Floristic survey and species richness of aquatic macrophytes in water sup p ly reservoirs

The present study aimed a floristic survey of aquatic macrophytes in four water supply reservoirs (Irai, Passauna, Piraquara I and II) of the Iguacu River basin, Parana, Brazil. Sampling and herborization of biological material followed methods described in literature. The species were classified by life forms. We found 90 species in 57 genera and 36 families, were 52.7% are monospecific. The richest reservoir was Passauna (40 spp.), followed by Irai, Piraquara I and Piraquara II (36 spp. each). Cyperaceae was the most representative with 17 spp., followed by Asteraceae, Onagraceae and Polygonaceae (7 spp. each). Amphibious and emergent life forms were equally express throughout species (41% each). Since aquatic macrophytes structure and contribute to environment biodiversity, the present study can assist management and implementation of biodiversity conservation efforts.


Introduction
Reservoirs are derived from rivers damming for industrial or public supply as well as power generation use.For public supply purposes, the State of Paraná have five reservoirs (Alagados Passaúna, Iraí, Piraquara I and II) located at the Iguaçu River basin.These reservoirs differ as to their trophic level (IAP 2009).The increase of nutrients in reservoirs water provides an increased proliferation of mostly aquatic macrophytes weeds species.The intense growing of such species can reduce the diversity of macrophytes and/or associated organisms, beyond inferring water multiple uses (e.g., navigation, public supply and energy generation) (Pompêo et al. 2005).
However, in great conditions, aquatic macrophytes promote a central structuring role in aquatic ecosystems, promoting complex habitat that determines the abundance and biodiversity of aquatic flora and fauna (Thomaz and Bini 2003).In this context, studies of floristic composition of aquatic macrophytes contribute to biodiversity patterns and knowledge processes (Thomaz and Bini 2003;Pompêo and Moschini-Carlos 2003).The basic information contained in species lists assist monitoring management (Thomaz andBini 1998, 2003;Pompêo 1999;Thomaz 2002) and may direct environmental classification (Maltchik et al. 2007).

Results
The floristic survey resulted in 90 species, 57 genera and 36 families of aquatic macrophytes (Table 1 2).

Discussion
The great number of families, genera and species in reservoirs has indicated the considerable biological diversity of these environments (Thomaz et al. 1997(Thomaz et al. , 1999;;Rocha and Martins 2011).Therefore among the species often is notice the presence of aquatic macrophyte weeds due to the fact that reservoirs are considered steppingstones for invasion species (Havel et al. 2014).Among the families, the number of Cyperaceae species stood out considerably.The predominance of Cyperaceae was also observed by Moura-Junior et al. (2013-70 spp.), Cervi et al. (2009-22 spp.), and Pivari et al. (2011-10 spp.).The significant presence of Cyperaceae species is attributed to its perennial nature and tolerance to drought periods (Bove et al. 2003).Indeed representatives of this family were present in all four seasons analyzed as well as Poaceae species.However the rhizomes forming the underground system are efficient in propagation (Pott et al. 1989) as well as the fruit dispersal made by water or wind (Judd et al. 2009).This leads us to consider that these qualities favor the floristic representation of these families.Asteraceae species are especially common in open regions.Its frequent presence is presumably from wind dispersal and/or the attract of inflorescences for generalist pollinators (Judd et al. 2009).Onagraceae and Polygonaceae species success is likely due to the pollination by bees, flies, moths and birds, reconciled with wind and water dispersal (Judd et al. 2009).Ludwigia species occur throughout Brazil, particularly in flooded areas.The representativeness of Ludwigia in floristic studies with aquatic macrophytes weeds is due mainly to certain floral and morphophysiological characteristics, such as the presence of floral resource (nectary) and pneumatophores.These structures allow representatives of genus greater efficiency in pollination and resistance to anoxic environments, i.e., typically as eutrophic reservoir Iraí (8 spp. of Ludwigia) (Sousa and Lorenzi 2012).
Emergent and amphibious life forms were also a remarkable representation observed by other authors (Bove et al. 2003;Matias et al. 2003;Pereira et al. 2012).Amphibian and emergent species exhibit morphological and physiological adjustments which make them able to survive between terrestrial and aquatic environments (Moura-Junior et al. 2013).Martins et al. (2008) reported the occurrence of 39 species in 18 reservoirs of five river basins of São Paulo State.The richness contrast with the present study may be related to the sampling method performed by Martins et al. (2008).According to Thomaz et al. (2004), the use of transects, even in large numbers, is still not enough for reliably sampled aquatic vegetation.Thus, the care in sampling becomes necessary since richness and diversity of species subsidize the management and conservation of aquatic environments.
The present study can be considered the third richest floristic survey for the Paraná State preceded by Cervi et al. (2009) with 117 spp and Ferreira et al. (2011) with 153 spp.Although the number of species can be affected by various environmental factors such as nutrients, fluctuation of water level, current velocity and spatial heterogeneity (Thomaz and Bini 2003).Pompeo et al. (2005) reported that if nutrients are not a limited factor at the environment, a great amount available can favor the proliferation of aquatic macrophytes weeds.Indeed in Iraí reservoir the proliferation of Alternanthera philoxeroides was considerably.The growth of opportunist species (Eichhornia crassipes, Salvinia auriculata and Altern anthera philoxeroides) hampers the colonization and development of aquatic macrophytes with low competition potential, thus reducing the ecosystem richness.Furthermore opportunist species promote decrease pH (Pedralli 2003); retention of nitrogen and phosphorus; increased biochemical oxygen demand (BOD); phytoplankton alteration, substrate retention, biodiversity reduction, and tubing obstruction (Thomaz 2002) raising the costs in reservoirs management (Pompêo 1999).The present survey reported relevant species richness in water supply reservoirs of the Iguaçu River basin.The endemism is restricted to the south, southeast and Paraná State for Cuphea glutinosa and Ludwigia hookeri respectively.The presence of opportunist species as Alternanthera philoxeroides, Eichhornia crassipes, and Salvinia auriculata must be considered, once in proliferation situation, they become problematic for noble reservoirs uses (navigation, public water supply and hydroelectric power generation).The present study is the first step to aquatic macrophytes community dynamics understanding.Moreover, for a correct management and implementation of biodiversity conservation efforts, basic information about the composition of communities is indispensable (Bini et al. 2006).
(Forzza et al. 2012)nospecific.Only Cuphea glutinosa is endemic to the south and southeast of the country.Ludwigia hookeri is endemic only for the State of Paraná.The species Centella asiatica, Drymaria cordata, Nympheae caerulea and Rumex obtusifolius are not native but naturalized in Brazil.All Cyperaceae except for Carex brasiliensis and Cyperus consanguineus as well as Juncaceae (Juncus micranthus and J. microcephalus) are found in the Atlantic forest, but without citation for the State of Paraná.All other species are native and not endemic to Brazil(Forzza et al. 2012).