IO - Artigos publicados em periódicos
URI permanente para esta coleçãohttps://rihomolog.furg.br/handle/1/362
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- ItemThe last 25,000 years in the Eastern Plateau of Southern Brazil according to Alpes de São Francisco record(Elsevier, 2010) Leonhardt, Adriana; Lorscheitter, Maria LuisaThe palaeoenvironmental history has been studied based on palynology of a sedimentary profile from the Alpes de São Francisco bog (29290 3500S, 50370 1800W), São Francisco de Paula municipality, Rio Grande do Sul eastern Plateau, extreme Southern Brazil. The results indicate a regional cold and dry climate between 25,000 and 12,500 yr BP, interpreted from the grassland vegetation, forest taxa were present in refuges and the shallow local lake began to fill in. Climatic conditions became more aride after 16,000 yr BP, when grassland became rare. From 12,500 yr BP onwards, the climate began to change and at 11,000–9700 yr BP a warm and moist climate permitted the slight migration of pioneer arboreal taxa from refuges and locally a marsh formation. Between 9700 and 6500 yr BP a warm and dry climate resulted in reduction of grassland, confined the forest in refuges, dried out the marsh. The gradual increase of humidity between 6500 and 4000 yr BP allowed migration of forests from refuges and a bog developed. Between 4000 and 2000 yr BP Araucaria forest spread, indicating moister climate. The local bog expanded. From 2000 yr BP onwards, humid but warmer climate seems to result in a lower reproductive capacity of Araucaria forest taxa limiting its expansion. The bog reached the present-day in a decline condition. The results are compared to previous records from Southern Brazil highlands and some places from Argentina in order to better elucidate the climatic and vegetational history of these important South America areas during the late Quaternary.
- ItemPalinomorfos do perfil sedimentar de uma turfeira em São Francisco de Paula, Planalto Leste do Rio Grande do Sul, Sul do Brasil(2007) Leonhardt, Adriana; Lorscheitter, Maria Luisa(Palynomorphs of the sedimentary profile of a bog, São Francisco de Paula, Eastern Plateau of Rio Grande do Sul, southern Brazil). This paper aims at giving basic reference material to the study of plant succession in the Quaternary Brazilian southern plateau. Therefore, it presents the palynological analysis of 22 samples, taken along one sedimentary profile of 286 cm, in a bog of Rio Grande do Sul Eastern Plateau, corresponding approximately to the last 25000 years. The chemical processing of the samples followed the conventional method and the analysis was made by light microscopy. Palynomorphs corresponding to 10 fungi, 6 algae, 3 bryophytes and 16 pteridophytes were examined. The material, especially spores, is described and illustrated. The descriptions are accompanied, whenever possible, by ecological data of the original organism.
- ItemPólen de gimnospermas e angiospermas do perfil sedimentar de uma turfeira em São Francisco de Paula, Planalto Leste do Rio Grande do Sul, Sul do Brasil(2008) Leonhardt, Adriana; Lorscheitter, Maria Luisa(Pollen of gymnosperms and angiosperms of the sedimentary profile of a bog, São Francisco de Paula, Eastern Plateau of Rio Grande do Sul, southern Brazil). This pollen catalogue aims at helping the study of paleoenvironmental reconstructions by palynology of sediments in southern Brazil Plateau. It presents gymnosperms and angiosperms pollen found in a sedimentary profile from a bog of Rio Grande do Sul Eastern Plateau. The profile has 286 cm long, corresponding approximately to the last 25,000 years. The 22 samples were collected in regular intervals in the profile, chemically treated following the standard method and analyzed by light microscopy. Pollen grains from two gymnosperms and 43 angiosperms (one Magnoliidae, five Hamamelidae, six Caryophyllidae, six Dillenidae and 25 Rosidae) are presented. The pollen material is described and illustrated. The descriptions are accompanied, whenever possible, by ecological data of the original sporophyte.
