Calcium Carbonate Dissolution Research Articles

Diagenetic evolution of Upper Cretaceous carbonate sequences (Sarvak Formation) in the Abadan Plain, Iran: evidence from petrographic, elemental, stable, and strontium isotopic data

ABSTRACT This study investigates the diagenetic evolution and geochemical variations within the Sarvak Formation by integrating the core, thin-section, scanning electron microscopy, X-ray diffraction, trace elements, carbon-oxygen, and strontium isotopic data from three wells in the Abadan Plain. The formation displays diverse diagenetic processes, influenced by multiple exposure surface condition including the Cenomanian-Turonian boundary (CT-ES) and middle Turonian (mT-ES). Meteoric diagenesis, shaped by tectonic activities and eustatic sea level changes, played a pivotal role, leading to dissolution (karstification), brecciation, cementation, and palaeosol formation. Geochemical analysis revealed significant elemental variations across the studied wells. Magnesium (Mg) exhibited peaks at sequence boundaries, responding to facies changes, while iron (Fe) and manganese (Mn) concentrations increased below disconformities, reflecting changes in redox conditions and karstification. Sodium (Na) concentrations varied with facies changes, showing peaks at sequence boundaries, indicative of palaeoexposure events. Strontium (Sr) isotopes aided in delineating stratigraphic positions of palaeoexposure surfaces and absolute dating of sequences. Increases in87Sr/86Sr ratios below disconformities suggested subaerial exposure events, with shorter durations at CT-ES and longer durations at mT-ES, contributing to dissolution features development. The δ13Ccarb and δ18Ocarb values indicated severe meteoric diagenesis below sequence boundaries, characterized by dissolution and reprecipitation of calcium carbonate as low-magnesium calcite (LMC) cements. Cross plots of δ13Ccarb vs. δ18Ocarb displayed inverted-J patterns, indicative of meteoric diagenesis effects. Comparison with previous studies highlighted similar trends in geochemical variations, with notable differences in element concentrations between wells. This study enhances our understanding of diagenetic history of the Sarvak Formation in the Abadan Plain and, in a larger scale, provides insights into diagenetic evolution of palaeoexposure-related carbonate sequences.

An analysis of seashell calcium carbonate dissolution caused by ocean acidification based on chemistry equilibrium

Ocean acidification is a serious marine ecosystem problem caused by the abundant human emission of CO2. It is now a prevalent cognition that the dissolution of CO2 tends to raise the concentration of H+ in the ocean and therefore make it more acidic. Anthropogenic CO2 emission exacerbates the situation. This will then lead to another obvious problem---the dissolution of calcium carbonate shells of certain ocean organisms. This article will present a brief dissolution model, which can provide an analysis of the acidification effects from two perspectives---both the forming and the dissolution of seashells. The model shows an exponential relationship between the dissolved Ca2+ concentration and the pH of seawater. It also presents the anticipation regarding a dissolution turning point in (approximately) 2090 under the RCP8.5 scenario. This turning point indicates an abrupt acceleration of calcium carbonate shells dissolution. The result depicts the drastic but possible change in the seawater solution system and gives a warning signal of a probable deadline for us to control the CO2 emission. Hopefully, it will attract more scholars to pay attention to this topic and figure out methodologies to avoid the possible tragedy.

Biological export production controls upper ocean calcium carbonate dissolution and CO2 buffer capacity.

Marine biogenic calcium carbonate (CaCO3) cycles play a key role in ecosystems and in regulating the ocean's ability to absorb atmospheric carbon dioxide (CO2). However, the drivers and magnitude of CaCO3 cycling are not well understood, especially for the upper ocean. Here, we provide global-scale evidence that heterotrophic respiration in settling marine aggregates may produce localized undersaturated microenvironments in which CaCO3 particles rapidly dissolve, producing excess alkalinity in the upper ocean. In the deep ocean, dissolution of CaCO3 is primarily driven by conventional thermodynamics of CaCO3 solubility with reduced fluxes of CaCO3 burial to marine sediments beneath more corrosive North Pacific deep waters. Upper ocean dissolution, shown to be sensitive to ocean export production, can increase the neutralizing capacity for respired CO2 by up to 6% in low-latitude thermocline waters. Without upper ocean dissolution, the ocean might lose 20% more CO2 to the atmosphere through the low-latitude upwelling regions.

