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  • Universidade Estadual de Maringá. Departamento de Biologia. Programa de Pós-Graduação em Ecologia de Ambientes Aquáticos Continentais.  (81)
  • American Association for the Advancement of Science
  • Copernicus
  • Public Library of Science (PLoS)
  • 2020-2023  (111)
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  • 1
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    The genesis of Yedoma Ice Complex permafrost – grain-size endmember modeling analysis from Siberia and Alaska (2020)
    Copernicus
    In:  EPIC3E&G Quaternary Sci. J., Copernicus, 69, pp. 33-53, ISSN: 0424-7116
    Details
    Publication Date: 2022-04-19
    Description: The late Pleistocene Yedoma Ice Complex is an ice-rich and organic-bearing type of permafrost deposit widely distributed across Beringia and is assumed to be especially prone to deep degradation with warming temperature, which is a potential tipping point of the climate system. To better understand Yedoma formation, its local characteristics, and its regional sedimentological composition, we compiled the grain-size distributions (GSDs) of 771 samples from 23 Yedoma locations across the Arctic; samples from sites located close together were pooled to form 17 study sites. In addition, we studied 160 samples from three non-Yedoma ice-wedge polygon and floodplain sites for the comparison of Yedoma samples with Holocene depositional environments. The multimodal GSDs indicate that a variety of sediment production, transport, and depositional processes were involved in Yedoma formation. To disentangle these processes, a robust endmember modeling analysis (rEMMA) was performed. Nine robust grain-size endmembers (rEMs) characterize Yedoma deposits across Beringia. The study sites of Yedoma deposits were finally classified using cluster analysis. The resulting four clusters consisted of two to five sites that are distributed randomly across northeastern Siberia and Alaska, suggesting that the differences are associated with rather local conditions. In contrast to prior studies suggesting a largely aeolian contribution to Yedoma sedimentation, the wide range of rEMs indicates that aeolian sedimentation processes cannot explain the entire variability found in GSDs of Yedoma deposits. Instead, Yedoma sedimentation is controlled by local conditions such as source rocks and weathering processes, nearby paleotopography, and diverse sediment transport processes. Our findings support the hypothesis of a polygenetic Yedoma origin involving alluvial, fluvial, and niveo-aeolian transport; accumulation in ponding waters; and in situ frost weathering as well as postdepositional processes of solifluction, cryoturbation, and pedogenesis. The characteristic rEM composition of the Yedoma clusters will help to improve how grain-size-dependent parameters in permafrost models and soil carbon budgets are considered. Our results show the characteristic properties of ice-rich Yedoma deposits in the terrestrial Arctic. Characterizing and quantifying site-specific past depositional processes is crucial for elucidating and understanding the trajectories of this unique kind of ice-rich permafrost in a warmer future.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
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  • 2
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    Dinâmica da comunidade de Chironomidae (Diptera) em eventos de cheias e secas extremas em um rio Neotropical. (2022)
    Universidade Estadual de Maringá. Departamento de Biologia. Programa de Pós-Graduação em Ecologia de Ambientes Aquáticos Continentais.
    Details
    Publication Date: 2022-05-04
    Description: Climate change can make extreme drought and flood events more frequent, while damming large rivers can alter the hydrological regime by making droughts more prolonged and floods less intense. Together, both factors can affect aquatic communities. Here, the variation of Chironomidae community attributes between extreme floods and droughts in a neotropical floodplain river was investigated. The hypothesis that the abundance, richness, diversity and variability attributes of the Chironomidae community are reduced after extreme events was tested. Sampling took place quarterly from 2000 to 2012, although only a few years were selected to investigate our predictions. Twelve sampling periods were selected, which were divided into years in which, El Niño (extreme flood) and La Niña (extreme drought) phenomena occurred. In the Paraná River, three points were determined for the collection of benthic material, in transect: right bank, center and left bank of the river. We recorded 75 morphospecies of Chironomidae. The most common taxa in periods of extreme flooding were Djalmabatista sp 2, Lopescladius sp 1 and Tanytarsus type E. For periods of extreme drought, the most common taxa were Polypedilum (Tripodura) sp 4, Polypedilum sp 3 and Lopescladius sp 1. A composition and attributes of the Chironomidae community in the Paraná River varied between before and after extreme flood and drought events. Attributes such as Shannon-Wiener abundance, richness and diversity were reduced after extreme floods and, in contrast, tended to increase after extreme drought events (except Shannon diversity). Thus, it can be stated that the evaluated flood and drought events, despite being extreme, have different consequences in the Chironomidae community of the Paraná River. Given the environmental and global conditions we experience today, including climate change and dams, extreme events could be even more frequent in aquatic ecosystems. Therefore, it is essential to understand the consequences of extreme flood and drought events on ecosystems with high biodiversity and that provide relevant ecosystem services such as floodplain rivers.
