CO2 Input Research Articles

Effects of Synechococcus sp. cyanobacteria inert biomass on olivine dissolution: Implications for the application of enhanced weathering methods

Chemical weathering of silicates represents an essential process of both the rock and carbon cycles. The application of this natural process on a global scale could be used to mitigate excess CO2 in the atmosphere. This concept is known as enhanced weathering where fine mineral powder is spread over the land surface for carbonation of silicates and expected CO2 sequestration. Within this context, organic matter, may promote or inhibit the processes of enhanced weathering, however this has not yet been fully quantified. Motivated by this knowledge gap, the present work studied the dissolution behaviour of olivine under inorganic conditions and in the presence of inert Synechococcus sp. biomass in batch reactor setups at various ionic strengths with a constant input of atmospheric CO2. Olivine, which represents one of the most obvious candidates for use in enhanced weathering, showed no significant statistical differences in the release of dissolved cations for all studied organic and inorganic experimental setups. For batch reactors containing inert biomass, a moderate increase in alkalinity and pH is found with respect to the inorganic conditions, which points to the buffering of H2CO3 by deprotonated functional groups on the inert biomass surface. Overall, the experimental results of this study indicate a negative combined effect of inert biomass and high ionic strengths on the olivine dissolution rates in natural aquatic systems. This suggests reduced carbonation rates on the Earth's surface and a lower potential of artificially dispersed olivine powder for CO2 sequestration.

Temporal variability of secondary processes in alkaline geothermal waters associated to granitic rocks: the Caldes de Boí geothermal system (Spain)

The Caldes de Boi geothermal waters show important differences in pH (6.5–9.6) and temperature (15.9oC–52oC) despite they have a common origin and a very simple circuit at depth (4km below the recharge area level). Thes differences are the result of secondary processes such as conductive cooling, mixing with colder shallower waters, and input of external CO2, which affect each spring to a different extent in the terminal part of the thermal circuit.In this paper, the secondary processes that control the geochemical evolution of this system have been addressed using a geochemical dataset spanning over 20 years and combining different approaches: classical geochemical calculations and geochemical modelling. Mixing between a cold and a thermal end-member, cooling and CO2 exchange are the processes affecting the spring waters with different intensity over time. These differences in the intensity of the secondary processes could be controlled by the effect of climate and indirectly by the geomorphological and hydrogeological setting of the different springs. Infiltration recharging the shallow aquifer is dominant during the rainy seasons and the extent of the mixing process is greater, at least in some springs.Moreover, significant rainfall can produce a decrease in the ground temperature favouring the conductive cooling. Finally, the geomorphological settings of the springs determine the thickness and the hydraulic properties of the saturated layer below them and, therefore, they affect the extent of the mixing process between the deep thermal waters and the shallower cold waters. The understanding of the compositional changes in the thermal waters and the main factors that could affect them is a key issue to plan the future management of the geothermal resources of the Caldes de Boi system. Here, we propose to use a simple methodology to assess the effect of those factors, which could affect the quality of the thermal waters for balneotherapy at long-term scale. Furthermore, the methodology used in this study can be applied to other geothermal systems.

PLEISTOCENE PALAEOCLIMATIC EVOLUTION FROM AGIOS GEORGIOS CAVE SPELEOTHEM (KILKIS, N. GREECE)

Palaeoclimatic reconstruction in N. Greece has been investigated in this study, using stable isotope analyses and U/Th dating of a speleothem (stalactite) from the cave of Agios Georgios (Kilkis). Sampling sequence was followed in detail in order to obtain high resolution analysis of the proxy. Speleothem δ18O entirely depends on two factors: changes in the δ18O of the percolation waters (a proxy for local rainfall δ18O) and the temperature of water-calcite fractionation inside the cave (a proxy for outside air temperatures). During periods of relatively stable temperatures, δ13C shifts are caused principally by variations in soil CO2 input and physico-chemical processes inside the cave. More important processes affect the δ13C signal of speleothem inside the cave are length of flow path and rates of CO2 degassing.The lower δ13C calcite values indicate greater respiratory activity of soils under wetter conditions. The stalagmite layers were dated through U/Th geochronological method, which places the carbonate precipitation in Middle Pleistocene (630-300ka BP). The isotopic composition of the layers was used in combination with the dating results to reconstruct the evolution of the area of Kilkis. Correlation with global climatic records shows that major climatic transitions that influenced northern hemisphere seem to have also affected the region of N. Greece.

