Morphometry and retention time as forcing functions to establishment and maintenance of aquatic macrophytes in a tropical reservoir.

M B Cunha-Santino,A T Fushita,A C Peret,I Bianchini-Junior

doi:10.1590/1519-6984.24214

M B Cunha-Santino, A T Fushita + Show 2 more

Open Access

https://doi.org/10.1590/1519-6984.24214

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Abstract

Macrophytes may constitute an important resource for several chemical, physical and biological processes within aquatic ecosystems. This study considers that in tropical reservoirs with low retention time and with low values of shoreline development (DL), the expansion and persistence of aquatic macrophytes are mainly reported to local conditions (e.g., hydrodynamic and wind exposure) rather than trophic status and depth of the euphotic zone. In this context, this study aimed at describing and comparing the incidence of aquatic macrophytes in a throughflowing, non-dendritic tropical reservoir. During February 2006 to November 2007, eight limnological surveys were performed quarterly within the Ourinhos Reservoir, and in the mouth areas of its tributaries. At the six sampling stations 30 variables were measured. The number of sites with plants varied between 21 and 38 and at the end of the 1st year the total richness was found. The sampling survey outcome the recognition of 18 species of aquatic macrophytes; Cyperaceae (2 genera and 1 species), Pontederiaceae (3 species) and Onarograceae (3 genera) were the families with higher diversity. Seven species (Typha domingensis Pers., Myriophyllum aquaticum (Vell.) Verdec, Salvinia auriculata Aubl., Eichhornia azurea (Sw.) Kunth, Eleocharis sp1, Eichhornia crassipes (Mart.) Solms, Oxycaryum cubense (Poepp. & Kunth) Lye) always were present and were more frequent in the sites. The occurrence of emergent species predominated (45.9%), followed by submersed rooted (24.5%), free floating (19.5%), floating rooted (9.7%) and free submersed (0.3%). Although limnological variables and the distribution of macrophytes have discriminated the same sampling points, the stepwise multiple linear regressions did not pointed out strong correspondences (or coherence) among the most constant and distributed macrophyte species and the selected limnological variables, as well the trophic statuses. Seeing the low relationship among limnological variables and macrophytes distribution, in the case of Ourinhos Reservoir, the results pointed out that the water turbulence, low DL and wind exposure are the main driving forces that determine its aquatic plant distribution, life forms and species composition.

Highlights

Neotropical aquatic ecosystems usually support several species of aquatic macrophytes (Neiff et al, 2008; Rolon et al, 2010; Piedade et al, 2010)
Taking into account the many factors that contribute to the establishment of aquatic plants, this study considered the following hypothesis: in a tropical reservoir with low retention time (i.e., RT < two weeks; Straškraba, 1999) and with low values of shoreline development (DL), the expansion and maintenance of aquatic macrophytes are mainly due to local conditions rather than customary factors such as, trophic status and depth of the euphotic zone
The budget between the output and Paranapanema River input flows (CBA, 2007) showed that, on average, the tributaries support with ca. 0.13 ± 1.67% of water content

Summary

Introduction

Neotropical aquatic ecosystems usually support several species of aquatic macrophytes (Neiff et al, 2008; Rolon et al, 2010; Piedade et al, 2010). The macrophytes are key resources to habitat structuring, and in supporting the trophic chains and several chemical, physical and biological processes within aquatic ecosystems (Thomaz and Cunha, 2010). Free-floating macrophytes (e.g., Eicchornia crassipes, Pistia stratiotes and Salvinia spp) are most common in several Neotropical man-made-lakes, but submersed and emergent species occur frequently, for instance: Egeria najas, Egeria densa, Utricularia ssp, Cabomba furcata, Najas sp, Eichhornia azurea, Eleocharis ssp, Ludwigia spp, Oxycaryum cubense, Echinochloa polystachya and Typha domingensis (Vilarrubia and Cova, 1993; Bini et al, 1999; Pompêo et al, 2001; Tanaka et al, 2002; Marcondes et al, 2003; Bini et al, 2005; Thomaz et al, 2006, 2009a, 2009b; Martins et al, 2008; Bianchini Junior et al, 2010)

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