    Description: As mudanças climáticas podem tornar eventos de secas e cheias extremas mais frequentes, enquanto barramentos de grandes rios podem alterar o regime hidrológico por tornar as secas mais prolongadas e as cheias menos intensas. Em conjunto, ambos fatores podem afetar as comunidades aquáticas. Aqui, a variação dos atributos da comunidade de Chironomidae entre as cheias e secas extremas em um rio de planície de inundação neotropical. Testou-se a hipótese de que os atributos abundância, riqueza, diversidade e variabilidade da comunidade de Chironomidae são reduzidos após eventos extremos. As amostragens ocorreram trimestralmente 2000 a 2012, embora apenas alguns anos foram selecionados para investigar nossas predições. Selecionou-se 12 períodos de amostragem, que foram divididos em anos que ocorreram fenômenos de El Niño (cheia extrema) e La Niña (seca extrema). No rio Paraná foram determinados três pontos para coleta do material bentônico, em transecto: margem direita, centro e margem esquerda do rio. Registrou-se 75 morfoespécies de Chironomidae. Os táxos mais comuns nos períodos de cheia extrema foram Djalmabatista sp 2, Lopescladius sp 1 e Tanytarsus tipo E. Para os períodos de seca extrema, os táxons mais comuns foram Polypedilum (Tripodura) sp 4, Polypedilum sp 3 e Lopescladius sp 1. A composição e os atributos da comunidade de Chironomidae no rio Paraná variaram entre antes e depois de eventos de cheia e seca extremas. Os atributos, como abundância, riqueza e diversidade de Shannon-Wiener, foram reduzidos após cheias extremas e em contrapartida, tenderam a aumentar após eventos de seca extrema (exceto diversidade de Shannon). Pode-se afirmar que os eventos de cheias e secas avaliados, apesar de extremos, acarretam em diferentes consequências na comunidade de Chironomidae do rio Paraná. Considerando que as condições ambientais e globais que vivenciamos hoje, incluindo mudanças climáticas e barragens, os eventos extremos poderão ser ainda mais frequentes nos ecossistemas aquáticos. Portanto, é fundamental compreendermos as consequências dos eventos de cheia e seca extremas em ecossistemas com elevada biodiversidade e que fornecem relevantes serviços ecossistêmicos como rios de planícies de inundação.
    Description: Masters
    Keywords: Chironomidae (Diptera: Insecta) ; Zoobentos de água doce ; Comunidades, Ecologia de ; Pulso de inundação ; Mudanças climáticas ; ASFA_2015::Y::Zoobenthos ; ASFA_2015::F::Freshwater ecology ; ASFA_2015::C::Communities (ecological) ; ASFA_2015::F::Floodplains ; ASFA_2015::C::Climatic changes
    Repository Name: AquaDocs
    Type: Thesis/Dissertation
    Format: 26pp.
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  • 3
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    Sucessão de macroinvertebrados na decomposição da planta aquática exótica Hydrilla verticillata e da nativa Egeria najas. (2022)
    Universidade Estadual de Maringá. Departamento de Biologia. Programa de Pós-Graduação em Ecologia de Ambientes Aquáticos Continentais.
