Presence Of Inorganic Carbon Research Articles

Seagrass Blue Carbon Stock and Air–Sea CO2 Fluxes in the Karimunjawa Islands, Indonesia during Southeast Monsoon Season

Research focusing on seagrass ecosystems as carbon storage has been conducted in various Indonesian waters. However, an essential aspect that remains unexplored is the simultaneous analysis of blue carbon storage in seagrass alongside carbon dioxide (CO2) flux values, particularly within Karimunjawa waters. This study aims to assess the organic carbon stock and sea–air CO2 flux in seagrass ecosystems in Karimunjawa. Our hypothesis posits that although seagrass ecosystems release CO2 into the water, their role as blue carbon ecosystems enables them to absorb and accumulate organic carbon within seagrass biomass and sediments. This investigation took place in Karimunjawa waters, encompassing both vegetated (seagrass meadows) and unvegetated (non-seagrass meadows) areas during August 2019, 2020, and 2022. Over this period, the organic carbon stock in seagrass and sediment displayed an increase, rising from 28.90 to 35.70 gCorg m−2 in 2019 and from 37.80 to 45.25 gCorg m−2 in 2022. Notably, the expanse of seagrass meadows in Karimunjawa dwindled by 328.33 ha from 2019 to 2022, resulting in a total carbon stock reduction of the seagrass meadows of 452.39 tC to 218.78 tC. Sediment emerges as a pivotal element in the storage of blue carbon in seagrass, with sedimentary organic carbon outweighing seagrass biomass in storage capacity. The conditions in Karimunjawa, including a high A:B ratio, low dry bulk density, and elevated water content, foster a favorable environment for sediment carbon absorption and storage, facilitated by the waters’ CO2 emission during the southeast monsoon season. Notably, our findings reveal that CO2 release within vegetated areas is lower compared to unvegetated areas. This outcome underscores how seagrass ecosystems can mitigate CO2 release through their adeptness at storing organic carbon within biomass and sediment. However, the presence of inorganic carbon in the form of calcium carbonate introduces a nuanced dynamic. This external source, stemming from allochthonous origins like mangroves, brown algae like Padina pavonica, and calcareous epiphytes, leads to an increase in sedimentary organic carbon stock of 53.2 ± 6.82 gCorg m−2. Moreover, it triggers the release of CO2 into the atmosphere, quantified at 83.4 ± 18.26 mmol CO2 m−2 d−1.

A low-cost method using steel-making slag to quench the residual phosphorus from wastewater effluent

This study demonstrates a novel application of steel-making slag for quenching residual phosphorus in wastewater effluent after chemical precipitation. The results showed that the phosphorus removal efficiency was low without the supernatant pH adjustment. Decreased pH of the supernatant resulted in increased removal efficiency. At the optimal conditions (i.e. pH 8.5 and steel-making slag dosage of 5 g/L), approximately 98% phosphorus removal could be achieved with the output level of less than 0.1 mg/L. The results also demonstrated that enhanced phosphorus removal by pH adjustment resulted from the involvement of adsorption in the removal process. This observation was evidenced via the compliance with Langmuir isotherm of the adsorption of phosphorus to steel-making slag at decreased pH. In addition, the results indicated that the presence of inorganic carbon in the supernatant could facilitate phosphorus removal via co-precipitation effects.

Effects of acidification on the isotopic ratios of Neotropical otter tooth dentin.

Stable carbon and nitrogen isotope ratios are widely used in ecological studies providing important information on the trophic ecology and habitat use of consumers. However, some factors may lead to isotopic variability, which makes difficult the interpretation of data, such as the presence of inorganic carbon in mineralized tissues. In order to remove the inorganic carbon, acidification is a commonly used treatment. The effects of two methods of acidification were tested: (i) dentin acidification with 10% HCl using the 'drop-by-drop' technique, and (ii) dentin acidification in an 'HCl atmosphere', by exposing the dentin to vaporous 30% hydrochloric acid. Results were compared with untreated subsamples. The stable carbon and nitrogen ratios of untreated and acidified subsamples were measured using an elemental analyzer coupled to an isotope ratio mass spectrometer. The nitrogen isotopic ratios were statistically different between the two acidification treatments, but no significant changes in carbon isotopic ratios were found in acidified and untreated samples. The results indicated that acidification had no effect on carbon isotopic ratios of Neotropical otter tooth dentin, while introducing a source of error in nitrogen isotopic ratios. Therefore, we conclude that acidification is an unnecessary step for C and N stable isotope analysis.

