Ocean seismic survey impacts on the movement and distribution of nearshore temperate marine species

Oregon State University, Corvallis OR

Investigators

Abstract

A National Science Foundation- funded seismic survey occurred in summer 2021 along the Cascadia Subduction Zone off Oregon, Washington, and British Columbia, employing the use of airguns over a period of about 2 months. This activity presented a novel opportunity to investigate the potential responses of important nearshore fish and invertebrate species to this soundscape-altering event. As the oceans become ever noisier from both chronic and discrete sounds, there is a need to understand how these events may alter the behavior of animals that are managed and conserved. Project scientists collected animal behavior information and acoustic data near Redfish Rocks Marine Reserve, Port Orford, Oregon between May and September 2021. Three-dimensional animal behavior data were measured using acoustic tracking devices that were implanted in several fish species as well as attached to Dungeness crab. Ocean sounds were measured using passive acoustic monitoring equipment that was deployed on the seafloor near the tagged animals. The information obtained over the project’s 5-month data collection period will provide new information on how increased man-made noises can affect animals in nearshore marine reserves. More so, it supports broad interests in understanding marine soundscapes, and will provide directly relevant information to marine resources and fisheries management, including for commercial fisheries and essential fish habitat. Project results will be important to future seismic surveys and can be extended to understanding concerns about upcoming offshore construction activities such as for offshore wind development. This work will continue to seek community engagement with educators, regulators, and local fishermen from Port Orford, the latter of whom assisted in the tracking of animals as well as deployment and retrieval of the monitoring equipment. Project findings will be shared at public events to engage communities along the Oregon coast, including Marine Science Day at Hatfield Marine Science Center and the Port Orford Marine Laboratory Open House. This project will also provide graduate student research training in STEM (science, technology, engineering, and mathematics) fields, including soundscape and animal movement analyses. Virtually all studies of airgun survey sound impacts in both open ocean and shallow-water environments focus on the pressure component of sound propagation; few have focused on the particle motion that accompanies the transmission of the sound to which many animals have sensitivity. Additionally, current regulatory guidelines to assess the effects of sound on aquatic life largely describe hearing thresholds in terms of sound pressure. It is therefore important to conduct studies considering both sound pressure level and particle motion. This project simultaneously measured the particle motion and pressure components of the seismic survey activity using the NoiseSpotter(R), an acoustic particle motion sensor array, while measuring behavioral responses of reef associated fishes and crab to seismic surveys using acoustic telemetry technology. These measurements will support testing of the project hypothesis that responses to high-intensity acoustic pulses depend on the habit (demersal or pelagic) and morphology/physiology (e.g., absence [lingcod, crab] or presence and type of swim bladder) of marine species. Accelerometer tag data will be used to assess rate of change in position and direction associated with individual pulse events from the seismic survey, including, but not limited to synchrony-in-response across tagged individuals within and across species, comparison of activity budget components, habituation, and geographic activity centers. Animal behavior will be evaluated in the context of NoiseSpotter(R) acoustic pressure and particle motion data, which will be analyzed for sound source, sound levels, cumulative exposure levels, spectral probability densities, and ecosystem-wide metrics (e.g., acoustic complexity index, acoustic richness index). Because the seismic survey made triplicate passes within range of Oregon’s Redfish Rocks Marine Reserve, the project team has a statistically robust opportunity to assess the soundscape and animal behavior before, multiple times during, and after seismic survey activity. The novel results of this project will advance understanding of the energetics of acoustic propagation in nearshore environments and the responses of animals to loud, impulsive noises. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.