A contribution for the limnological knowledge of basaltic knickzones

Brambilla, Eduardo Meneguzzi; Ruocco, Ana Maria Cirino; Nogueira, Marcos Gomes

doi:10.1590/1519-6984.172985

Cited by 6 publications

(12 citation statements)

References 14 publications

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“…On the whole, the compressed body shape displays better performance at moving in topographically complex environments (Breda, Oliveira, & Goulart, 2005). In a fast‐flowing environment, such as a plateau river (Brambilla et al, 2018), current velocity introduces an additional element of physical complexity that influences fishes' use of aquatic habitats, both horizontally and vertically. In this aspect, the generalised “tetra” appearance of ostariophysian fish (Lima et al, 2003; Ornelas‐García et al, 2017) was exhibited by all the species analysed ( Astyanax and Bryconamericus ).…”

Section: Discussionmentioning

confidence: 99%

“…The physical complexity of upland rivers provides topological and hydrodynamic diversity translated into the occurrence of complex mesohabitats like pools, riffles and runs (Brambilla, Ruocco, & Nogueira, 2018). The large variations in rainfall in these regions (Feow, 2018), occurring either seasonally (dry and rainy seasons) or due to short‐term events (episodic storm events), are additional factors that lead to flow and current velocity disparities at the scale of both mesohabitats and the entire landscape.…”

Section: Introductionmentioning

confidence: 99%

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Morphological traits correlated with resource partitioning among small characin fish species coexisting in a Neotropical river

Delariva

Neves

2020

Ecology of Freshwater Fish

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Body shape variation should play a central role in determining the feeding ability of a fish species. We tested whether variations in feeding resource use of sympatric and closely related fish species could be explained by differences in ecologically relevant metrics, such as body morphology, trophic apparatus or combinations thereof. Fish were sampled at 14 sampling sites from Pelotas River and tributaries, Upper Uruguay, Brazil. The stomach contents of five species of Characidae (Astyanax and Bryconamericus) were analysed by the volumetric method. A geometric morphometric approach was used together with internal morphological traits to predict their patterns of prey use. Significant differences in body depth, snout and caudal peduncle lengths were found. Concomitant pronounced variations were verified to occur among species in structures related to digestion and absorption. Increased numbers of cusps, more pyloric caeca and higher intestinal coefficient values were observed in species that consumed greater proportions of plants. The opposite trends occurred in species that consumed greater proportions of insects. Mixed linear models indicated that the characin species differed significantly in the use of algae, aquatic insects, terrestrial insects, plant remains/seeds and detritus. Dietary differences reflected in low trophic niche overlap. Partial least squares regression results indicated strong correlations between morphological divergences and the corresponding variations in species diet. These outcomes combined confirm that the morphological traits that best enables the exploration of certain resource were an important factor in the resource‐related divergence and were the underlying reasons for these species' respective feeding modes.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Morphological traits correlated with resource partitioning among small characin fish species coexisting in a Neotropical river

Delariva

Neves

2020

Ecology of Freshwater Fish

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“…Fluvial systems integrate landscapes and can exhibit distinct structural and functional stretches along their courses. Knickzones are environments that have intrinsic ecological characteristics, which have been scientifically unexplored because the difficulties of access and methodological constraints -impossibility to apply standard sampling techniques to the distinct habitats (Brambilla et al, 2018). The precautionary principle (CNUMAD, Rio-92) calls for early measures to avoid and mitigate environmental damage in the face of the uncertainty.…”

Section: Discussionmentioning

confidence: 99%

“…Some works have analysed the spatial distribution and geological formation of fluvial knickzones (Walsh et al, 2012;Pederson and Tressler, 2012;Lima and Binda, 2013), but they did not focus on the environmental and biotic changes related to human interferences. Brambilla et al (2018) characterized basaltic knickzones (volcanic origin) as a complex aquatic habitat, composed of riffles, runs and pools distributed in a mosaic. They pointed the differences in depth, turbulence, velocity and flow as well as the degree of connectivity of the distinct habitats with the main river flow resulting in very high local heterogeneity in these macrohabitats.…”

