Species inventory of aquatic macrophytes in the last undammed stretch of the Upper Paraná River, Brazil

Abstract

Abstract:The last undammed stretch of the Upper Paraná River in the Brazilian territory is, to date, not completely inventoried, which rises concerns given the rapid rates of species extinctions. Aim: Here, we provide an inventory of macrophyte taxa recorded in the last undammed 230 km stretch of the Upper Paraná River. Methods: We inventoried macrophyte taxa in 27 sampling stations including lakes, the main channel of the river, and the tributary confluences in November 2013 and in May and November 2014. Macrophyte were sampled in littoral zones. We explored taxonomic and life form aspects of the recorded species. We used species accumulation curves and ordination techniques to summarize the variation in richness and composition of macrophyte species. Results: We recorded 71 macrophyte taxa in 35 families. Most species were emergent, amphibian, free-floating, and rooted submerged. At the main channel of the Upper Paraná River, Eichhornia azurea, E. crassipes, and Paspalum repens represented the most frequent species. The most frequent species in the tributary confluences were Ludwigia sp., E. azurea, and Polygonum ferrugineum, while in lakes, Ludwigia sp., Oxycaryum cubense, and E. azurea were the most representative taxa. In regard to macrophyte composition, the invasive Hydrilla verticillata mostly influenced sites in the Upper Paraná River, in the ordination space, while floodplain lakes were mostly characterized by the presence of species such as Scleria melaleuca, Panicum maximum, and Thelypteris sp., among others. Conclusions: Our study indicates that the last undammed stretch of the Upper Paraná River contains a large number of macrophyte species, suggesting that this stretch is an important area for the conservation of macrophyte species. In addition, the occurrence of invasive species (e.g., Hydrilla verticillata) within the investigated stretch deserves attention in terms of potential impacts for which management action may be necessary.

Inventory of Aquatic Macrophyte Species in Coastal Rivers of the São Paulo State, Brazil

“…In relation to the sampling effort, we observed from the extrapolation of species richness provided by the taxa accumulation curve that more than 80% of the total expected richness of the coastal region was sampled in our study. Similar percentage was also sampled by Souza et al (2017a). Thus, probably increasing the sampling effort we would record other rare species in some tributaries.…”

“…The amphibious H. coronarium is native to Tropical Asia and it has been very common in the Brazilian coastal zone where it is invasive in wetlands, along water courses and in the sub-forest of the Atlantic Rainforest (Soares & Barreto 2008). Although these three exotic species did not present expressive frequencies of occurrence in the São Paulo state coast, their monitoring and management can be actions to avoid their dispersion and establishment in new areas, and consequently avoid changes in ecosystem functioning (Bove et al 2003, Souza et al 2017a.…”

“…From the total taxa recorded in the coastal rivers of São Paulo, 51.1% of these taxa were also found in the Guarapiranga Reservoir, in the São Paulo state Metropolitan Region (Rodrigues et al 2017), 35.5% in the Upper Paraná River (Floodplain ecosystems in Southern Brazil) (Souza et al 2017a) and 24.4% in coastal lakes in the Santa Catarina state (Southern Brazil) (Ferreira et al 2017). Although the aquatic environments are quite distinct, that is, coastal rivers, reservoir, floodplain and coastal lakes; the greatest similarity occurs due to the geographically close locations.…”

“…The species richness recorded in inventories is varied and this variation may be related to the sampling effort, approach and area (Moura-Júnior et al 2013), as well as the aquatic ecosystems heterogeneity (Souza et al 2017b) and habitat diversity (Moura-Júnior et al 2013). For example, Souza et al (2017a) sampled the main river channel, tributaries and floodplain lakes in the Upper Paraná River (Southern Brazil) totaling 230 km of river stretch and 71 taxa; and Henry-Silva et al (2010) sampled 40 macrophyte taxa in about 210 km long of the Apodi/Mossoró River Basin (Northeast Brazil). We sampled only the main rivers of the coastal basins totaling less than 60 km of rivers and, nevertheless, we found species richness (N = 45) in the same order of magnitude of these other inventories.…”

“…Floating and submerged macrophytes were recorded only in the two largest rivers, possibly because they present backwater and semi-abandoned meandering areas with lower current velocity and sediment deposition due to the greatest rivers length and coastal plains width. Although well distributed in Neotropical aquatic ecosystems (Pott et al 2011, Souza et al 2017a, floating species can be limited by salt (Paudel et al 2018) and water flow (Camargo et al 2003) in coastal lotic ecosystems. Some submerged macrophyte species may be salt tolerant, but they occur in lower richness in coastal areas (Adair et al 1994, Abu-Hena et al 2010, Henry-Silva et al 2010, Ferreira et al 2017.…”