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1. Effect of Salinity on the Shell Formation of Eastern Oysters at Different Climactic Regions

   Colfer, S; Telesca, L (February 2024, Proceedings American Geophysical Union)

   Telesca, L (Ed.)

   Rapid environmental changes are predicted to impact shellfish abundance and their commercial value. The Eastern Oyster, Crassostrea virginica, a key foundation species with high environmental and commercial value has dramatically declined due to climate and anthropogenic impacts over the last century. Our current understanding of oyster vulnerability mostly stems from laboratory-based experiments but lacks studies in natural systems. Here, we investigated how shell production and composition of C. virginica are affected by natural salinity gradients under different temperature regimes. We studied variations in oyster shell shape, production, structure, composition, and organic matrix content in oysters from a temperate, Hudson River (NY), and subtropical, Galveston Bay (TX), estuary. parameters such as weight, area, density, chalk production, and organic matrix to see how the shells varied based on salinity and temperature. Our findings showed that Eastern oysters produced shells with higher chalk content under calcification-limiting environments (i.e., low temperature and low salinity). In comparison, shells with lower chalk content were produced in high predation environments (i.e., high temperatures and salinity). Temperate oyster's shell structure preferentially favored chemical protection against dissolution while subtropical oysters preferentially favored mechanical protection against predation. Oyster’s shell showed a strong capacity for protective responses under calcification- and predation-controlled environments. 

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2. Atmospheric oxidation of cyanobacterial aerosols emitted from lakes and estuaries during harmful algal blooms

   https://doi.org/10.1016/j.envpol.2025.126959  

   Jang, Myoseon; Vuong, Quang Tran; Madhu, Azad; Kim, Ganghan (November 2025, Environmental Pollution)

   Harmful algal blooms (HABs) in lakes and estuaries, caused by cyanobacteria, pose various threats to humans and the environment. Cyanobacteria produce microcystins (MCs) that make animals and people sick. Once airborne, cyanobacterial aerosols are rapidly transformed through heterogeneous reactions with atmospheric oxidants, which tend to occur much faster in air than in water. The important aspects of these transformations include the degradation of MCs and the production of reactive oxygen species (ROS) from oxidized organic matter (OM) in cyanobacterial aerosol. In this study, MCs in aerosols and water samples, collected in lakes (Lake Okeechobee, Georges Lake, and Doctors Lake) of Florida during HABs, were measured using enzyme-linked immunosorbent assay kits. Organic hydroperoxides (OHP) and the oxidative potential (OP) associated with aerosols collected at Doctors Lake were measured with 4-nitrophenylboronic acid and dithiothreitol assays, respectively. The decay of MCs and the evolution of ROS in cyanobacterial aerosols were also demonstrated in an outdoor chamber under ambient sunlight. MC concentrations (0.4–2.1 μg/L) during HAB periods were higher than the US EPA guideline (0.3 μg/L for pre-school age and 1.6 μg/L for school-age and above). Airborne MC concentrations ranged from 0.2 to 5.7 ng/m3. Regulations for airborne MC concentrations are yet to be established. In both field and chamber data, MCs decomposed but ROS substantially increased as aerosols atmospherically oxidized. Aerosolized OM concentrations during HABs were higher than those in dormant periods. OM in cyanobacterial aerosols was enriched at estuary Doctors Lake with high inorganic salt concentrations due to salting-out of water-soluble organics into lake-surface layers. Aerosolized OM concentrations were positively corelated to OP and OHP (r = 0.96 and 0.85, respectively) at Doctors Lake suggesting that cyanobacterial aerosols might adversely influence respiratory health. The longitudinal health impacts of aerosolized cyanobacteria emitted from HABs should be investigated in the future. 

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3. Atom Probe Tomography (APT) Characterization of Organics Occluded in Single Calcite Crystals: Implications for Biomineralization Studies

   https://doi.org/10.3390/c5030050  

   Pérez-Huerta, Alberto; Suzuki, Michio; Cappelli, Chiara; Laiginhas, Fernando; Kintsu, Hiroyuki (September 2019, C — Journal of Carbon Research)

   Occlusion of organic components in synthetic calcite crystals has been recently used as a model to understand the role of intra-crystalline organics in biominerals. However, the characterization of the distribution of both types of organics inside these calcite crystals is very challenging. Here, we discuss the potential of using the technique of atom probe tomography (APT) for such characterization, focusing on the analysis of chitin incorporation in single crystals. Additionally, APT has at least the same spatial resolution as TEM tomography, yet with the advantage of obtaining quantitative chemical data. Results show that chitin, either after degradation with yatalase or in the form of nanofibers, forms discrete clusters (2 to 5 nm) in association to water and hydronium molecules, rather than forming a 3D network inside crystals. Overall findings indicate that APT can be an ideal technique to characterize intra-crystalline organic components in abiogenic and biogenic carbonates to further advance our understanding of biomineralization. 