- ItemLong-term changes in the age structure, mortality and biomass of the king weakfish Macrodon atricauda (Günther, 1880) in southern Brazil: is it resilient enough to avoid collapse?(2015) Cardoso, Luis Gustavo; Haimovici, ManuelWorldwide overfishing has caused the collapse of populations of excessively exploited marine fish. The coastal demersal sciaenid fish “pescadinha”, Macrodon atricauda, has been intensely fished since the 1960s along the southern Brazilian coast, resulting not only in decreasing abundance but also in increasing growth rates and decreasing age and length at first maturity. We analyzed the time series of several population indicators, such as catch per unit effort (CPUE), age composition of the stock, total and natural mortality and exploitation rate to investigate the long-term impact of fishing on the mortality, age structure and biomass of M. atricauda. Furthermore, we modeled the time-trajectory of the total biomass under an assumption of constant recruitment and discuss the limits of resilience and the risk of collapse of the fishery. The CPUE (kg/day at sea) has decreased almost 50%. Total mortality increased from 0.5 yr−1 in the almost unexploited stock in the 1950s to around 1.9 yr−1 in the 2000s, while the age structure changed dramatically: fishes in the landings were not older than 9 years old in the 1960s, 7 years old in the 1970s and no fish over 5 years old has been observed since the 1990s. Taking into account the growth changes, a deterministic model estimated a reduction of 67% in total biomass over five decades. In the last 30 years, the stock has withstood high exploitation rates (between 0.5 and 0.7 yr−1) and has suffered a steady decline in biomass but has not collapsed, probably due to life-history traits that favor resilience: early maturation and rapid individual growth. However, the stock is at risk of collapse, taking into consideration the present non-stabilized level of high mortality, changed age structure and life history, low biomass and high exploitation rates. A precautionary approach suggests the need to reduce fishing effort
- ItemFirst record of the dusky grouper Epinephelus marginatus(Actinopterygii: Epinephelidae) undergoing sexual transition in the South Western Atlantic, Brazil(2013) Condini, Mario Vinicius Lopes; Seyboth, Elisa; Vieira Sobrinho, João Paes; Varela Junior, Antonio Sergio; Barreiros, João Pedro; Fávaro, Luís Fernando; Garcia, Alexandre MirandaThe dusky grouper Epinephelus marginatus by fisheries is a marine species historically exploited showing slow growth, late maturation and protogynous hermaphroditism. Currently, it is considered as endangered by the IUCN. Therefore, it is essential to increase the knowledge about its biology and ecology to help conservation of this species. The present study reports the first record of a dusky grouper individual undergoing sexual transition, from female to male, in the Atlantic Ocean based on histological analyses of gonads. The specimen with total length: 770 mm; total weight: 8.1 kg and age: 21 years was captured in a rocky bottom along the coastline of the southernmost in state Brazil.
- ItemAn ecotrophic model of southern Brazil continental shelf and fisheries scenarios for Engraulis anchoita (Pisces, Engraulididae)(2005) Canziani, Gonzalo Velasco; Castello, Jorge PabloOs modelos ecotróficos de balanço de biomassa vem sendo utilizados cada vez mais como ferramentas para melhorar o entendimento da estrutura e funcionamento dos ecossistemas afetados pela pesca. Neste sentido foi construído um modelo preliminar, para entender a estrutura e os processos da plataforma continental do Sul do Brasil. Foram incluídos apenas os principais grupos para poder observar a importância relativa de cada um deles, testar cenários de exploração pesqueira e assim avaliar as possíveis consequências da pressão pesqueira sobre um recurso ou grupo em particular e o tipo de detalhamento que deverão ter os modelos futuros. Um exercício de simulação mostrou que a eventual pressão pesqueira sobre o pequeno peixe pelágico anchoíta (Engraulis anchoita) poderia também ter efeitos negativos na biomassa de seus predadores, mas favoreceria outros grupos de peixes competidores e camarões também explorados.
- ItemIndicative value of non-pollen palynomorphs (NPPs) and palynofacies for palaeoreconstructions: Holocene Peat, Brazil(2010) Medeanic, Svetlana; Silva, Maristela BagatinThe results of the palynological study of the samples from the core, performed in the Aguas Claras peatland, RS, Brazil (50°45′00″W, 30°00′15″S), focus on detailed taxonomic analysis of non-pollen palynomorphs (NPPs) and palynofacies from the Holocene peat and underline the Late Pleistocene mud and sandy mud that were represented. NPPs from the samples revealed taxonomic variety of fungal palynomorphs, presented by Brachysporium, Clastesporium, Dicellaesporites, Dicellaeporisporites, Gelasinospora, Glomus, Sordaria, Helicoon, and others. The habitats of above mentioned taxa are varied: aquatic, mycorrhizal, parasitic, organic matter decaying, and dung-coprophilous. Freshwater algal palynomorphs were composed of Botryococcus, Closterium, Debarya, Mougeotia, Pseudoschizaea, Spirogyra, and Zygnema. The percentage ratio between algal and fungal palynomorphs was changed from the different samples of the core, reflecting climatic oscillations (more humid-dryer). Prevalence of fungal palynomorphs was connected with dryer climate, and on the contrary, freshwater algal palynomorph predominance was related with increasing humidity. The six palynomorph zones that corresponded to the six principal phases of environmental and climatic changes were determined. The zone from the uppermost part of peat was characterized by relatively frequent dungcoprophilous and parasitic fungi, as a result of agricultural and domestic activities. Palynofacies analysis combined to NPPs was used for palaeoenvironmental and paleoclimatic reconstructions. Palynofacies from the samples were characterized by evident changes in relationship (%) between the different types of organic matter, their quality, and quantity and fluorescence index. The obtained data contribute to the understanding of the peat deposition. The combined use of NPPs and palynofacies analyses provided a valuable approach for the paleoenvironmental and paleoclimatic reconstructions.
