Abstract
AIM: The aim of this study was to evaluate the richness and distribution of the aquatic macrophytes in the basin of the Apodi/Mossoró River, in the semi-arid region (caatinga) of Rio Grande do Norte, Brazil; METHODS: A survey of the floristic composition of the aquatic macrophytes was made at 20 sampling stations in the basin at four seasons (August/2007, November/2007, February/2008, May/2008). Specimens of each species were collected and deposited in the Dárdano de Andrade Lima Herbarium of the Universidade Federal Rural do Semi-Árido; RESULTS: We found 40 species of aquatic macrophytes, in 33 genera and 22 families. The families with the most species were Poaceae and Cyperaceae, and the most species-rich genera were Cyperus and Eleocharis. The most common plant form was amphibian (42.5%), followed by emergent (27.5%), free-floating (12.5%), rooted-submersed (10.0%), and floating-leaved (7.5%). The lowest richness was observed at the estuarine region (3 species), and the highest richness in the upper basin (17 species). The rooted-submersed Hydrothrix gardneri Hooker f. and Ceratophyllum demersum L. were observed in great abundance and frequency in the Santa Cruz Reservoir of Apodi, especially in areas close to cage farms of Nile tilapia (Oreochromis niloticus) (Linnaeus, 1758). The most common free-floating species were Eichhornia crassipes (Mart.) Solms., Pistia stratiotes L., and Salvinia auriculata Aubl., predominantly in stretches that run through urban centers; CONCLUSION: The species richness of aquatic macrophytes in aquatic environments of the caatinga is similar to that observed in other basins of Brazil. Because of the many dams and reservoirs in the semi-arid Northeast, inventory and monitoring of aquatic macrophytes have become essential, especially in basins that will receive water from the diversion of the São Francisco River.
Highlights
The principal characteristics of the Brazilian semi-arid region are the low rainfall, generally concentrated in certain periods of the year; and the narrow temperature range (Maltchik and Florín, 2002)
Studies on aquatic ecosystems of the Brazilian semi-arid region have evidenced the high biodiversity of these environments, including aquatic macrophytes, and have demonstrated that patterns of diversity are related to the hydrological extremes of flood and drought (Medeiros and Maltchik, 1999; Silva-Filho and Maltchik, 2000; Medeiros and Maltchik, 2001; Pedro et al, 2006)
Studies of aquatic macrophyte communities have intensified, because of the ecological importance of these plants, and because of the possibility of using them as biological indicators, as well as the proliferation of some species in basins impacted by organic pollution, reservoir construction, and water diversion (Pieterse and Murphy, 1990; Mackay et al, 2003; Thomaz et al, 2003; Camargo et al, 2003; Martins et al, 2008)
Summary
The principal characteristics of the Brazilian semi-arid region are the low rainfall, generally concentrated in certain periods of the year; and the narrow temperature range (Maltchik and Florín, 2002). The two largest drainage basins of the State of Rio Grande do Norte (Piranhas/Açu and Apodi/ Mossoró) will receive water from the São Francisco River through the Eixo Norte (North Axis) waterway (ANA, 2007). These basin-integration projects may lead to physical and chemical changes of the water, and will mix the aquatic biological communities through the introduction of species from one basin to another
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