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4. Molecular investigation of the multi-phase photochemistry of Fe( iii )–citrate in aqueous solution

   https://doi.org/10.1039/D1EM00503K  

   West, Christopher P.; Morales, Ana C.; Ryan, Jackson; Misovich, Maria V.; Hettiyadura, Anusha P.; Rivera-Adorno, Felipe; Tomlin, Jay M.; Darmody, Andrew; Linn, Brittany N.; Lin, Peng; et al (February 2023, Environmental Science: Processes & Impacts)

   Iron (Fe) is ubiquitous in nature and found as Fe II or Fe III in minerals or as dissolved ions Fe 2+ or Fe 3+ in aqueous systems. The interactions of soluble Fe have important implications for fresh water and marine biogeochemical cycles, which have impacts on global terrestrial and atmospheric environments. Upon dissolution of Fe III into natural aquatic systems, organic carboxylic acids efficiently chelate Fe III to form [Fe III –carboxylate] 2+ complexes that undergo a wide range of photochemistry-induced radical reactions. The chemical composition and photochemical transformations of these mixtures are largely unknown, making it challenging to estimate their environmental impact. To investigate the photochemical process of Fe III –carboxylates at the molecular level, we conduct a comprehensive experimental study employing UV-visible spectroscopy, liquid chromatography coupled to photodiode array and high-resolution mass spectrometry detection, and oil immersion flow microscopy. In this study, aqueous solutions of Fe III –citrate were photolyzed under 365 nm light in an experimental setup with an apparent quantum yield of ( φ ) ∼0.02, followed by chemical analyses of reacted mixtures withdrawn at increment time intervals of the experiment. The apparent photochemical reaction kinetics of Fe 3+ –citrates (aq) were expressed as two generalized consecutive reactions of with the experimental rate constants of j 1 ∼ 0.12 min −1 and j 2 ∼ 0.05 min −1 , respectively. Molecular characterization results indicate that R and I consist of both water-soluble organic and Fe–organic species, while P compounds are a mixture of water-soluble and colloidal materials. The latter were identified as Fe–carbonaceous colloids formed at long photolysis times. The carbonaceous content of these colloids was identified as unsaturated organic species with low oxygen content and carbon with a reduced oxidation state, indicative of their plausible radical recombination mechanism under oxygen-deprived conditions typical for the extensively photolyzed mixtures. Based on the molecular characterization results, we discuss the comprehensive reaction mechanism of Fe III –citrate photochemistry and report on the formation of previously unexplored colloidal reaction products, which may contribute to atmospheric and terrestrial light-absorbing materials in aquatic environments. 

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5. Formation of insoluble brown carbon through iron-catalyzed reaction of biomass burning organics

   https://doi.org/10.1039/d2ea00141a  

   Hopstock, Katherine S.; Carpenter, Brooke P.; Patterson, Joseph P.; Al-Abadleh, Hind A.; Nizkorodov, Sergey A. (January 2023, Environmental Science: Atmospheres)

   Biomass burning organic aerosol (BBOA) is one of the largest sources of organics in the atmosphere. Mineral dust and biomass burning smoke frequently co-exist in the same atmospheric environment. Common biomass burning compounds, such as dihydroxybenzenes and their derivatives, are known to produce light-absorbing, water-insoluble polymeric particles upon reaction with soluble Fe( iii ) under conditions characteristic of aerosol liquid water. However, such reactions have not been tested in realistic mixtures of BBOA compounds. In this study, model organic aerosol (OA), meant to replicate BBOA from smoldering fires, was generated through the pyrolysis of Canary Island pine needles in a tube furnace at 300, 400, 500, 600, 700, and 800 °C in nitrogen gas, and the water-soluble fractions were reacted with iron chloride under dark, acidic conditions. We utilized spectrophotometry to monitor the reaction progress. For OA samples produced at lower temperatures (300 and 400 °C), particles (P300 and P400) formed in solution, were syringe filtered, and extracted in organic solvents. Analysis was conducted with ultrahigh pressure liquid chromatography coupled to a photodiode array spectrophotometer and a high-resolution mass spectrometer (UHPLC-PDA-HRMS). For OA samples formed at higher pyrolysis temperatures (500–800 °C), water-insoluble, black particles (P500–800) formed in solution. In contrast to P300 and P400, P500–800 were not soluble in common solvents. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) and transmission electron microscopy (TEM) were used to image P600 and determine bulk elemental composition. Electron microscopy revealed that P600 had fractal morphology, reminiscent of soot particles, and contained no detectable iron. These results suggest that light-absorbing aerosol particles can be produced from Fe( iii )-catalyzed reactions in aging BBOA plumes produced from smoldering combustion in the absence of any photochemistry. This result has important implications for understanding the direct and indirect effects of aged BBOA on climate. 

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