The role of microorganisms in the formation of calcitic moonmilk deposits and speleothems in Altamira Cave

Bacteria are able to induce carbonate precipitation although the participation of microbial or chemical processes in speleothem formation remains a matter of debate. In this study, the origin of carbonate depositions such as moonmilk, an unconsolidated microcrystalline formation with high water content, and the consolidation of carbonate precipitates into hard speleothems were analyzed. The utilized methods included measurements of the composition of stable isotopes in these precipitates, fluorimetric determinations of RNA/DNA ratios and respirometric estimations in Altamira Cave. Results from isotope composition showed increases of the δ18O and δ13C ratios from moonmilk in the very first stages of formation toward large speleothems. Estimates of RNA/DNA ratios suggested an inactivation of microorganisms from incipient moonmilk toward consolidated deposits of calcium carbonate. Respiratory activity of microorganisms also showed a significant decrease in samples with accumulated calcite. These results suggest that bacterial activity induces the conditions required for calcium carbonate precipitation, initiating the first stages of deposition. Progressive accumulation of carbonate leads towards a less favorable environment for the development of bacteria. On consolidated speleothems, the importance of bacteria in carbonate deposition decreases and chemical processes gain importance in the deposition of carbonates.

Pliocene-Pleistocene stack of globally distributed benthic stable oxygen isotope records

We present a 5.3-Myr stack (the ''LR04'' stack) of benthic d18O records from 57 globally distributed sites aligned by an automated graphic correlation algorithm. This is the first benthic delta18O stack composed of more than three records to extend beyond 850 ka, and we use its improved signal quality to identify 24 new marine isotope stages in the early Pliocene. We also present a new LR04 age model for the Pliocene-Pleistocene derived from tuning the delta18O stack to a simple ice model based on 21 June insolation at 65 N. Stacked sedimentation rates provide additional age model constraints to prevent overtuning. Despite a conservative tuning strategy, the LR04 benthic stack exhibits significant coherency with insolation in the obliquity band throughout the entire 5.3 Myr and in the precession band for more than half of the record. The LR04 stack contains significantly more variance in benthic delta18O than previously published stacks of the late Pleistocene as the result of higher resolution records, a better alignment technique, and a greater percentage of records from the Atlantic. Finally, the relative phases of the stack's 41- and 23-kyr components suggest that the precession component of delta18O from 2.7-1.6 Ma is primarily a deep-water temperature signal and that the phase of d18O precession response changed suddenly at 1.6 Ma.

(Table 2) Stable carbon and oxygen isotope record of benthic foraminifera of eastern Mediterranean Sea sediment cores

The paleoproductivity, paleo-oxygenation, and paleohydrographic configuration of the southeastern Mediterranean during the late Holocene was reconstructed on the basis of the isotopic composition of the epibenthic Heterolepa floridana, shallow-endobenthic Uvigerina mediterranea, and the deeper endobenthic Bulimina inflata from two high-resolution cores GA-112 (470 m) and GA-110 (670 m). The Delta d13C between H. floridana and U. mediterranea reveals four intervals of enhanced productivity, from 3.3-2.6, 2.3-1.9, 1.5-1.1, and 0.8-0.4 kyr BP, coinciding with increased nutrient supply by the Nile River. The entire basin was well aerated, with oxygen consumption varying between 1.0 and 3.5 mL O2/L. Oxygen consumption increases toward present day, probably because of higher accumulation of total organic carbon at 1.7 kyr BP, coinciding with the appearance of the mesotropic benthic species. The hydrographic configuration of the basin has changed during the course of the last 3.75 kyr. The Levantine Intermediate Water (LIW) deepens below 470 m between 3.3 and 2.0 kyr, and especially between 2.5 and 2.0 kyr. During the last 1.5 kyr, the LIW becomes shallower than 470 m, similar to the present day. The change in the hydrographic configuration reflects changes in evaporation/precipitation ratio and in temperature.

