnacle (Balanus improvisus) protection achieved by trace amounts of a macrocyclic lactone (ivermectin) included in rosin-based coatings

Abstract

Rosin-based coatings loaded with 0.1% (w/v) ivermectin were found to be effective in preventing colonization by barnacles (Balanus improvisus) both on test panels as well as on yachts for at least two fouling seasons. The leaching rate of ivermectin was determined by mass-spectroscopy (LC/MS-MS) to be 0.7 ng cm 72 day 71. This low leaching rate, as deduced from the Higuchi model, is a result of the low loading, low water solubility, high affinity to the matrix and high molar volume of the model biocide. Comparison of ivermectin and control areas of panels immersed in the field showed undisturbed colonisation of barnacles after immersion for 35 days. After 73 days the mean barnacle base plate area on the controls was 13 mm 2 , while on the ivermectin coating it was 3 mm 2 . After 388 days, no barnacles were observed on the ivermectin coating while the barnacles on the control coating had reached a mean of 60 mm 2 . In another series of coated panels, ivermectin was dissolved in a cosolvent mixture of propylene glycol and glycerol formal prior to the addition to the paint base. This method further improved the anti-barnacle performance of the coatings. An increased release rate (3 ng cm 72 day 71 ) and dispersion of ivermectin, determined by fluorescence microscopy, and decreased hardness of the coatings were the consequences of the cosolvent mixture in the paint. The antifouling mechanism of macrocyclic lactones, such as avermectins, needs to be clarified in further studies. Beside chronic intoxication as ivermectin is slowly released from the paint film even contact intoxication occurring inside the coatings, triggered by penetration of the coating by barnacles, is a possible explanation for the mode of action and this is under investigation.

The impact and control of biofouling in marine aquaculture: a review

“…As the technology for vessels improves, the transfer (trickle-down) of technology to aquaculture industries will occur. New approaches for marine shipping and infrastructure are targeting well-documented pharmaceuticals (Pinori et al 2011), bioactives (Dahlstro¨m and Elwing 2006;Pinori et al 2011), and commercially available enzymes (Pettitt et al 2004;Aldred et al 2008) as antifoulants, or innovations with existing technologies such as copper (Vucko et al 2012). These approaches may prove productive if they can be specifically tailored to aquaculture, however, they still involve a chemical entity and their use will attract close scrutiny of any chemical effects on cultured organisms.…”

The impact of coating hardness on the anti-barnacle efficacy of an embedded antifouling biocide

“…The results of the embedded biocide approach presented in Pinori et al (2011) were promising in terms of anti-barnacle efficacy both in static field tests and in boat experiments, and demonstrated a very low release rate and multi-seasonal effect even when trace amounts of the biocide (0.1% wt ivermectin) were used. Nevertheless, it was not possible to prove that efficacy was via a penetration triggered route; alternative explanations such as intoxication could not be ruled out.…”

“…The environmental cost/ benefit analyses are very good although economic cost/ benefit analyses are still not comparable with those for biocide-based coatings. A novel approach that combines the environmental cost/benefit balance of fouling-release systems with the economic cost/efficacy balance of the biocide approach is to use tethered or embedded biocides, a strategy recently discussed by Pinori et al (2011). The central idea behind this new principle is to use a biocide-based strategy, but eliminate exposure and release of biocides into the surrounding water.…”

“…The softer coating should allow barnacle penetration while this should be prevented (or reduced) on the harder coating. The antibarnacle efficacy of these two formulations was tested without addition of ivermectin (controls) and with the addition of ivermectin at the same concentration used by Pinori et al (2011).…”

Mini-review: Molecular mechanisms of antifouling compounds

“…Among the various avermectins produced by Streptomyces avermitilis, ivermectin enhances post-settlement mortality, but has no effect on the settlement of the cypris larvae of barnacles (Pinori et al 2011). Protein toxins from the bacterium Pseudomonas fluorescens CL0145A are specifically lethal to mussels by destroying their digestive systems without causing non-target mortality (Molloy 2001).…”