Distribution of aquatic macrophytes along depth gradients in Lajeado Reservoir, Tocantins River, Brazil

Abstract

Aim The present study investigated the diversity of aquatic macrophytes in the littoral zone of Lajeado Reservoir, Tocantins River. We characterized spatial variations in species richness, composition and abundance along depth gradients. Methods Macrophyte sampling occurred at the end of the dry season (September and October 2014) in four sites of the reservoir. We established transects perpendicular to the shoreline, each 25 m long, divided in 3 sections (plots of 5 x 5 m). Results In total, we recorded 18 taxa of aquatic macrophytes, belonging to nine families and four life forms. Najas microcarpa, Echinodorus tenellus. and Chara sp. were the more frequent and abundant taxa. Considering depth gradients, we recorded 18 taxa in the section closer to the shoreline, 13 in the middle section and 10 in the section more distant to the shoreline. Submerged and emergent species were more frequent and abundant, especially in the section close to the shoreline; epiphytes and free-floating species were rare. Plot species richness (total, emergent and submerged) decreased along the gradient, and a Non-Metric Multidimensional Scaling (NMDS) revealed that the plot close to the shoreline had different composition when compared to adjacent sections. Individual species showed particular behaviors, but most tended to decline in abundance and occurrence along the gradient. Conclusions The present study revealed that small-scale environmental gradients affect the distribution of aquatic plants in Lajeado Reservoir, with greater diversity in habitats close to the shoreline.

Rapid morphological change in multiple cichlid ecotypes following the damming of a major clearwater river in Brazil

“…Cichla species have been reported to rapidly colonize, and undergo population expansion, within dammed sections of rivers (Santos, 1995;Santos & Oliveira Jr., 1999). This is likely because they will readily consume a wide variety of fish species (Fugi, Luz-Agostinho, & Agostinho, 2008;Novaes, Caramaschi, & Winemiller, 2004;Williams, Winemiller, Taphorn, & Balbas, 1998).…”

“…Further, while cannibalism is a common phenomenon in this genus (e.g., C. monoculus, C. kelberi), it has been reported to occur more frequently in systems affected by dam operation (Novaes et al, 2004;Rosemara Fugi et al, 2008).…”

Ecology of Aquatic Macrophytes in Brazil: The Legacy of Francisco De Assis Esteves

“…The primary goal of papers about community ecology (the second most important theme) is to explain patterns in species distributions, a topic well described by Chico in his seminal books mentioned earlier. The substitution of life forms across a depth gradient is one of the first known patterns of aquatic macrophyte community organization (e.g., Noleto et al 2019). Eugene Warming, the so-called 'father of Plant Ecology', called attention to such macrophyte zonation pattern in 'Lagoa Santa' (a lake situated in Central Brazil) in his book published in 1892 ("Lagoa Santa.…”

“…In general, the excessive growth of macrophytes, as stated long ago by Cook (1993), is a symptom rather than the cause of problems and, therefore, aquatic macrophytes are reliable indicators of the effects of several anthropogenic activities (e.g., eutrophication and river regulation). Accordingly, our review found, for example, several studies on macrophyte communities in reservoirs (Bini et al 1999, Noleto et al 2019, and focused on the effects of invasive species on native communities (Bora et al 2020, Lolis et al 2020.…”