Hydrological versus volcanic processes affecting fluid circulation at Mt. Etna: Inferences from 10 years of observations at the volcanic aquifer

The time series of geochemical data available for the network of wells and drainage galleries at Mt. Etna has been analyzed to identify the changes in water chemistry related to the input of volcanic CO2 and those related to hydrogeological dynamics. The dynamics of hydrological systems is mainly affected by changes in the rainfall, since this influences the yields of both springs and drainage galleries and the height of the water table of unconfined aquifers. In addition, the characteristics of hydrological systems can change with the fluid pressure. These mechanisms are probably enhanced by changes in the crustal strain, which can cause interbasin transfer of water. The changes in water circulation are paralleled by variations in physicochemical characteristics of groundwater, since water transfer probably occurs among water bodies with different temperatures and compositions.Based on the above mechanisms, the contribution of different water types has been estimated according to their chemical composition: it has been assumed that water circulating in the volcanic pile has a typical HCO3−-rich composition, whereas Cl−, SO4=, and NO3− could be contributed by rainfall, anthropogenic pollution, and sedimentary fluids rich in Na+ and Cl−. The compositionally different end members have been identified based on the results of factor analysis, which allowed those chemicals accounted for by a single water end member to be grouped within the same factor. In some cases the SO4= enrichment is related to the dissolution of SO4=-bearing alteration minerals contained in volcanic sequences, and in such cases this is associated with HCO3−. We hypothesize a binary mixing between the HCO3−-rich volcanic end member and an end member polluted with Cl−, SO4=, and NO3− related to water circulation at shallow levels. These two end members are identified by their HCO3−/(Cl−+SO4=+NO3−) ratio and Cl−, SO4=, and NO3− contents measured at each sampling site. The extent of mixing between these different water types changes over time, probably due to changes in their circulation patterns, with water being transferred from/to water bodies with different compositions. Once the proportion of the HCO3− content related to the binary mixing is determined, we can compute the amount of HCO3− related to the variable input of CO2 over time into the aquifer. The obtained temporal trends are—over a long time period—synchronous in the two sectors of the volcano where the maximal CO2 degassing occurs, namely the Paternò-Belpasso area on the southwestern flank and the Zafferana-S. Venerina area on the eastern flank. This provides evidence for a common deep mechanism underlying the CO2 variations that is related to the dynamics of the volcano. Some inconsistent trends are observed in the two sectors during specific periods, such as in 2012, which is probably due to the marked dynamics affecting the eastern flank compared to the more stable southwestern one.

Pyrolysis-catalytic dry (CO2) reforming of waste plastics for syngas production: Influence of process parameters

Catalytic dry (CO2) reforming of waste plastics was carried out in a two stage, pyrolysis-catalytic reforming fixed bed reactor to optimise the production of syngas (H2+CO). The effects of changing the process parameters of, catalyst preparation conditions, catalyst temperature, CO2 input rate and catalyst:plastic ratio were investigated. The plastics used was a mixture of plastics simulating that found in municipal solid waste and the catalyst used was Ni-Co-Al2O3. The results showed that changing each of the process conditions investigated, all significantly influenced syngas production. An increase of 17% of syngas production was achieved from the experiment with the catalyst prepared by rising-pH technique compared to preparation via the impregnation method. The optimum syngas production of 148.6mmolsyngasg−1swp was attained at the catalytic dry reforming temperature of 800°C and catalyst:plastic ratio of 0.5. The increase of CO2 input rate promoted a higher yield of syngas.

