The red alga Gelidium corneum forms stands meadows between depths of 3 and 12 meters. Its flexible frond allows it to live in places exposed to strong waves and its perennial vertical structure allows the prosperityof fish and invertebrates.

In recent years, there have been dramatic changes: the fronds of Geldidium corneum are thinner and discolored, becoming weaker in its branches and losing its density until it disappears completely. There are large areas without this alga. Instead, opportunistic algae such as Falkenbergia rufolanosa and Codium decorticatum now cover these open spaces. Moreover, in the first few meters of depth, the sea urchin Paracentrotus lividus is very abundant. Where have the rest of the species gone?

The Marine Benthos UPV/EHU research group has been studying these ecosystems for decades, recording the richness and abundance of the benthic flora and fauna. These organisms are indicators of the health of the ecosystem as they integrate the environmental conditions of their surroundings because they live fixed to the substrate. In addition, they are the base of the food chain. Countless species, including humans, depend on their health.

In 2010, a study was undertaken to understand the causes of the decline of Gelidium corneum. Its biochemistry, physiology and morphology in relation to light and temperature were studied. Transplants were also made of individuals between 3 and 5 meters to simulate changes in light intensity. The fronds exposed to greater radiation were the most stressed, showing lower productivity, greater yellowing and greater deterioration of the fronds. Light seems to be a determining factor in the health of Gelidium corneum. However, it would be necessary to extend this study to know the interaction with other environmental factors.

The decline of Gelidium corneum in Bizkaia is generalized. The red alga Gelidium corneum is vital for this ecosystem: the other species depend on it. If it disappears, so will the rest. "You only protect what you love and you only love what you know".

Idea and realization of the video: Alberto Santolaria and Mila Márquez (Nakusarbe Association)

Music: “Izarren Hautsa” (Xabier Lete/Mikel Laboa) and “Tango para Calude” (Elur Arrieta and Iraide Sarria)