● One of the sensors in the GEN-GOB network, funded by Ibiza & Formentera Preservation, recorded 39 days in which temperatures exceeded 28ºC at depths of 11.5 meters during 2025
● At ground level, 45 days were recorded above this critical threshold, the second highest figure since monitoring began in 2023
Ibiza, July 30, 2026 – The Ibiza & Formentera Preservation Sustainability Observatory has analyzed data collected during 2025 by the network of temperature sensors installed by GEN-GOB in Talamanca Bay. The data shows that ocean warming is now reaching the deep Posidonia oceanica seagrass meadows. The sensor located at a depth of 11.5 meters recorded 39 days with maximum daily temperatures exceeding 28°C, the threshold at which mortality of this marine plant increases. At the surface, the sensor installed at four meters recorded 45 days above this limit that same year, indicating that high temperatures are also reaching the deeper Posidonia meadows and not just the surface layers of the sea.
The data shows that, after the decrease recorded in 2024, sea temperatures in 2025 reached values very similar to those of 2023. At the sensor located four meters deep, daily maximum temperatures exceeded 28°C for 46 days in 2023, decreased to 24 days in 2024, and increased again to 45 days in 2025. At the sensor located 11.5 meters deep, the trend was even more pronounced: after recording 32 days above the threshold in 2023 and 9 days in 2024, it reached 39 days in 2025, more than four times the figure recorded the previous year.
Comparing different depths allows us to understand how the temperature evolves in the water column and how far summer warming episodes penetrate. 28°C is used as a reference threshold because, according to a study by Núria Marbà and Carlos Duarte published in the journal Nature Climate Change, mortality increases above this temperature for Posidonia oceanica, a marine plant essential for Mediterranean biodiversity and coastal conservation.
“Sea temperatures are reaching levels that were exceptional years ago and are now becoming a recurring phenomenon,” warns Elisa Langley, coordinator of the Ibiza & Formentera Preservation Sustainability Observatory. She also explains that “monitoring sea temperatures in Posidonia seagrass meadows allows us to observe in greater detail how the temperature changes on the nearby coast and within the habitat itself. Concern about how these increases affect the meadows has led to an increase in the number of temperature monitoring stations, as the health of the habitat is compromised.”
Currently, GEN-GOB maintains a network of seven temperature sensors distributed across six Posidonia seagrass meadows in Ibiza: two in Talamanca Bay and one each in Cala Vedella, Porroig, s’Xanga, Cala Llentrisca, and Cala d’Hort. Most of this network is maintained thanks to funding from Ibiza & Formentera Preservation, with the collaboration of the women’s clothing brand Hoss Intropia, while the Cala Vedella sensor is supported by the local beach concessionaires.
The heat reaches deeper waters
In addition to the increasing number of days above the critical threshold, both stations also show an increasingly similar trend. In 2023, the sensor located at 4 meters recorded 46 days with temperatures above 28°C, while the one at 11.5 meters recorded 32, a difference of 14 days. In 2025, that difference narrowed to just six days, with 45 and 39 days, respectively. According to the analysis carried out by the Observatory, with financial support from the Consell Insular d’Eivissa (Island Council of Ibiza), the warming is penetrating to greater depths, and the thermocline, the layer separating warm and cold waters, is shifting to deeper layers during the summer.
The Sustainability Observatory also highlights the earlier onset of last year’s major warming event. While in 2023 the maximum sea temperature was recorded on August 24th and in 2024 on August 13th, in 2025 the annual peak arrived on July 6th, more than a month earlier than the previous year. On that day, the sensor located at four meters recorded 29.48°C and the one installed at 11.5 meters recorded 29.54°C, the highest temperatures of the entire year.
The GEN-GOB group points out that this trend is a direct result of advancing climate change. “The projections are very worrying: last year we already exceeded the 1.5°C threshold, and the trend is worsening,” warns Xisco Sobrado, coordinator of the Marine Area of the environmental group, who reminds us that the Paris Agreement calls for limiting global warming to 1.5°C above pre-industrial levels through a drastic reduction in emissions. The group warns that the situation could worsen in 2026 and 2027 due to the influence of a strong El Niño event, with abnormally high sea temperatures and a greater risk of heat waves, droughts, fires, and other extreme weather events. To protect the Posidonia oceanica seagrass meadows and the activities that depend on them, GEN-GOB is calling for fundamental measures such as “implementing policies to reduce tourism.”
The Ibiza Sustainability Observatory also points out that, while it may not be possible to directly address rising sea temperatures, other impacts on Posidonia seagrass can be mitigated. “We can’t cool the sea, but we can protect Posidonia. We must take action against poor navigation practices, uncontrolled anchoring, spills, and coastal pollution, while also mitigating the impact of outfalls and brine discharges. This plant is the foundation of our coastal and marine ecosystems and an essential part of Ibiza’s landscape. Protecting it and reducing our carbon footprint also increases our resilience to climate change,” concludes Langley.