Open System Condition Serpentinization of Host-rock Magnesite in Süleymaniye, Tutluca and Margı Region of Eskişehir, NW Turkey

Host rock of magnesite occurrences in three areas (Suleymaniye, Margi, Tutluca) are the altered peridotite which on the northernmost outcrops of the Izmir-Ankra suture zone. Magnesite is formed in the cracks and fractures of highly altered harzburgite in these three areas. Chrysotile and lizardite are the abundant serpentinite mineral and orthopyroxene, olivine, magnetite, talc, brucite and chromite consist of these rocks which have mesh to hourglass texture. Source of Mg+2 for magnesite formation is coming from serpentinite. During serpentinization processes H2O and CO2 input mineralogic structure and form mineral transform. H2O content in system increases, MgO, CaO and SiO2 content decreases because of remove the systems. According to mineralogic association serpentinization of harzburgite occurs low temperature below 350℃ and represents the open system serpentinization condition. These rocks show positive La, Nd, Eu, Ho, Tm, Lu anomalies but negative Ce, Pr, Sm, Gd, Er, Yb anomalies to chondrite/normalize diagram. REE content of serpentinite are consumed according to chondrite. According to mineralogical and geochemical properties is these rock related to the SSZ type ophiolities.

Reconstructing the seasonal dynamics and relative contribution of the major processes sustaining CO2 emissions in northern lakes

AbstractLake CO2 emissions are an important component of the carbon balance of northern landscapes, yet the temporal dynamics of the underlying mechanisms sustaining CO2 emissions are less understood. Here, we reconstruct the major biotic and abiotic processes influencing CO2 dynamics over an annual cycle in three limnologically different lakes, using a combination of empirical measurements and process‐based modeling. Our results suggest that the relative importance of each process sustaining CO2 emissions is not only variable among lakes, but also highly variable among seasons within one lake. Spring CO2 emissions were largely sustained by the release of under ice accumulation (between about 50–100%), although photo‐chemical DOC mineralization and hydrologic CO2 loading were also relatively important. In summer, due to warmer temperature, pelagic and benthic metabolism were the main sources of CO2 emissions. In the fall, lake CO2 emissions were generally sustained by hydrologic CO2 inputs, while hypolimnetic CO2 accumulation and release also contributed to fall CO2 emission in the deepest lake. On an annual basis, lake CO2 emissions ranged between 21.4 g C m−2 yr−1 and 55.5 g C m−2 yr−1. Our results confirm that the major processes all contributed significantly to CO2 emissions, but their relative contributions were modulated by the seasonal patterns in climate and hydrology, and by differences in morphology and organic carbon inputs among lakes. These lake‐ and season‐specific features need to be considered both in the upscaling of lake processes at regional scales, and in predicting lake CO2 emissions under scenarios of climate and environmental change.

Observations of Atmospheric Δ14CO2 at the Global and Regional Background Sites in China: Implication for Fossil Fuel CO2 Inputs.

Six months to more than one year of atmospheric Δ14CO2 were measured in 2014-2015 at one global background site in Waliguan (WLG) and four regional background sites at Shangdianzi (SDZ), Lin'an (LAN), Longfengshan (LFS) and Luhuitou (LHT), China. The objectives of the study are to document the Δ14CO2 levels at each site and to trace the variations in fossil fuel CO2 (CO2ff) inputs at regional background sites. Δ14CO2 at WLG varied from 7.1 ± 2.9‰ to 32.0 ± 3.2‰ (average 17.1 ± 6.8‰) in 2015, with high values generally in autumn/summer and low values in winter/spring. During the same period, Δ14CO2 values at the regional background sites were found to be significantly (p < 0.05) lower than those at WLG, indicating different levels of CO2ff inputs at those sites. CO2ff concentrations at LAN (12.7 ± 9.6 ppm) and SDZ (11.5 ± 8.2 ppm) were significantly (p < 0.05) higher than those at LHT (4.6 ± 4.3 ppm) in 2015. There were no significant (p > 0.05) seasonal differences in CO2ff concentrations for the regional sites. Regional sources contributed in part to the CO2ff inputs at LAN and SDZ, while local sources dominated the trend observed at LHT. These data provide a preliminary understanding of atmospheric Δ14CO2 and CO2ff inputs for a range of Chinese background sites.