    Details
    Publication Date: 2022-05-04
    Description: Decomposition is a process of great importance to the ecosystem. Macroinvertebrates together with fungi and bacteria play a very important role in the cycling of organic matter. Through decomposition, nutrients that make up the organisms can be reused and macroinvertebrates act by fractionating the organic matter in this process. The exotic species Hydrilla verticillata (L.f) Royle usually causes problems in various regions of the globe such as economic damage in hydroelectric plants. This exotic species competes with native species and can facilitates new invasions. The objective of the present work is to evaluate how the colonization of macroinvertebrates occurs during the decomposition of H. verticillata and E. najas macrophytes, as well as other community attributes during the process such as density, richness, Shannon diversity and Pielou evenness. The experiment was carried out in Garças Lake and the macrophytes were collected in Paraná River. Macrophytes were dried at room temperature and 5 g of each species were added in two types of litterbags, one thin mesh (0.5 mm) and another with thick mesh (4 mm), totalling 100 litterbags. The litterbags were fixed at 5 points in the lake and removed each 4 days. In the laboratory the litterbags were washed with a 0.2 μm mesh sieve, the decomposing material was sorted and the remainder was oven dried for further decay calculation. There was no significant difference in community attributes, except when time was applied assigned to analysis. The decomposition was similar in both species because both had similar characteristics, including phylogenetic proximity. The most observed taxon during the process was Chironomidae. Thus, it is worth noting that more studies are needed to elucidate questions related to the colonization process and quantify the degradation of organic matter of exotic and native species in the Upper Paraná River floodplain.
    Description: A decomposição é um processo de grande importâcia para os ecossistemas, e os macroivertebrados juntamente com fungos e bactérias possuem um importante papel na ciclagem da matéria orgânica. Pela decomposição, os nutrientes que compõem os organismos podem ser novamente reutilizados, e os macroinvertebrados atuam fracionando essa matéria orgânica. A espécie exótica Hydrilla verticillata (L.f) Royle é uma espécie de macrófita submersas que atualmente tem causado problemas em diversas regiões do globo. Além de causar prejuízos econômicos em usinas hidroelétricas H. verticillata causa prejuízos para as espécies nativas devido a competição por recursos, o que pode facilitar novas invasões. Avaliou-se como ocorre a colonização de macroinvertebrados durante a decomposição das macrófitas H. verticillata e E. najas, além de avaliar outros atributos de comunidade durante o processo como, por exemplo, densidade, riqueza, diversidade de Shannon e equitabilidade de Pielou. O experimento foi realizado na Lagoa das Garças e as macrófitas foram coletadas no Rio Paraná. Após a coleta, as plantas foram secas em temperatura ambiente. Foram acondicionadas 5 g de material seco de cada espécie em dois tipos de litterbag, um com malha fina (0,5mm) e outro com malha grossa (4 mm), totalizando 100 litterbags. Os litterbags foram fixados em 5 pontos na lagoa e retirados em um intervalo de 4 em 4 dias. Em laboratório, os litterbags foram lavados com auxílio de peneira de malha de 0,2 μm. O material em decomposição foi triado e o restante foi seco em estufa para posterior cálculo de decaimento. Não houve diferença significativa nos atributos de comunidade, exceto quando o tempo foi aplicado como uma variável à análise. A decomposição foi similar nas duas espécies devido a ambas possuírem características semelhantes. Talvez, a proximidade filogenética entre as macrófitas possa ter gerado a similaridade dos resultados obtidos durante o experimento. O táxon mais observado durante o processo foi de Chironomidae e o processo de colonização ocorreu de forma muito semelhante para ambos os tratamentos. Os tipos de malhas mostraram resultados parecidos, pois podem não ter influenciado a colonização e a entrada dos macroinvertebrados durante o processo de decomposição. Desse modo, a colonização dos invertebrados não dependeu das espécies de macrófita e/ou tipo de malha. Por isso ressalta-se a importância de novos estudos para melhor direcionar questões voltadas para a colonização e quantificar a degradação da matéria orgânica relativa a espécies exóticas e nativas na planície de inundação do alto rio Paraná.
