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1.
Rapid Commun Mass Spectrom ; 38(17): e9842, 2024 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-38923691

RESUMO

RATIONALE: Stable carbon and oxygen isotope data of biogenic and abiogenic aragonite are of fundamental relevance in paleoclimate research. Wet-chemical analysis of such materials requires well-homogenized, fine-grained powder. In the present study, the effect of different grinding/milling methods on sample homogeneity and the potential risk of unintentional calcite formation and isotope shift were evaluated. METHODS: Shells of Arctica islandica and aragonite sputnik crystals were pulverized using a set of commonly used methods, including a hand-held drill, a vibromill operated at various settings (with and without liquid nitrogen cooling, changes in ball diameters, frequencies, and processing durations), and an agate mortar and pestle. Stable isotope values were measured using an isotope ratio mass spectrometer operated in continuous flow mode. Identification of mineral phases was obtained by powder X-ray diffraction (PXRD), Raman spectroscopy, and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Calcite content was quantified by PXRD Rietveld refinement. RESULTS: Samples showed substantial homogeneity, in particular after vibromilling (duration 3-10 min). More vigorous grinding resulted in larger fractions of calcite (0.5-4.2 wt%) and a concomitant δ18O and δ13C decrease, specifically in bivalve shells. The only method for producing pure aragonite powder was by pounding the aragonite sputniks manually with an agate mortar and pestle. CONCLUSIONS: None of the studied, commonly used machine-based pulverization methods produced pure aragonite powder from samples consisting originally of aragonite. These findings have significant implications for light-stable isotope-based paleoclimate reconstructions. Except for abiogenic aragonite powder produced by pounding in an agate mortar, paleotemperatures would be overestimated.

2.
Biol Lett ; 15(1): 20180665, 2019 01 31.
Artigo em Inglês | MEDLINE | ID: mdl-30958223

RESUMO

Over the past century, the dendrochronology technique of crossdating has been widely used to generate a global network of tree-ring chronologies that serves as a leading indicator of environmental variability and change. Only recently, however, has this same approach been applied to growth increments in calcified structures of bivalves, fish and corals in the world's oceans. As in trees, these crossdated marine chronologies are well replicated, annually resolved and absolutely dated, providing uninterrupted multi-decadal to millennial histories of ocean palaeoclimatic and palaeoecological processes. Moreover, they span an extensive geographical range, multiple trophic levels, habitats and functional types, and can be readily integrated with observational physical or biological records. Increment width is the most commonly measured parameter and reflects growth or productivity, though isotopic and elemental composition capture complementary aspects of environmental variability. As such, crossdated marine chronologies constitute powerful observational templates to establish climate-biology relationships, test hypotheses of ecosystem functioning, conduct multi-proxy reconstructions, provide constraints for numerical climate models, and evaluate the precise timing and nature of ocean-atmosphere interactions. These 'present-past-future' perspectives provide new insights into the mechanisms and feedbacks between the atmosphere and marine systems while providing indicators relevant to ecosystem-based approaches of fisheries management.


Assuntos
Clima , Ecossistema , Animais , Mudança Climática , Oceanos e Mares , Árvores
3.
Rapid Commun Mass Spectrom ; 28(12): 1371-5, 2014 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-24797948

RESUMO

RATIONALE: Milling of wood samples is a widely applied preparation method for pooling tree-rings from different trees or periods of several years for determination of δ(13)C and δ(18)O values. In this study, whole wood samples were milled using different procedures in order to evaluate potential effects of this preparation method on δ(13)C and δ(18)O values. METHODS: Subsamples of a 5 cm(3) wood piece of a single tree-ring from a lowland white fir were used. The samples were milled with different setups: (i) two and three stainless-steel balls, (ii) 3, 5 and 8 min milling time, and (iii) discontinuous and continuous milling. The δ(13)C values were measured using an elemental analyser connected to an IsoPrime mass spectrometer and δ(18)O values using a Thermo Scientific MAT 253 mass spectrometer and a TC/EA connected by a ConFlo IV. RESULTS: The results show that varying the milling procedure does not alter the δ(13)C and δ(18)O values in comparison to non-milled blank samples. For shorter milling times, an increased variance of δ(18)O values is recorded, probably caused by isotopic gradient between early- and latewood portions of the tree-ring and thereby biasing the insufficiently homogenised samples. No overheating effects on the δ(13)C and δ(18)O values were detected. CONCLUSIONS: Milling of wood samples for carbon and oxygen isotope analyses is an appropriate preparation method.

