Do physiography and hydrology determine the physico-chemical properties and trophic status of coastal lagoons? A comparative approach

Coastal lagoons are very heterogeneous systems covering a wide range of physiographical and hydrological characteristics. The hypothesis of the present investigation was that physiographical and hydrological characteristics of coastal lagoons affect their physico-chemical properties and their buffering capacity against nutrient enrichment. We compared data collected during a complete annual cycle in six coastal lagoons which were representative of the different lagoon types proposed by Kjerfve (1986) and were subjected to different anthropogenic pressures. The greater exchange of water with the sea in the leaky lagoon of Ria Formosa (type 3) reduced the seasonal differences in the physico-chemical variables and increased the buffer capacity against nutrient enrichment when compared to the restricted (type 2) and chocked (type 1) lagoon types. The lagoon types also showed important differences regarding nutrient limitation, with types 1 and 2 being P-limited and type 3 being N-limited. Our approach can be applied to other coastal lagoons representative of transitional water types in order to provide a general framework for the rational management and policy strategies of coastal lagoons.