Portonovo, July 13, 2026 – The sea off the coast of our region is witnessing a strange phenomenon: the water is incredibly cold, with temperatures that approach winter levels in depth. This was reported by the two fishermen of the Portonovo Cooperative, Massimo Mengarelli and Massimiliano Stecconi, who dive every day to collect the wild mussel from the rocks. “Yesterday – says Mengarelli – at 12 meters depth we recorded 14°. Every now and then we had to surface, where it was only 18°, to recover from the cold of the seabed.”
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Temperatures recorded 900 meters from the coast
These temperatures were recorded about 900 meters from the coast, in front of the Tower. Stecconi also found cold temperatures: “I was in front of the little church, a few hundred meters from the shore – he said – and the onboard instruments recorded 15° at 7/8 meters depth and 17.5 on the surface.
The App Welling phenomenon
Explaining what is happening is Roberto Danovaro, full professor of Ecology at the Department of Life and Environmental Sciences of the Polytechnic University of Marche: “In a static system, waters warm at the surface and heat progressively transmits to greater depths. In a dynamic system, like the sea, three-dimensional, other things happen. Imagine a wind blowing from the coast towards the open sea, moving surface water offshore and drawing deep water that rises to the surface replacing the displaced water. This phenomenon is called App Welling. A kind of conveyor belt and represents the most effective mechanism we hoped for to cool coastal waters, preventing the death of mussels.” Our mussels, in fact, cannot survive if the water reaches, as happened in recent years, temperatures above 30°.
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Water temperature decreased by 2°
“In the last week we noticed – continues Danovaro – that at the Fano buoy, which we use as the University, a decrease of 2° in surface water temperature was recorded. This gives us an extra week of delay in the warming process. The effect does not change the amount of heat the sea receives because this depends on the atmosphere, but it certainly cools surface temperatures by bringing waters to the surface richer in nutrients and better oxygenated. Very positive factors not only for the mussels but to prevent, in the coming weeks, large mortality events in marine communities. This dynamic allows us to reach the end of July fairly calmly in a situation that has returned to pre-2024 mass mortality levels. We hope this condition lasts long to definitively prevent the risk of heat waves.”
