Drum. Croaker. Snapping Shrimp. Names of these marine creatures evoke the vibrant soundscape of our oceans, from calls of organisms to sounds of human activity or even weather activity: the ocean is rich in sound. Passive Acoustic Monitoring (PAM) provides a unique window into this underwater world, offering critical insights for both scientific research and community-based conservation efforts.

Passive Acoustic Monitoring

PAM offers a cost-effective and efficient method for gathering data from ocean ecosystems. With the possibility of extended underwater recording periods, PAM equipment allows us to monitor the ecosystem without disturbing it. This is particularly notable at night when monitoring often involves artificial lighting. Furthermore, PAM has proven to be a valuable tool during harsh weather conditions that make fieldwork difficult or even impossible.

PAM technology continues to improve, from reduced size and weight, to longer battery life, and increased data storage capabilities. These advancements have led to the evolution of PAM devices from massive cabled arrays to compact recorders. These newer models are roughly the size of a GoPro camera and can cost as little as $100.

Such improvements enable researchers to collect substantial data even with limited resources. However, the richness of the data collected presents its own challenges, whether those challenges lie in the volume, quality, or interpretation of the information.

Dr. Heather Spence and Scuba Instructor Brando Gonzalez deploy the EAR (Ecological Acoustic Recorder) back in 2016. (Image credit: Ocean World of Sound)

Current analysis methods use specialized software for visual interpretation, listening/playback analysis, and computational techniques. While Artificial Intelligence (AI) shows promise in managing large datasets, human verification is still required.

More importantly, AI cannot replace the vital role that community engagement plays in conservation efforts. Humans must be active participants in the solution.

The Mesoamerican Reef (MAR), the world's second-largest reef barrier, remains under-researched despite its ecological significance. This reef system stretches from the tip of the Yucatan Peninsula through Belize, Guatemala, and Honduras. Almost half of the MAR is located along the state of Quintana Roo in Mexico.

The Ocean World of Sound initiative maintains long-term monitoring at three sites in the northern part of the MAR: Isla Contoy, Isla Mujeres, and Punta Nizuc. Equipment such as the Loggerhead SNAP records 30-second soundscapes every 15 minutes. This allows for nearly four months deployment periods. The data is stored on a micro SD card and collected every couple of months. Due to the simplicity and size of our systems, a two-person team on a small boat can complete deployments and retrievals in under an hour.

Andrea Luengas, a member of the field crew, retrieves a Loggerhead SNAP—a device considerably smaller than the previous EAR—to download data from the SD card and replace the batteries. (Image credit: Ocean World of Sound)

Almost half of the MAR is situated along the coast of Quintana Roo, which is divided into eight Marine Protected Areas (MPAs). Despite the ecological importance of these areas, the Mexican government has significantly reduced funding for Natural Protected Areas in recent years. Consequently, these MPAs are often understaffed and underfunded, yet are responsible for managing vast areas frequented by tourists. One example is the Parque Nacional Costa Occidental de Isla Mujeres, Punta Cancún y Punta Nizuc (PNCOIMPCPN). This park spans 3,348.7 square miles and accommodates over 6,000 tourists daily. Despite its size and visitor volume, it has only a few park rangers and a single boat for monitoring. In this context, Passive Acoustic Monitoring (PAM) serves as an invaluable tool, offering 24/7 monitoring capabilities that far surpass traditional visual surveys.

We have been monitoring PNCOIMPCPN for over a decade. Last year alone, our station at Punta Nizuc recorded 22,500 soundscapes, yielding more than 180 hours of data.

Through analysis of past recordings, we found that fish sounds were more frequent, more persistent, and more diverse at night—after the Marine Park closes at 5 pm—compared to during daytime hours. Such findings are critical for evaluating the efficacy of MPA policies, informing future planning, and contributing to successful conservation efforts.

Conservation Through Listening

Ocean World of Sound brings together scientists, resource managers, artists, architects, scuba divers, and other interested individuals. We have a central need to translate across disciplines and cultures. What started as an effort to collaboratively collect and interpret monitoring data has evolved into a series of interactive workshops. Some of these workshops were designed to be accessible from home, some were dynamic for children, and others focused on artists or tourism operators. However, all of them provide active listening skills while educating people on the importance of ocean soundscapes and the role they play in conservation.

Citizen Science allows us to tackle the data analysis needs while also strengthening the community. It taps into their skills and motivations, enhancing the outcome of our efforts and ensuring long-term success. This cultivates future leaders in conservation.

Spectrogram depicting a graph of underwater sound in Isla Contoy during equipment maintenance. The prominent vertical light bars indicate sounds from breathing with SCUBA. (Image credit: Ocean World of Sound)

Some of our workshops have led to the formation of Citizen Science groups. These groups help us address the challenges of data analysis while simultaneously strengthening the community. By building on existing capacity and interests we not only enhance the results of our projects but also secure their long-term success. Prior to starting the workshops, we conducted surveys to understand participants' motivations. Despite varying interests, the majority expressed a desire to learn about and connect with the marine ecosystem in a new way.

PAM is a great opportunity to monitor, create baseline and support research in the MAR, but also a channel to communicate with local communities. This effort brings them closer to knowledge that often remains within academic circles, giving them a deeper understanding of the space they inhabit. Consequently, it fosters a stronger sense of belonging and identity. In tourist-focused areas like Cancún and the Riviera Maya, recreational options for residents are often limited to restaurants and bars. These workshops, therefore, become essential spaces where community members can gather to discuss topics ranging from conservation to personal experiences. This new awareness, and hopefully, the connection with their reef, could greatly help conservation efforts, leading to more aware and resilient communities and ecosystems.

Find out more about World of Sound and their 30-Day Challenge: http://oceanworldofsound.com/challenge.html