Why? Remember that in autumn, the seagrass leaves fall and rot in the meadow to form a layer of dead organic matter known as litter and to a lesser degree, the matte. Normally, the litter is exported out of the meadow by the winter storms. “But because of the very mild winter in 2006-07, this matter remained in the meadow and lay rotting there until the beginning of spring”, Alberto Borges explains. “We therefore assumed that its presence blocked part of the primary production (development of the algae that is supposed to grow at the bottom of the meadow), like a tarpaulin that has been used to cover a lawn to prevent the grass from growing. That year, the meadow was therefore less productive than in the following years”. Thanks to the long-term measurements captured on the mooring line, it is possible to observe how exceptional events, mainly meteorological ones, influence the functioning of the seagrass meadow. “In a context where the climate models forecast fewer and fewer storms in the Mediterranean owing to the northward shift of the Atlantic storm track, the phenomenon observed in the winter of 2006-07 can, if extrapolated, give an idea of what could happen in the future: more rotting and therefore a decline in primary production”. The researchers are continuing their observations and the measuring device shall remain in place. Their hope? To be able to observe another exceptional phenomenon, such as a scorching hot summer. To be continued...