Trace metal adsorption in three serial flow-through systems: implications for foraminiferal culturing experiments
Year: 2025
Type: article
Abstract: Benthic foraminifera have been utilized extensively in laboratory culturing experiments to study the effects of elevated and/or depleted seawater concentrations of trace metals (e.g., on morphological shell abnormalities). In addition, past oceanic concentrations of various elements have been reconstructed through the analyses of benthic foraminiferal calcite. Paleoproxies of several trace metals have been used to track geologically ancient surficial processes (e.g., weathering and redox) by using black shales; however, analyses of foraminiferal calcite remain underconstrained for many transition metals. Growth experiments with trace elements, such as molybdenum (Mo) in this study, could be used to explore their potential as proxies to expand the sedimentary archives beyond those of black shales. Additional calcite proxies would provide more robust long-term paleo-redox reconstructions, especially for periods of Earth's history with limited archives. Concentrations of trace elements in seawater are often extremely low and measurements can be altered by adsorption, contamination, and/or stratification. To assess possible effects in calcifying organisms from trace metal concentration fluctuations, closed-system experiments using serial flow-through culturing devices can help ensure reliable results. Minor concentration changes in a trace element, particularly near or lower than seawater concentrations, can alter the equilibration time required for the modified source seawater to normalize with the seawater that has passed through the experimental setup. In this study, the stabilization was investigated after Mo-enriched seawater passed through three serial flow-through culturing systems. System A was an apparatus using a typical 24-well plastic cell culture plate, System B was based on System A but included modifications such as a customized block of polytetrafluoroethylene (PTFE) in place of the plastic cell culture plate, and System C was a serial system of synthetic perfluoroalkoxy alkane (PFA) vials connected using polytetrafluoroethylene tubing. The three systems were tested for the duration required to reach steady state to examine Mo adsorption by each system (A, B, and C) using 5-times and 2-times natural seawater concentrations of Mo ([Mo] sw ). Though the three serial flow-through culturing systems reached equilibrium early in the process when [Mo] sw was 5-times seawater concentration, the experiments demonstrated that, when the Mo concentration was closer to modern seawater levels, systems reached equilibrium at different times. Specifically, systems that incorporated more adsorption-resistant materials and minimized seawater contact with “common” plastic (e.g., polypropylene and polystyrene) components reached equilibrium more quickly, where System C was the fastest. At low concentrations, equilibration takes longer due to the abundance of the element that can be adsorbed by components over time being lower, while the amount of time may become insignificant at far higher concentrations. Since equilibration time at lower concentrations with this trace metal differed by system, other foraminiferal trace element experiments should also consider the effect of adsorption. These setups were further tested in two experiments that compared the incorporation of Mo at various [Mo] sw into foraminiferal calcite, and their very low measurements, near current detection limits, demonstrate the importance of minimizing external effects such as adsorption. Importantly, with the best experimental setup tested, there was a small but measurable difference in the foraminiferal incorporation. Therefore, greater utilization of adsorption-resistant materials in experimental design is advised when studying very low oceanic elemental concentrations and their incorporation into foraminiferal calcite.