Decoupling of carbon dioxide and dissolved organic carbon in boreal headwater streams

AbstractStreams and rivers emit large quantities of carbon dioxide (CO2) to the atmosphere. The sources of this CO2 are in‐stream mineralization of organic carbon (OC) and CO2 input via groundwater inflow, but their relative importance is largely unknown. In this study, we quantified the role of in‐stream OC mineralization as a source of CO2 in a number of nested boreal headwater streams. The results showed that mineralization of stream OC contributed 3% of CO2 supersaturation at time scales comparable to the estimated water travel times in the streams (&lt;24 h). Mass balances showed that downstream losses of OC were ≤3% in low‐order streams, whereas up to 16% of the OC was lost in the largest (fourth order) streams. In contrast, 85% of the CO2 was lost along the stream network (longest total stream length = 17 km). Under the assumption that in‐stream OC mineralization was the main source of stream CO2, higher rates of OC mineralization (6% of OC) than those reported across the literature (≤0.7% of OC) would be required to sustain observed CO2 supersaturation. Further, model results indicated that groundwater inflows were sufficient to sustain observed stream CO2 concentrations. We hence conclude that in‐stream OC mineralization was a minor source of CO2 in these boreal headwater systems and that the main source of stream CO2 was inflowing groundwater transporting CO2 originating from soil respiration.

A Consuming Passion for Entomophagy

In March 2015, levels of carbon dioxide in the atmosphere topped a global average of 400 ppm for the first time since monitoring began (Allen 2015). This increase, up from 280 ppm in pre-industrial days, has been accompanied, not coincidentally, by an increase of 1.6 °F in global temperatures (Kahn 2015). On 12 December, representatives from 195 nations signed a historic agreement to get serious about reducing CO2 inputs (Davenport 2015). It turns out, though, that, even in nations committed to stopping, slowing, or reversing climate change, there are limits on what individual citizens are willing to do. Some individuals, including, e.g., 182 members of the 116th United States Congress (Herzog 2016, Ellingboe and Koronowski 2016), aren't even willing to acknowledge that it's a thing. If, however, you're among those who feel that the evidence indicates that global temperatures are increasing as a result of anthropogenic inputs into the atmosphere, you might want to make a small lifestyle change for the good of the planet—cut down on your daily vertebrate intake and start eating insects. “No thanks–I'm anti-anty-GMO.” Admittedly, convincing Americans to eat insects is a tougher sell than convincing them to, say, install a programmable thermostat. The argument for entomophagy, though, is pretty compelling, at least on sustainability grounds (van Huis et al 2013, 2015). For example, CO2 production per kg of mass gain for insects is only 12% of that for cattle, and in the process of gaining all that mass, insects generate less than 3% of the ammonia and methane that cattle produce (Oonincx et al. …

Soil-frost-enabled soil-moisture–precipitation feedback over northern high latitudes

Abstract. Permafrost or perennially frozen ground is an important part of the terrestrial cryosphere; roughly one quarter of Earth's land surface is underlain by permafrost. The currently observed global warming is most pronounced in the Arctic region and is projected to persist during the coming decades due to anthropogenic CO2 input. This warming will certainly have effects on the ecosystems of the vast permafrost areas of the high northern latitudes. The quantification of such effects, however, is still an open question. This is partly due to the complexity of the system, including several feedback mechanisms between land and atmosphere. In this study we contribute to increasing our understanding of such land–atmosphere interactions using an Earth system model (ESM) which includes a representation of cold-region physical soil processes, especially the effects of freezing and thawing of soil water on thermal and hydrological states and processes. The coupled atmosphere–land models of the ESM of the Max Planck Institute for Meteorology, MPI-ESM, have been driven by prescribed observed SST and sea ice in an AMIP2-type setup with and without newly implemented cold-region soil processes. Results show a large improvement in the simulated discharge. On the one hand this is related to an improved snowmelt peak of runoff due to frozen soil in spring. On the other hand a subsequent reduction in soil moisture enables a positive feedback to precipitation over the high latitudes, which reduces the model's wet biases in precipitation and evapotranspiration during the summer. This is noteworthy as soil-moisture–atmosphere feedbacks have previously not been the focus of research on the high latitudes. These results point out the importance of high-latitude physical processes at the land surface for regional climate.

