On May 8–9, 2025, the GAME-CSIC team returned to Portlligat Bay in Pilot Area 1 for a focused scientific expedition aimed at deepening blue carbon understanding through direct sediment sampling. This time, the mission was fully led by GAME-CSIC, with the dive vessel provided and operated by the company MésdeMar.

The expedition targeted the central mid-depth zone (5–10 m) of the Posidonia oceanica seagrass meadow, a key habitat for Mediterranean blue carbon storage. A total of 8 new sediment cores were collected during a series of four scientific dives, bringing the project’s total to 32 cores to date. Each core, extracted with a 1.5-meter PVC tube, captures the historical and ecological record of the benthic environment—critical for both characterizing sediment composition and validating non-destructive carbon estimation methods.

In addition to core collection, this expedition had a strong training component. Three master’s level students were integrated into the field team. Under the supervision of senior divers, the students participated in each core collection dive, progressively building skills in underwater sampling, field protocols, and safety. By the end of the expedition, each student had achieved full proficiency in scientific core collection—a testament to the hands-on mentorship approach of GAME-CSIC.

The sediment cores were pre-processed on site and transported to CEAB-CSIC laboratories for further analysis.

These efforts not only contribute essential ground truth data to the EFFECTIVE Project but also foster the next generation of marine scientists in blue carbon research.