Euendolith borings in Chancelloria and Nisusia from the middle Cambrian (Miaolingian) of North Greenland (Laurentia).

Borings of microscopic organisms (euendoliths) are described from the Henson Gletscher Formation (middle Cambrian, Miaolingian Series, Wuliuan Stage) of Peary Land, North Greenland (Laurentia). Partially phosphatised sclerites of Chancelloria and valves of the brachiopod Nisusia reveal abundant casts of borings following dissolution of skeletal calcium carbonate in weak acetic acid. Threads referred to Scolecia dominate, occurring together with coccoids (Planobola) and the branching Fascichnus, in a suite comparable to a lower Cambrian assemblage from the Maidiping Formation of Sichuan, China.

Implementation of a non-destructive method to assess weathering deterioration of sandstones in cultural heritage

This paper proposes a non-destructive approach based on the Equotip hardness tester to assess weathering deterioration in a protected sandstone monument located in the historic centre of Camerino (Italy). The approach is tested on one sandstone column, where various forms of weathering, such as discolouration, scaling and loss of stone volume, are observed. The mechanical characterisation with Equotip was performed on 24 measuring points, systematically distributed in the column. Innovatively, the two probes available from Proceq (Proceq© 2010) were used to assess differences among surface and in-depth hardness values of the column. In addition, an un-weathered rock core from the original extraction site was also analysed and compared with the rock matrix of the column. The obtained results show a 15% hardness reduction from depth to the surface of the column and a 25% overall hardness reduction with respect to the fresh sandstone core samples. Equotip results were coupled with grain size analyses, mercury intrusion porosimetry, scanning electron microscopy and X-ray diffractometry results, and a correlation between hardness and grain size was evaluated. By combining these approaches, it was possible to identify the processes that occurred during weathering: (a) freeze-thaw cycles that caused a decrease in micropore volume and an increase in macropores connected with low Equotip values; (b) iron oxide and sulphuric acid released from pyrite oxidation contribute to the dissolution and precipitation of calcium carbonate, which can be rearranged in the outer and surface macroporosity. The quantitative approach proposed in this study may be a valid low-cost and quick tool to assess weathering heterogeneities on building stone materials and to provide insights for effective preservation strategies of historical monuments.

Short-Term Spatiotemporal Variability in Seawater Carbonate Chemistry at Two Contrasting Reef Locations in Bocas del Toro, Panama

There is growing concern about the effects of ocean acidification (OA) on coral reefs, with many studies indicating decreasing calcium carbonate production and reef growth. However, to accurately predict how coral reefs will respond to OA, it is necessary to characterize natural carbonate chemistry conditions, including the spatiotemporal mean and variability and the physical and biogeochemical drivers across different environments. In this study, spatial and temporal physiochemical variability was characterized at two contrasting reef locations in Bocas del Toro, Panama, that differed in their benthic community composition, reef morphology, and exposure to open ocean conditions, using a combination of approaches including autonomous sensors and spatial surveys during November 2015. Mean and diurnal temporal variability in both physical and chemical seawater parameters were similar between sites and sampling depths, but with occasional differences in extreme values. The magnitude of spatial variability was different between the two sites, which reflected the cumulative effect from terrestrial runoff and benthic metabolism. Based on graphical vector analysis of TA–DIC data, reef metabolism was dominated by organic over inorganic carbon cycling at both sites, with net heterotrophy and net calcium carbonate dissolution dominating the majority of observations. The results also highlight the potentially strong influence of terrestrial freshwater runoff on surface seawater conditions, and the challenges associated with evaluating and characterizing this influence on benthic habitats. The Bocas del Toro reef is a unique system that deserves attention to better understand the mechanisms that allow corals and coral reefs to persist under increasingly challenging environmental conditions.

