Enriching Marine Soundscapes to Restore Australia's Lost Native Oyster Reefs
Date
2023
Authors
Williams, Brittany Ruth
Editors
Advisors
Connell, Sean
McAfee, Dominic
McAfee, Dominic
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Thesis
Citation
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Abstract
Australia’s native flat oyster reefs (Ostrea angasi) are considered functionally extinct, which has prompted ambitious restoration efforts that aim to revive this lost ecosystem and deliver ecological and economic returns on investment. However, many of these restorations are occurring in systems where oysters are recruitment limited and where larvae must compete with opportunistic species to establish a foothold on reefs. These challenges combine to limit the success of restorations. Consequently, there are calls for novel solutions that can overcome these limitations and boost the recovery process. Healthy, habitat-related soundscapes can provide navigational information for dispersing life-stages. However, these biological signals are being muted by the loss of habitat from which they originate and masked by rising anthropogenic noise. Subsequently, dispersing larvae that rely on acoustic cues for navigation are lost at sea, limiting the success of restorations that rely upon a steady supply of recruits. This thesis presents a novel solution for restoring lost oyster reefs: acoustic enrichment of healthy, habitat-related sounds using marine speakers. By reprovisioning the sounds of healthy reefs that have been lost, we might guide oyster larvae towards new restorations and kick-start the early successional stages of reef development which are critical to their success. In this thesis, I combine aquarium and field experiments to present new evidence for acoustic enrichment as a tool that can convey navigable information for dispersing oysters in search for adult habitat. I demonstrate that acoustic cues tend to be silenced as habitat is lost, creating negative feedbacks that hinder restoration efforts. In the aquarium and field, I demonstrate that oyster larvae have increased recruitment in the presence of playback of healthy, habitat-related reef sounds. I also discover that larval recruitment increases along a gradient of sound intensity associated with healthy reefs, with larvae being capable of horizontal swimming behaviour to navigate towards this sound. Furthermore, I reveal that anthropogenic noise might not only reduce the effectiveness of acoustic enrichment for restoration by masking biological signals, but that it might also disrupt recruitment patterns. Finally, I reveal the value of combining ecology and technology, using artificial kelp and acoustic enrichment, to boost oyster recruitment to the reef-building and binding components of oyster reefs. On coasts in which habitats and their biological soundscapes have been eliminated, combining ecology with acoustic technology could provide signals that attract larvae from passing currents and repair recruitment processes. However, as I demonstrate, there appears to be context dependency in the success of acoustic enrichment enhancing recruitment, having limited value in noisy locations. The idea that habitat degradation is global and the resulting ‘muted-scapes’ have dampened navigational cues for their replenishment, suggests that acoustic enrichment could be used to recreate gradients of sound needed to boost ecosystem restoration and recovery.
School/Discipline
School of Biological Sciences
Dissertation Note
Thesis (Ph.D.) -- University of Adelaide, School of Biological Sciences, 2023
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