4.
PLoS One ; 19(3): e0299958, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38446809

RESUMO

In around 716 AD, the city of Santarém, Portugal, was conquered by the Berber and Arab armies that swept the Iberian Peninsula and went on to rule the region until the 12th century. Archaeological excavations in 2007/08 discovered an Islamic necropolis (Avenida 5 de Outubro #2-8) that appears to contain the remains of an early Muslim population in Santarém (8th- 10th century). In this study, skeletal material from 58 adult individuals was analysed for stable carbon (δ13Ccol; δ13Cap), nitrogen (δ15N) and sulphur (δ34S) isotope ratios in bones, and stable oxygen (δ18O), carbon (δ13Cen) and radiogenic strontium (87Sr/86Sr) isotopes in tooth enamel. The results of this study revealed a dietary pattern of predominantly C3-plant and domestic C3-fed herbivore consumption during adulthood (δ13Ccol and δ15N, respectively) but a higher proportion of C4-plant input during childhood (δ13Cen) for some individuals-interpreted as possible childhood consumption of millet porridge, a common practice in North Africa-in those with unorthodox burial types (Groups 1 and 2) that was not practiced in the individuals with canonical burials (Group 3). In this first mobility study of a medieval Muslim population in Portugal, δ18ODW values revealed greater heterogeneity in Groups 1 and 2, consistent with diverse origins, some in more humid regions than Santarém when compared to regional precipitation δ18O data, contrasting the more homogenous Group 3, consistent with the local precipitation δ18O range. Ancient DNA analysis conducted on three individuals revealed maternal (mtDNA) and paternal (Y-chromosome) lineages compatible with a North African origin for (at least) some of the individuals. Additionally, mobility of females in this population was higher than males, potentially resulting from a patrilocal social system, practiced in Berber and Arab communities. These results serve to offer a more detailed insight into the ancestry and cultural practices of early Muslim populations in Iberia.


Assuntos
Islamismo , Isótopos de Estrôncio , Humanos , Adulto , Feminino , Masculino , Portugal , Carbono
5.
Sci Total Environ ; 888: 164011, 2023 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-37172859

RESUMO

The Baltic Sea serves as a model region to study processes leading to oxygen depletion. Reconstructing past low-oxygen occurrences, specifically hypoxia, is crucial to understand current ecological disturbances and developing future mitigation strategies. The history of dissolved oxygen (DO) concentration in some Baltic Sea basins has been investigated in previous studies, but temporally well-constrained, inter-annual and better resolved DO reconstructions are still scarce. Here, we present precisely dated, high-resolution DO record since the mid-19th century reconstructed from Mn/Cashell values of Arctica islandica (Bivalvia) collected in the Mecklenburg Bight. According to the data, this area experienced similar low oxygenation during the second half of the 19th century and the late 20th century, but DO variability increased: A 12-15-yr oscillation prevailed in the 19th century, but a 4-6-year period dominated in the late 20th century. Shortly after the onset of the Industrial Revolution around 1850, Mn/Cashell values increased, indicating a DO decrease, probably caused by strong anthropogenic nutrient input. More recently, phosphate levels and inflows of oxygen-rich North Sea water have been identified as major factors controlling the bottom water oxygenation. For example, the increase in DO in the mid-1990s was linked to the decrease in phosphate content and several Major Baltic Inflows. The strong Ba/Cashell rise between the 1860s and the turn of the century most likely reflects changes in diatom community structure rather than a bloom of mass phytoplankton. This is supported by largely unchanged Mn/Cashell and shell growth. Decadal and multi-decadal cycles of shell growth rate correlated strongly with the Atlantic Multidecadal Variability, likely reflecting changes in atmospheric circulation patterns, precipitation rate and riverine nutrient supply. To further improve the management and protection of ecosystems in the Baltic Sea, a larger number of such high-resolution retrospective studies covering long periods of time and large regions are needed.