Laboratory Observation of the Buffering Effect of Aragonite Dissolution at the Seafloor

AbstractCarbon dioxide entering and acidifying the ocean can be neutralized by the dissolution of calcium carbonate, which is mainly found in two mineral forms. Calcite is the more stable form and is often found in deep‐sea sediments, whilst aragonite is more soluble and therefore rarely preserved. Recent research shows aragonite may account for a much larger portion of marine calcium carbonate export to the ocean interior via the biological pump than previously thought, and that aragonite does reach the deep sea and seafloor despite rarely being buried. If aragonite is present and dissolving at the seafloor it will raise local pH and calcium and carbonate concentrations, potentially enough to inhibit calcite dissolution, representing a deep‐sea, carbonate version of galvanization. Here, we test this hypothesis by simulating aragonite dissolution at the sediment‐water interface in the laboratory and measuring its effects on pH using microsensors. We show that the addition of aragonite to calcite sediment, overlain by seawater undersaturated with respect to both minerals, results in an unchanged alkalinity flux out of the dissolving sediment, suggesting a decrease the net dissolution rate of calcite. In combination with a diagenetic model, we show that aragonite dissolution can suppress calcite dissolution in the top millimeters of the seabed, locally leading to calcite precipitation within 1 day. Future research efforts should quantify this galvanization effect in situ, as this process may represent an important component of the marine carbon cycle, assigning a key role to aragonite producers in controlling ocean alkalinity and preserving climatic archives.

The additionality problem of ocean alkalinity enhancement

Abstract. Ocean alkalinity enhancement (OAE) is an emerging approach for atmospheric carbon dioxide removal (CDR). The net climatic benefit of OAE depends on how much it can increase CO2 sequestration relative to a baseline state without OAE. This so-called “additionality” can be calculated as follows: Additionality=COAE-ΔCbaseline. So far, feasibility studies on OAE have mainly focussed on enhancing alkalinity in the oceans to stimulate CO2 sequestration (COAE); however, the primary focus has not been on how such anthropogenic alkalinity would modify the natural alkalinity cycle and associated baseline CO2 sequestration (ΔCbaseline). Here, I present incubation experiments in which materials considered for OAE (sodium hydroxide, steel slag, and olivine) are exposed to beach sand to investigate the influence of anthropogenic alkalinity on natural alkalinity sources and sinks. The experiments show that anthropogenic alkalinity can strongly reduce the generation of natural alkalinity, thereby reducing additionality. This is because the anthropogenic alkalinity increases the calcium carbonate saturation state, which reduces the dissolution of calcium carbonate from sand, a natural alkalinity source. I argue that this “additionality problem” of OAE is potentially widespread and applies to many marine systems where OAE implementation is considered – far beyond the beach scenario investigated in this study. However, the problem can potentially be mitigated by dilute dosing of anthropogenic alkalinity into the ocean environment and the avoidance of OAE in natural alkalinity cycling hotspots, such as in marine sediments. Understanding a potential slowdown of the natural alkalinity cycle through the introduction of an anthropogenic alkalinity cycle will be crucial for the assessment of OAE.

Experimental evaluation of cement integrity on exposure to supercritical CO2 using NMR: Application to geostorage

Carbon sequestration is one approach to achieve carbon dioxide reduction in the atmosphere. Underground storage of CO2 requires an understanding of geochemical and geomechanical alteration on the integrity of the injection wellbore. In this study, we investigate the reactivity of supercritical CO2 (scCO2) at 65 °C and 20.7 MPa on Portland class G cement plugs used for oil and gas well completion, for exposure of up to 5 weeks.For nanoporous media, such as cement, diffusion is believed to be the major mass transport mechanism (Perkins and Johnston, 1963) [1]. To quantify the extent of the alteration (mineralization/dissolution) on fluid diffusivity through the cement matrix, a novel approach based on Nuclear Magnetic Resonance (NMR) is employed to derive diffusional tortuosity. Comparing pre- and post-scCO2 exposure, deuterium oxide (D2O) intrusion profiles allow us to determine flow path alteration in the cement plugs. Additional characterizations include Fourier Transform Infrared Spectroscopy (FTIR) to observe the change in cement composition, micro X-ray Computed Tomography (μXCT), along with Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) to determine invasion extent and microstructure modifications, Mercury Injection Capillary Pressure (MICP) for pore throat size distribution and BET N2 isothermal adsorption for surface area and pore size distribution.The results show that exposure to scCO2 promotes both calcium carbonate precipitation and dissolution simultaneously. However, the alteration is pore size dependent. After 5 weeks of exposure, there is evidence of carbonate dissolution in smaller pores (<30 nm) and both precipitation and dissolution in larger pores (30–200 nm). The alteration of the cement plugs leads to a decrease in the storage and connectivity of the cement. The porosity decreased from 37 to 33 % in 5 weeks, while the matrix tortuosity increased by 6 and 3 times after 2 and 5 weeks of exposure, respectively. The experimental results imply that the cement carbonate precipitation can limit the migration of scCO2 through the cement matrix.This work also highlights an alternative laboratory approach to quantify the risk associated with scCO2 exposure on Portland cement using NMR-derived tortuosity.