    Description: Masters
    Keywords: Macroinvertebrados de água doce ; Colonização ; Lagos rasos ; Indicadores biológicos ; Macrófitas aquáticas submersas ; Decomposição ; Ecologia de lagos rasos ; Processos ecossistêmicos ; ASFA_2015::M::Macrophytes ; ASFA_2015::F::Freshwater ecology ; ASFA_2015::F::Floodplains ; ASFA_2015::D::Decomposition ; ASFA_2015::C::Colonization ; ASFA_2015::L::Lakes
    Repository Name: AquaDocs
    Type: Thesis/Dissertation
    Format: 25pp.
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  • 4
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    Future climate response to Antarctic Ice Sheet melt caused by anthropogenic warming (2020)
    American Association for the Advancement of Science
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Sadai, S., Condron, A., DeConto, R., & Pollard, D. Future climate response to Antarctic Ice Sheet melt caused by anthropogenic warming. Science Advances, 6(39), (2020): eaaz1169, doi:10.1126/sciadv.aaz1169.
    Description: Meltwater and ice discharge from a retreating Antarctic Ice Sheet could have important impacts on future global climate. Here, we report on multi-century (present–2250) climate simulations performed using a coupled numerical model integrated under future greenhouse-gas emission scenarios IPCC RCP4.5 and RCP8.5, with meltwater and ice discharge provided by a dynamic-thermodynamic ice sheet model. Accounting for Antarctic discharge raises subsurface ocean temperatures by 〉1°C at the ice margin relative to simulations ignoring discharge. In contrast, expanded sea ice and 2° to 10°C cooler surface air and surface ocean temperatures in the Southern Ocean delay the increase of projected global mean anthropogenic warming through 2250. In addition, the projected loss of Arctic winter sea ice and weakening of the Atlantic Meridional Overturning Circulation are delayed by several decades. Our results demonstrate a need to accurately account for meltwater input from ice sheets in order to make confident climate predictions.
    Description: This research was supported by the NSF Office of Polar Programs through NSF grant 1443347, the Biological and Environmental Research (BER) division of the U.S. Department of Energy through grant DE-SC0019263, the NSF through ICER 1664013, and by a grant to the NASA Sea Level Science Team 80NSSC17K0698.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
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    A continuous pathway for fresh water along the East Greenland shelf (2020)
    American Association for the Advancement of Science
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Foukal, N. P., Gelderloos, R., & Pickart, R. S. A continuous pathway for fresh water along the East Greenland shelf. Science Advances, 6(43), (2020): eabc4254, doi:10.1126/sciadv.abc4254.
    Description: Export from the Arctic and meltwater from the Greenland Ice Sheet together form a southward-flowing coastal current along the East Greenland shelf. This current transports enough fresh water to substantially alter the large-scale circulation of the North Atlantic, yet the coastal current’s origin and fate are poorly known due to our lack of knowledge concerning its north-south connectivity. Here, we demonstrate how the current negotiates the complex topography of Denmark Strait using in situ data and output from an ocean circulation model. We determine that the coastal current north of the strait supplies half of the transport to the coastal current south of the strait, while the other half is sourced from offshore via the shelfbreak jet, with little input from the Greenland Ice Sheet. These results indicate that there is a continuous pathway for Arctic-sourced fresh water along the entire East Greenland shelf from Fram Strait to Cape Farewell.
    Description: Funding for this work comes from the NSF under grant numbers OCE-1756361 and OCE-1558742 (N.P.F. and R.S.P.) and grant numbers OCE-1756863 and OAC-1835640 (R.G.).
