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Résumé :
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Rice cultivation in the Ebro Delta (Catalonia, Spain) has inverted the natural hydrological cycles of coastal lagoons and decreased water salinities for over 150 years. Adjustments in the water management practices-in terms of source and amount of freshwater inputs-have resulted in changes in the diversity, distribution and productivity of submerged angiosperms. Between the 1970s and late 1980s, a massive decline of the aquatic vegetation occurred in the Encanyissada-Clot and Tancada lagoons, but little information on the status is available after the recovery of macrophytes in the 1990s. Here, we evaluate the influence of salinity regimes resulting from current water management practices on the composition, distribution, seasonal abundance and flowering rates of submersed macrophytes, as well as on the occurrence of epiphyte and drift macroalgae blooms in three coastal lagoons. Our results show that Ruppia cirrhosa is the dominant species in the Encanyissada lagoon (185.97 +/- 29.74 g DW m(-2) year(-1); 12-27 aEuro degrees salinity) and the only plant species found in the Tancada lagoon (53.26 +/- 10.94 g DW m(2) year(-1); 16-28 aEuro degrees salinity). Flowering of R. cirrhosa (up to 1,011 +/- 121 flowers m(-2)) was only observed within the Encanyissada and suggests that mesohaline summer conditions may favor these events. In contrast, low salinities in Clot lagoon (similar to 3-12 aEuro degrees) favor the development of Potamogeton pectinatus (130.53 +/- 13.79 g DW m(2) year(-1)) with intersperse R. cirrhosa (8.58 +/- 1.71 g DW m(-2)) and mixed stands of P. pectinatus and Najas marina (up to similar to 57 g DW m(-2) year(-1)) in some reduced areas. The peak biomasses observed during the study are
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