Uncovering the Fungal Diversity and Biodeterioration Phenomenon on Archaeological Carvings of the Badami Cave Temples: A Microcosm Study.

The Badami Caves are a significant example of ancient Indian rock-cut architecture, dating back to the 6th century. These caves are situated in the Malaprabha River valley and are part of the candidate UNESCO World Heritage Site known as the "Evolution of Temple Architecture-Aihole-Badami-Pattadakal", which is considered to be the cradle of temple architecture in India. Our study aimed to investigate the diversity, distribution, and biodeterioration phenomena of the fungal communities present on the cave surfaces. The study also conducted a comprehensive analysis of fungal biodeterioration on the cave carvings. Utilizing specialized techniques, the dissolution of calcite, alterations in pH levels, and biomineralization capabilities of isolated fungal strains were monitored. Additionally, this study analyzed fungal acid production using high-performance liquid chromatography (HPLC). Our findings revealed that the major genera of fungi found on the cave surfaces included Acremonium, Curvularia, Cladosporium, Penicillium, and Aspergillus. These isolated fungi were observed to produce acids, leading to the dissolution of calcium carbonate and subsequent decrease in pH values. Notably, the dominant genus responsible for acid production and the promotion of biomineralization was Aspergillus. These discoveries provide valuable insight into the ecology and functions of fungi inhabiting stone surfaces, contributing to our understanding of how to preserve and protect sculptures from biodeterioration.

A review on corrosion of cement-based materials in CO2-rich karst groundwater

In karst areas, groundwater has high concentrations of carbon dioxide. It causes decalcification of cement-based materials by reacting with calcium hydroxide and calcium silicate hydrate. Therefore, the corrosion by CO2-rich groundwater has become a significant concern as it may reduce the service life of concrete structure. Based on the chemical reactions, the corrosion can be divided into leaching corrosion, carbonic acid corrosion, and acid corrosion. Calcium carbonate formation and dissolution are critical steps in corrosion process. The loss of calcium from cement results in cracking and spalling of the cement-based materials. The environmental and material factors had a significant effect on the corrosion rate. Based on the study in simulated karst water, adding supplementary cementitious materials or low-calcium alkali-activated materials can improve the corrosion resistance of the cementitious materials.

Adsorption of sodium alginate on calcium carbonate microparticles: Effect of molar mass and composition

Sodium alginate and calcium carbonate are natural materials with a high compositional variability. The molar mass and structural composition of sodium alginate and the crystalline structure of calcium carbonate can affect their interactions in pure water. Herein, we studied the adsorption of sodium alginate onto calcium carbonate microparticles in pure water. The adsorption appears to be driven by electrostatic interactions stabilized by calcium ions at the surface of the particles and in solution due to the dissolution of calcium carbonate in pure water. We found that the adsorption of sodium alginate is favored onto microparticles with more calcite. We also found that the adsorption of sodium alginate polymers with low guluronate content (~ 30%) onto calcium carbonate particles tends to increase for polymers with lower average molar mass and more flexible polymer chains. In contrast, polymers with high guluronate content (~ 65%) tend to adsorb more onto calcite when they present a lower average molar mass polymers as well as a higher proportion of guluronate monomers.

