Trophic transfer of 110mAg in the turbot Scophthalmus maximus through natural prey and compounded feed

• Transfer of 110mAg to the predator is not influenced by 110mAg activity or subcellular distribution in the prey.
• 110mAg is poorly assimilated by turbot fed on 110mAg-labelled food items.
• Physiological mechanism(s) occurring in predator's digestive tract prevent(s) assimilation of 110mAg.

Industrial incidents can result in radionuclide release in the environment, among which 110mAg. Indeed, under particular circumstances, non-negligible amounts of 110mAg have been measured in the marine environment (as observed in Fukushima Dai-ichi incident). This element can therefore be accumulated by aquatic organisms through different pathways including the trophic transfer. The present study aimed at examining the variation of 110mAg assimilation efficiency (AE) by turbots, Scophthalmus maximus, when exposed through different feeds. Pulse-chase feeding experiments were carried out in mesocosms, using radiolabelled feeds (natural prey and commercial pellets). Depuration kinetics of 110mAg over 21 days were generally fitted by a two-component exponential model; the ingested radioelement was poorly assimilated by turbots regardless of the food item that was used (AE always <3%). Concentration and subcellular distribution of 110mAg in prey did not seem to influence its assimilation by turbot. These results suggest that physiological mechanisms could occur in fish that would prevent the transfer of 110mAg from gut lumen to internal organs (e.g. 110mAg neutralization in the lumen of the stomach, detoxification mechanisms occurring in the gut).