Assuntos
Bivalves , Oxigênio , Animais , Ecossistema , Estudos Retrospectivos , Hipóxia
6.
Sci Rep ; 12(1): 3111, 2022 02 24.
Artigo em Inglês | MEDLINE | ID: mdl-35210501

RESUMO

Prehistoric shell middens hold valuable evidence of past human-environment interactions. In this study, we used carbon (δ13C) and oxygen (δ18O) stable isotopes of Mytilus galloprovincialis shells excavated from El Perro, La Fragua and La Chora, three Mesolithic middens in Cantabria, Northern Spain, to examine hunter-gatherer subsistence strategies in terms of seasonality and collection areas. Furthermore, we used shell δ18O to reconstruct water temperature during the early Holocene. Stable isotopes reveal a shellfish harvesting diversification trend represented by the gradual establishment of the upper estuaries as new procurement areas and an increase of harvesting mobility in both coastal and in-land sites. These innovations in subsistence strategies during the Mesolithic coincided with major changes in the surrounding environment as attested by the water temperature reconstructions based on δ18O and backed by several global and regional records. Overall, our results show that shell δ13C and δ18O stable isotopes have an underexplored potential as provenance proxies which stimulates their application to the archaeological record to further understand prehistoric human resource procurement and diet.

7.
PLoS One ; 16(2): e0247968, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33635907

RESUMO

Bivalve shells are increasingly used as archives for high-resolution paleoclimate analyses. However, there is still an urgent need for quantitative temperature proxies that work without knowledge of the water chemistry-as is required for δ18O-based paleothermometry-and can better withstand diagenetic overprint. Recently, microstructural properties have been identified as a potential candidate fulfilling these requirements. So far, only few different microstructure categories (nacreous, prismatic and crossed-lamellar) of some short-lived species have been studied in detail, and in all such studies, the size and/or shape of individual biomineral units was found to increase with water temperature. Here, we explore whether the same applies to properties of the crossed-acicular microstructure in the hinge plate of Arctica islandica, the microstructurally most uniform shell portion in this species. In order to focus solely on the effect of temperature on microstructural properties, this study uses bivalves that grew their shells under controlled temperature conditions (1, 3, 6, 9, 12 and 15°C) in the laboratory. With increasing temperature, the size of the largest individual biomineral units and the relative proportion of shell occupied by the crystalline phase increased. The size of the largest pores, a specific microstructural feature of A. islandica, whose potential role in biomineralization is discussed here, increased exponentially with culturing temperature. This study employs scanning electron microscopy in combination with automated image processing software, including an innovative machine learning-based image segmentation method. The new method greatly facilitates the recognition of microstructural entities and enables a faster and more reliable microstructural analysis than previously used techniques. Results of this study establish the new microstructural temperature proxy in the crossed-acicular microstructures of A. islandica and point to an overarching control mechanism of temperature on the micrometer-scale architecture of bivalve shells across species boundaries.


Assuntos
Adaptação Fisiológica/fisiologia , Exoesqueleto/química , Exoesqueleto/crescimento & desenvolvimento , Bivalves/crescimento & desenvolvimento , Laboratórios , Temperatura , Animais , Processamento de Imagem Assistida por Computador/métodos , Aprendizado de Máquina , Microscopia Eletrônica de Varredura/métodos , Paleontologia/métodos , Porosidade , Software , Água/química
8.
PLoS One ; 15(8): e0238040, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32853273