Impacts of agroforestry practices on the physico-chemical, water and soil fertility properties in semi-arid environments: The case of Bordjias Plain (Mesra, North-West Algeria)

Abstract All problems related to conventional agriculture are a reference to the search for sustainable solutions. In this context, a comparative study between three agroforestry practices (AFP): Citrus sinensis, Olea europaea, and Punica granatum, each associated with Vicia faba (Fabaceae), was conducted on Bordjias Plain. In order to study the impacts of each association on the physico-chemical properties and water and soil fertility, the soil samples were taken from two profiles (P1 under the tree and P2 between trees), through three horizons (Sh, Mh and Lh), before and after the establishment of culture. The results of the analyses show that moisture variability appears to be influenced by the type of soil and the woody species. By increasing the organic matter content, these associations improve the structural stability of the soil, accelerating the process of dissolution of calcium carbonate, changing the pH, EC, P2O5, CEC, and ion exchange in soil. The statistical approach (ANOVA) allowed us to bring out the positive impact of agroforestry practices on soil fertility.

Surface fertilisation and organic matter delivery enhanced carbonate dissolution in the western South Atlantic

The last glacial inception was characterised by rapid changes in temperature, atmospheric pCO2, and changes in the water mass geometry of the major ocean basins. Although several climatic feedback mechanisms have been proposed to explain the glacial/interglacial cycles witnessed in the Quaternary, the exact mechanistic responses of these processes are still under constrained. In this study we use proxies including planktonic foraminifera compositional assemblages and oxygen stable isotopes to reconstruct past changes in sea surface productivity, stratification, and carbonate dissolution. We use core SIS-249 (2,091 mbsl, western South Atlantic 30°S 47°W), spanning 30–110 thousand years ago (ka), and currently bathed by modern Northern Component Water. We test existing hypotheses suggesting that the orbital obliquity cycle modulates the biological pump in the study area. Spectral analysis run on our synthesised productivity proxies recognises a ~43 kyr-cycle, related to the obliquity cycle. We propose that the enhanced productivity is produced by two mechanisms: i) the glacial upwelling of subsurface nutrient-rich waters and, ii) the continental (wind-driven dust and riverine outflows) fertilisation of the photic zone, with the latter process being obliquity-paced. We also suggest that not only the increased organic matter export but also a change in its bioavailability (from refractory to labile) led to calcium carbonate dissolution, as the degradation of the more soluble organic matter decreased the pH of the glacial bottom water, partially dissolving the calcium carbonate. Although our correlation analyses show a strong benthic-pelagic coupling through the relation between the enhanced biological pump and carbonate dissolution (ρ&amp;lt;0.05, r=0.80), we cannot reject the potential of corrosive Southern Component Water bathing the site during the glacial. Finally, we highlight that these processes are not mutually exclusive and that both can be modulated by the obliquity cycle.

Ocean acidification enhances primary productivity and nocturnal carbonate dissolution in intertidal rock pools

Abstract. Human CO2 emissions are modifying ocean carbonate chemistry, causing ocean acidification and likely already impacting marine ecosystems. In particular, there is concern that coastal, benthic calcifying organisms will be negatively affected by ocean acidification, a hypothesis largely supported by laboratory studies. The inter-relationships between carbonate chemistry and marine calcifying communities in situ are complex, and natural mesocosms such as tidal pools can provide useful community-level insights. In this study, we manipulated the carbonate chemistry of intertidal pools to investigate the influence of future ocean acidification on net community production (NCP) and calcification (NCC) at emersion. Adding CO2 at the start of the tidal emersion to simulate future acidification (+1500 µatm pCO2, target pH 7.5) modified net production and calcification rates in the pools. By day, pools were fertilized by the increased CO2 (+20 % increase in NCP, from 10 to 12 mmol O2 m−2 h−1), while there was no measurable impact on NCC. During the night, pools experienced net community dissolution (NCC &lt; 0), even under present-day conditions, when waters were supersaturated with regard to aragonite. Adding CO2 to the pools increased nocturnal dissolution rates by 40 % (from −0.7 to −1.0 mmol CaCO3 m−2 h−1) with no consistent impact on nocturnal community respiration. Our results suggest that ocean acidification is likely to alter temperate intertidal community metabolism on sub-daily timescales, enhancing both diurnal community production and nocturnal calcium carbonate dissolution.