    Repository Name: Woods Hole Open Access Server
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  • 6
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    Reduced El Niño variability in the mid-Pliocene according to the PlioMIP2 ensemble (2021)
    Copernicus
    In:  EPIC3Climate of the Past, Copernicus, 17(6), pp. 2427-2450, ISSN: 1814-9332
    Details
    Publication Date: 2022-01-10
    Description: The mid-Pliocene warm period (3.264–3.025 Ma) is the most recent geological period during which atmospheric CO2 levels were similar to recent historical values (∼400 ppm). Several proxy reconstructions for the mid-Pliocene show highly reduced zonal sea surface temperature (SST) gradients in the tropical Pacific Ocean, indicating an El Niño-like mean state. However, past modelling studies do not show these highly reduced gradients. Efforts to understand mid-Pliocene climate dynamics have led to the Pliocene Model Intercomparison Project (PlioMIP). Results from the first phase (PlioMIP1) showed clear El Niño variability (albeit significantly reduced) and did not show the greatly reduced time-mean zonal SST gradient suggested by some of the proxies. In this work, we study El Niño–Southern Oscillation (ENSO) variability in the PlioMIP2 ensemble, which consists of additional global coupled climate models and updated boundary conditions compared to PlioMIP1. We quantify ENSO amplitude, period, spatial structure and “flavour”, as well as the tropical Pacific annual mean state in mid-Pliocene and pre-industrial simulations. Results show a reduced ENSO amplitude in the model-ensemble mean (−24 %) with respect to the pre-industrial, with 15 out of 17 individual models showing such a reduction. Furthermore, the spectral power of this variability considerably decreases in the 3–4-year band. The spatial structure of the dominant empirical orthogonal function shows no particular change in the patterns of tropical Pacific variability in the model-ensemble mean, compared to the pre-industrial. Although the time-mean zonal SST gradient in the equatorial Pacific decreases for 14 out of 17 models (0.2 ∘C reduction in the ensemble mean), there does not seem to be a correlation with the decrease in ENSO amplitude. The models showing the most “El Niño-like” mean state changes show a similar ENSO amplitude to that in the pre-industrial reference, while models showing more “La Niña-like” mean state changes generally show a large reduction in ENSO variability. The PlioMIP2 results show a reasonable agreement with both time-mean proxies indicating a reduced zonal SST gradient and reconstructions indicating a reduced, or similar, ENSO variability.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 7
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    Evaluating the large-scale hydrological cycle response within the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) ensemble (2021)
    Copernicus
    In:  EPIC3Climate of the Past, Copernicus, 17(6), pp. 2537-2558, ISSN: 1814-9332
    Details
    Publication Date: 2022-01-10
    Description: The mid-Pliocene (∼3 Ma) is one of the most recent warm periods with high CO2 concentrations in the atmosphere and resulting high temperatures, and it is often cited as an analog for near-term future climate change. Here, we apply a moisture budget analysis to investigate the response of the large-scale hydrological cycle at low latitudes within a 13-model ensemble from the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2). The results show that increased atmospheric moisture content within the mid-Pliocene ensemble (due to the thermodynamic effect) results in wetter conditions over the deep tropics, i.e., the Pacific intertropical convergence zone (ITCZ) and the Maritime Continent, and drier conditions over the subtropics. Note that the dynamic effect plays a more important role than the thermodynamic effect in regional precipitation minus evaporation (PmE) changes (i.e., northward ITCZ shift and wetter northern Indian Ocean). The thermodynamic effect is offset to some extent by a dynamic effect involving a northward shift of the Hadley circulation that dries the deep tropics and moistens the subtropics in the Northern Hemisphere (i.e., the subtropical Pacific). From the perspective of Earth's energy budget, the enhanced southward cross-equatorial atmospheric transport (0.22 PW), induced by the hemispheric asymmetries of the atmospheric energy, favors an approximately 1∘ northward shift of the ITCZ. The shift of the ITCZ reorganizes atmospheric circulation, favoring a northward shift of the Hadley circulation. In addition, the Walker circulation consistently shifts westward within PlioMIP2 models, leading to wetter conditions over the northern Indian Ocean. The PlioMIP2 ensemble highlights that an imbalance of interhemispheric atmospheric energy during the mid-Pliocene could have led to changes in the dynamic effect, offsetting the thermodynamic effect and, hence, altering mid-Pliocene hydroclimate.
