Embryonic exposure to irgarol impacts development and larval and juvenile swimming in zebrafish ( <i>Danio rerio</i> )

The primary method for mitigating the growth of biofouling organisms on submerged surfaces is through the use of broad-spectrum biocides, such as irgarol, which can impact non-target species. We assessed the developmental and bioenergetic impacts of early-life-stage irgarol exposure on zebrafish (<i>Danio rerio</i>), including impacts on survival, hatching, developmental abnormalities, heart rate, mitochondrial function, and behaviour. We exposed zebrafish embryos 6-144 h post-fertilisation (hpf) to irgarol at concentrations currently detected in the environment and at pharmacological concentrations. At environmental concentrations, irgarol did not impact survival, hatching, morphological development or mitochondrial function. However, significant changes to heart rate and swimming behaviour occurred. Larvae were significantly hyperactive following exposure, then hypoactive after being grown in clean conditions for weeks. Our study showed that while irgarol is not acutely toxic at environmental levels, it has sublethal impacts on cardiac and neurological functions that could result in decreased fish fitness. The risks that irgarol presents to food security, environmental health, and human health warrant study.