&lt;b&gt;Limnology of a lateral lagoon system connected to a Neotropical reservoir (Rosana reservoir, São Paulo/Paraná, Brazil)

The knickzones are defined as locally steep riverbed segments, such as a convex reach in a concave-up longitudinal profile. They are worldwide distributed and geologically well studied, but despite their distinctiveness as a particular kind of macrohabitat there is a notorious lack of ecological knowledge. In this context, this research proposal aims to provide a physical description, in terms of kind of habitats, and a limnological characterization of a basaltic knickzone. Information is based on a case study carried out in the Sapucaí-Mirim River, Southeast Brazil. Samplings were performed in three different habitats well represented in the knickzone (runs, riffles and pools) during rainy and dry conditions. A clear discrimination in terms of habitat type and seasonality was demonstrated through a principal component analysis. Pools exhibited higher amplitude of variation for most limnological parameters when compared to runs and riffles, probably due to a great influence of the internal metabolism (photosynthetic production and community respiration). Despite of their geological ancient formation and the little understanding of their ecological role, the knickzones are in imminent threat in several regions of the world by hydropower dams implementation. The lack of ecological information on knickzones is probably due to inherent access difficulties and how to compare the distinct kinds of habitats. Thereby, further studies should be encouraged.Keywords: run, riffle, pool, river longitudinal profile, limnological variables. Uma contribuição para o conhecimento limnológico dos pedrais basálticos ResumoOs pedrais são definidos como segmentos de rio com leito localmente íngreme, tais como um alcance convexo em um perfil longitudinal côncavo. Eles são mundialmente distribuídos e geologicamente bem estudados, mas apesar de sua distinção como um tipo particular de macrohabitat há uma notória falta de conhecimento ecológico. Neste contexto, a proposta desta pesquisa é fornecer uma descrição física, em termos de tipo de habitats, e uma caracterização limnológica de um pedral basáltico. A informação é baseada em um estudo de caso realizado no rio Sapucaí-Mirim, no Sudeste do Brasil. As amostragens foram realizadas em três diferentes habitats bem representados na zona de pedral (rápidos, corredeiras e poças) durante as condições chuvosa e seca. Uma clara discriminação em termos de tipo de habitat e sazonalidade foi demonstrada através de uma análise de componentes principais. As poças apresentaram maior amplitude de variação para a maioria dos parâmetros limnológicos quando comparadas aos rápidos e corredeiras, provavelmente devido a grande influência do metabolismo interno (produção fotossintética e respiração das comunidades). Apesar de sua formação geológica antiga e da pouca compreensão de seu papel ecológico, os pedrais estão em ameaça iminente em várias regiões do mundo pela implementação de barragens hidrelétricas. A falta de informações ecológicas sobre os pedrais é provavelmente devido às dificuldades i...

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“…This pattern also occurs regionally in river lateral lagoons (Martins and Henry, 2004;Granado and Henry, 2012;Ferrareze et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

“…The opposite occurs in the dry period when the homogenization process is less effective with a higher differentiation among habitats. This dynamics is evidenced when compared river channels and lateral ecosystems such as floodplains and lagoons (Domitrovic, 2003;Thomaz et al, 2007;Ferrareze et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

A contribution for the limnological knowledge of basaltic knickzones

2017

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“…When there are no lotic remnants between reservoirs built in series along a river (this varies according to the water level of the next reservoir in the cascade), the possibilities to compare lotic and lentic environments in a cascade are more limited. Nevertheless, a few studies have demonstrated fish diversity impacts in lotic stretches between dams in a reservoir cascade (Ferrareze, Casatti, & Nogueira, ; Ferrareze, Nogueira, et al., ; Miranda & Dembkowski, ; Miranda et al., ; Silva et al., ). Moreover, there are indications that lotic stretches associated with lentic environments are important for the maintenance of fish diversity (Agostinho et al., ; Marques et al., ; Miranda & Dembkowski, ; dos Santos et al., ).…”

Section: Introductionmentioning

confidence: 99%

Temporal changes in fish diversity in lotic and lentic environments along a reservoir cascade

Loures

2019

Freshwater Biology

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Long‐term modifications in hydrological conditions due to river damming result in varied effects on fish diversity, which can be stronger in a reservoir cascade. Therefore, we assessed changes in fish diversity over a 28‐year period, in a series of reservoirs along the Araguari River Basin, a Neotropical drainage in Brazil, in both lentic environments (reservoirs) and the lotic stretches between them. We used linear mixed models to assess long‐term changes in fish diversity. Diversity was measured as α diversity (fish species richness) and β diversity (Jaccard's and Raup–Crick's dissimilarity index). Beta diversity was then partitioned into turnover (species replacement) and nestedness (species loss). To understand fish species replacement along the cascade, we modelled turnover with four covariates: age, richness of native and non‐native fish species, and longitudinal position of sampling site along the cascade. The reduction of total richness and the increase in non‐native richness were related to reservoir age. These effects were similar in both lotic and lentic environments, with no significant difference between them. We also observed a decrease in native fish richness over time, with a slight tendency for lentic environments to lose more species than lotic environments. Dissimilarity in fish assemblage increased over time and β Raup–Crick results corroborated those derived from β Jaccard, yielding similar significant temporal trends. Changes in fish species composition occurred predominantly due to turnover, compared to nestedness. We observed a greater species loss in reservoirs, suggesting that the transformation from a lotic environment into a lentic had greater impact on fish assemblages than the flow regulation of the lotic stretches downstream of the dams. Our results suggest that species replacement can be explained mainly by the increase of non‐native fish richness, followed by the longitudinal position along the cascade in an upstream–downstream direction, and reservoir age. This study reveals that, even after 2 decades of monitoring, we still observe important changes in fish assemblages, demonstrating the importance of long‐term monitoring to assess biodiversity. Our findings reinforce the importance of long‐term fish monitoring schemes for the investigation of the effects of non‐native fish species on native fish assemblages.

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“…Thus, the parental care becomes effective in habitats with high transparency and small oscillations in water level and other limnological variables (such as turbidity, nutrients, and pH), as seen upstream to the Rosana Reservoir (Ferrareze et al, 2014). Therefore, this behaviour favours the establishment of the species in this new area.…”

Section: Nogueiramentioning

confidence: 99%

New occurrence of a non-native ornamental cichlid in the Paranapanema River, southern Brazil

Garcia

Casimiro

Costa

et al. 2017

Neotropical Biology and Conservation

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Fish introductions are common practices due to intentionally or unintentionally translocations of species between watersheds. Herein we report the spread of the non-native cichlid Laetacara araguaiae Ottoni & Costa 2009 in the Paranapanema River basin, southern Brazil. Native from the Araguaia River (Central Brazil), this species was probably introduced by releases made by aquarists. Its new area of occurrence is characterized as natural nursery and important for the life cycle of native fish. Due to its biological characteristics, the species has the ability to cause a negative impact on the aquatic biota through possible interactions, such as predation of eggs, larvae and juveniles of native fish, and spread of parasites.

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<b>Limnology of a lateral lagoon system connected to a Neotropical reservoir (Rosana reservoir, São Paulo/Paraná, Brazil)

Cited by 8 publications

References 31 publications

A contribution for the limnological knowledge of basaltic knickzones

A contribution for the limnological knowledge of basaltic knickzones

Temporal changes in fish diversity in lotic and lentic environments along a reservoir cascade

New occurrence of a non-native ornamental cichlid in the Paranapanema River, southern Brazil

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