Abstract: 

In the marine environment, biofouling often refers to the unwanted settlement of marine organisms on underwater, often artificial surfaces. Biofouling causes substantial economic and environmental challenges across marine related industries. To prevent biofouling, antifouling coatings that slowly leach biocides were designed and applied on underwater surfaces. However, some of these biocides caused significant environmental concerns due to their perceived toxicity and bioaccumulation. 
Amid environmental concerns related to antifouling biocides, medetomidine, known by its commercial name Selektope®, was developed as a potential low-impact alternative: it was demonstrated to inhibit the settlement of barnacles at a low concentration of 1 nM with nonlethal, receptor-specific mode of action. As a chiral compound, medetomidine exists as R- and S-enantiomers, while often applied as a racemic mixture for antifouling purposes. However, previous ecotoxicological investigations generally focused on the racemic mixture of medetomidine, without clearly distinguishing stereochemical effects. In addition, barnacles and tubeworms were discovered as the most sensitive groups to medetomidine during previous R&D efforts, but little discussion focused on how medetomidine might affect barnacles or tubeworms that occur in their natural habitats.
This study uses antifouling bioassays spanning multiple phyla to systematically investigate how stereochemistry affects the antifouling bioactivity and toxicity of medetomidine. Preliminary results suggest that (1) the antifouling performance of medetomidine was highly enantiomer-specific; (2) previously predicted environmental concentration range of racemic medetomidine overlap with its EC50 in preventing barnacle settlement under laboratory conditions, which indicates potential ecological risk of medetomidine toward the natural populations of barnacles and warrant future investigations in more environmentally relevant conditions.