Expedition log by Graduate Fellow Javiera Fuentes Guíñez and Science Communication Fellow Marike Pinsonneault

After several days of strong winds and heavy swell, the ocean finally settled enough on Sunday and Monday for the MiniROV team to return to our original dive site at Sur Ridge. We deployed the vehicle at a striking rock formation on the northern side of Sur Ridge, approximately 1,230 meters (4,035 feet) below the surface. 

MBARI has conducted extensive research at Sur Ridge, and we often revisit the same sites to understand how seafloor communities change over time. This particular rock formation was first encountered in 2017. Approximately 25 meters (82 feet) long, almost 10 meters (33 feet) tall, and covered in large corals, its size and scale impressed MiniROV pilot Frank Flores, who nicknamed it “Big Dinosaur Rock.” 

Sunday kicked off with a stunning sunrise—a good omen for the day ahead. The MiniROV successfully reached the seafloor, where the team began mapping surveys around the rock, exploring the site, and collecting forward-looking mapping data.

As the dive progressed, currents along the ridge began to strengthen. The team adapted the plan, capturing imagery of the coral communities and collecting coral samples for Steve and rock samples for Olívia. The MiniROV and pilots pushed through the challenging conditions, testing the vehicle’s limits, but increasing currents and fiber connection issues ultimately led us to recover the vehicle early. Back on deck, work continued immediately: Scientists processed the samples while engineers prepared the vehicle for the next dive, resolving the connection issue and getting the MiniROV ready to head back into the deep. 

Monday brought strong currents once again at the seafloor, keeping the pilots busy as they maneuvered around Sur Ridge. Despite the conditions, we completed one full survey, 30 meters by 30 meters (about 100 feet by 100 feet) in steep, rugged terrain, and mapped nearly two-thirds of Big Dinosaur Rock. Each pass across the seafloor added another piece to the puzzle, showcasing the capability of the MiniROV and the determination of the expedition team to keep exploring the deep.

Overall, the past few days have offered a valuable opportunity to better understand how the MiniROV performs in demanding scenarios. We’re pleased to see all of the CoMPAS Lab’s innovative tools and team working together so effectively. 

Tomorrow we head back to Moss Landing, with one final stop near MBARI at Portuguese Ledge to gather some final data along the way. Back on shore, a new phase begins—turning this data into insight, and laying the groundwork for our next return to Sur Ridge.