Paleoproductivity changes during the Holocene in the inner shelf of Cabo Frio, southeastern Brazilian continental margin: Benthic foraminifera and sedimentological proxies

Sedimentological and benthic foraminifera analyses carried out on a core (length 4.15 in, collected at 22 degrees 56`31 `` S and 41 degrees 58`48 `` W, at a water depth of 43 in) sampled from the inner shelf of Cabo Frio, southeastern Brazilian continental margin, allowed identification of different hydrodynamic and productivity regimes related to sea-level fluctuations and/or climatic changes, during the last 9.4 ka cal BP. Prior to 7.0 ka cal BP, a less intense hydrodynamic and lower productivity regime occurred at lower sea levels and under drier climatic conditions. Between 7.0 and 5.0 ka cal BP, relatively stronger local oceanic circulation and relatively high productivity were observed, in a scenario of rising sea levels and more humid conditions. From 5.0 to 3.0 ka cal BP, bottom currents weakened and input of nutrients increased, with productivity levels similar to the previous phase at lower sea level and in a drier climate. From 3.0 ka cal BP up to the present, stronger hydrodynamic conditions and a higher productivity regime are linked to the establishment of the upwelling process in Cabo Frio. From 2.5 ka cal BP to the present, upwelling enhancement has been recognized, resulting from the combined action of NE winds and the intensification of the meandering pattern of the Brazil Current (BC). (C) 2008 Elsevier Ltd and INQUA. All rights reserved.

Investigating South American biogeographic history using patterns of skull shape variation on Cerdocyon thous (Mammalia: Canidae)

Patterns of geographic variation of the canid Cerdocyon thous have historically been obscured by its remarkable intraspecific morphological variability. The observed distribution is highly associated with phytophysiognomy, a feature considered highly dynamic along geological time. In the present study, we tested whether vegetation distribution during the Holocene Glacial Maximum of South America (HGM) explains the patterns of morphological variation within Cerdocyon thous. The species was divided in groups according to paleohabitats that could support their presence during the HGM, and then tested for differences in skull morphometrics. The results obtained demonstrate that the climatic changes during the HGM influenced the population structure of this species, resulting in the establishment of geographical groups with different degrees of morphological cohesion. Higher morphological cohesion found in the Northern group might be explained by the marked discontinuity between its geographical range and the rest of the species`distribution. The Eastern and Southern morphological divergence is less striking and, although this could be related to past vegetation distribution, the disappearance of those barriers leads to a population structure that could be slowly breaking down. (C) 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 77-84.

Carbon and nitrogen stock and fluxes in coastal Atlantic Forest of southeast Brazil: potential impacts of climate change on biogeochemical functioning

The Atlantic Forest is one of the most important biomes of Brazil. Originally covering approximately 1.5 million of km(2), today this area has been reduced to 12% of its original size. Climate changes may alter the structure and the functioning of this tropical forest. Here we explore how increases in temperature and changes in precipitation distribution could affect dynamics of carbon and nitrogen in coastal Atlantic Forest of the southeast region of Brazil The main conclusion of this article is that the coastal Atlantic Forest has high stocks of carbon and nitrogen above ground, and especially, below ground. An increase in temperature may transform these forests from important carbon sinks to carbon sources by increasing loss of carbon and nitrogen to the atmosphere. However, this conclusion should be viewed with caution because it is based on limited information. Therefore, more studies are urgently needed to enable us to make more accurate predictions.

GEOGRAPHICAL GENETIC STRUCTURING AND PHENOTYPIC VARIATION IN THE VELLOZIA HIRSUTA (VELLOZIACEAE) OCHLOSPECIES COMPLEX

Premise of the study: Vellozia hirsuta forms a complex presenting wide morphological and anatomical variation, resulting in five specific names and 14 morpho-anatomical patterns occurring in disjunct populations. We carried out a phylogeographical study to investigate the existence of correlation among the genetic and morphological patterns within this complex, and to determine whether it is composed of various species or should be treated as an ochlospecies, a species having widely polymorphic and weakly polytypic complex variation, with morphological characteristics varying independently. Methods: We carried out phylogeographical analyses using cpDNA rpl32F-trnL intergenic region. Key results: We found 20 haplotypes in 23 populations sampled. The populations are genetically structured (Phi(ST) = 0.818) into four phylogeographical groups demonstrating geographical structuring but with no correlation with morpho-anatomical patterns. Our analyses do not support recognizing any of the species now synonymized under Vellozia hirsuta. The northern populations were the most genetically differentiated and could be considered a distinct taxon, as they are also morphologically different. Conclusions: It is recommended that Vellozia hirsuta be considered a single enormously variable species. The patterns of variation within V. hirsuta probably are related to climatic changes that occurred during the Pleistocene Epoch in tropical Brazil when reductions in forest cover favored the expansion of V. hirsuta populations into extensive lowland areas. The expansion of forest cover at the end of the glaciations would have again restricted the occurrence of campos rupestres vegetation to high elevations, which constitute the current centers of diversity of this species.

