Effects of elevated CO₂on predator avoidance behaviour by reef fishes is not altered by experimental test water

Abstract

Pioneering studies into the effects of elevated CO2 on the behaviour of reef fishes often tested high-CO2 reared fish using control water in the test arena. While subsequent studies using rearing treatment water (control or high CO2) in the test arena have confirmed the effects of high CO2 on a range of reef fish behaviours, a further investigation into the use of different test water in the experimental arena is warranted. Here, we used a fully factorial design to test the effect of rearing treatment water (control or high CO2) and experimental test water (control or high CO2) on antipredator responses of larval reef fishes. We tested antipredator behaviour in larval clownfish Amphiprion percula and ambon damselfish Pomacentrus amboinensis, two species that have been used in previous high CO2 experiments. Specifically, we tested if: (1) using control or high CO2 water in a two channel flume influenced the response of larval clownfish to predator odour; and (2) using control or high CO2 water in the test arena influenced the escape response of larval damselfish to a startle stimulus. Finally, (3) because the effects of high CO2 on fish behaviour appear to be caused by altered function of the GABA-A neurotransmitter we tested if antipredator behaviours were restored in clownfish treated with a GABA antagonist (gabazine) in high CO2 water. Larval clownfish reared from hatching in control water (496 µatm) strongly avoided predator cue whereas larval clownfish reared from hatching in high CO2 (1,022 µatm) were attracted to the predator cue, as has been reported in previous studies. There was no effect on fish responses of using either control or high CO2 water in the flume. Larval damselfish reared for four days in high CO2 (1,051 µatm) exhibited a slower response to a startle stimulus and slower escape speed compared with fish reared in control conditions (464 µatm). There was no effect of test water on escape responses. Treatment of high-CO2 reared clownfish with 4 mg l−1 gabazine in high CO2 seawater restored the normal response to predator odour, as has been previously reported with fish tested in control water. Our results show that using control water in the experimental trials did not influence the results of previous studies on antipredator behaviour of reef fishes and also supports the results of novel experiments conducted in natural reef habitat at ambient CO2 levels.

Acid–base physiology, neurobiology and behaviour in relation to CO2-induced ocean acidification

“…Gabazine also significantly alters the behaviour of control rockfish and pink salmon (Ou et al, 2015). However, no other study found any effect of gabazine on behaviour (Chivers et al, 2014;Lai et al, 2015;Lopes et al, 2016;Munday et al, 2016;Nilsson et al, 2012;Watson et al, 2014) or visual processing (Chung et al, 2014) in control fish. This is an interesting point because gabazine should also affect normal inhibitory GABA regulation, inducing neuronal excitation; in fact, one of the features precluding the use of gabazine as a therapeutic agent in humans is the risk of convulsions resulting from inappropriate neuronal excitation (Enna and Bowery, 1997).…”

“…However, subsequent laboratory experiments on marine fish exposed to values of pH/CO 2 predicted for the end of this century and beyond revealed impacts on additional organisms and processes, such as embryonic and larval development (Frommel et al, 2012(Frommel et al, , 2016Rossi et al, 2015), otolith growth (Checkley et al, 2009;Munday et al, 2011), reproduction (Miller et al, 2013), metabolic rate Rummer et al, 2013;Enzor et al, 2013) and behaviour (Allan et al, 2013;Dixson et al, 2010;Domenici et al, 2012;Hamilton et al, 2013;Munday et al, 2009Munday et al, , 2010Munday et al, , 2016Rossi et al, 2015); however, it is worth noting that these effects are highly variable and depend on the species, experimental conditions, parameters analyzed and experimental techniques used. Most of these effects were proposed to be due to acid-base (A-B) regulatory processes, leading to altered ionic concentrations, energy expenditure and allocation; however, the specific molecular and cellular mechanisms remain largely unexplored.…”

Ocean warming has a greater effect than acidification on the early life history development and swimming performance of a large circumglobal pelagic fish

“…To minimise any change in temperature and pCO 2 in the arena water, the arena was drained and reset with fresh treatment water every 20 min. The rate of pCO 2 loss from the testing arena has been found to be negligible within this time frame (Munday, Welch et al, 2016). Trials were conducted between 08:00 and 16:00 hr over three consecutive days.…”

Impacts of Global Warming and Elevated CO2 on Sensory Behavior in Predator-Prey Interactions: A Review and Synthesis

“…However, longerterm exposure to warming allows escape responses to return to control levels, demonstrating that physiological plasticity is dependent on length of exposure. Damselfish acclimated to elevated CO 2 conditions are less responsive and they take longer to respond to a stimulus (i.e., a weight dropped on the surface of the water) while locomotor activities are maintained, suggesting a deficit in processing these mechanosensory cues (Munday et al, 2016). Likewise, the probability of a startle response from marine medaka to a mechanosensory stimulus is decreased in elevated CO 2 conditions due a deficit in processing (Wang et al, 2017).…”