Late Paleocene to Eocene stable isotope record od ODP Site 143-865

An expanded and largely complete upper Paleocene to upper Eocene section was recovered from the pelagic cap overlying Allison Guyot, Mid-Pacific Mountains at Ocean Drilling Program (ODP) Site 865 (18°26'N, 179°33'W; paleodepth 1300-1500 m). Reconstructions show that the site was within a few degrees of the equator during the Paleogene. Because no other Paleogene sections have been recovered in the Pacific Ocean at such a low latitude, Site 865 provides a unique record of equatorial Pacific paleoceanography. Detailed stable isotopic investigations were conducted on three planktonic foraminiferal taxa (species of Acarinina, Morozovella, and Subbotina). We studied benthic foraminiferal isotopes at much lower resolution on species of Cibicidoides and Lenticulina, Nuttallides truempyi and Gavelinella beccariiformis, because of their exceptional rarity. The d18O and d13C stratigraphies from Site 865 are generally similar to those derived from other Paleocene and Eocene sections. The planktonic foraminiferal records at Site 865, however, include significantly less short-term, single-sample variability than those from higher-latitude sites, indicating that this tropical, oligotrophic location had a comparatively stable water column structure with a deep mixed layer and less seasonal variability. Low-amplitude (0.1-0.8 per mil) oscillations on timescales of 250,000 to 300,000 years correlate between the d13C records of all planktonic taxa and may represent fluctuations in the mixing intensity of surface waters. Peak sea surface temperatures of 24°-25°C occurred in the earliest Eocene, followed by a rapid cooling of 3-6°C in the late early Eocene. Temperatures remained cool and stable through the middle Eocene. In the late Eocene, surface water temperatures decreased further. Vertical temperature gradients decreased dramatically in the late Paleocene and were relatively constant through much of the Eocene but increased markedly in the late Eocene. Intermediate waters warmed through the late Paleocene, reaching a maximum temperature of 10°C in the early Eocene. Cooling in the middle and late Eocene paralleled that of surface waters, with latest Eocene temperatures below 5°C. Extinction patterns of benthic foraminifera in the latest Paleocene were similar to those observed at other Pacific sites and were coeval with a short-term, very rapid negative excursion in d13C values in planktonic and benthic taxa as at other sites. During this excursion, benthic foraminiferal d18O values decreased markedly, indicating warming of 4 to 6°C for tropical intermediate waters, while planktonic taxa show slight warming (1°C) followed by 2°C of cooling. Convergence of d18O values of planktonic and benthic foraminifera suggests that thermal gradients in the water column in this tropical location collapsed during the excursion. These data are consistent with the hypothesis that equatorial Pacific surface waters were a potential source of warm, higher salinity waters which filled portions of the deep ocean in the latest Paleocene. Oxygen isotopic data indicate that equator to high southern latitude sea surface thermal gradients decreased to as little as 4°C at the peak of the excursion, suggesting some fundamental change in global heat transport.

Stable isotope record of foraminifera from South Atlantic sediments with reconstruction of paleotemperatures and paleosalinities