Lipid removal and acidification affect nitrogen and carbon stable isotope ratios of beluga whales (Delphinapterus leucas) and their potential prey species in the Beaufort Sea ecosystem

Carbon and nitrogen stable isotope ratios are ecological tracers that can provide insights into the diets of marine mammals. As a generalist predator, beluga whales (Delphinapterus leucas) consume a variety of prey; however, differences in lipid content and the presence of inorganic carbon in prey may cause variability in the δ13C signal that is not related to food sources. We examined the effects of carbonate and/or lipid removal in beluga and potential prey and tested whether the C:N ratio was a valid indicator of lipid content. The C:N ratio was a good predictor of the change in δ13C after lipid removal in capelin (Mallotus villosus), octopus (Cirroteuthis muelleri), green shrimp (Argis dentata), and circumpolar eualid (Eualus gaimardii). Despite relatively low C:N ratios, lipid removal significantly increased δ13C values, but also affected δ15N. Removal of carbonates from invertebrate samples significantly decreased δ13C values and had variable effects on δ15N. Overall, the variability in δ13C within a species decreased after removing lipids and carbonates. Variability in δ15N did not change for species requiring only lipid removal, but increased after acidification. We also evaluated the effect of these sample preparation methods on niche dispersion metrics. After lipid and carbonate treatments, centroid locations differed significantly in all species except beluga muscle, and niche breadth and mean distance to the centroid decreased. Failure to remove lipids and carbonates for δ13C values may lead to incorrect interpretations for isotopic niche, which may have major ecological implications, such as predicting the impacts of invasive species or determining the dietary linkages of beluga whales.

Low-crystallinity products of trace-metal precipitation in neutralized pit-lake waters without ferric and aluminous adsorbent: Geochemical modelling and mineralogical analysis

AbstractThe removal of dissolved trace metals during neutralization of acid mine drainage has usually been described and modelled as a progressive, pH-dependent sorption onto standard ferric or aluminous adsorbent. In the absence of adsorbent mineral surfaces, trace metals tend to form amorphous to low-crystallinity compounds which are often difficult to characterize. Here, we study the behaviour of the more soluble metals (Cu2+, Zn2+, Mn2+, Co2+, Ni2+, Cd2+) in the absence of ferric and aluminous adsorbent by neutralization experiments with waters from two acidic pit lakes. The objectives of our study were to identify the mineral products formed by trace-metal precipitation and the pH ranges at which these metals are removed from the solutions. Both geochemical modelling and detailed mineralogical and chemical analyses (XRD, SEM, TEM, XRF, ICP-AES) were undertaken to characterize the products. The schwertmannite and hydrobasaluminite colloids formed in the initial neutralization stages were removed from the waters at pH 3.5 and 5.1, respectively. These two minerals had previously adsorbed the Cr3+and Pb2+initially present in the solutions. The Cu precipitates were amorphous to X-rays, though chemical and modelling data suggest that Cu probably precipitated as a precursor of brochantite (Cu4(SO4)(OH)6·2H2O) at pH >6.0, together with minor quantities of other Cu hydroxysulfates (langite, antlerite) and Cu(OH)2. At higher pH, other divalent metals (Zn2+, Mn2+) precipitated as silicates, carbonates and/or (possibly) minor oxides and (oxy)hydroxides. The high concentration of aqueous SiO2in the solutions allowed Zn to precipitate as willemite (Zn2SiO4) at pH >7.0. Similarly, the presence of inorganic carbon (originally as CO2(aq.)) greatly influenced the nature of the corresponding precipitate of Mn. This metal was initially present as Mn2+and experienced a partly oxidative precipitation forming, in combination with Mg2+, the hydroxyl carbonate desautelsite (Mg6Mn2(CO3)(OH)16·4H2O) at pH 9.0–10.0. The formation of Mn3+/Mn4+oxides and hydroxides (hausmannite, manganite, birnessite) could not be demonstrated, although geochemical calculations support their subordinate formation. Other metallic cations such as Co2+, Ni2+and Cd2+did not form discrete mineral phases but were totally removed by sorption onto and/or incorporation into the cited Zn and Mn compounds. The discrepancies between theoretical and demonstrated mineralogy and the significance of these minerals for future pit-lake remediation initiatives are discussed.

Variation of photoautotrophic fatty acid production from a highly CO2 tolerant alga, Chlorococcum littorale, with inorganic carbon over narrow ranges of pH.