    Repository Name: EPIC Alfred Wegener Institut
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  • 8
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    INSTANCE – the Italian seismic dataset for machine learning (2021)
    Copernicus
    Details
    Publication Date: 2021-12-14
    Description: The Italian earthquake waveform data are collected here in a dataset suited for machine learning analysis (ML) applications. The dataset consists of nearly 1.2 million three-component (3C) waveform traces from about 50 000 earthquakes and more than 130 000 noise 3C waveform traces, for a total of about 43 000 h of data and an average of 21 3C traces provided per event. The earthquake list is based on the Italian Seismic Bulletin (http://terremoti.ingv.it/bsi, last access: 15 February 2020​​​​​​​) of the Istituto Nazionale di Geofisica e Vulcanologia between January 2005 and January 2020, and it includes events in the magnitude range between 0.0 and 6.5. The waveform data have been recorded primarily by the Italian National Seismic Network (network code IV) and include both weak- (HH, EH channels) and strong-motion (HN channels) recordings. All the waveform traces have a length of 120 s, are sampled at 100 Hz, and are provided both in counts and ground motion physical units after deconvolution of the instrument transfer functions. The waveform dataset is accompanied by metadata consisting of more than 100 parameters providing comprehensive information on the earthquake source, the recording stations, the trace features, and other derived quantities. This rich set of metadata allows the users to target the data selection for their own purposes. Much of these metadata can be used as labels in ML analysis or for other studies. The dataset, assembled in HDF5 format, is available at http://doi.org/10.13127/instance (Michelini et al., 2021).
    Description: Published
    Description: 5509–5544
    Description: 4T. Sismicità dell'Italia
    Description: JCR Journal
    Keywords: 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    Efeito temporal na parasitofauna do bagre invasor Trachelyopterus galeatus (Linnaeus, 1766) de uma planície Neotropical. (2022)
    Universidade Estadual de Maringá. Departamento de Biologia. Programa de Pós-Graduação em Ecologia de Ambientes Aquáticos Continentais.
    Details
    Publication Date: 2022-12-06
    Description: Aquatic environments have been anthropically influenced over the years, mainly with the construction of dams and hydroelectric plants. However, few studies evaluate how the parasitic fauna can be influenced in the long term by these environmental changes. Possible changes in the composition of endoparasites of the invasive fish Trachelyopterus galeatus in the upper Paraná River floodplain were investigated over a 27-year study period. 79 fish were analyzed in period 1 (1993) and 31 in period 2 (2019/2020). In the first period, the fish showed higher values in the variables weight (g) and standard length (cm), when compared to period 2. A total of five species of endoparasites were found, three per period. Although the richness was the same, the composition of endoparasites differed between the periods, as only one species of digenetic (Microrchis oligovitellum) parasitized the host in both periods of study. It was found that both the development of the fish and its endoparasites were affected over time. It is noteworthy that the beginning of operation of the Porto Primavera dam, located upstream of the plain, occurred between the two sampling periods (1999), and caused several environmental changes, possibly being the main responsible for these changes in the parasitofauna. Most endoparasites require intermediate hosts to complete their life cycles. Therefore, a modified environment may lose diversity and ecological interactions, as it affects the populations they use during the transmission process between hosts. This may explain the difference found in the infracommunities of T. galeatus parasites, emphasizing, through the results obtained, the importance of including these organisms in studies that evaluate environmental impacts caused by anthropic actions
    Description: Ambientes aquáticos têm sido influenciado antropicamente ao longo dos anos, principalmente com a construção de barragens e usinas hidrelétricas. Contudo, poucos estudos avaliam como a fauna parasitária pode ser influenciada a longo prazo por essas mudanças ambientais. Investigou-se possíveis alterações na composição de endoparasitas do peixe invasor Trachelyopterus galeatus na planície de inundação do alto rio Paraná, em um intervalo de 27 anos de estudo. Foram analisados 79 peixes no período 1 (1993) e 31 no período 2 (2019/2020). No primeiro período, os peixes apresentaram maiores valores nas variáveis peso (g) e comprimento padrão (cm), quando comparados com o período 2. Encontrou-se um total de cinco espécies de endoparasitas, sendo três por período. Apesar da riqueza ter sido igual, a composição de endoparasitas diferiu entre os períodos, pois apenas uma espécie de digenético (Microrchis oligovitellum) parasitou o hospedeiro nos dois períodos de estudo. Constatou-se que tanto o desenvolvimento do peixe quanto seus endoparasitas foram afetados ao longo do tempo. Destaca-se que o início do funcionamento da barragem de Porto Primavera, localizada à montante da planície, ocorreu entre os dois períodos de amostragem (1999), e provocou diversas alterações ambientais, sendo, possivelmente, a principal responsável por essas mudanças da parasitofauna. A maioria dos endoparasitas requer hospedeiros intermediários para completar seus ciclos de vida. Portanto, um ambiente modificado, pode perder diversidade e interações ecológicas, visto que afeta as populações que eles utilizam durante o processo de transmissão entre hospedeiros. Isso pode explicar a diferença encontrada nas infracomunidades de parasitas de T. galeatus, enfatizando, por meio dos resultados obtidos, a importância de incluir esses organismos nos estudos que avaliam impactos ambientais causados por ações antrópicas.
