Investigations of temperature and pH variations on metal trophic transfer in turbot (Scophthalmus maximus).

Studying dietary metal transfer kinetics is essential to gain a better understanding in global metal accumulation rates and its impacts in marine fish. While there exists a solid understanding on the influence of various biotic factors on this transfer, metal assimilation in fish might be also affected by abiotic factors, as has been observed in marine invertebrates. The present study therefore aims to understand the potential effects of two climate-related master variables, temperature and pH, on the assimilation efficiency (AE) of essential (Co and Zn) and non-essential (Ag) metals in the turbot Scophthalmus maximus using radiotracer tools. Juvenile turbots were acclimated for 8 weeks at two temperatures (17 and 20 °C) and pH (7.5 and 8.0) regimes, under controlled laboratory conditions, and then fed with radiolabelled shrimp (Co, Zn and Ag). Assimilation efficiencies of Co and Ag in juvenile turbot, determined after a 21-day depuration period, were not affected by pre-exposition to the different environmental conditions. In contrast, temperature did significantly influence Zn AE (p < 0.05), while pH variations did not affect the assimilation of any of the metals studied. In fact, temperature is known to affect gut physiology, specifically the membrane properties of anterior intestine cells where Zn is adsorbed and assimilated from the ingested food. These results are relevant to accurately assess the influence of abiotic factors in AEs of metals in fish as they are highly element-dependent and also modulated by metabolic processes.