Reactive transport modelling of potential near-well mineralogical changes during seasonal heat storage (HT-ATES) in Danish geothermal reservoirs

Potential near-well mineralogical changes caused by seasonal high temperature aquifer thermal storage were investigated by numerical reactive transport modelling for two mineralogically different Danish geothermal reservoirs; the mineralogical mature and calcite free Gassum Fm. and the calcite containing Bunter Sandstone Fm. Modelling scenarios simulated injection of heated formation water with temperatures up to 150 °C into the reservoirs for a period of 6 months. For the Bunter Sandstone Fm., the formation water was modified to a saturation index for calcite of −0.1 prior to injection to replicate a situation where precautions are made to avoid loss of injectivity due to calcium carbonate scaling at elevated temperatures. Based on mineral dissolution and precipitation calculated by the numerical model, the changes in porosity as a result of heat storage were estimated. For the Gassum Fm., no significant changes in porosity were calculated when injecting formation water with temperatures up to 100 °C. At temperatures ≥120 °C, the content of albite and siderite was significantly reduced due to dissolution, but these mineralogical changes were not expected to significantly affect the reservoir porosity due to the low content of these minerals in the reservoir. However, significant precipitation of calcite near the injection well at temperatures ≥120 °C may reduce injectivity at these temperatures. For the calcite containing Bunter Sandstone Fm., injection of the slightly modified formation water led to significant calcite dissolution in the reservoir at all investigated temperatures and to dolomitisation at 150 °C. In the case of dolomitisation, our results suggest a risk for clogging of the near well environment by freshly precipitated dolomite. For the remaining temperatures, the calcite dissolution causes an increased porosity and a potential risk for compromising the rock integrity which should be further investigated. For both reservoirs, only very small changes were predicted in the aqueous composition of the formation water. The mineralogical changes in the reservoir are therefore not easily detected by monitoring changes in the aqueous composition of the formation water.Our results imply that high temperature aquifer thermal energy storage in reservoirs with a high calcium carbonate content such as the Bunter Sandstone Fm. is challenging. If precautions are taken to avoid calcium carbonate scaling by reducing the calcium content of the formation water, injection of the Ca-depleted formation water into the reservoir will cause dissolution of calcium carbonates. On the other hand, if precautions are not taken, it is well-known that precipitation of calcium carbonates will cause scaling and clogging problems. In contrast, our results suggest that storage of excess heat in mineralogical mature and calcite free sandstones such as the Gassum Fm. may be feasible. This is especially the case at temperatures <100 °C.

Temporal variability in seawater Sr/Ca ratios within a coral atoll as an indicator of marine calcifier community diversity

Coral reefs are marine environments where calcium carbonate production and dissolution along with photosynthesis and respiration can have a large impact on the daily biogeochemical cycles of seawater dissolved inorganic carbon (DIC), total alkalinity (TA), oxygen (O2), and major nutrients. Using seawater samples from Tetiaroa Atoll, French Polynesia, we apply isotope dilution thermal ionization mass spectrometry (ID-TIMS) to show that these daily cycles of variability extend to the dissolved seawater Sr/Ca ratio (Sr/Casw). Hourly measurements over a 27+ hour period indicate that Sr/Casw covaries with DIC and TA and exhibits up to a 2% relative difference compared to the regional Pacific Ocean source water Sr/Casw value of 8.53 mmol/mol. We hypothesize that the primary mechanism of hourly variability in Sr/Casw is carbonate precipitation/dissolution by corals and other marine calcifiers on the Tetiaroa reef, while sedimentary redox processes may significantly contribute to an apparent decoupling between net calcification rates estimated from TA compared to dissolved calcium [Ca]sw concentrations. Using a simple Rayleigh distillation model and a two-member mixing equation, we estimate the net partition coefficient of Sr (KD-Sr) for each hourly sample as a mixture of coral (aragonite; KD-Sr ∼ 1.06) and crustose coralline algae (high Mg-calcite; KD-Sr ∼ 0.39) contributions to the measured variability of [Ca]sw and Sr/Casw. As the high Mg-calcites of crustose coralline algae are (1) integral components to the structure and stability of the reef framework and (2) more soluble than aragonite under more acidic conditions, we propose that continued analyses of Sr/Casw within coral reef environments could be a useful tool for monitoring the ecological distribution and contributions of marine calcifiers on reefs as ocean warming and acidification intensify in response to anthropogenic climate change. Additionally, seasonal, interannual, and/or centennial-scale offsets between the Sr/Casw of open ocean source seawater and ambient reef seawater may have significant implications for interpreting past changes in sea surface temperatures derived from the coral Sr/Ca paleothermometer.