Section: Introductionmentioning

confidence: 99%

Potential impact of small hydroelectric power plants on river biota: a case study on macroinvertebrates associated to basaltic knickzones

2019

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Small hydroelectric power plants (SHP) have been considered as an alternative for the generation of electricity with reduced environmental impacts. Nevertheless, no studies have addressed changes in a particular kind of river macrohabitat commonly affected by SHPs, the knickzones. This study aimed to assess the impact of a SHP construction on the aquatic macroinvertebrate fauna associated with two basaltic knickzones located in Sapucaí-Mirim River, Southeast Brazil. The first, considered as a functional knickzone, follows the natural dynamics of the river flow and preserves the original rock substrate. The second, considered as non-functional knickzone, was permanently flooded after the SHP construction and the consolidated rock substrate was changed by fine sediment. Sampling was carried out in two seasonal periods and the data were analysed through multivariate analysis. It was observed differences in composition and structure of the macroinvertebrates community between the knickzones and periods. The functional knickzone exhibited a much higher richness, 72 taxa compared to 44 in the non-functional, as well as a large number of exclusive taxa (38, being only nine exclusive to the non-functional). Diversity, equitability and density mean values were also higher in the functional knickzone. The limnological parameters varied significantly between dry and rainy seasons but not between the distinct knickzones. This kind of macrohabitats and its potential role for the rivers biodiversity is practically unknown. In the scenery of fast SHP expansion, further studies and protection measures are necessary.

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“…Knickzones are river stretches often formed by changes in bed cover, channel geometry and erosion processes (Haykawa & Oguchi, 2009;Dibiase et al, 2014). They are ecologically characterized by large rock outcrops forming a complex of habitats composed by riffles, runs and pools with distinct magnitudes and are highly influenced by flood pulses (Brambilla et al, 2018). The immersed or exposed condition of the substrate of a knickzone is highly variable and differences are mainly seasonal (summer-rainy and winter-dry periods), but can also occur stochastically throughout the year, in short-term periods of storms and dry spell events (Brambilla et al, 2018).…”

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confidence: 99%

Influence of habitat connectivity and seasonality on the ichthyofauna structure of a riverine knickzone

Brambilla

Uieda

Nogueira

2018

Iheringia, Sér. Zool.

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Knickzones are originated from basaltic outcroppings, present runs, riffles and pools and are highly influenced by flood pulses, which maintain their natural dynamic. However, the construction of hydroelectric power plants alters or eliminate the dynamism of this area and can affect the resident fauna that may be dependent on it. The aim of this study was to evaluate the organization of a knickzone’s ichthyofauna considering the influence of seasonality and connectivity of habitats. The study was performed in a knickzone located in the Sapucaí-Mirim River, Southeast Brazil. We sampled four rocky pools connected to the river and three isolated pools, during rainy and dry conditions. The analysis of the two factors (connectivity and seasonality) and of their interaction showed a significant influence only for seasonality on ichthyofauna structure, with higher values of abundance in the rainy season. The species that most contributed to the high dissimilarity between seasons were Knodus moenkhausii (50% of contribution) and Astyanax bockmanni (21%). The former is the most abundant species in the rainy season and the later in the dry season. The alteration between low and high water level occurs frequently in knickzones, as it is a rocky shallow platform in the middle of a river, with floods occurring seasonally or in stochastic short-term periods. This hydrological seasonal dynamic, high limnological variability and complex interactions of different habitats (pools, runs and rapids) explain the particular ichthyofauna structure in such small area. Our results also indicate the potential importance of basaltic knickzones for regional fish diversity conservation, especially due to the imminent threat by intensive hydropower reservoir construction.

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A contribution for the limnological knowledge of basaltic knickzones

Cited by 6 publications

References 14 publications

Morphological traits correlated with resource partitioning among small characin fish species coexisting in a Neotropical river

Morphological traits correlated with resource partitioning among small characin fish species coexisting in a Neotropical river

Potential impact of small hydroelectric power plants on river biota: a case study on macroinvertebrates associated to basaltic knickzones

Influence of habitat connectivity and seasonality on the ichthyofauna structure of a riverine knickzone

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