RESUMO

In this study we attempted to assess whether seasonal upwelling or a steady thermocline persisted at the western margin of the Tethys Ocean during the late Turonian-early Coniacian interval. For this scope, we employed novel and published stable oxygen isotope (δ18O) data of various organisms (bivalves, bivalves, brachiopods, fish and belemnites). New seasonally resolved temperature estimates were based on the δ18O record of sequentially sampled inoceramid (Inoceramus sp.) and rudist (Hippurites resectus) shells from the Scaglia Rossa and Gosau deposits of northern Italy and western Austria, respectively. Diagenetic screening was performed using reflected light, cathodoluminescence (CL), scanning electron microscopy (SEM) and stable isotope analysis. Originally preserved δ13C and δ18O values were used to characterize the lifestyle of the bivalves and detect vital effects that could have biased oxygen isotope-based temperature reconstructions. Inoceramid δ18O values provide-for the first time-information on temperatures of Tethyan benthic waters, which were, on average, 14.4 ± 0.6 °C and fluctuated seasonally within a range of less than 2 °C. Such a thermal regime is in line with the temperatures postulated for late Turonian boreal water masses and support the existence of a cold water supply from the North Atlantic to the Tethyan bottom. Bottom cooling, however, did not affect the shallow water environment. In fact, the rudist-based temperature estimates for shallow water environment revealed a mean annual range of 11 °C, between 24 and 35 °C (assuming a seasonally constant δ18Ow = 1.0 ‰), which are among the warmest temperatures recorded over the entire Late Cretaceous. Our findings, thus, suggest a strong thermal and food web decoupling between the two environments. The absence of a seasonal vertical homogenization of different water bodies suggests the existence of a steady thermocline and, therefore, contrasts with the presence of an active coastal upwelling in the region as hypothesized by previous authors.


Assuntos
Bivalves , Oceanos e Mares , Estações do Ano , Temperatura , Animais , Bivalves/química , Isótopos de Oxigênio/química , Paleontologia , Água/química
9.
Sci Total Environ ; 705: 135501, 2020 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-31846816

RESUMO

Trace elements of bivalve shells can potentially record the physical and chemical properties of the ambient seawater during shell formation, thereby providing valuable information on environmental conditions and provenance of the bivalves. In an acidifying ocean, whether and how seawater acidification affects the trace elemental composition of bivalve shells is largely unknown. Here, we investigated the transgenerational effects of OA projected for the end of the 21st century on the incorporation of trace elements into shells of the Manila clam, Ruditapes philippinarum. Neither seawater pH nor transgenerational exposure affected the Mg and Sr composition of the shells. Compared with clams grown under ambient conditions, specimens exposed to elevated CO2 levels incorporated significantly higher amounts of Cu, Zn, Ba and Pb into their shells, in line with the fact that at lower pH, these elements in seawater occur at higher fractions in free forms which are biologically available. Transgenerational effects manifested themselves significantly during the incorporation of Cu and Zn into the shells, most likely because Cu and Zn are biologically essential trace elements for metabolic processes. In addition, the plasticity of metabolism toward energetic efficiency following transgenerational exposure confers the clams enhanced ability to discriminate against Cu and Zn during the uptake from the ambient environment to the site of calcification. In the context of near-future OA scenarios, these findings may provide unique insights into the two primary applications of trace elements of bivalve shells as geographical tracers and proxies of environmental conditions.


Assuntos
Bivalves , Animais , Concentração de Íons de Hidrogênio , Alimentos Marinhos , Água do Mar , Oligoelementos
10.
Mar Environ Res ; 150: 104759, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31344588

RESUMO

Due to its outstanding longevity (decades), the shallow-water bivalve Glycmeris pilosa represents a prime target for sclerochronological research in the Mediterranean Sea. In the present study, we analyzed the microgrowth patterns and the stable carbon (δ13Cshell) and oxygen (δ18Oshell) isotopes of the outer shell layer of live-collected G. pilosa specimens from four different sites along the Croatian coast, middle Adriatic Sea. Combined analysis of shell growth patterns and temporally aligned δ18Oshell data indicated that the main growing season lasts from April to December, with fastest growth rates occurring during July and August when seawater temperatures exceeded 22 °C. Slow growth in the cold season (<12 °C) coincided with the formation of winter growth lines on the outer shell surface. The growth cessation occurred in winter, but on the outer shell surface the brown summer bands are more pronounced than the winter lines. Mutvei-staining of cross-sections facilitated the recognition of the growth lines. δ13Cshell values reflect ontogenetic changes in physiology as well as seasonal changes in primary production and salinity.


