Carbonate Precipitation In Lake Research Articles

Periphyton development during summer stratification in the presence of a metalimnetic bloom of Planktothrix rubescens

Cyanobacterial blooms have become common all over the world, negatively affecting various ecosystem components. Planktothrix rubescens is a planktonic cyanobacterium that frequently causes blooms in temperate (mostly mesotrophic) lakes in Europe and, unlike other cyanobacteria, it is usually associated with ecosystem re-oligotrophication. The potential effects of P. rubescens on periphyton development have not been estimated in any recently published studies. The objective of the present paper was to assess how a Planktohrix rubescens bloom affects periphyton development in a temperate freshwater reservoir. A field study was performed in the Vrutci reservoir (western Serbia), where P. rubescens blooms have occurred since December of 2013. Periphyton was grown on glass slides that were incubated following lake stratification and sampled monthly from July to October of 2015. Dry mass, ash free dry mass and content of chlorophyll a, as well as composition of the community of developed periphyton, were estimated, together with P. rubescens biomass in the water column at the particular depths where substrates for periphyton were incubated. The metalimnetic bloom of P. rubescens induced calcite precipitation on the incubated substrates, which was reflected in obstructed colonization. The periphyton community composition was mainly determined by the depth gradient, which was potentially related to reduced light availability driven by shading effects caused by the P.rubescens bloom. Our results provide a significant update on periphyton ecology in relation to cyanobacterial blooms, elucidating complex interactions in the ecosystem. They also represent a stimulus for further studies on the capacity of P. rubescens for induction of calcium carbonate precipitation in lakes.

A lake classification concept for a more accurate global estimate of the dissolved inorganic carbon export from terrestrial ecosystems to inland waters

The magnitude of lateral dissolved inorganic carbon (DIC) export from terrestrial ecosystems to inland waters strongly influences the estimate of the global terrestrial carbon dioxide (CO2) sink. At present, no reliable number of this export is available, and the few studies estimating the lateral DIC export assume that all lakes on Earth function similarly. However, lakes can function along a continuum from passive carbon transporters (passive open channels) to highly active carbon transformers with efficient in-lake CO2 production and loss. We developed and applied a conceptual model to demonstrate how the assumed function of lakes in carbon cycling can affect calculations of the global lateral DIC export from terrestrial ecosystems to inland waters. Using global data on in-lake CO2 production by mineralization as well as CO2 loss by emission, primary production, and carbonate precipitation in lakes, we estimated that the global lateral DIC export can lie within the range of {0.70}_{-0.31}^{+0.27} to {1.52}_{-0.90}^{+1.09} Pg C yr−1 depending on the assumed function of lakes. Thus, the considered lake function has a large effect on the calculated lateral DIC export from terrestrial ecosystems to inland waters. We conclude that more robust estimates of CO2 sinks and sources will require the classification of lakes into their predominant function. This functional lake classification concept becomes particularly important for the estimation of future CO2 sinks and sources, since in-lake carbon transformation is predicted to be altered with climate change.

Evaluating abiotic and microbial factors on carbonate precipitation in Lake Acigöl, a hypersaline lake in Southwestern Turkey

The recent carbonate precipitation occurs in Lake Acıgöl, a hypersaline playa lake. Elucidating precipitation mechanisms of carbonate minerals under particularly supersaturated ionic solution at low temperature may hold key understanding to recognize microbial fingerprints throughout the Earth history. In the presented study abiotic and microbial factors controlling carbonate precipitation mechanisms are investigated by using geochemical, isotopic and chemical approaches. Our data demonstrated that aragonite, calcite and dolomite are readily precipitated in oxic column of lake water in decreasing order. Major metabolites profile of pore water showed that carbonate alkalinity and pH increased by microbial activity seems to be insignificant in the lake sediments to support precipitation. On the contrary a positive correlation between δ13C and δ18O values of carbonates suggest that carbonate super-saturation occurs as a result of evaporation and associated degassing of CO2in the lake basin. However, a putative microbial role such as binding of cations to microbial cell wall or EPS to overcome kinetic inhibitors (e.g Mg2+) is likely possible in the lake as a driving carbonate precipitation mechanism. Overall, the present study demonstrated that carbonate precipitation in the lake is the result of complex players, such as lake water chemistry, ionic interactions, evaporation and EPS-organic compounds (e.g EPS) in addition to kinetic microbial processes. The data also provide a fundamental insight which is that revealing of changes in carbonate mineralogy of the lake, strongly influenced by evaporation, would provide significant insights about paleoclimatic conditions of the region.

English

Carbon dioxide and calcium oxides may be used to neutralize acidic lakes. In lignite producing areas combustion power plants producing CO2 are often close to pit lakes. If fly ashes from these power plants could be used as calcium oxide source, carbonate precipitation in lakes could as also as a mineral trap to dispose of CO2. In a preliminary step the feasibility of this treatment scheme is investigated and includes a model based assessment of expected effects on the surface water, the reactivity of the chemical components, and the technical prerequisites. A pit lake in the Lausitz (Lusatia) post mining area in Germany was chosen as a test site, where fly ash has been deposited for more than 25 years. The feasibility of re-suspending these deposits to neutralize the lake was demonstrated in the years 2000 and 2003, and additional CO2 is proposed to increase the buffering capacity of the lake water, to precipitate, and store carbonates in the lake sediments.

Impact of Carbonate Precipitation on Riverine Inorganic Carbon Mass Transport from a Mid-continent, Forested Watershed

Physiochemical controls on the carbonate geochemistry of large river systems are important regulators of carbon exchange between terrestrial and marine reservoirs on human time scales. Although many studies have focused on large-scale river carbon fluxes, there are few investigations of mechanistic aspects of carbonate mass balance and transport at the catchment scale. We determined elemental and carbonate geochemistry and mass balances for net carbonate dissolution fluxes from the forested, mid-latitude Huron River watershed, established on carbonate-rich unconfined glacial drift aquifers. Shallow groundwaters are near equilibrium with respect to calcite at pCO2 values up to 25 times atmospheric values. Surface waters are largely groundwater fed and exhibit chemical evolution due to CO2 degassing, carbonate precipitation in lakes and wetlands, and anthropogenic introduction of road salts (NaCl and CaCl2). Because the source groundwater Mg2+/HCO3 − ratio is fairly constant, this parameter permits mass balances to be made between carbonate dissolution and back precipitation after groundwater discharge. Typically, precipitation does not occur until IAP/K calcite values exceed 10 times supersaturation. Stream chemistry changes little thereafter even though streams remain highly supersaturated for calcite. Our data taken together with historical United States Geological Survey (USGS) data show that alkalinity losses to carbonate precipitation are most significant during periods of lowest discharge. Thus, on an annual basis, the large carbon flux from carbonate dissolution in soil zones is only decreased by a relatively small amount by the back precipitation of calcium carbonate.