Mar Menor (W Mediterranean, Spain) is the largest hypersaline coastal lagoon in Europe. In spring 2016, chl a concentration exceeded the average values (< 1 µg L-1) reported for this variable since reliable measurements started in the 1980’s [1] by two orders of magnitude. The high values of 2016 were unprecedented and pointed to a “phase change” in the eutrophication process of Mar Menor initiated many years before by a long history of anthropogenic pressures including urban discharges, intensive agriculture, livestock, dredging, construction of marinas, artificial beaches, etc.