Abstract:
Anthropogenic noise has changed the underwater soundscape of many coastal locations worldwide. This has been linked to several negative effects on marine taxa, from behavioural changes and masking of biologically important sounds, to major barotrauma injuries. Respirometry is increasingly being employed to measure oxygen uptake (MO2) as a proxy for metabolic rates and ultimately as a stress response to anthropogenic noise. This study used automated intermittent-flow respirometry to measure the stress responses of juvenile snapper (Pagrus auratus) exposed to ship and pile driving sounds. The experimental design used two controls, a "no sound" treatment group and "before" treatment within individual measurement. MO2 data alone suggest there is no effect of either anthropogenic sounds on routine metabolic rate (RMR). Taking activity into account resulted in the RMR of pile driving exposed fish to increase, however there was no effect observed on fish exposed to ship sound. These results are different to other studies (Simpson et al., 2015; Simpson et al., 2016; Harding et al., 2018), where it was shown that motorboat noise increases the rate of oxygen consumption. There are a number of potential reasons for this but experimental technique is possibly key. Here, intermittent-flow respirometry gave long recovery times and took many measures of MO2 before and during sound exposure. In contrast, the other studies used short recovery times and a simple 'fish in a bottle' type approach that is limited in the number of oxygen consumption measures and is potentially fraught with fish activity artefacts. While species-specific differences cannot be excluded at present, this work highlights a need for robust, standardised methods to assess the effects of anthropogenic noise on metabolism.
