Copper bioavailability and impact on bacterial growth in flow-through rainbow trout aquaculture systems

Copper is an important additive in the aquaculture industry for control of algal growth and ecto-parasites. However, copper may impact microbial communities depending on its biological availability and hence negatively affect microbial degradation of organic matter or other microbial ecosystem services. Here we applied a whole-cell bacterial biosensor to determine copper bioavailability (proportion of bioavailable vs. total copper) in water from three rainbow trout aquaculture facilities. Copper bioavailability varied between 24 and 37% and the differences were compatible with differences in carbonate alkalinity, concentration of dissolved organic matter and amounts of suspended matter in the water. Subsequently, we determined the effect of copper on bacterial growth activity at concentrations realistic for aquacultures. Although a field exposure to ca. 0.1 μM bioavailable Cu had no effect, laboratory exposure to comparable concentrations reduced the bacterial growth activity. Hence, common copper amendment procedures may lead to concentrations close to the threshold that impacts bacterial activity.

► Copper is an additive used in fish ponds but may adversely impact microbial activity.
► Bioavailable Cu was successfully determined in pond water with a bacterial biosensor.
► The biosensor indicated that Cu application did not influence the bacterial growth.
► Accumulation of Cu in pond sediment might impose an environmental risk.