Supporting Acoustic Research to Improve Monitoring and Conservation

Below 200m the ocean is completely dark. Many animals have evolved to thrive in these conditions through the use of other senses besides sight, especially sound. Sound travels differently in water than in air– around 4x faster, allowing some animal vocalizations to travel throughout ocean basins. 

With all these organisms going about their daily lives, the ocean is not a quiet place.

Physical processes, biological noise from snapping shrimp, marine mammals like whales and dolphins, and even fish contribute to the cacophony of natural sounds.

Credit: Anastasia Kunz; Sound clip of an “ocean soundscape” from the Channel Islands National Marine Sanctuary in California in April 2020, collected under the SanctSound program.

We stand to learn a lot by listening in on the ocean. We can understand whole reproductive cycles of fish without ever seeing a single individual, get a snapshot of localized biodiversity by detecting specific species, and discern behaviors of organisms just by their calls. 

Importantly, we can better paint a picture of how humans are impacting the ocean soundscape.

Increasingly, we find that anthropogenic (human-created) noise is encroaching on the symphony of natural sounds. Construction and pile driving, energy development, explosions, and vessels large and small have become commonplace among the natural sounds of the ocean.

Credit: Robert Schwemmer (NOAA Channel Islands). Pictured: Lindsey Peavey Reeves (National Marine Sanctuary Foundation) with a newly deployed hydrophone in the proposed Chumash Heritage National Marine Sanctuary.

California Marine Sanctuary Foundation is part of a larger, nationwide collaboration to better understand and manage ocean noise led by NOAA’s Office of National Marine Sanctuaries (ONMS) through the ONMS Sound project, formerly SanctSound. This program utilizes passive acoustic monitoring (PAM) to create a holistic picture of both natural and anthropogenic sound throughout NOAA’s National Marine Sanctuaries. Researchers do this by using a network of hydrophones, or underwater microphones, which are anchored to the ocean floor to record ocean sound 24/7. 

Sound can benefit conservation in a number of ways. CMSF’s Marine Resource Protection Program utilizes sound monitoring to complement their whale conservation initiatives. Whales face many threats, chief among them fatal collisions with container ships in their migration and feeding habitats. CMSF supports the Vessel Speed Reduction (VSR) program and the Protecting Blue Whales Blue Skies (BWBS) Program that works to slow large vessels over 300 gross tons to mitigate ships strike risk. 

Slowing these vessels down has compounding benefits beyond reducing the risk of fatal collisions. When these vessels reduce their speed to 10 knots or less, air pollution and the noise emitted by the propeller cavitation, or the formation and dissolution of bubbles, is also reduced. Ship noise occurs at low frequencies, similar in range to what most baleen whales use to communicate, which can result in call masking and can have impacts including behavior change, physical damage to listening structures, and in some severe cases, stranding. When ships slow down, as they are encouraged to do through the VSR and BWBS programs, we are able to track the decrease in ocean noise on nearby hydrophones. 

Credit: Anastasia Kunz; Sound clip of vessel noise and a humpback from Olympic Coast National Marine Sanctuary in September 2019, collected under the SanctSound program.

As California pursues offshore wind energy, the need to better understand ocean sound through PAM will continue to increase. Off of Morro Bay, California in the proposed Chumash Heritage National Marine Sanctuary, CMSF researchers and partners have already begun documenting baseline sound levels so we can better understand the impact that wind energy construction and use will have on the ocean soundscape, and begin to tease out the implications for marine organisms. 

Credit: Cory Hom-Weaver, Pictured: Anastasia Kunz (CMSF) (left), Lindsey Peavey Reeves (NMSF) (right) in the proposed Chumash Heritage National Marine Sanctuary ready to deploy a hydrophone and recorder.

Much of the underwater world remains a mystery, but perceiving the ocean through the primary sensory modality of many of these organisms can help us understand the challenges to their survival, and hopefully, allow us to create positive change to help them thrive in the future. 

Want to learn more? Check out other stories on the acoustics work we and our partners are doing. 

• https://www.montereybayaquarium.org/stories/policy-at-sea

• https://www.fisheries.noaa.gov/science-blog/sound-bytes-what-we-can-learn-how-indigenous-peoples-listen