Medetomidine as a candidate antifoulant: Sublethal effects on juvenile turbot (Psetta maxima L.)

Medetomidine is proposed as a candidate antifouling compound proven effective against barnacles. It is routinely used as a sedative in veterinary medicine. It is therefore important to also investigate possible adverse effects on non-target organisms. Thus, sublethal effects on two different ages of juvenile turbot (Psetta maxima) exposed to a wide concentration range of medetomidine (0.063–420 nM) were assessed after exposure under semistatic as well as flow-through conditions, for a maximum of 96 h. Effects on respiration frequency and amount of oxygen consumed were assessed, as well as the ability of turbot to adapt to a dark background. A significant decrease was seen both in respiration frequency with a lowest observed effect concentration (LOEC) of 2.1 nM as well as in amount of oxygen consumed (LOEC = 420 nM) and colour adaptation (LOEC = 4.2 nM). Colour adaptation was also evaluated in a short exposure experiment, 1 h, where significant effects were observed (LOEC = 2.1 nM). Reversibility, when fish were incubated in clean seawater following exposure, was seen for all observed effects. Ecological relevance of the observed effects is discussed.