| Summary: | Marine macroalgae (MM) present a great biological potential since they are a source of many essential natural compounds with physiological benefits. Despite this, there is little knowledge about the impact of MM supplementation on protecting fish health from exposure to environmental contaminants. Mercury (Hg) is well known for its high toxicity, and it can be found at low levels in farm-raised fish. The present dissertation was design in this context, with the aim of addressing a possible protection by a diet supplemented with MM to the juvenile white sea bream (Diplodus sargus), particularly after exposure via water to realistic levels of inorganic Hg (iHg). Thus, the toxicokinetics of iHg was studied, antioxidant protection and neuroprotection as well as anti-genotoxic properties. For this purpose, the fish were fed for 3 months with a MM-enriched diet [total incorporation of 5 %, with the species Fucus vesiculosus, Gracilaria gracilis and Ulva rigida in equal parts - algae-supplemented fish group (AC)], while the non-supplemented fish were fed with a standard feed (SC). Then, both groups on different baseline diets were exposed to realistic levels of iHg (2 μg L-1) via water for 7 days (E7) (AHg and SHg groups), followed by a 14-day post-exposure period (PE14). Control groups, not exposed to iHg, were maintained throughout the experiment (AC and SC). At E7 and PE14, the fish from the different groups (AC, SC, AHg, SHg) were sacrificed and the gills, blood, liver and brain were collected to determine total Hg (tHg) levels, in parallel with the assessment of oxidative stress related endpoints in the gills, liver and brain, where the following biochemical parameters were determined: (i) enzymatic antioxidants [catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione-S-transferase (GST), glutathione reductase (GR)] and non-enzymatic antioxidants (total glutathione (GSHt)); (ii) damage indicators (lipid peroxidation - LPO); (iii) acetylcholinesterase (AChE) activity, used as an ...
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