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Aim To produce an inventory of south-west Atlantic saltmarshes (from latitude 31°48′ S to 43°20′ S) using remotely sensed images and field sampling; to quantify their total area; to describe the biogeographical variation of the main habitats characterized by dominant vascular plants, in relation to major environmental factors; to test the hypothesis of predominance of the reversal pattern in plant distribution (sedges and grasses dominate the lower, regularly inundated zones, while the upper zones are occupied by more halophytic species) previously described; and to compare these south-west Atlantic saltmarshes with others world-wide. Location South-western Atlantic saltmarshes Methods Field samples of dominant emergent plant species positioned by the global positioning system (GPS) were obtained from most coastal saltmarshes (14) between southern Brazil and northern Patagonia, Argentina. Landsat satellite images were obtained and coastal saltmarsh habitats were quantified by supervised classification, utilizing points gathered in the field. Results Three main plant species dominated the low and middle intertidal saltmarsh, Spartina alterniflora Loesel., Spartina densiflora Brong. and Sarcocornia perennis (P. Mill.) A.J. Scott. The total area of the studied coastal saltmarshes was 2133 km2, comprising 380 km2 of Sp. alterniflora marsh, 366 km2 of Sp. densiflora marsh, 746 km2 of Sar. perennis marsh and 641 km2 of brackish marsh (dominated by Juncus acutus L., Juncus kraussii Hochst., Scirpus maritimus L., Scirpus americanus Pers. and Phragmites australis (Cav.) Trin.). Cluster analysis showed three habitat types: saltmarshes dominated by (1) Sp. densiflora and brackish species,(2) Sp. alterniflora and Sar. perennis and (3) Sp. densiflora only. The analysis of abiotic variables showed significant differences between groups of habitats and coordinated gradients of the abiotic variables. The south-west Atlantic coast showed decreasing mean annual rainfall (1200 to 196 mm) and increasing mean tidal amplitude (< 0.5 to > 2.5 m) from latitude 31° to 43°. Main conclusions South-west Atlantic saltmarshes are globally important by virtue of their total extent. Remote sensing showed that the reversal pattern in plant distribution is not widespread. Indeed, south-west Atlantic saltmarshes are better characterized by the presence of the halophytic genera Spartina and Sarcocornia. Our results support the interpretation that south-west Atlantic saltmarshes constitute a class of temperate type ( sensu Adam, 1990 ) with transitional characteristics between Australasian–South African saltmarshes and west Atlantic saltmarshes. [ABSTRACT FROM AUTHOR]

Lake Rodó (Montevideo, Uruguay) is a small, urban, hypertrophic lake undergoing restoration. In this study, we evaluated the nutrient removal efficiency and water quality improvement attributable to a water recirculation system, consisting of the lake and three connected pools converted to artificial wetlands dominated by free-floating hydrophytes.Eichhornia crassipesandSpirodela intermediadominated the hydrophyte community during summer and winter, respectively, with the biomass production being maintained throughout the year. The maximum production values ofE. crassipeswere 11.3 and 5.6 g DW m−2 d−1 in the summers of 1998 and 2000, respectively, while those ofS. intermediawere 2.7 and 0.8 g DW m−2 d−1 in the summers of 1999 and 2000, respectively. The aquatic plant community reduced the concentration of nutrients in the water column but did not significantly affect the sediment concentrations. Harvesting the hydrophytes removed the equivalent of 58–88% and 39–78% of the nitrogen (N) and phosphorus (P) load associated with the water column, respectively. In contrast, the harvests accounted for only 1–2% of the N and P load associated with the sediments. In the pools, the combination of water recirculation and hydrophytes generally diminished the algal biomass and the associated N and P, compared to that observed for the lake. The combined use of adequate aquatic plant harvests and hydraulic management increased the efficiency of the system and, therefore, seems to be a useful tool for restoring small, shallow lakes in tropical and subtropical regions. [ABSTRACT FROM AUTHOR]