Assuntos
Bivalves , Monitoramento Ambiental , Animais , Bivalves/química , Bivalves/crescimento & desenvolvimento , Mar Mediterrâneo , Salinidade , Estações do Ano , Água do Mar
11.
Sci Rep ; 9(1): 6753, 2019 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-31043648

RESUMO

The abrupt 8.2 ka cold event has been widely described from Greenland and North Atlantic records. However, its expression in shelf seas is poorly documented, and the temporal resolution of most marine records is inadequate to precisely determine the chronology of major events. A robust hydrographical reconstruction can provide an insight on climatic reaction times to perturbations to the Atlantic Meridional Overturning Circulation. Here we present an annually-resolved temperature and water column stratification reconstruction based on stable isotope geochemistry of Arctica islandica shells from the Fladen Ground (northern North Sea) temporally coherent with Greenland ice core records. Our age model is based on a growth increment chronology obtained from four radiometrically-dated shells covering the 8290-8100 cal BP interval. Our results indicate that a sudden sea level rise (SSLR) event-driven column stratification occurred between ages 8320-8220 cal BP. Thirty years later, cold conditions inhibited water column stratification but an eventual incursion of sub-Arctic waters into the North Sea re-established density-driven stratification. The water temperatures reached their minimum of ~3.7 °C 55 years after the SSLR. Intermittently-mixed conditions were later established when the sub-Arctic waters receded.

12.
Mar Environ Res ; 134: 138-149, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29395260

RESUMO

Seasonal shell growth patterns were analyzed using the stable oxygen and carbon isotope values of live-collected specimens of the bivalve Callista chione from two sites in the Adriatic Sea (Pag and Cetina, Croatia). Micromilling was performed on the shell surface of three shells per site and shell oxygen isotopes of the powder samples were measured. The timing and rate of seasonal shell growth was determined by aligning the δ18Oshell-derived temperatures so that the best fit was achieved with the instrumental temperature curve. According to the data, shells grew only at very low rates or not at all during the winter months, i.e., between January and March. Shell growth slowdown/shutdown temperatures varied among sites, i.e., 13.6 °C at Pag and 16.6 °C at Cetina, indicating that temperature was not the only driver of shell growth. Likely, seasonal differences in seawater temperature and food supply were the major component explaining contrasting growth rates of C. chione at two study sites. Decreasing shell growth rates were also associated with the onset of gametogenesis suggesting a major energy reallocation toward reproduction rather than growth. These results highlight the need to combine sclerochronological analyses with ecological studies to understand life history traits of bivalves as archives of environmental variables.


Assuntos
Fatores Biológicos , Bivalves/fisiologia , Animais , Isótopos de Carbono , Croácia , Isótopos de Oxigênio
13.
PLoS One ; 13(6): e0199212, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29902260

RESUMO

The Atlantic surfclam (Spisula solidissima) is a commercially important species in North American waters, undergoing biological and ecological shifts. These are attributed, in part, to environmental modifications in its habitat and driven by climate change. Investigation of shell growth patterns, trace elements, and isotopic compositions require an examination of growth lines and increments preserved in biogenic carbonates. However, growth pattern analysis of S. solidissima is challenging due to multiple disturbance lines caused by environmental stress, erosion in umbonal shell regions, and constraints related to sample size and preparation techniques. The present study proposes an alternative method for describing chronology. First, we analyzed growth patterns using growth lines within the shell and hinge. To validate the assumption of annual periodicity of growth line formation, we analyzed the oxygen isotope composition of the outer shell layer of two specimens (46°54'20"N; 56°18'58"W). Maximum δ18Oshell values occurred at the exact same location as internal growth lines in both specimens, confirming that they are formed annually and that growth ceases during winter. Next, we used growth increment width data to build a standardized growth index (SGI) time-series (25-year chronology) for each of the three parts of the shell. Highly significant correlations were found between the three SGI chronologies (p < 0.001; 0.55 < τ < 0.68) of all specimens. Thus, ligament growth lines provide a new method of determining ontogenetic age and growth rate in S. solidissima. In a biogeographic approach, the shell growth performance of S. solidissima in Saint-Pierre and Miquelon was compared to those in other populations along its distribution range in order to place this population in a temporal and regional context.