Seaweed community response to a massive CO2 input

Changes in the structure of seaweed communities were examined following a massive CO2 input caused by a submarine eruption near the coast of El Hierro island (Canary Islands, Spain). The event lasted almost five months (October 2011–March 2012) and created a significant pH gradient. Specifically, we compared three different zones: highly affected with extreme low pH (6.7–7.3), affected with low pH (7.6–7.8), and unaffected ambient pH zone (∼8.1) according to the pH gradient generated by the predominate currents and waves in the south of the island. Studies were carried out before, during and after the CO2 input event in each zone. We found community-wide effects on seaweed communities during the eruption; these included changes in species abundance and changes in the diversity. However, changes in all these community traits were only evident in the highly affected zone, where there were major shifts in the seaweed community, with a replacement of Lobophora variegata by ephemeral seaweeds. Lobophora variegata dropped in cover from 87–94 to 27% while ephemeral seaweeds increased 6–10 to 29%. When the impact ended Lobophora variegata began to recover reaching a cover higher than 60%. In the moderate affected area the Lobophora variegata canopies maintained their integrity avoiding phase shifts to turfs. Here the only significant changes were the reduction of the cover of the crustose and geniculate coralline algae.

Significant discharge of CO2 from hydrothermalism associated with the submarine volcano of El Hierro Island.

The residual hydrothermalism associated with submarine volcanoes, following an eruption event, plays an important role in the supply of CO2 to the ocean. The emitted CO2 increases the acidity of seawater. The submarine volcano of El Hierro, in its degasification stage, provided an excellent opportunity to study the effect of volcanic CO2 on the seawater carbonate system, the global carbon flux, and local ocean acidification. A detailed survey of the volcanic edifice was carried out using seven CTD-pH-ORP tow-yo studies, localizing the redox and acidic changes, which were used to obtain surface maps of anomalies. In order to investigate the temporal variability of the system, two CTD-pH-ORP yo-yo studies were conducted that included discrete sampling for carbonate system parameters. Meridional tow-yos were used to calculate the amount of volcanic CO2 added to the water column for each surveyed section. The inputs of CO2 along multiple sections combined with measurements of oceanic currents produced an estimated volcanic CO2 flux = 6.0 105 ± 1.1 105 kg d−1 which is ~0.1% of global volcanic CO2 flux. Finally, the CO2 emitted by El Hierro increases the acidity above the volcano by ~20%.

Groundwater, Acid and Carbon Dioxide Dynamics Along a Coastal Wetland, Lake and Estuary Continuum

