ocean acidification undermines larval fish orientation via altered hearing and marine soundscape modification

The dispersal of larvae and their settlement to suitable habitat is fundamental to the replenishment of marine populations and the communities in which they live. Sound plays an important role in this process because for larvae of various species, it acts as an orientational cue towards suitable settlement habitat. Because marine sounds are largely of biological origin, they not only carry information about the location of potential habitat, but also information about the quality of habitat. While ocean acidification is known to affect a wide range of marine organisms and processes, its effect on marine soundscapes and its reception by navigating oceanic larvae remains unknown. Here, we show that ocean acidification causes a switch in role of present-day soundscapes from attractor to repellent in the auditory preferences in a temperate larval fish. Using natural CO2 vents as analogues of future ocean conditions, we further reveal that ocean acidification can impact marine soundscapes by profoundly diminishing their biological sound production. An altered soundscape poorer in biological cues indirectly penalizes oceanic larvae at settlement stage because both control and CO2-treated fish larvae showed lack of any response to such future soundscapes. These indirect and direct effects of ocean acidification put at risk the complex processes of larval dispersal and settlement.

幼虫的扩散及其在适宜栖息地的定居，是海洋种群及其生存群落补充的基础。声音在这一过程中扮演重要角色，因为对多种物种的幼虫而言，声音是其朝向适宜定居栖息地的定向线索。由于海洋声音大多源于生物，它们不仅携带潜在栖息地位置的信息，还包含栖息地质量的信息。尽管海洋酸化已知会影响广泛的海洋生物和过程，但其对海洋声景（soundscapes）的影响，以及导航中的海洋幼虫对声景的接收情况，仍不为人知。在此，我们揭示，海洋酸化会导致温带鱼类幼虫的听觉偏好发生转变——当前声景的角色从吸引因子变为排斥因子。利用天然CO₂喷口作为未来海洋条件的模拟物，我们进一步发现，海洋酸化可通过显著减少生物声音的产生，来影响海洋声景。生物线索匮乏的改变后声景，会间接对定居阶段的海洋幼虫造成不利影响，因为对照组和经CO₂处理的鱼类幼虫，均未对此类未来声景表现出任何反应。海洋酸化的这些间接和直接效应，将幼虫扩散与定居这一复杂过程置于风险之中。