Changes in surface water hydrography in the Southern Ocean (eastern Atlantic sector) could be reconstructed on the basis of isotope-geochemical and micropaleontological studies. A total of 75 high quality multicorer sediment surface samples from the southern South Atlantic Ocean and three Quaternary sediment cores, taken on a meridional transect across the Antarctic Circumpolar Current, have been investigated. The results of examining stable oxygen isotope compositions of 24 foraminiferal species and morphotypes were compared to the near-surface hydrography. The different foraminifera have been divided into four groups living at different depths in the upper water column. The 8180 differences between shallow-living (e.g. G. bulloides, N. pachyderma) and deeper-dwelling (e. g. G. inflata) species reflect the measured temperature gradient of the upper 250 m in the water column. Thus, the 6180 difference between shallow-living and deeper-living foraminifera can be used as an indicator for the vertical temperature gradient in the surface water of the Antarctic Circumpolar Current, which is independent of ice volume. All planktonic foraminifera in the surface sediment samples have been counted. 27 species and morphotypes have been selected, to form a reference data Set for statistical purposes. By using R- and Q-mode principal component analysis these planktonic foraminifera have been divided into four and five assemblages, respectively. The geographic distribution of these assemblages is mainly linked to the temperature of sea-surface waters. The five assemblages (factors) of the Q-mode principal component analysis account for 97.l % of the variance of original data. Following the transferfunction- technique a multiple regression between the Q-mode factors and the actual mean sea-surface environmental parameters resulted in a set of equations. The new transfer function can be used to estimate past sea-surface seasonal temperatures for paleoassemblages of planktonic foraminifera with a precision of approximately ±1.2°C. This transfer function F75-27-5 encompasses in particular the environmental conditions in the Atlantic sector of the Antarctic Circumpolar Current. During the last 140,000 years reconstructed sea-surface temperatures fluctuated in the present northern Subantarctic Zone (PS2076-1/3) at an amplitude of up to 7.5°C in summer and of up to 8.5°C in winter. In the present Polarfrontal Zone (PS1754-1) these fluctuations between glacials and interglacials show lower temperatures from 2.5 to 8.5°C in summer and from 1.0 to 5.0°C in winter, respectively. Compared to today, calculated oxygen isotope temperature gradients in the present Subantarctic Zone were lower during the last 140,000 years. This is an indicator for a good mixing of the upper water column. In the Polarfrontal Zone also lower oxygen isotope temperature gradients were found for the glacials 6, 4 and 2. But almost similar temperature gradients as today were found during the interglacial stages 5, 3 and the Holocene, which implicates a mixing of the upper water column compared to present. Paleosalinities were reconstructed by combining d18O-data and the evaluated transfer function paleotemperatures. Especially in the present Polarfrontal Zone (PS1754-1) and in the Antarctic Zone (PS1768-8), a short-term reduction of salinity up to 4 %o, could be detected. This significant reduction in sea-surface water salinity indicates the increased influx of melt-water at the beginning of deglaciation in the southern hemisphere at the end of the last glacial, approximately 16,500-13,000 years ago. The reconstruction of environmental Parameters indicates only small changes in the position of the frontal Systems in the eastern sector of the Antarctic Circumpolar Current during the last 140,000 years. The average position of the Subtropical Front and Subantarctic Front shifted approximately three latitudes between interglacials and glacials. The Antarctic Polar Front shifted approximately four latitudes. But substantial modifications of this scenario have been interpreted for the reconstruction of cold sea-surface temperatures at 41Â S during the oxygen isotope stages 16 and 14 to 12. During these times the Subtropical Front was probably shified up to seven latitudes northwards.

(Table T1) Stable carbon and oxygen isotope ratios of benthic foraminifera in the Late Pliocene-Pleistocene section of ODP Site 181-1123 in the Southwest Pacific

Stable isotope records were generated for a late Pliocene-early Pleistocene interval from Ocean Drilling Program (ODP) Site 1123 in the southwest Pacific (41°47 S, 171°30 W; 3290 m water depth). Based on these data, new revisions were made to the shipboard splice and composite section. The isotope records will be used to evaluate the influence of North Atlantic and Southern Ocean deepwater masses on water entering the Pacific in the Deep Western Boundary Current. Three holes were cored at Site 1123, yielding a complete composite section over approximately the last 4.7 m.y. A representative spliced record ("the splice") was developed aboard ship based on magnetic susceptibility, gamma ray attenuation bulk density, and percent reflectance data from the three adjacent holes (Carter, McCave, Richter, Carter, et al., 1999, doi:10.2973/odp.proc.ir.181.2000). No gaps in the sedimentary record were detected for the multiple-cored section of Site 1123. In addition to the isotope data, postcruise revisions to the splice and composite section based on stable isotope data are described here.