- ItemRepresentativity of quaternary mammals from the southern Brazilian Continental shelf(2012) Aires, Alex Sandro Schiller; Lopes, Renato PereiraFossils of terrestrial mammals from the southern Brazilian continental shelf have been known since the late 19th century. The fossils are relatively common and represent several taxonomic groups of the Pleistocene megafauna. Although the systematics of the fossil assemblage is well known, the relative proportions among taxonomic groups and their skeletal elements have not been evaluated yet. Here are presented the results of a survey of the diversity of skeletal elements and taxa among 2,391 specimens belonging to the paleontological collection of the Universidade Federal do Rio Grande (FURG). The survey revealed that the most common taxa are the artiodactyls, ground sloths, glyptodontids and toxodontids, while carnivores, rodents and litopterns are very scarce. The most abundant skeletal elements are osteoderms of cingulates (mostly glyptodontids) and teeth of other groups. Although paleoecological and paleoenvironmental inferences are very hard to obtain because the fossils do not have a stratigraphic setting, encompass a wide time span, of some 700 ky BP, and represent several environments and climates, some patterns of taxonomic abundance are apparently related to ecological factors, while others seem to result from taphonomic processess.
- ItemHabitat use patterns of franciscana dolphin (Pontoporia blainvillei) off southern Brazil in relation to water depth(2009) Danilewicz, Daniel; Secchi, Eduardo Resende; Ott, Paulo Henrique; Moreno, Ignacio Benites; Bassoi, Manuela; Martins, Márcio BorgesThe patterns of habitat use by the franciscana dolphins (Pontoporia blainvillei) along its distribution are poorly known. This study investigates the patterns of habitat use with respect to depth for 181 individuals of different age, size, gender and reproductive condition off Rio Grande do Sul, southern Brazil. The results reveal that franciscanas are very homogeneously distributed according to depth. Individuals from all lengths utilize nearly the entire range of depths of the surveyed area. Larger or older animals do not use deeper waters than younger animals, indicating that body size and age are not limiting factors for franciscanas that occupy deeper or offshore waters. Gestation seems to not cause a change in the distribution of females. Although the sex-ratio of the overall data did not vary from 1:1 in different depth intervals, a small-scale comparison between the northern and southern coast demonstrated the existence of some kind of sexual segregation. Franciscana by-catch in Rio Grande do Sul is not sustainable and it is agreed that management procedures are needed. Nevertheless, the available data on species distribution do not allow the designing of a protected area in order to minimize the by-catches of a particular sex/reproductive class.
- ItemStatus of white croaker Micropogonias furnieri exploited in southern Brazil according to different hypotheses of stock discretness(2006) Vasconcellos, Marcelo Cunha; Haimovici, ManuelThe exploitation status of white croaker Micropogonias furnieri in southern Brazil is assessed using a production model constructed according to three hypotheses of stock discreetness: an isolated stock in southern Brazil; a straddling stock shared between Brazil and Uruguay; and a straddling stock shared among Brazil, Uruguay and Argentina. Estimates of virgin stock size and maximum sustainable yield were more sensitive to the hypothesis assumed correct, the posterior means varying respectively from 177,648 to 1,007,256 tonnes and from 7459 to 38,677 tonnes. Estimates of stock status in relation to management reference points were more robust to the uncertainties in stock discreetness and indicate that the species in currently overfished (biomass at 60% of Bmsy) and under heavy overfishing (F between approximately 2 and 6 times higher than Fmsy). Results suggest that the relative stability of catches in the region occurs at the expense of a steady decline in stock abundance and that concerted management actions by the three countries are needed to bring the stock to safer levels of exploitation.