Assuntos
Exoesqueleto/crescimento & desenvolvimento , Ligamentos/crescimento & desenvolvimento , Oceanos e Mares , Spisula/crescimento & desenvolvimento , Animais , América do Norte , Isótopos de Oxigênio/análise , Spisula/química
14.
Chemosphere ; 203: 132-138, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29614406

RESUMO

Marine bivalves inhabiting naturally pCO2-enriched habitats can likely tolerate high levels of acidification. Consequently, elucidating the mechanisms behind such resilience can help to predict the fate of this economically and ecologically important group under near-future scenarios of CO2-driven ocean acidification. Here, we assess the effects of four environmentally realistic pCO2 levels (900, 1500, 2900 and 6600 µatm) on the shell production rate of Mya arenaria juveniles originating from a periodically pCO2-enriched habitat (Kiel Fjord, Western Baltic Sea). We find a significant decline in the rate of shell growth as pCO2 increases, but also observe unchanged shell formation rates at moderate pCO2 levels of 1500 and 2900 µatm, the latter illustrating the capacity of the juveniles to partially mitigate the impact of high pCO2. Using recently developed geochemical tracers we show that M. arenaria exposed to a natural pCO2 gradient from 900 to 2900 µatm can likely concentrate HCO3- in the calcifying fluid through the exchange of HCO3-/Cl- and simultaneously maintain the pH homeostasis through active removal of protons, thereby being able to sustain the rate of shell formation to a certain extent. However, with increasing pCO2 beyond natural maximum the bivalves may have limited capacity to compensate for changes in the calcifying fluid chemistry, showing significant shell growth reduction. Findings of the present study may pave the way for elucidating the underlying mechanisms by which marine bivalves acclimate and adapt to high seawater pCO2.


Assuntos
Exoesqueleto/crescimento & desenvolvimento , Bicarbonatos/análise , Bivalves/crescimento & desenvolvimento , Dióxido de Carbono/farmacologia , Cloretos/análise , Ecossistema , Frutos do Mar , Exoesqueleto/efeitos dos fármacos , Exoesqueleto/metabolismo , Animais , Bivalves/efeitos dos fármacos , Bivalves/metabolismo , Concentração de Íons de Hidrogênio
15.
Sci Total Environ ; 645: 913-923, 2018 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-30032087

RESUMO

Long-term and high-resolution environmental proxy data are crucial to contextualize current climate change. The extremely long-lived bivalve, Arctica islandica, is one of the most widely used paleoclimate archives of the northern Atlantic because of its fine temporal resolution. However, the interpretation of environmental histories from microstructures and elemental impurities of A. islandica shells is still a challenge. Vital effects (metabolic rate, ontogenetic age, and growth rate) can modify the way in which physiochemical changes of the ambient environment are recorded by the shells. To quantify the degree to which microstructural properties and element incorporation into A. islandica shells is vitally or/and environmentally affected, A. islandica specimens were reared for three months under different water temperatures (3, 8 and 13 °C) and food concentrations (low, medium and high). Concentrations of Mg, Sr, Na, and Ba were measured in the newly formed shell portions by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The microstructures of the shells were analyzed by Scanning Electron Microscopy (SEM). Shell growth and condition index of each specimen were calculated at the end of the experimental period. Findings indicate that no significant variation in the morphometric characteristics of the microstructures were formed at different water temperatures or different food concentrations. Shell carbonate that formed at lowest food concentration usually incorporated the highest amounts of Mg, Sr and Ba relative to Ca+2 (except for Na) and was consistent with the slowest shell growth and lowest condition index at the end of the experiment. These results seem to indicate that, under food limitation, the ability of A. islandica to discriminate element impurities during shell formation decreases. Moreover, all trace element-to­calcium ratios were significantly affected by shell growth rate. Therefore, physiological processes seem to dominate the control on element incorporation into A. islandica shells.