Can climate shape flight activity patterns of Plebeia remota (Hymenoptera, Apidae)?

Flight activity of foragers of four colonies of Plebeia remota (Holmberg, 1903) was registered from December 1998 to December 1999, using an automated system (photocells and PLC system). The colonies originated from two different regions: Cunha, state of Sao Paulo, and Prudentopolis, state of Parana, Brazil. Flight activity was influenced by different climatic factors in each season. In the summer, the intensity of the correlations between flight activity and climatic factors was smaller than in the other seasons. During the autumn and winter, solar radiation was the factor that most influenced flight activity, while in the spring, this activity was influenced mainly by temperature. Except in the summer, the various climatic factors similarly influenced flight activity of all of the colonies. Flight activity was not affected by geographic origin of the colonies. Information concerning seasonal differences in flight activity of P. remota will be useful for prediction of geographic distribution scenarios under climatic changes.

Activity, movement and secretive behavior of a threatened arboreal folivore, the thin-spined porcupine, in the Atlantic forest of southern Bahia, Brazil

Activity and behavior patterns are important components of a given species ecological strategy, as they have profound implications for its survival and reproduction. Here, we studied the activities, movements and secretive behavior of the thin-spined porcupine Chaetomys subspinosus (Rodentia: Erethizontidae), a threatened arboreal folivore in the Brazilian Atlantic rainforest. We aimed to ascertain the behavioral strategies used by this species as well as its responses to seasonal and daily climatic changes. Four radio-collared individuals were followed continuously for 72-h in the summer and winter, as well as during 146 half-night sessions conducted from April 2005 to September 2006 in forest remnants in southern Bahia. The thin-spined porcupines were nocturnally active (17:30-05:40 h), with peaks in activity and movement from 19:00 to 20:00 h and 03:00 to 04:00 h. Animals followed a circadian rhythm of activity during both the summer and winter. During the diel cycle, porcupines spent 74% of their time resting, 14% feeding, 11% traveling and 2% performing other activities. Distance traveled during the diel cycle averaged 277.5 +/- 117.9 m sd. The mean movement rate during the night was 21.6 +/- 30.1 m/h sd. No significant changes in activity budget or daily distance traveled were observed between seasons, most likely in response to the low fluctuations in climatic conditions and food availability throughout the year in the study region. However, rainfall reduced the time that the animals spent on feeding activities and explained day-to-day differences in activity budgets. We also provide details about intraspecific interactions and defecation behavior. Our observations confirmed that thin-spined porcupines, similar to other folivorous species, present low activity levels and short daily movements, and have adopted various cryptic habits, such as nocturnality, a solitary lifestyle, the tendency to leave offspring alone most of the time and defecation in concealed latrines.

Can climate shape flight activity patterns of Plebeia remota Hymenoptera, Apidae)?

Flight activity of foragers of four colonies of Plebeia remota (Holmberg, 1903) was registered from December 1998 to December 1999, using an automated system (photocells and PLC system). The colonies originated from two different regions: Cunha, state of São Paulo, and Prudentópolis, state of Paraná, Brazil. Flight activity was influenced by different climatic factors in each season. In the summer, the intensity of the correlations between flight activity and climatic factors was smaller than in the other seasons. During the autumn and winter, solar radiation was the factor that most influenced flight activity, while in the spring, this activity was influenced mainly by temperature. Except in the summer, the various climatic factors similarly influenced flight activity of all of the colonies. Flight activity was not affected by geographic origin of the colonies. Information concerning seasonal differences in flight activity of P. remota will be useful for prediction of geographic distribution scenarios under climatic changes.

