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Felisberto S.A.,Federal University of Goais | Leandrini J.A.,University Federal da Fronteira Sul | Rodrigues L.,Programa de Pos Graduacao em Ecologia de Ambientes Aquaticos Continentais PEA
Acta Limnologica Brasiliensia | Year: 2011

Aim: The effect of different concentrations of nutrients on algal communities living at the bottom of mesocosms was examined; Methods: The experiment was carried out in the tributary of Rosana reservoir (Corvo river) from November 22 nd to December 16 th of 2003. Mesocosms were set up in triplicate, with four treatments: nitrogen (N); phosphorus (P); nitrogen plus phosphorus (NP); plus a control treatment (C), consisting in addition of water from the reservoir; Results: Results of the Principal Components Analysis applied on the abiotic variables have shown that two axes explained 93.6% of the total variability (69.6 and 23.9%, respectively). It was possible to identify a group of P (positive) and N (negative) treatments of axis 1. The addition of nutrients in the experiment resulted in changes in algal composition. Mean values of density ranged from 8.383 to 34.510 ind.mL -1. Higher densities occurred in the phosphorus and nitrogen plus phosphorus treatments. The most representative classes were Zygnemaphyceae, Chlorophyceae, Bacillariophyceae and Cyanobacteria, both in density and species richness; Conclusions: Phosphorus seems to be beneficial to green algae in general, since a marked increase in Zygnemaphyceae and Chlorophyceae was found in the treatments containing phosphorus and nitrogen plus phosphorus. In the nitrogen treatment, however, green algae decreased dramatically, while Cyanobacteria remained constant, indicating their capacity to live in changed environments and confirms the limiting role played by phosphorus on the algal groups. Source

Figueiredo B.R.S.,Programa de Pos Graduacao em Ecologia de Ambientes Aquaticos Continentais PEA | Mormul R.P.,Programa de Pos Graduacao em Ecologia de Ambientes Aquaticos Continentais PEA | Benedito E.,Nucleo de Pesquisa em Limnologia
Hydrobiologia | Year: 2013

Habitat complexity, turbidity and prey type availability affect trophic dynamics, and an improved understanding of how these three factors work together could facilitate interpretations of trophic dynamics in environments with regime shifts. We conducted an experiment to cross these three factors, hypothesising that increasing both turbidity and macrophyte cover reduce consumption of Chironomids more than they reduce consumption of Cypridids. Our results did not support our hypothesis, suggesting that the effect of macrophyte cover on predation depends on turbidity. However, the magnitude of this combined effect is the same as that of turbidity alone. Moreover, turbidity affected predation on both prey types similarly. In addition, the effect of macrophyte cover on predation also depended on prey type. We argue that visual and physical refuges may be as effective as shelter, but macrophyte cover may benefit smaller prey items. This may lead to higher predation rates by small-sized fish on invertebrates during periods of low turbidity devoid of macrophyte cover and to similar predation rates on invertebrates during periods of low turbidity and abundant macrophytes, high turbidity and scarce macrophytes or high turbidity and abundant macrophyte cover. © 2013 Springer Science+Business Media Dordrecht. Source

Dunck B.,Programa de Pos Graduacao em Ecologia de Ambientes Aquaticos Continentais PEA | Bortolini J.C.,Programa de Pos Graduacao em Ecologia de Ambientes Aquaticos Continentais PEA | Rodrigues L.,Nucleo de Pesquisas em Limnologia | Rodrigues L.C.,Nucleo de Pesquisas em Limnologia | And 2 more authors.
Revista Brasileira de Botanica | Year: 2013

Functional diversity and adaptative strategies of planktonic and periphytic algae in isolated tropical floodplain lake. This study aimed to test the hypothesis that after a great magnitude and high duration of flood pulse in floodplain, functional diversity of phytoplankton and phycoperiphyton communities will be higher during high water. The strategies' dynamics evaluated during high and low water periods consisted of size classes, life forms, and functional groups. For the phytoplankton, the adaptations to floating, and for phycoperiphyton, the intensity and structure for attachment to substrate were also analyzed. Functional diversity was calculated from functional dendrograms of species. Functional diversity, richness, and density of both communities presented the greatest values during the high waters. In the high waters, Cryptomonas marsonii Skuja was dominant in plankton and Pseudoanabaena skujae Claus in periphyton, while in the low water, Merismopedia tenuissima Lemm. was dominant in plankton and Fragilaria capucina Desm. was dominant in periphyton. Thus, the flood pulse promoted the dominance of free-floating species in plankton, during the high water, and of metaphytic species in periphyton. In the low water, we observed the dominance of species with higher surface/volume ratio in plankton, and strongly attached in periphyton. We concluded that, in isolated floodplain lake, possibly the flood pulse directs the functional diversity of phytoplankton and phycoperiphyton. © 2013 Botanical Society of Sao Paulo. Source

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