Photoautotrophic fatty acid production of a highly CO2 -tolerant green alga Chlorococcum littorale in the presence of inorganic carbon at 295 K and light intensity of 170 µmol-photon m(-2) s(-1) was investigated. CO2 concentration in the bubbling gas was adjusted by mixing pure gas components of CO2 and N2 to avoid photorespiration and β-oxidation of fatty acids under O2 surrounding conditions. Maximum content of total fatty acid showed pH-dependence after nitrate depletion of the culture media and increased with the corresponding inorganic carbon ratio. Namely, [HCO3 (-) ]/([CO2 ]+n[ CO32-]) ratio in the culture media was found to be a controlling factor for photoautotrophic fatty acid production after the nitrate limitation. At a CO2 concentration of 5% (vol/vol) and a pH of 6.7, the fatty acid content was 47.8 wt % (dry basis) at its maximum that is comparable with land plant seed oils.

Sustainable hydrogen photoproduction by phosphorus-deprived marine green microalgae Chlorella sp.

Previously it has been shown that green microalga Chlamydomonas reinhardtii is capable of prolonged H2 photoproduction when deprived of sulfur. In addition to sulfur deprivation (-S), sustained H2 photoproduction in C. reinhardtii cultures can be achieved under phosphorus-deprived (-P) conditions. Similar to sulfur deprivation, phosphorus deprivation limits O2 evolving activity in algal cells and causes other metabolic changes that are favorable for H2 photoproduction. Although significant advances in H2 photoproduction have recently been realized in fresh water microalgae, relatively few studies have focused on H2 production in marine green microalgae. In the present study phosphorus deprivation was applied for hydrogen production in marine green microalgae Chlorella sp., where sulfur deprivation is impossible due to a high concentration of sulfates in the sea water. Since resources of fresh water on earth are limited, the possibility of hydrogen production in seawater is more attractive. In order to achieve H2 photoproduction in P-deprived marine green microalgae Chlorella sp., the dilution approach was applied. Cultures diluted to about 0.5–1.8 mg Chl·L−1 in the beginning of P-deprivation were able to establish anaerobiosis, after the initial growth period, where cells utilize intracellular phosphorus, with subsequent transition to H2 photoproduction stage. It appears that marine microalgae during P-deprivation passed the same stages of adaptation as fresh water microalgae. The presence of inorganic carbon was essential for starch accumulation and subsequent hydrogen production by microalgae. The H2 accumulation was up to 40 mL H2 gas per 1iter of the culture, which is comparable to that obtained in P-deprived C. reinhardtii culture.

Effect on physico-chemical and structural properties of soil amended with distillery effluent and ameliorated by cropping two cereal plant spp.

Molasses-based distilleries are one of the most polluting industries generating large volume of wastewater. Distillery effluent (DE) on its discharge alters the physical and chemical properties of the soil. This study has been conducted to assess the distribution of heavy metals and its effect on physiochemical and structural changes of soil which has been treated with diluted and undiluted effluents. The soil has been assayed both before and after crop plantation. Out of the crop plants studied, Cicer arietinum was least effected and more effective than Pisum sativum in diminishing the heavy metals from soil. However, only at higher concentration DE has some adverse impact on the nutrient contents of the soil. Fourier transform infrared spectrum (FTIR) study of the soil indicated the presence of –OH, –NH, –COOH groups. It was also noted that the soil amended with different concentration of DE and on which Cicer and Pisum were grown has varied IR spectrum. These variations show the presence of different functional groups of soil before and after plants were grown. The presence of inorganic carbonate was found in soil planted with Cicer from 10 to 50% of DE, whereas aliphatic primary amides were observed up to 25 and 100% concentrations of DE in soil planted with Pisum. The appearance of inorganic nitrates, carbonates, aliphatic hydrocarbons and aliphatic primary amides at various concentrations of DE showed a change in functional groups probably because of the differential breakdown of parent component present in the effluent. Besides our main finding that Cicer is a very useful crop species in remediating the soil which has inflicted with even undiluted DE, it is also validated through FTIR spectra that IR technique is an efficient tool in studying the structural changes of soil and with some degree of caution may be summed up that FTIR may be used to correlate the relative efficacy of plants to transform organic contaminants.