Mid- to late-Holocene paleoceanographic changes on the southeastern Brazilian shelf based on grain size records

; High-resolution grain size analyses of three AMS (14)C-dated cores from the Southeastern Brazilian shelf provide a detailed record of mid- to late-Holocene environmental changes in the Southwestern Atlantic Margin. The cores exhibit millennial variability that we associate with the previously described southward shift of the Inter Tropical Convergence Zone (ITCZ) average latitudinal position over the South American continent during the Holocene climatic maximum. This generated changes in the wind-driven current system of the SW Atlantic margin and modified the grain size characteristics of the sediments deposited there. Centennial variations in the grain size are associated with a previously described late-Holocene enhancement of the El Nino-Southern Oscillation (ENSO) amplitude, which led to stronger NNE trade winds off eastern Brazil, favouring SW transport of sediments from the Paraiba do Sul River. This is recorded in a core from off Cabo Frio as a coarsening trend from 3000 cal. BP onwards. The ENSO enhancement also caused changes in precipitation and wind pattern in southern Brazil, allowing high discharge events and northward extensions of the low-saline water plume from Rio de la Plata. We propose that this resulted in a net increase in northward alongshore transport of fine sediments, seen as a prominent fine-shift at 2000 cal. BP in a core from similar to 24 degrees S on the Brazilian shelf. Wavelet-and spectral analysis of the sortable silt records show a significant similar to 1000-yr periodicity, which we attribute to solar forcing. If correct, this is one of the first indications of solar forcing of this timescale on the Southwestern Atlantic margin.

PALEOPRODUCTIVITY CHANGES DURING THE LATE QUATERNARY IN THE SOUTHEASTERN BRAZILIAN UPPER CONTINENTAL MARGIN OF THE SOUTHWESTERN ATLANTIC

Changes in the Brazilian continental margin`s oceanic productivity and circulation over the last 27,000 years were reconstructed based on sedimentological and microfaunal analyses. Our results suggest that oceanic paleoproductivity and the supply of terrigenous sediments to the Brazilian continental margin were higher during the Last Glacial Maximum (LGM) than during the Holocene. These changes may have been primarily influenced by significant sea level fluctuations that have occurred since the late Pleistocene. During the LGM, the lower sea level, higher productivity and lower sea-surface paleotemperatures may have been the result of the offshore displacement of the main flow of the Brazil Current. However, during the Holocene, the warm waters of the Brazil Current were displaced toward the coast. This displacement contributed to the increase in water temperature and prevented an increase in oceanic productivity. The decrease in terrigenous supply since the LGM could be related to the increase of the extension of the continental shelf and/or drier climatic conditions.

Changes in the intermediate water mass formation rates in the global ocean for the Last Glacial Maximum, mid-Holocene and pre-industrial climates

The paleoclimate version of the National Center for Atmospheric Research Community Climate System Model version 3 (NCAR-CCSM3) is used to analyze changes in the water formation rates in the Atlantic, Pacific, and Indian Oceans for the Last Glacial Maximum (LGM), mid-Holocene (MH) and pre-industrial (PI) control climate. During the MH, CCSM3 exhibits a north-south asymmetric response of intermediate water subduction changes in the Atlantic Ocean, with a reduction of 2 Sv in the North Atlantic and an increase of 2 Sv in the South Atlantic relative to PI. During the LGM, there is increased formation of intermediate water and a more stagnant deep ocean in the North Pacific. The production of North Atlantic Deep Water (NADW) is significantly weakened. The NADW is replaced in large extent by enhanced Antarctic Intermediate Water (AAIW), Glacial North Atlantic Intermediate Water (GNAIW), and also by an intensified of Antarctic Bottom Water (AABW), with the latter being a response to the enhanced salinity and ice formation around Antarctica. Most of the LGM intermediate/mode water is formed at 27.4 < sigma(theta) < 29.0 kg/m(3), while for the MH and PI most of the subduction transport occurs at 26.5 < sigma(theta) < 27.4 kg/m(3). The simulated LGM Southern Hemisphere winds are more intense by 0.2-0.4 dyne/cm(2). Consequently, increased Ekman transport drives the production of intermediate water (low salinity) at a larger rate and at higher densities when compared to the other climatic periods.