Climate change manipulations show Antarctic flora is more strongly affected by elevated nutrients than water

Climate change is expected to affect the high latitudes first and most severely, rendering Antarctica one of the most significant baseline environments for the study of global climate change. The indirect effects of climate warming, including changes to the availability of key environmental resources, such as water and nutrients, are likely to have a greater impact upon continental Antarctic terrestrial ecosystems than the effects of fluctuations in temperature alone. To investigate the likely impacts of a wetter climate on Antarctic terrestrial communities a multiseason, manipulative field experiment was conducted in the floristically important Windmill Islands region of East Antarctica. Four cryptogamic communities (pure bryophyte, moribund bryophyte, crustose and fructicose lichen-dominated) received increased water and/or nutrient additions over two consecutive summer seasons. The increased water approximated an 18% increase in snow melt days (0.2 degrees C increase in temperature), while the nutrient addition of 3.5g Nm(-2) yr(-1) was within the range of soil N in the vicinity. A range of physiological and biochemical measurements were conducted in order to quantify the community response. While an overall increase in productivity in response to water and nutrient additions was observed, productivity appeared to respond more strongly to nutrient additions than to water additions. Pure bryophyte communities, and lichen communities dominated by the genus Usnea, showed stronger positive responses to nutrient additions, identifying some communities that may be better able to adapt and prosper under the ameliorating conditions associated with a warmer, wetter future climate. Under such a climate, productivity is overall likely to increase but some cryptogamic communities are likely to thrive more than others. Regeneration of moribund bryophytes appears likely only if a future moisture regime creates consistently moist conditions.

Using nitrogen stable isotope ratios ( d15N) of macroalgae to monitor changes in the extent of sewage impacts in Moreton Bay, Australia

During the past decade the use of stable isotopes to investigate transport pathways of nutrients in aquatic ecosystems has contributed new understanding and knowledge to many aspects of ecology; from the trophic structure of food webs to the spatial extent of nutrient discharges. At the same time aquatic monitoring programs around the world have become more interested in quantifying ecosystem health rather than simply measuring the physical and chemical properties of water (nutrients, pH, temperature and turbidity). A novel technique was initiated in 1998 as part of the development of the Ecosystem Health Monitoring Program in S.E. Queensland Australia (EHMP) using changes in the 15N value of the red macroalgae Catenella nipae, to indicate regions impacted by sewage nitrogen. Sewage plume mapping, using the 15N of C. nipae, has demonstrated that over the past 5 years there has been a large reduction in the magnitude and spatial extent of 15N enrichment at sites close to sewage treatment plants (STPs) discharging into Moreton Bay. This presentation will discuss how the 15N signatures of the C. nipae in the plume at the mouth of the Brisbane River have declined since it was first sampled in 1998 and will evaluate causes that may be responsible for these variations. A series of laboratory experiments were conducted to investigate how environmental conditions influence the 15N signature of C, nipae over the incubation period. These data will be used to discuss the observed in situ decline in 15N in an attempt to determine if the reduction can be attributed solely to improvements in the wastewater discharge.

Chemical characterization of soil organic matter in an oligotrophic, subtropical, freshwater wetland system: Sources, diagenesis and preservation

Freshwater wetland soils of the Everglades were studied in order to assess present environmental conditions and paleo-environmental changes using organic geochemistry techniques. Organic matter in dominant vegetation, peat and marl soils was characterized by geochemical means. Samples were selected along nutrient and hydrology gradients with the objective to determine the historical sources of organic matter as well as the extent of its preservation. Effective molecular proxies were developed to differentiate the relative input of organic matter from different biological sources to wetland soils. Thus historical vegetation shifts and hydroperiods were reconstructed using those proxies. The data show good correlations with historical water management practices starting at the turn of the century and during the mid 1900's. Overall, significant shortening of hydroperiods during this period was observed. The soil organic matter (SOM) preservation was assessed through elemental analysis and molecular characterizations of bulk 13C stable isotopes, solid state 13C NMR spectroscopy, UV-Vis spectroscopy, and tetramethyl ammonium hydroxide (TMAH) thermochemolysis-GC/MS. The relationship of the environmental conditions and degradation status of the soil organic matter (SOM) among the sites suggested that both high nutrient levels and long hydroperiod favor organic matter degradation in the soils. This is probably the result of an increase in the microbial activity in the soils which have higher nutrient levels, while longer hydroperiods may enhance physical/chemical degradation processes. The most significant transformations of biomass litter in this environment are controlled by very early physical/chemical processes and once the OM is incorporated into surface soils, the diagenetic change, even over extended periods of time is comparatively minimal, and SOM is relatively well preserved regardless of hydroperiod or nutrient levels. SOM accumulated in peat soils is more prone to continued degradation than the SOM in the marl soils. The latter is presumably stabilized early on through direct air exposure (oxidation) and thus, it is more refractory to further diagenetic transformations such as humification and aromatization reactions.