16.
Mar Environ Res ; 63(3): 185-99, 2007 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-17045331

RESUMO

Annual growth increments were examined from shells of the ocean quahog (Arctica islandica L.) from northwest Norway and from tree-ring samples of the Scots pine (Pinus sylvestris L.) from nearby coastal areas. The reconstructed annual growth increments were used to compare growth variability in marine and terrestrial ecosystems. Spatiotemporal comparison of the growth records showed statistically significant correlation during the 19th century A.D., indicative of ecosystem-independent response to pre-anthropogenic climate variations. Geographical correlation between marine and terrestrial records was only observed at the local scale. Years with particularly low winter or high summer North Atlantic Oscillation (NAO) indices showed the best synchronization of marine and terrestrial growth. Despite strong correlation during historical time, our palaeoecological evidence suggests that marine and terrestrial ecosystems may show dissimilar growth reaction to recently observed positive winter-NAO phases.


Assuntos
Bivalves/crescimento & desenvolvimento , Clima , Ecossistema , Pinus sylvestris/crescimento & desenvolvimento , Animais , Noruega , Estações do Ano , Estatística como Assunto , Fatores de Tempo
17.
Sci Total Environ ; 577: 360-366, 2017 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-27823823

RESUMO

Ocean acidification is likely to have profound impacts on marine bivalves, especially on their early life stages. Therefore, it is imperative to know whether and to what extent bivalves will be able to acclimate or adapt to an acidifying ocean over multiple generations. Here, we show that reduced seawater pH projected for the end of this century (i.e., pH7.7) led to a significant decrease of shell production of newly settled juvenile Manila clams, Ruditapes philippinarum. However, juveniles from parents exposed to low pH grew significantly faster than those from parents grown at ambient pH, exhibiting a rapid transgenerational acclimation to an acidic environment. The sodium composition of the shells may shed new light on the mechanisms responsible for beneficial transgenerational acclimation. Irrespective of parental exposure, the amount of Na incorporated into shells increased with decreasing pH, implying active removal of excessive protons through the Na+/H+ exchanger which is known to depend on the Na+ gradient actively built up by the Na+/K+-ATPase as a driving force. However, the shells with a prior history of transgenerational exposure to low pH recorded significantly lower amounts of Na than those with no history of acidic exposure. It therefore seems very likely that the clams may implement less costly and more ATP-efficient ion regulatory mechanisms to maintain pH homeostasis in the calcifying fluid following transgenerational acclimation. Our results suggest that marine bivalves may have a greater capacity to acclimate or adapt to ocean acidification by the end of this century than currently understood.

18.
Mar Environ Res ; 119: 144-55, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-27285613

RESUMO

Raised atmospheric emissions of carbon dioxide (CO2) result in an increased ocean pCO2 level and decreased carbonate saturation state. Ocean acidification potentially represents a major threat to calcifying organisms, specifically mollusks. The present study focuses on the impact of elevated pCO2 on shell microstructural and mechanical properties of the bivalve Cerastoderma edule. The mollusks were collected from the Baltic Sea and kept in flow-through systems at six different pCO2 levels from 900 µatm (control) to 24,400 µatm. Extreme pCO2 levels were used to determine the effects of potential leaks from the carbon capture and sequestration sites where CO2 is stored in sub-seabed geological formations. Two approaches were combined to determine the effects of the acidified conditions: (1) Shell microstructures and dissolution damage were analyzed using scanning electron microscopy (SEM) and (2) shell hardness was tested using nanoindentation. Microstructures of specimens reared at different pCO2 levels do not show significant changes in their size and shape. Likewise, the increase of pCO2 does not affect shell hardness. However, dissolution of ontogenetically younger portions of the shell becomes more severe with the increase of pCO2. Irrespective of pCO2, strong negative correlations exist between microstructure size and shell mechanics. An additional sample from the North Sea revealed the same microstructural-mechanical interdependency as the shells from the Baltic Sea. Our findings suggest that the skeletal structure of C. edule is not intensely influenced by pCO2 variations. Furthermore, our study indicates that naturally occurring shell mechanical property depends on the shell architecture at µm-scale.


