Navegando por Autor "Nobre, Regina Lúcia Guimarães"
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Tese Evaluating the influence of land use, landscape properties, precipitation and fish on aquatic ecosystem functioning and biodiversity through large temporal and spatial scale assessments across lakes and reservoirs(2020-02-14) Nobre, Regina Lúcia Guimarães; Carneiro, Luciana Silva; Silva, Adriano Caliman Ferreira da; ; ; ; Dias, Juliana Deo; ; Guariento, Rafael Dettogni; ; Menezes, Rosemberg Fernandes de; ; Becker, Vanessa;Nutrient cycling is a fundamental ecosystem service as it provides an adequate balance of elements that are necessary for life. In freshwaters, the balance of nitrogen (N) and phosphorus (P) are of special interest as they often limit or control primary production and biomass formation. While the availability of these nutrients is fundamental for the maintenance of biodiversity and productivity of freshwaters, their excess can lead to eutrophic conditions that are associated with impaired water quality and biodiversity loss. The nutrient balance in freshwaters can potentially be affected by a variety of biotic and abiotic, external and internal pathways. In this thesis, two frameworks were explored. First, a spatial framework focused on external processes, where we investigated the direct and indirect effects that land use (i.e. type, extent), precipitation and landscape properties (i.e. lake origin, lake and catchment absolute and relative size and geomorphology) have on biotic and abiotic properties of freshwater systems. More specifically, in chapter one we evaluated, across 98 tropical lakes and reservoirs, the individual and interactive effects of land use, precipitation and landscape properties on patterns of water quality parameters (N, P and chlorophyll-a). In chapter two, we characterized the 98 lakes as natural or artificial and compared them regarding the landscape properties of their surroundings, their morphometry, and their physico/chemical characteristics to verify whether those factors can be associated with average patterns of phytoplankton community structure at both local and regional scales. The second approach, presented in Chapter 3, was a long-term temporal framework focused on internal processes related to nutrient cycling where we assessed whether an omnivorous fish with high biomass and growth rate is a source or sink of N and P to the pelagic zone of a temperate eutrophic lake, at various time scales ranging from days to 20 years.Dissertação A tale of two lakes: Fish introduction and the biodiversity of upland Amazonian lakes(2016-02-29) Nobre, Regina Lúcia Guimarães; Carneiro, Luciana Silva; Caliman, Adriano; http://lattes.cnpq.br/4147444251852878; ; ; Ger, Kemal Ali; ; Bozelli, Reinaldo Luiz;Astyanax bimaculatus was artificially introduced in Violão lake, an upland Amazonian lake located on Serra dos Carajás/Brazil. This fish became abundant there, but is absent across nearby fishless lakes with similar characteristics, as is the case of Amendoim lake. This study aimed to test predictions of food-web theory regarding effects of a top predator fish introduction in these systems. Data series of biotic variables sampled on both Violão and Amendoin lakes from 2010 to 2013 were used. Lakes were very distinct regarding the structure and composition of macroinvertebrates, with communities being richer and more abundant in Amendoim lake. A difference on zooplankton composition was detected but no consistent effects were observed regarding zooplankton structure. Phytoplankton in Violão lake presented higher richness and chlorophyll-a biomass. Differences found at ecosystem-scale for macroinvertebrates community suggests descendent effects of A. bimaculatus translocation are more consistent in benthic-littoral communities than on planktonic communities. Results also indicates that A. bimaculatus has potential to couple pelagic and littoral habitat trough nutrient recycling. Our results showed differences between lakes are within the description of omnivorous fish effects on aquatic systems and thus, considering the effects of fish translocation in such aquatic ecosystems is pivotal for preserving local biodiversity.