Water Uptake Patterns of an Invasive Exotic Plant in Coastal Saline Habitats

Schinus terebinthifolius Raddi (Schinus) is one of the most widely found woody exotic species in South Florida. This exotic is distributed across environments with different hydrologic regimes, from upland pine forests to the edges of sawgrass marshes and into saline mangrove forests. To determine if this invasive exotic had different physiological attributes compared to native species in a coastal habitat, we measured predawn xylem water potentials (Ψ), oxygen stable isotope signatures (δ18O), and sodium (Na+) and potassium (K+) contents of sap water from plants within: (1) a transition zone (between a mangrove forest and upland pineland) and (2) an upland pineland in Southwest Florida. Under dynamic salinity and hydrologic conditions, Ψ of Schinus appeared less subject to fluctuations caused by seasonality when compared with native species. Although stem water δ18O values could not be used to distinguish the depth of Schinus and native species' water uptake in the transition zone, Ψ and sap Na+/K+ patterns showed that Schinus was less of a salt excluder relative to the native upland species during the dry season. This exotic also exhibited Na+/K+ ratios similar to the mangrove species, indicating some salinity tolerance. In the upland pineland, Schinus water uptake patterns were not significantly different from those of native species. Differences between Schinus and native upland species, however, may provide this exotic an advantage over native species within mangrove transition zones.

Seasonal and spatial variation in the stable isotopic composition (δ18O and δD) of precipitation in south Florida

Precipitation data collected from five sites in south Florida indicate a strong seasonal and spatial variation in δ18O and δD, despite the relatively limited geographic coverage and low-lying elevation of each of the collection sites. Based upon the weighted-mean stable isotope values, the sites were classified as coastal Atlantic, inland, and lower Florida Keys. The coastal Atlantic sites had weighted-mean values of δ18O and δD of −2.86‰ and −12.8‰, respectively, and exhibited a seasonal variation with lower δ18O and δD values in the summer wet-season precipitation (δ18O = −3.38‰, δD = −16.5‰) as compared to the winter-time precipitation (δ18O = −1.66‰, δD = −3.2‰). The inland site was characterized as having the highest d-excess value (+13.3‰), signifying a contribution of evaporated Everglades surface water to the local atmospheric moisture. In spite of its lower latitude, the lower Keys site located at Long Key had the lowest weighted-mean stable isotope values (δ18O = −3.64‰, δD = −20.2‰) as well as the lowest d-excess value of (+8.8‰). The lower δD and δ18O values observed at the Long Key site reflect the combined effects of oceanic vapor source, fractionation due to local precipitation, and slower equilibration of the larger raindrops nucleated by a maritime aerosol. Very low δ18O and δD values (δ18O < −6‰, δD < −40‰) were observed just prior to the passage of hurricanes from the Gulf of Mexico as well as during cold fronts from the north-west. These results suggest that an oceanic vapor source region to the west, may be responsible for the extremely low δD and δ18O values observed during some tropical storms and cold fronts.