Coastal wetlands are hotspots for biodiversity and biological productivity, yet the hydrology and carbon cycling within these systems remains poorly understood due to their complex nature. By using a novel spatiotemporal approach, this study quantified groundwater discharge and the related inputs of acidity and CO2 along a continuum of a modified coastal acid sulphate soil (CASS) wetland, a coastal lake and an estuary under highly contrasting hydrological conditions. To increase the resolution of spatiotemporal data and advance upon previous methodologies, we relied on automated observations from four simultaneous time-series stations to develop multiple radon mass balance models to estimate groundwater discharge and related groundwater inputs of acidity and dissolved inorganic carbon (DIC), along with surface water to atmosphere CO2 fluxes. Spatial surveys indicated distinct acid hotspots with minimum surface water pH of 2.91 (dry conditions) and 2.67 (flood conditions) near a non-remediated (drained) CASS area. Under flood conditions, groundwater discharge accounted for ∼14.5 % of surface water entering the lake. During the same period, acid discharge from the acid sulphate soil section of the continuum produced ∼4.8 kg H2SO4 ha−1 day−1, a rate much higher than previous studies in similar systems. During baseflow conditions, the low pH water was rapidly buffered within the estuarine lake, with the pH increasing from 4.22 to 6.07 over a distance of ∼250 m. The CO2 evasion rates within the CASS were extremely high, averaging 2163 ± 125 mmol m−2 day−1 in the dry period and 4061 ± 259 mmol m−2 day−1 under flood conditions. Groundwater input of DIC could only account for 0.4 % of this evasion in the dry conditions and ∼5 % during the flood conditions. We demonstrated that by utilising a spatiotemporal (multiple time-series stations) approach, the study was able to isolate distinct zones of differing hydrology and biogeochemistry, whilst providing more reasonable groundwater acid input estimates and air–water CO2 flux estimates than some traditional sampling designs. This study highlights the notion that modified CASS wetlands can release large amounts of CO2 to the atmosphere because of high groundwater acid inputs and extremely low surface water pH.

Apparent increase in coccolithophore abundance in the subtropical North Atlantic from 1990 to 2014

Abstract. As environmental conditions evolve with rapidly increasing atmospheric CO2, biological communities will change as species reorient their distributions, adapt, or alter their abundance. In the surface ocean, dissolved inorganic carbon (DIC) has been increasing over the past several decades as anthropogenic CO2 dissolves into seawater, causing acidification (decreases in pH and carbonate ion concentration). Calcifying phytoplankton, such as coccolithophores, are thought to be especially vulnerable to ocean acidification. How coccolithophores will respond to increasing carbon input has been a subject of much speculation and inspired numerous laboratory and mesocosm experiments, but how they are currently responding in situ is less well documented. In this study, we use coccolithophore (haptophyte) pigment data collected at the Bermuda Atlantic Time-series Study (BATS) site together with satellite estimates (1998–2014) of surface chlorophyll and particulate inorganic carbon (PIC) as a proxy for coccolithophore abundance to show that coccolithophore populations in the North Atlantic subtropical gyre have been increasing significantly over the past 2 decades. Over 1990–2012, we observe a 37 % increase in euphotic zone-integrated coccolithophore pigment abundance at BATS, though we note that this is sensitive to the period being analyzed. We further demonstrate that variability in coccolithophore chlorophyll a here is positively correlated with variability in nitrate and DIC (and especially the bicarbonate ion) in the upper 30 m of the water column. Previous studies have suggested that coccolithophore photosynthesis may benefit from increasing CO2, but calcification may eventually be hindered by low pHT (&lt; 7.7). Given that DIC has been increasing at BATS by ∼ 1.4 µmol kg−1 yr−1 over the period of 1991–2012, we speculate that coccolithophore photosynthesis and perhaps calcification may have increased in response to anthropogenic CO2 input.

Monitoring of CO2-rich waters with low pH and low EC: an analogue study of CO2 leakage into shallow aquifers

The geochemistry of CO2-rich springs and wells was monitored as a natural analogue study of CO2 leakage into shallow aquifers. In result, within the relatively small study area, diluted CO2-rich waters (DCWs), concentrated CW (CCW), and ordinary groundwaters were observed. DCWs showed an exceptionally low pH (mean 4.8) and low EC (mean 150 μS/cm). The low pH and EC as well as the time-invariant geochemistry of DCWs were probably due to continuous CO2 inputs into the open system, which had a short reaction time and rarely consisted of reactive minerals. DCWs showed the low concentrations of SiO2 (mean 20.4 mg/L) and the average tritium concentration of 3.4 TU, which indicates the low CO2–H2O–rock interaction. In addition, \(\delta^{13} {\text{C}}_{{{\text{CO}}_{ 2} {\text{g}}}}\) in equilibrium with water was estimated using the mass balance equation and δ13CDIC measured in water samples. The results of the stable carbon isotope analysis showed that the CO2 originated from a deep-seated source to the shallow DCW aquifer (<80 m deep below the surface), whereas the deeper CCW aquifer was affected by soil organic CO2 near the surface. To detect the CO2 leakage from CO2 storage sites, the geochemistry of shallow aquifers should be monitored. This study result suggests that at least pH, EC, DIC, and carbon isotopes should be monitored because the monitoring of pH is helpful in an aquifer with low buffering capacity; while EC can be low despite CO2 leakage and the subsequently low pH at early stages, depending on the subsurface environment. Above all, this present study indicates that understanding the characteristics of aquifer conditions is of great importance for CO2 leakage detection.

