Valentín asks for the rope that moors the boat to land to be released and puts the engine in reverse. Everything is ready. As if in slow motion, the speedboat breaks free from the coastline and gently enters the intense flow that carries the fresh water to the Atlantic. A few metres away, after passing the train bridge, Valentín drops the anchor and turns off the outboard. The GPS indicates that they are right next to one of the checkpoints. Divers adjust the equipment. They put on their fins, bring the regulator to their mouths and fall back off the side. It's not very deep. The bottom is sandy, and through the density of the bubbles they release, it's possible to see how they drive down the PVC tube that will collect the sediment sample.
After repeating the operation in a dozen places, the boat returns to the dock. Guillermo Díaz, one of the people responsible for the project on behalf of the USC, puts the samples in his car to later take them about 20 kilometres away, to the Mariña Bioloxía Station in A Graña, where every day he examines the quality of these ecosystems that have such a fragile balance. There, all the information from the sample will be extracted to begin to compose a puzzle that sheds some light on the notable drop in productivity of shellfish banks.
Between the microscopes and laboratory tables, another important factor emerges to this problem: climate change. The increase in global temperature may also be behind this phenomenon. In about a year's time, when USC technicians finish their work, we will have the answer.