Water source utilization and foliar nutrient status differs between upland and flooded plant communities in wetland tree islands

Tree islands in the Everglades wetlands are centers of biodiversity and targets of restoration, yet little is known about the pattern of water source utilization by the constituent woody plant communities: upland hammocks and flooded swamp forests. Two potential water sources exist: (1) entrapped rainwater in the vadose zone of the organic soil (referred to as upland soil water), that becomes enriched in phosphorus, and (2) phosphorus-poor groundwater/surface water (referred to as regional water). Using natural stable isotope abundance as a tracer, we observed that hammock plants used upland soil water in the wet season and shifted to regional water uptake in the dry season, while swamp forest plants used regional water throughout the year. Consistent with the previously observed phosphorus concentrations of the two water sources, hammock plants had a greater annual mean foliar phosphorus concentration over swamp forest plants, thereby supporting the idea that tree island hammocks are islands of high phosphorus concentrations in the oligotrophic Everglades. Foliar nitrogen levels in swamp forest plants were higher than those of hammock plants. Linking water sources with foliar nutrient concentrations can indicate nutrient sources and periods of nutrient uptake, thereby linking hydrology with the nutrient regimes of different plant communities in wetland ecosystems. Our results are consistent with the hypotheses that (1) over long periods, upland tree island communities incrementally increase their nutrient concentration by incorporating marsh nutrients through transpiration seasonally, and (2) small differences in micro-topography in a wetland ecosystem can lead to large differences in water and nutrient cycles.

Ecohydrology, evapotranspiration and hydrogeochemistry of carbonate mangrove wetlands

Coastal environments can be highly susceptible to environmental changes caused by anthropogenic pressures and natural events. Both anthropogenic and natural perturbations may directly affect the amount and the quality of water flowing through the ecosystem, both in the surface and subsurface and can subsequently, alter ecological communities and functions. The Florida Everglades and the Sian Ka'an Biosphere Reserve (Mexico) are two large ecosystems with an extensive coastal mangrove ecotone that represent a historically altered and pristine environment, respectively. Rising sea levels, climate change, increased water demand, and salt water intrusion are growing concerns in these regions and underlies the need for a better understanding of the present conditions. The goal of my research was to better understand various ecohydrological, environmental, and hydrogeochemical interactions and relationships in carbonate mangrove wetlands. A combination of aqueous geochemical analyses and visible and near-infrared reflectance data were employed to explore relationships between surface and subsurface water chemistry and spectral biophysical stress in mangroves. Optical satellite imagery and field collected meteorological data were used to estimate surface energy and evapotranspiration and measure variability associated with hurricanes and restoration efforts. Furthermore, major ionic and nutrient concentrations, and stable isotopes of hydrogen and oxygen were used to distinguish water sources and infer coastal groundwater discharge by applying the data to a combined principal component analysis-end member mixing model. Spectral reflectance measured at the field and satellite scales were successfully used to estimate surface and subsurface water chemistry and model chloride concentrations along the southern Everglades. Satellite imagery indicated that mangrove sites that have less tidal flushing and hydrogeomorphic heterogeneity tend to have more variable evapotranspiration and soil heat flux in response to storms and restoration. Lastly, water chemistry and multivariate analyses indicated two distinct fresh groundwater sources that discharge to the phosphorus-limited estuaries and bays of the Sian Ka'an Biopshere Reserve; and that coastal groundwater discharge was an important source for phosphorus. The results of the study give us a better understanding of the ecohydrological and hydrogeological processes in carbonate mangrove environments that can be then be extrapolated to similar coastal ecosystems in the Caribbean.

The trophic structure of Spongosorites coralliophaga-coral rubble communities at two northeast Atlantic cold water coral reefs

Funding for the JC073 cruise was provided by the Natural Environment Research Council (NERC) UK Ocean Acidification (UKOA) research programme’s Benthic Consortium project (NE/H017305/1 to J Murray Roberts). Funding for analytical costs and field work was provided by the Marine Alliance for Science and Technology Scotland (MASTS) (Biodiversity Grant to Ursula FM Witte, 140 SF10003-10). Georgios Kazanidis was funded by a MASTS PhD scholarship.