Ecosystem-level effects of re-oligotrophication and N:P imbalances in rivers and estuaries on a global scale by Ibáñez, C, Caiola, N, Barquín, J, Belmar, O, Benito-Granell, X, Casals, F, Fennessy, S, Hughes, J, Palmer, M, Peñuelas, J, Romero, E, Sardans, J, Williams, M