Natural biopatina on historical petroglyphs in the Austrian Alps: To clean or not to clean?

Some of Austria's most important petroglyphs are located in the alpine region of Dachstein, carved in the local limestone. Favored by the humid and shady environment, most of the engravings are covered by extensive biological colonization. In order to assess whether and to what extent the biopatinas present on the stone cause biodeterioration, we investigated their interactions with the rock substrate by microscopy methods (and PAS-staining), in combination with a metagenomic analysis to identify the biofilms' composition. The microscopy methods highlighted a general biodeterioration state of the stone and the great boring ability of the biofilms, especially of those with filamentous cyanobacteria (e.g., Nostocales and Oscillatoriales), and showed that a thick moss biofilm (with high abundance of Bacteroidota taxa) was the most harmful for the stone support, causing severe disruption of the underlying rock. Interestingly, the analysis of stone without visible biofilm revealed a microbiome dominated by ammonia-oxidizing archaea (AOAs), probably indicating the presence of a previous degraded biofilm (source of ammonia), and a current state of deterioration (dissolution of calcium carbonate). Removal of the biopatinas, or their alteration, would expose an already altered surface, potentially giving rise to a new colonization and new cycles of biodeterioration.

Ocean alkalinity enhancement through restoration of blue carbon ecosystems

AbstractBlue carbon ecosystems provide a wide range of ecosystem services, are critical for maintaining marine biodiversity and may potentially serve as sites of economically viable carbon dioxide removal through enhanced organic carbon storage. Here we use biogeochemical simulations to show that restoration of these marine ecosystems can also lead to permanent carbon dioxide removal by driving ocean alkalinity enhancement and atmosphere-to-ocean CO2 fluxes. Most notably, our findings suggest that restoring mangroves, which are common in tropical shallow marine settings, will lead to notable local ocean alkalinity enhancement across a wide range of scenarios. Enhanced alkalinity production is linked to increased rates of anaerobic respiration and to increased dissolution of calcium carbonate within sediments. This work provides further motivation to pursue feasible blue carbon restoration projects and a basis for incorporating inorganic carbon removal in regulatory and economic incentivization of blue carbon ecosystem restoration.

Boring bryozoans: an investigation into the endolithic bryozoan family Penetrantiidae

An endolithic lifestyle in mineralized substrates has evolved multiple times in various phyla including Bryozoa. The family Penetrantiidae includes one genus with ten extant and two fossil species. They predominantly colonize the shells of molluscs and establish colonies by chemical dissolution of calcium carbonate. Based on several morphological characters, they were described to be either cheilostome or ctenostome bryozoans. For more than 40 years, neither the characters of species identity and systematics nor the problem of their phylogeny was approached. Consequently, the aim of this study is to reevaluate species identities and the systematic position of the genus Penetrantia by analyzing at least six different species from eight regions with the aid of modern methods such as confocal laser scanning microscopy and 3D-reconstruction techniques. This study demonstrates that the musculature associated with the operculum and brood chamber shows significant differences from the cheilostome counterparts and seems to have evolved independently. Together with the presence of other ctenostome-like features such as true polymorphic stolons and uncalcified body wall, this finding supports a ctenostome affinity. Operculum morphology reveals many new species-specific characters, which, together with information about gonozooid morphology, tentacle number, and zooid size ranges, will enhance species identification. It also revealed a probable new species in Japan as well as potential cryptic species in France and New Zealand. In addition, this study increases the known distribution range of the family and its substrate diversity. Altogether, the new information collated here provides the basis for future work on a neglected taxon.