Polygodial: a contact active antifouling biocide

Abstract

Ongoing investigation of the candidate antifouling (AF) biocide polygodial (PG) has revealed that this compound may be contact active, whereby it can confer effect while remaining bound within a stable matrix. To test this hypothesis, the AF activity of PG-laced coatings was compared to that of seawater in which PG-laced coatings had been soaked. Four coating types spanning high to low affinity for PG were examined and AF activity was assessed based on inhibition of settlement and metamorphosis of larvae of three fouling organisms: Ciona savignyi Herdman, Mytilus galloprovincialis Lamarck and Spirobranchus caraniferus Gray. Direct exposure to the coatings had a significantly greater impact on larval metamorphosis than indirect exposure to seawater in which the coatings had been soaked. In particular, metamorphosis was almost completely inhibited by high-affinity coatings containing ≥ 200 ng of PG per replicate, while corresponding soaking waters had no detectable effect. These findings support the assertion that PG is contact active.

Keywords:

• acrylic
• biocide
• Ciona savignyi
• coating
• Mytilus galloprovincialis
• rosin
• Spirobranchus caraniferus

Acknowledgements

This study was funded by the National Institute of Water and Atmospheric Research (New Zealand) Coasts and Oceans Research Programme 4 – Marine Biosecurity (2013/14 SCI). The authors are grateful for statistical advice provided by Dr Javier Atalah, analytical testing by Mr Roel van Ginkel, and editing by Dr Grant Hopkins and Dr Oliver Floerl (all Cawthron Institute, Nelson, New Zealand).