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Several anthropogenic factors, including contamination by oil spills, constitute a threat to coral reef health. Current methodologies to remediate polluted marine environments are based on the use of chemical dispersants; however, these can be toxic to the coral holobiont. In this study, a probiotic bacterial consortium was produced from the coral Mussismilia harttii and was trained to degrade water-soluble oil fractions (WSFs). Additionally, we assessed the effect of WSFs on the health of M. harttii in tanks and evaluated the bacterial consortium as a bioremediation agent. The consortium was responsible for the highly efficient degradation of petroleum hydrocarbons and it minimised the effects of WSFs on coral health, as indicated by raised photosynthetic efficiencies. Moreover, the impact of WSFs on the coral microbiome was diminished by the introduced bacterial consortium. Following introduction, the bacterial consortium thus had a dual function, i.e promoting oil WSF degradation and improving coral health with its probiotic features.

The ammonia (NH 3 ) and nitrate (NO 3 − ) threshold concentrations in rearing water of juvenile pikeperch ( Sander lucioperca ) were assessed. Pikeperch with an initial mean (SD) weight of 17.7 (4.2) g were exposed to 0.9 (control), 3.6, 5.2, 7.1, 11.2 and 18.9 μM NH 3 in the water for 42 days. Plasma NH 4 + concentrations stayed at control levels (~ 650 μM) up to 11.2 μM NH 3 in the water. At the highest water NH 3 concentration tested, plasma NH 4 + had more than doubled to 1400 μM. Based on the specific growth rate, the EC 10 value for NH 3 was 5.7 μM. When pikeperch (initial mean (SD) weight of 27.0 (4.9) g) were exposed to 0.1 (control), 1.5, 2.3, 3.7, 6.1, 10.2, 15.8 and 25.6 mM NO 3 − for 42 days, mean (SD) plasma NO 3 − concentrations increased linearly from 88 (47) to 5993 (899) μM at the highest ambient NO 3 − level. Feed intake, specific growth rate and feed conversion ratio were not affected. Neither NH 3 nor NO 3 − exposure significantly affected haematocrit, plasma concentrations of cortisol, glucose, lactate, osmolality, gill morphology or branchial Na + /K + -ATPase activity in pikeperch. For juvenile pikeperch we advise not to exceed a water NH 3 concentration of 3.4 μM (0.05 mg NH 3 –N/L), the lower limit of the 95% confidence interval of the EC 10 value for SGR, to ensure proper physiology and growth. For NO 3 − we advise not to exceed 25 mM (350 mg NO 3 − –N/L). This criterion is based on the highest NO 3 − concentration tested (25.6 mM). As no negative effects were detected at the highest concentration tested, the actual NO 3 − threshold probably exceeds 25.6 mM.

The effects of the dietary administration of two bacterial probiotic strains (Ppd11 and Pdp13) from the Alteromonadaceae family for 60 days, were assessed by measuring growth and feed efficiency, activities of leucine aminopeptidase and alkaline phosphatase and structural changes in the intestine of juvenile Senegalese sole. In addition, the profile of intestinal microbiota was studied by Denaturing Gradient Gel Electrophoresis. Growth and nutrient utilization were significantly higher in fish receiving probiotics than in those fed the control diet. No differences were observed in proximal composition between treatments, though higher lipid muscle content was measured in fish receiving Pdp13. Those fish also exhibited higher activities of AP when compared to Ppd11 and control groups. The profile of intestinal microbiota clearly separated those fish receiving probiotics from those of the control group. Microscopical examination revealed accumulation of lipid droplets in the enterocytes of fish receiving the control diet, but not in those fed on probiotics. Interactions between those structural changes and growth performance are discussed