    Description: Masters
    Keywords: Fauna endoparasitária (Platyhelminthes). ; Trachelyopterus galeatus (Linnaeus, 1766) “cangati”. ; Peixes siluriformes. ; Parasitismo. ; Ecologia. ; Parasitismo em peixes de água doce. ; ASFA_2015::F::Freshwater fish ; ASFA_2015::F::Freshwater ecology ; ASFA_2015::P::Parasitism ; ASFA_2015::P::Parasites
    Repository Name: AquaDocs
    Type: Thesis/Dissertation
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  • 10
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    Variations in export production, lithogenic sediment transport and iron fertilization in the Pacific sector of the Drake Passage over the past 400 kyr (2022)
    Copernicus
    In:  EPIC3Climate of the Past, Copernicus, 18, pp. 147-166, ISSN: 1814-9324
    Details
    Publication Date: 2022-11-14
    Description: Changes in Southern Ocean export production have broad biogeochemical and climatic implications. Specifically, iron fertilization likely increased subantarctic nutrient utilization and enhanced the efficiency of the biological pump during glacials. However, past export production in the subantarctic Southeast Pacific is poorly documented, and its connection to Fe fertilization, potentially related to Patagonian Ice Sheet dynamics is unknown. We report on biological productivity changes over the past 400 ka, based on a combination of 230Thxs-normalized and stratigraphy-based mass accumulation rates of biogenic barium, organic carbon, biogenic opal, and calcium carbonate as indicators of paleo-export production in a sediment core upstream of the Drake Passage. In addition, we use fluxes of iron and lithogenic material as proxies for terrigenous matter, and thus potential micronutrient supply. Stratigraphy-based mass accumulation rates are strongly influenced by bottom-current dynamics, which result in variable sediment focussing or winnowing at our site. Carbonate is virtually absent in the core, except during peak interglacial intervals of the Holocene, and Marine Isotope Stages (MIS) 5 and 11, likely caused by transient decreases in carbonate dissolution. All other proxies suggest that export production increased during most glacial periods, coinciding with high iron fluxes. Such augmented glacial iron fluxes at the core site were most likely derived from glaciogenic input from the Patagonian Ice Sheet promoting the growth of phytoplankton. Additionally, glacial export production peaks are also consistent with northward shifts of the Subantarctic and Polar Fronts, which positioned our site south of the Subantarctic Front and closer to silicic acid-rich waters of the Polar Frontal Zone, as well as a with a decrease in the diatom utilization of Si relative to nitrate under Fe-replete conditions. However, glacial export production near the Drake Passage was lower than in the Atlantic and Indian sectors of the Southern Ocean, which may relate to complete consumption of silicic acid in the study area. Our results underline the importance of micro-nutrient fertilization through lateral terrigenous input from South America rather than aeolian transport, and exemplify the role of frontal shifts and nutrient limitation for past productivity changes in the Pacific entrance to the Drake Passage.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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