School of Marine and Tropical Biology, James Cook University, Townsville, Australia.
PLoS One. 2011;6(7):e22736. doi: 10.1371/journal.pone.0022736. Epub 2011 Jul 28.
Changes in olfactory-mediated behaviour caused by elevated CO(2) levels in the ocean could affect recruitment to reef fish populations because larval fish become more vulnerable to predation. However, it is currently unclear how elevated CO(2) will impact the other key part of the predator-prey interaction--the predators. We investigated the effects of elevated CO(2) and reduced pH on olfactory preferences, activity levels and feeding behaviour of a common coral reef meso-predator, the brown dottyback (Pseudochromis fuscus). Predators were exposed to either current-day CO(2) levels or one of two elevated CO(2) levels (∼600 µatm or ∼950 µatm) that may occur by 2100 according to climate change predictions. Exposure to elevated CO(2) and reduced pH caused a shift from preference to avoidance of the smell of injured prey, with CO(2) treated predators spending approximately 20% less time in a water stream containing prey odour compared with controls. Furthermore, activity levels of fish was higher in the high CO(2) treatment and feeding activity was lower for fish in the mid CO(2) treatment; indicating that future conditions may potentially reduce the ability of the fish to respond rapidly to fluctuations in food availability. Elevated activity levels of predators in the high CO(2) treatment, however, may compensate for reduced olfactory ability, as greater movement facilitated visual detection of food. Our findings show that, at least for the species tested to date, both parties in the predator-prey relationship may be affected by ocean acidification. Although impairment of olfactory-mediated behaviour of predators might reduce the risk of predation for larval fishes, the magnitude of the observed effects of elevated CO(2) acidification appear to be more dramatic for prey compared to predators. Thus, it is unlikely that the altered behaviour of predators is sufficient to fully compensate for the effects of ocean acidification on prey mortality.
海洋中二氧化碳水平升高导致的嗅觉介导行为变化可能会影响到珊瑚鱼种群的补充，因为幼鱼更容易受到捕食。然而，目前还不清楚升高的二氧化碳将如何影响捕食者-猎物相互作用的另一个关键部分——捕食者。我们研究了升高的二氧化碳和降低的 pH 值对一种常见的珊瑚礁中型捕食者——褐色点鲷（Pseudochromis fuscus）的嗅觉偏好、活动水平和摄食行为的影响。捕食者暴露于当前的二氧化碳水平或两种升高的二氧化碳水平（约 600µatm 或约 950µatm）之一，根据气候变化预测，这两种水平可能会在 2100 年出现。暴露于升高的二氧化碳和降低的 pH 值导致捕食者从偏好受伤猎物的气味转变为回避，与对照相比，暴露于升高的二氧化碳的捕食者在含有猎物气味的水流中停留的时间减少了约 20%。此外，高二氧化碳处理组的鱼类活动水平较高，中二氧化碳处理组的鱼类摄食活动较低；这表明未来的条件可能会降低鱼类对食物供应波动快速做出反应的能力。然而，高二氧化碳处理组捕食者的活动水平升高可能会弥补嗅觉能力的下降，因为更大的运动有助于视觉发现食物。我们的研究结果表明，至少对于迄今为止测试的物种而言，捕食者-猎物关系的双方都可能受到海洋酸化的影响。虽然捕食者嗅觉介导行为的受损可能会降低幼鱼被捕食的风险，但与捕食者相比，升高的二氧化碳酸化对猎物的影响似乎更为显著。因此，捕食者行为的改变不太可能足以完全补偿海洋酸化对猎物死亡率的影响。