Fatty acid production from a highly CO 2 tolerant alga, Chlorocuccum littorale, in the presence of inorganic carbon and nitrate

Photoautotrophic fatty acid production of a highly CO 2-tolerant green alga Chlorococcum littorale was investigated in the presence of inorganic carbon and nitrate at 295 K and a light intensity of 170 μmol-photon m −2 s −1. CO 2 concentration in the bubbling gas was adjusted by mixing pure gas components of CO 2 and N 2 to avoid photorespiration and β-oxidation of fatty acids under O 2 atmosphere conditions. Fatty acid content was almost constant for the CO 2 concentrations ranging from 5% to 50% under nitrate-rich conditions corresponding to the logarithmic growth phase. After nitrate depletion, the content drastically increased with a decrease in CO 2 concentration. HCO 3 - / CO 2 ratio in the culture media was found to be a controlling factor for fatty acid production after the nitrate limitation phase. For a CO 2 concentration of 5%, the fatty acid content was ca. 34 wt.% at maximum, which is comparable with other land plant seed oils.

The evolution of photosynthesis...again?

'Replaying the tape' is an intriguing 'would it happen again?' exercise. With respect to broad evolutionary innovations, such as photosynthesis, the answers are central to our search for life elsewhere. Photosynthesis permits a large planetary biomass on Earth. Specifically, oxygenic photosynthesis has allowed an oxygenated atmosphere and the evolution of large metabolically demanding creatures, including ourselves. There are at least six prerequisites for the evolution of biological carbon fixation: a carbon-based life form; the presence of inorganic carbon; the availability of reductants; the presence of light; a light-harvesting mechanism to convert the light energy into chemical energy; and carboxylating enzymes. All were present on the early Earth. To provide the evolutionary pressure, organic carbon must be a scarce resource in contrast to inorganic carbon. The probability of evolving a carboxylase is approached by creating an inventory of carbon-fixation enzymes and comparing them, leading to the conclusion that carbon fixation in general is basic to life and has arisen multiple times. Certainly, the evolutionary pressure to evolve new pathways for carbon fixation would have been present early in evolution. From knowledge about planetary systems and extraterrestrial chemistry, if organic carbon-based life occurs elsewhere, photosynthesis -- although perhaps not oxygenic photosynthesis -- would also have evolved.

In vivo bicarbonate requirement for water oxidation by Photosystem II in the hypercarbonate-requiring cyanobacterium Arthrospira maxima

While the presence of inorganic carbon in the form of (bi)carbonate has been known to be important for activity of Photosystem II (PSII), the vast majority of studies on this “bicarbonate effect” have been limited to in vitro studies of isolated thylakoid membranes and PSII complexes. Here we report an in vivo requirement for bicarbonate that is both reversible and selective for this anion for efficient water oxidation activity in the hypercarbonate-requiring cyanobacterium Arthrospira (Spirulina) maxima, originally isolated from highly alkaline soda lakes. Using a non-invasive internal probe of PSII charge separation (variable fluorescence), primary electron acceptor (QA-/QA) reoxidation rate, and flash-induced oxygen yield, we report the largest reversible bicarbonate effect on PSII activity ever observed, which is due to the requirement for bicarbonate at the water-oxidizing complex. Temporal separation of this donor side bicarbonate requirement from a smaller effect of bicarbonate on the QA- reoxidation rate was observed. We expect the atypical way in which Arthrospira manages intracellular pH, sodium, and inorganic carbon concentrations relative to other cyanobacteria is responsible for this strong in vivo bicarbonate requirement.

Carbonate effects on hexavalent uranium removal from water by nanocrystalline titanium dioxide

A novel nanocrystalline titanium dioxide was used to treat depleted uranium (DU)-contaminated water under neutral and alkaline conditions. The novel material had a total surface area of 329 m 2/g, total surface site density of 11.0 sites/nm 2, total pore volume of 0.415 cm 3/g and crystallite size of 6.0 nm. It was used in batch tests to remove U(VI) from synthetic solutions and contaminated water. However, the capacity of the nanocrystalline titanium dioxide to remove U(VI) from water decreased in the presence of inorganic carbonate at pH > 6.0. Adsorption isotherms, Fourier transform infrared (FTIR) spectroscopy, and surface charge measurements were used to investigate the causes of the reduced capacity. The surface charge and the FTIR measurements suggested that the adsorbed U(VI) species was not complexed with carbonate at neutral pH values. The decreased capacity of titanium dioxide to remove U(VI) from water in the presence of carbonate at neutral to alkaline pH values was attributed to the aqueous complexation of U(VI) by inorganic carbonate. The nanocrystalline titanium dioxide had four times the capacity of commercially available titanium dixoide (Degussa P-25) to adsorb U(VI) from water at pH 6 and total inorganic carbonate concentration of 0.01 M. Consequently, the novel material was used to treat DU-contaminated water at a Department of Defense (DOD) site.

