Award: OCE-1536782

For coral reefs, factors influencing larval supply can have major impacts on community structure and population replenishment of the fish and coral that inhabit those reefs. Historically, research focused on fortuitous oceanographic conditions that may passively conduct larvae over large, open-water distances to suitable habitat. However, substantial new evidence indicates that larval settlement is also an active response that involves orientation toward certain habitat-associated cues. Addressing the relevance of such cues, especially in relation to levels of habitat degradation, is critical to fully understanding marine population and community dynamics, the efficacy of marine protected areas, factors governing biodiversity, and the replenishment of communities under stress. The overarching goal of this study was to understand the extent to which larval orientation and settlement is influenced by the biophysical soundscape of coral reefs and how, in turn, these soundscapes are determined by reef communities and biodiversity. A soundscape includes all sounds in an area including many fish and invertebrates that produce sound as part of natural behaviors. A densely populated place such as coral reefs can be rich with biological sounds. Over the course of this study we were able to listen to, and monitor, 10 reefs in the US Virgin Islands (Figure 1). Our important results include: (1) Sound can mediate and induce the settlement of coral larvae. The settlement of larval corals belonging to the genus Porites was highest in an acoustic environment with abundant, low-pitch fish sounds, typical of a healthy reef. This enhancement of coral settlement by healthy reefs soundscapes suggests a positive feedback where reefs soundscape properties high coral and fish abundance may facilitate larval recruitment back to that reef (Figure 2). (2) Sound also can mediate reef fish settlement, but taxa and biophysical conditions play a large role in these processes. Together, this suggests that reef sounds may be a way to attract and encourage larval settlement on reefs, perhaps helping to restore our reefs under stress. (3) We describe how animal sounds in the reef soundscape can be used to infer habitat health, specifically coral cover and fish community diversity. However, soundscapes vary substantially, as fish and invertebrate call patterns change on daily and lunar timeframes. Thus, using soundscapes to infer biodiversity should be done carefully, taking such variability into account. Yet there is substantial promise in marine acoustic diversity assessment methods and listening to reefs is a vital way to monitor habitats. This project provided diverse broader impacts to society as well as specific educational groups. Much of the rationale for studying reef biodiversity and ecology has been driven by the recent degradation of coral reef ecosystems, which have been impacted by ocean warming and other anthropogenic impacts such as eutrophication, overfishing and ocean acidification. Settlement studies of fish species can provide information for fisheries management and can form the basis for overfishing indicators. Investigations of coral settlement may address climatological impacts and system changes. Together, these data can provide an understanding of the efficacy of marine protected areas, levels of reef biodiversity, and the influence that larval settlement has on the resilience of these ecosystems after being subjected to perturbations. Thus, coral reefs and their associated settlement patterns represent a critically important system and process ideal for evaluating the ecological role of biophysical soundscapes. The results of this research will be valuable to scientists, managers and policy makers as they seek to understand and manage resources and marine protected areas. Further, this research lays the foundation for investigating how anthropogenic noise pollution may impact a central component of ecosystem function. Additionally, this research has been incorporated into educational programs that span Pre-K to grade school to college and has trained 35 students (undergraduate, graduate and post-doctoral level) in this relatively new area of soundscape study. Last Modified: 10/27/2020 Submitted by: T. Aran Mooney