Listening to the Living Gulf

The Gulf of Mexico has long been a crossroads of biodiversity and culture, a region shaped by mighty rivers and powerful hurricanes, oil platforms and vibrant coral reefs. 

Yet, beneath its surface, an unseen world pulses with sound: clicks, whistles, ship rumbles, and the songs of whales. 

In summer 2025, an international team of scientists embarked on an ambitious expedition to chronicle and understand this soundscape, armed with state-of-the-art acoustic technology and a spirit of collaboration that bridged nations and disciplines.

At its core, the Long-term Investigations into Soundscapes, Trends, Ecosystems, and Noise in the Gulf of Mexico (LISTEN) Project expedition aims to unravel the acoustic ecology of the Gulf by deploying and recovering High-Frequency Acoustic Recording Packages (HARPs) across a swath of habitats and jurisdictions. These long-term, stationary devices serve as digital ears on the seafloor, capturing sounds from physical ocean processes, marine life, and human activities over periods spanning up to a year. The data they return fuel predictive models of whale distribution and abundance, reveal the spatial and temporal patterns of ship noise, and offer critical information for the management of sensitive and endangered marine mammals, including the Rice’s whale.

The 2025 cruise unfolded over two legs and more than a month at sea, launched from Cocodrie, Louisiana, aboard Louisiana Universities Marine Consortium’s R/V Pelican and coordinated by teams from Scripps Institution of Oceanography at UC San Diego, Universidad Veracruzana (UV), the National Autonomous University of Mexico (UNAM), and NOAA's Southeast Fisheries Science Center and collaborating labs. The cruise served as the central effort uniting five major research initiatives, each focused on advancing knowledge of the Gulf of Mexico’s dynamic ecosystem. 

At the forefront were the Deepwater Horizon Natural Resource Damage Assessment funded LISTEN Project, which expands long-term acoustic datasets for shipping and ocean noise research, and RESTORE Science Program projects, dedicated to acoustic-based monitoring of marine mammal abundance and distribution over seasonal to decadal timescales. Together, these efforts generate critical population and habitat data for Gulf marine mammal conservation and noise management 

Special emphasis was placed on a pilot study of a species known as Rice’s whale. It targeted shallow continental slope regions in hopes of capturing rare acoustic signatures of this whale and better understanding of its distribution in the Gulf. 

Finally, the Deep-Sea Benefits project pioneered integrated studies of deep seafloor and open ocean community interactions, employing both passive and active acoustic instruments such as Acoustic Doppler Current Profilers (ADCPs) to investigate ocean currents and prey movement patterns, thus illuminating the vertical connectivity within the marine ecosystem.

A total of 24 HARPs were recovered, including eight in the U.S. Exclusive Economic Zone (EEZ), 15 in Mexico’s EEZ, and one in international waters, logging data at sampling rates of 200 kHz and spanning effective frequency bands from 10 Hz to 100 kHz. This range is capable of catching everything from the low moans of baleen whales to the crackles of snapping shrimp. In continuation of the research, 18 HARPs were deployed in the U.S. EEZ, and four more in the Mexican EEZ on this cruise, maintaining a spatially balanced monitoring array.

The scientific staff on board divided into two teams: one operating within the U.S. EEZ and the other within the Mexican EEZ. The first scientific team included the co-chief scientist of the cruise, oceanographer Kaitlin Frasier, and project scientist Sean Wiggins; marine technicians Bruce Thayre and Kieran Lenssen, postdoctoral researcher Vanessa ZoBell, and graduate student Anabell Espinosa, all affiliated with Scripps Oceanography. 

The team also included Laura Chesed Hernández Hernández, a graduate student from UV, during both legs of the cruise. The scientific team operating in Mexican waters was led by co-chief scientist Itzel G. Perez Carballo and included Scripps technicians Jonathan Stewart and Isabelle Curran, and Scripps graduate students Katrina Johnson and Morgane Dackiw. The team also included a Mexican cruise observer, Catalina I. Díaz Barrera, a scientist with the Instituto de Ciencias del Mar y Limnología from the UNAM.

As of July 2025, all acoustic and auxiliary datasets had been returned for analysis at Scripps and collaborating labs. These data capture between 219 and 317 days of sound per instrument, promising an unprecedented continuous record of Gulf soundscapes across shelf, slope, and deep-sea environments. Processing is underway to identify marine mammal detections, quantify anthropogenic noise with special attention to shipping routes, and refine population models for key species.

The cruise’s innovative approach, combining long-term ecological monitoring, cutting-edge instrumentation, and international collaboration, sets new standards for holistic marine ecosystem observation. Long after R/V Pelican returned to Louisiana, the sounds it recorded will continue to inform and inspire science, management, and stewardship of the Gulf’s living ocean.

Katrina Johnson is a fourth-year PhD candidate in the Machine Listening Lab at Scripps. Her research focuses on quantifying human noise, particularly from commercial shipping, in underwater soundscapes and investigating its impacts on marine mammals that depend on sound for communication, navigation, foraging, and other essential behaviors.