Differential fractionation of δ13C and δ15N among fish tissues: implications for the study of trophic interactions

1. Stable isotopes of nitrogen and carbon are widely used in the evaluation and understanding of trophic interactions, and especially so in aquatic food‐webs. However, differences among tissues which occur in consumers such as fish may confound resolution of these ecological relationships, and greatly affect dietary compositions calculated through mass‐balance equations. 2.δ13C and δ15N were determined for homogenized whole fry (≈ 2·7 g) and particular tissues (white muscle, red muscle, liver and heart) of juveniles (≈ 20·6 g) of Rainbow Trout Oncorhynchus mykiss. 3. Differences in δ13C and δ15N were observed among tissues; removal of lipid resulted in these tissues becoming statistically indistinguishable but more variable in δ13C, particularly in tissues with higher lipid content. Differences in δ15N among tissues may be related to the relative composition of ‘essential’ and ‘non‐essential’ amino acids. 5. Acidification, which is used to reduce variability caused by the presence of inorganic carbonate, had a significant effect on δ15N, while having a non‐significant effect on the δ13C. This was the case for whole ground fish‐fry, which contained 22·6% inorganic carbonates in the form of bones and scales, and for individual fish tissues which contained only very small amounts of inorganic carbonate. 6. White muscle was found to be less variable in δ13C and δ15N than all other tissues, and is probably the best tissue for use in ecological work. Red muscle, which is often closely associated with white muscle, is more variable in δ13C and may constitute a source of significant error in source material identification and dietary overlap.

The effects of inorganic carbon and oxygen on fluorescence in the cyanobacterium Synechococcus UTEX 625

The active transport of inorganic carbon and the accumulation of the internal pool caused quenching of chlorophyll a fluorescence both when CO2 fixation was allowed or when CO2 fixation was inhibited. Upon the addition of inorganic carbon in the presence of 240 μM oxygen the rate of change in fluorescence (or quenching) was correlated (r = 0.98) with the rate of active CO2 uptake, and the extent of quenching was correlated (r = 0.99) with the size of the internal inorganic carbon pool. Fluorescence was quenched by the fixation of inorganic carbon in the absence of oxygen but the reoxidation of QA following a flash of light was slow. In the presence of inorganic carbon, with or without the inhibition of CO2 fixation, oxygen quenched fluorescence. If CO2 fixation was inhibited, the degree of quenching depended upon the oxygen concentration with a K1/2 (O2) of about 42 μM. Below 60 μM oxygen there was a further reduction of QA following a flash of light and the reoxidation of QA was slow. Rapid reoxidation of QA following a flash of light required about 240 μM oxygen. From the response to added 3-(3,4-dichlorophenyl)-1, 1-dimethylurea, the quenching by oxygen was photochemical quenching and nonphotochemical quenching did not seem to be present. For reasons that are unknown, however, only about 80% of the quenching could be reversed with high intensity flashes of light. The photoreduction of oxygen was regulated by the presence of inorganic carbon, although fixation of CO2 was not required. The mechanism of this regulation is not known but it may be due to bicarbonate relief of electron transfer between QA and QB. Some results on measuring Fo, F′o, Fm, and F′m, in Synechococcus UTEX 625 are presented. Key words: cyanobacteria, fluorescence, oxygen photoreduction, active inorganic carbon transport.

Nature of the Light-Induced H+ Efflux and Na+ Uptake in Cyanobacteria

We investigated the nature of the light-induced, sodium-dependent acidification of the medium and the uptake of sodium by Synechococcus. The rate of acidification (net H(+) efflux) was strongly and specifically stimulated by sodium. The rates of acidification and sodium uptake were strongly affected by the pH of the medium; the optimal pH for both processes being in the alkaline pH range. Net proton efflux was severely inhibited by inhibitors of adenosine triphosphatase activity, energy transfer, and photosynthetic electron transport, but was not affected by the presence of inorganic carbon (C(i)). Light and C(i) stimulated the uptake of sodium, but the stimulation by C(i) was observed only when C(i) was present at the time sodium was provided. Amiloride, a potent inhibitor of Na(+)/H(+) antiport and Na(+) channels, stimulated the rate of acidification but inhibited the rate of sodium uptake. It is suggested that acidification might stem from the activity of a light dependent proton excreting adenosine triphosphatase, while sodium transport seems to be mediated by both Na(+)/H(+) antiport and Na(+) uniport.