Cruise Experience Spotlight: eDNA Sampling on the Fall 2025 CalCOFI Cruise

My name is Ella Crotty, a recent college graduate and lab volunteer at Scripps Institution of Oceanography, and the Fall 2025 CalCOFI cruise was my first multi-day research cruise! I was aboard as a volunteer on the MOSAIC (MURI Ocean Sampling Across an Integrated Continuum) project, a project that uses environmental DNA (eDNA) to detect marine mammals along the route of the CalCOFI cruise. As marine mammals move through the ocean, they shed DNA in forms such as shed skin and feces, and by filtering seawater and extracting DNA, we can detect them! I worked the night shift, midnight to noon, filtering water from the ship’s water collection system and the CTD (an instrument that we lower into the ocean to take water samples and measure Conductivity, Temperature, and Depth). I also occasionally sampled for the NASA PACE project, which required filtering water for particulates and phytoplankton pigments to calibrate the PACE satellite’s readings.

During my first shift, the thing that surprised me the most was the fact that some seabirds try to fly into the ship because of our lights, and we had to keep them safe until we could release them at dawn! Learning to do familiar lab techniques aboard a moving vessel was difficult sometimes, but I got the hang of it eventually. I had been warned that ships can be noisy, but one thing I wasn’t expecting was that certain large waves hitting the metal hull can make sudden loud bangs. I learned some new card games, met lots of new people, and overall had a great time at sea. The coolest part of the cruise was seeing humpback whales swim close to the ship while we had stopped at a station! We are still waiting on our DNA extraction and sequencing results, but hopefully we detected those whales and many others that we didn’t see up close.