Climatic oscillations shape the phylogeographical structure of Atlantic Forest fire-eye antbirds (Aves: Thamnophilidae)

In the present study, mitochondrial (mt)DNA sequence data were used to examine the genetic structure of fire-eye antbirds (genus Pyriglena) along the Atlantic Forest and the predictions derived from the river hypothesis and from a Last Glacial Maximum Pleistocene refuge paleomodel were compared to explain the patterns of genetic variation observed in these populations. A total of 266 individuals from 45 populations were sampled over a latitudinal transect and a number of phylogeographical and population genetics analytical approaches were employed to address these questions. The pattern of mtDNA variation observed in fire-eye antbirds provides little support for the view that populations were isolated by the modern course of major Atlantic Forest rivers. Instead, the data provide stronger support for the predictions of the refuge model. These results add to the mounting evidence that climatic oscillations appear to have played a substantial role in shaping the phylogeographical structure and possibly the diversification of many taxa in this region. However, the results also illustrate the potential for more complex climatic history and historical changes in the geographical distribution of Atlantic Forest than envisioned by the refuge model. (c) 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 900824.

RegCM3 nested in HadAM3 scenarios A2 and B2: projected changes in extratropical cyclogenesis, temperature and precipitation over the South Atlantic Ocean

The RegCM3 (Regional Climate Model-version 3) was nested in HadAM3 model to simulate present (1975-1989, referred hereafter as RegHad) and two future climate scenarios (A2 and B2 from 2071 to 2085, referred as RegA2 and RegB2) over the South America (SA) and South Atlantic Ocean (SAO). Projected changes in the air temperature, precipitation, low level circulation and cyclogenesis climatology were investigated. The cyclogenesis were identified using an automatic scheme for tracking based on the minimum of relative vorticity (zeta) from 10-m height wind. During summer, a general decrease (increase) in the precipitation is projected by RegA2 and RegB2 over the northeastern SA (center-west and south Brazil, north Argentina and Uruguay). For winter, an anomalous low level anticyclonic circulation is associated with the reduction in the rainfall over the central part of southern Brazil in RegA2 and RegB2 scenarios. Similar to HadAM3, RegCM3 projects larger warming in A2 scenario. For the present climate, when compared to HadAM3, RegHad defines better both the location of the main cyclogenetic areas and its annual cycle near southwestern SAO. The projections indicate a reduction in the total number of cyclones of -7.2% and -4.7% for RegA2 and RegB2, respectively, while HadAM3 reduction is -4.5% for both scenarios. The decrease is larger for initially intense cyclones (zeta <=-<= 2.5 x 10(-5) s-(1)): -20.9% (RegA2) and -11.3% (RegB2). For the lifetime, distance traveled and mean velocity of the cyclones, the A2 and B2 scenarios present mean values close to the present climate ( 3 days, 1900 km, and 9 m s(-1), respectively). Regarding the initial mean vorticity of the systems, RegB2 simulates values similar to the present climate, but they are initially weaker in RegA2. In general, RegA2 and RegB2 show a large decrease in the number of cyclones over the southern SAO due to an anticyclonic anomaly covering SAO between 30-55A degrees S. The reduction is larger in the scenario with higher concentrations of greenhouse gases (RegA2).

Geochemical evidence of the 8.2 ka event and other Holocene environmental changes recorded in paleolagoon sediments, southeastern Brazil

The paleoclimatic record of Jureia Paleolagoon, coastal southeastem Brazil, includes cyclic and gradual changes with different intensities and frequencies through geological time, and it is controlled by astronomical, geophysical, and geological phenomena. These variations are not due to one single cause, but they result from the interaction of several factors, which act at different temporal and spatial scales. Here, we describe paleoenvironmental evidence regarding climatic and sea level changes from the last 9400 cal yr BP at the Jureia Paleolagoon - one of the main groups of protected South Atlantic ecosystems. Geochemical evidences were used to identify anomalies from multi-proxy analyses of a paleolagoon sediment core. The anomalies of centennial scale were correlated to climate and transgression-regression cycles from the Holocene period. Decadal scale anomalous oscillations in the Quaternary paleolagoon sediments occur between 9400 and 7500 cal yr BP, correlated with long- and short-term natural events, which generated high sedimentation rates, mainly between 8385 and 8375 cal yr BP (10 cm/yr). Our results suggest that a modem-day short-duration North Atlantic climatic event, such as the 82 ka event, could affect the environmental equilibrium in South America and intensify the South American Summer Monsoon. (C) 2011 University of Washington. Published by Elsevier Inc. All rights reserved.