Nutrient uptake and lipid yield in diverse microalgal communities grown in wastewater

Microalgae show great potential as feedstock for biofuel production. Some of the advantages they offer over terrestrial energy crops are a high productivity and the possibility to use waste streams (e.g., wastewater for inorganic nutrients and flue gas for CO2 input). Most of the published literature on microalgal cultivation has focused on monocultures of a single strain. An alternative approach would be to cultivate multispecies communities, which can increase production if the different species in the culture have different requirements and complement each other. To study the effect of multispecies communities, we cultivated 12 different species in monocultures and randomly selected communities of three, five and seven species. This was performed using municipal wastewater, with no further nutrient addition. Growth rate, biomass production, nutrient depletion and lipid production were measured. In general, it was observed that the mean growth and nutrient depletion increased with increasing number of species in the community. The variability (e.g., nutrient removal, resource use efficiency) between communities decreased with an increasing number of species. Biomass production in communities with the strongest growth was similar to, but not higher than the production in monocultures with the strongest growth (i.e., non-transgressive overyielding). However, the highest lipid content was obtained from some of the multispecies communities, which indicates transgressive overyielding in terms of lipid production. Combining communities randomly is probably not the best approach to increase algal biomass production, carefully selecting species, based on prior knowledge of physiology and ecology, might be a more effective approach to increase productivity.

Variability in climate and productivity during the Paleocene–Eocene Thermal Maximum in the western Tethys (Forada section)

Abstract. The Forada section (northeastern Italy) provides a continuous, expanded deep-sea record of the Paleocene–Eocene Thermal Maximum (PETM) in the central-western Tethys. We combine a new, high-resolution, benthic foraminiferal assemblage record with published calcareous plankton, mineralogical and biomarker data to document climatic and environmental changes across the PETM, highlighting the benthic foraminiferal extinction event (BEE). The onset of the PETM, occurring ∼ 30 kyr after a precursor event, is marked by a thin, black, barren clay layer, possibly representing a brief pulse of anoxia and carbonate dissolution. The BEE occurred within the 10 cm interval including this layer. During the first 3.5 kyr of the PETM, several agglutinated recolonizing taxa show rapid species turnover, indicating a highly unstable, CaCO3-corrosive environment. Calcareous taxa reappeared after this interval, and the next ∼9 kyr were characterized by rapid alternation of peaks in abundance of various calcareous and agglutinated recolonizers. These observations suggest that synergistic stressors, including deepwater CaCO3 corrosiveness, low oxygenation, and high environmental instability caused the extinction. Combined faunal and biomarker data (BIT index, higher plant n-alkane average chain length) and the high abundance of the mineral chlorite suggest that erosion and weathering increased strongly at the onset of the PETM, due to an overall wet climate with invigorated hydrological cycle, which led to storm flood events carrying massive sediment discharge into the Belluno Basin. This interval was followed by the core of the PETM, characterized by four precessionally paced cycles in CaCO3 %, hematite %, δ13C, abundant occurrence of opportunistic benthic foraminiferal taxa, and calcareous nannofossil and planktonic foraminiferal taxa typical of high-productivity environments, radiolarians, and lower δDn-alkanes. We interpret these cycles as reflecting alternation between an overall arid climate, characterized by strong winds and intense upwelling, and an overall humid climate, with abundant rains and high sediment delivery (including refractory organic carbon) from land. Precessionally paced marl–limestone couplets occur throughout the recovery interval of the carbon isotope excursion (CIE) and up to 10 m above it, suggesting that these wet–dry cycles persisted, though at declining intensity, after the peak PETM. Enhanced climate extremes at mid-latitudes might have been a direct response to the massive CO2 input in the ocean atmosphere system at the Paleocene–Eocene transition, and may have had a primary role in restoring the Earth system to steady state.