Assuntos
Exoesqueleto/química , Dióxido de Carbono/análise , Cardiidae/fisiologia , Monitoramento Ambiental , Água do Mar/química , Exoesqueleto/fisiologia , Animais , Carbonatos , Concentração de Íons de Hidrogênio , Mar do Norte
19.
Isotopes Environ Health Stud ; 52(6): 694-705, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27090102

RESUMO

δ(13)C and δ(18)O values from sapwood of a single Pinus uncinata tree, from a high elevation site in the Spanish Pyrenees, were determined to evaluate the differences between whole wood and resin-free whole wood. This issue is addressed for the first time with P. uncinata over a 38-year long period. Results are also compared with published isotope values of α-cellulose samples from the same tree. The differences in δ(13)C and δ(18)O between whole wood and resin-free whole wood vary within the analytical uncertainty of 0.3 and 0.5 ‰, respectively, indicating that resin extraction is not necessary for sapwood of P. uncinata. Mean differences between cellulose and whole wood are 0.9 ‰ (δ(13)C) and 5.0 ‰ (δ(18)O), respectively. However, further analyses of different species and other sites are needed to evaluate whether the findings reported here are coherent more generally.


Assuntos
Isótopos de Carbono/análise , Celulose/química , Isótopos de Oxigênio/análise , Madeira/química , Pinus , Espanha
20.
Acta Biomater ; 10(9): 3911-21, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-24704696

RESUMO

Mollusk shells contain a plethora of information on past climate variability. However, only a limited toolkit is currently available to reconstruct such data from the shells. The environmental data of some proxies (e.g. Sr/Ca ratios) is obscured by physiological effects, whereas other proxies, such as δ(18)O, simultaneously provide information on two or more different environmental variables. The present study investigates whether microstructures of the freshwater gastropod Viviparus viviparus provide an alternative means to reconstruct past water temperature. Cold and highly variable temperature regimes resulted in the precipitation of highly unordered first-order lamellae of simple crossed-lamellar (XLM) structures if new shell formed from scratch. However, during stable and warm conditions, well-ordered first-order lamellae were laid down irrespective of pre-existing shell material. Homogeneous first-order lamellae also formed during times of cold and highly variable temperatures if the new shell was deposited onto existing shell material with well-ordered first-order lamellae. The growth front seems to contain instructions for building specific microstructure variants, irrespective of environmental conditions. However, if this template is missing, the animal forms a deviating microstructure. Under extremely stressful situations (e.g. removal from habitat, calcein staining, extreme temperature shifts), the gastropod precipitates an evolutionarily older microstructure (irregular simple prisms) rather than XLM structures. These shell portions were macroscopically described as disturbance lines. In addition, repetitive, presumably periodic growth patterns were observed, which consisted of gradually changing third-order lamellae between consecutive faint, organic-rich growth lines. These growth patterns were probably controlled by intrinsic biological clocks and exhibited a two-daily periodicity. The results of this study may provide the basis for using changes in the microstructure of shell sections as a new sensor (environmental proxy) for past water temperature.


Assuntos
Exoesqueleto/anatomia & histologia , Água Doce , Gastrópodes/anatomia & histologia , Temperatura , Exoesqueleto/crescimento & desenvolvimento , Exoesqueleto/ultraestrutura , Animais , Gastrópodes/ultraestrutura , Tamanho do Órgão
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