Analysis of Sensitive CO2 Pathways and Genes Related to Carbon Uptake and Accumulation in Chlamydomonas reinhardtii through Genomic Scale Modeling and Experimental Validation.

The development of microalgae sustainable applications needs better understanding of microalgae biology. Moreover, how cells coordinate their metabolism toward biomass accumulation is not fully understood. In this present study, flux balance analysis (FBA) was performed to identify sensitive metabolic pathways of Chlamydomonas reinhardtii under varied CO2 inputs. The metabolic network model of Chlamydomonas was updated based on the genome annotation data and sensitivity analysis revealed CO2 sensitive reactions. Biological experiments were performed with cells cultivated at 0.04% (air), 2.5, 5, 8, and 10% CO2 concentration under controlled conditions and cell growth profiles and biomass content were measured. Pigments, lipids, proteins, and starch were further quantified for the reference low (0.04%) and high (10%) CO2 conditions. The expression level of candidate genes of sensitive reactions was measured and validated by quantitative real time PCR. The sensitive analysis revealed mitochondrial compartment as the major affected by changes on the CO2 concentrations and glycolysis/gluconeogenesis, glyoxylate, and dicarboxylate metabolism among the affected metabolic pathways. Genes coding for glycerate kinase (GLYK), glycine cleavage system, H-protein (GCSH), NAD-dependent malate dehydrogenase (MDH3), low-CO2 inducible protein A (LCIA), carbonic anhydrase 5 (CAH5), E1 component, alpha subunit (PDC3), dual function alcohol dehydrogenase/acetaldehyde dehydrogenase (ADH1), and phosphoglucomutase (GPM2), were defined, among other genes, as sensitive nodes in the metabolic network simulations. These genes were experimentally responsive to the changes in the carbon fluxes in the system. We performed metabolomics analysis using mass spectrometry validating the modulation of carbon dioxide responsive pathways and metabolites. The changes on CO2 levels mostly affected the metabolism of amino acids found in the photorespiration pathway. Our updated metabolic network was compared to previous model and it showed more consistent results once considering the experimental data. Possible roles of the sensitive pathways in the biomass metabolism are discussed.

Microstructural shell strength of the Subantarctic pteropod Limacina helicina antarctica

Anthropogenic inputs of CO2 are changing ocean chemistry and will likely affect calcifying marine organisms, particularly aragonite producers such as pteropods. This work seeks to set a benchmark analysis of pteropod shell properties and variability using nanoindentation and electron microscopy to measure the structural and mechanical properties of Subantarctic pteropod shells (Limacina helicina antarctica) collected in 1998 and 2007. The 1998 shells were collected by a sediment trap deployed at 2000 m, 47°S, 142°E, and the 2007 shells were collected using nets from mixed-layer waters in the region (44°–54°S, 140°–155°E). Transmission electron microscopy revealed that the shells are composed of a polycrystalline structure, and no obvious porosity was visible. The hardness and modulus of the shells were measured using shell cross-section nanoindentation, across various regions of the shell from the inner to outer whorl. No change in mechanical properties was found with respect to the region of the shell cross-section probed. There was no statistically significant difference in the mean modulus or hardness of the shells between the 1998 and 2007 data sets. No major changes in the mechanical properties of these pteropod shells were detected between the 1998 and 2007 data sets, and we discuss the possible biases in the sampling techniques in complicating our analysis. However, quantifying the mechanical properties and microstructure of calcified may still provide insights into the responses of calcification to environmental changes, such as ocean acidification.