Source: Journal of Micropalaeontology
Language: English
Subfield: Paleontology
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $841
Awards: G1138554163, THE TIMING OF THE INITIAL ACCUMULATION OF OXYGEN IN THE ATMOSPHERE AND OCEANS HAS BEEN DEBATED FOR THE PAST SEVERAL DECADES. OXYGENATION OF THE OCEAN, THE REDOX STATE OF ATMOSPHERE-OCEAN SYSTEM IS STRONGLY COUPLED TO THE EVOLUTION OF THE CLIMATE THAT LIKELY CONTROLLED BIOLOGICAL INNOVATION. THE NEOPROTEROZOIC ERA (~1 000-542 MYR AGO) WAS A PERIOD OF DRASTIC ENVIRONMENTAL CHANGE WITH AT LEAST TWO LOW-LATITUDE 'SNOWBALL EARTH' GLACIATIONS AND CARBON CYCLE PERTURBATION AS OBSERVED IN CARBON ISOTOPE FLUCTUATION. EVIDENCE HAS SHOWN THAT THE ATMOSPHERIC OXYGEN INCREASED FROM AMBIGUOUSLY LOW CONCENTRATIONS TO NEAR MODERN LEVELS PRIOR TO THE PHANEROZOIC WHICH LIKELY HAD A MAJOR EFFECT ON THE ORGANIC CARBON BURIAL REMINERALIZATION RATE AND CARBON ISOTOPE RECORD. COUPLED TO THIS LARGE ENVIRONMENTAL SHIFT IS THE OBSERVED EVOLUTION OF COMPLEX MULTICELLULAR LIFE. THESE BROAD OBSERVATIONS HAVE DOCUMENTED THE CONNECTIONS AMONG LARGE SCALE ENVIRONMENTAL CHANGE OCEAN-ATMOSPHERE OXYGENATION AND THE EVOLUTION OF THE LIFE. EVEN WITH AN INTENSE DEDICATED TO UNDERSTANDING EARTH'S OXYGENATIONTIMING INITIAL RISE OF OCEAN OXYGENATION AND QUANTIFICATIONREMAINS AMBIGUOUS LARGELY DUE TO PROXY LIMITATIONS. IT HAS BEEN ESPECIALLY DIFFICULT TO UNAMBIGUOUSLY TRACK LOW OXYGEN ENVIRONMENTS IN THE PALEO-OCEAN AS CURRENT PROXIES LACK THE ABILITY TO UNIQUELY TRACK NON-SULFIDIC LOW-OXYGEN CONDITIONS WHICH IS CRITICAL TO UNRAVEL THE MECHANISM(S) BETWEEN ATMOSPHERE/OCEAN OXYGENATION EMERGENCE AND EVOLUTION OF METAZOANS. THE PROPOSED PROJECT WILL FOCUS ON VANADIUM (V) ISOTOPES IN THE NEO-PROTEROZOIC AS A FINGERPRINT FOR DETERMINING LOW OXYGEN NONSULFIDIC CONDITIONS. THE FRAMEWORK FOR THIS STUDY IS BASED ON OUR MODERN V ISOTOPE SIGNATURES THAT CAPTURE VARIABLE BOTTOM WATER OXYGEN CONDITIONS. WE HAVE OBSERVED REMARKABLE V ISOTOPE VARIATIONS OF MODERN SAMPLES THAT ARE RELATED TO LOCAL BOTTOM WATER OXYGEN CONTENTS. IMPORTANTLY THE SHIFT OF THE V ISOTOPE SIGNATURE STARTS AT SUBOXIC (REDUCED BUT NONE-ZERO OXYGEN) CONDITIONS. THUS SEDIMENTARY V ISOTOPES FOR THE FIRST TIME HAVE THE POTENTIAL TO TRACK CHANGES IN MARINE LOW OXYGEN CONDITIONS. MOREOVER V CONCENTRATIONS BEGIN ENRICHING UNDER LOW OXYGEN ENVIRONMENTS THUS THE REDUCTIVE ENRICHMENT OF V IN MARINE SEDIMENTS OCCURS WITHOUT THE PRESENCE OF SULFIDE. MODERN OBSERVATION ALSO DOCUMENTS SIGNIFICANTLY DIFFERENT V ISOTOPE SIGNATURES BETWEEN MARINE SEDIMENTS AND HYDROTHERMAL SEDIMENTS THUS V ISOTOPES CAN DISTINGUISH THE MECHANISM OF ENRICHMENT (REDOX OR HYDROTHERMAL). FURTHERMORE GIVEN THAT V HAS A LONG MODERN MARINE RESIDENCE TIME THE CHARACTERISTIC V ISOTOPE FRACTIONATION PATTERN HAS THE POTENTIAL TO TRACK THE GLOBAL OXYGEN CONTENT WHEN COMBINED WITH OTHER PROXIES. THUS COMBINING OUR CURRENT UNDERSTANDING OF V SYSTEMATICS A HIGH-RESOLUTION ANCIENT STUDY CAN ILLUMINATE SEDIMENT BURIAL UNDER LOW OXYGEN CONDITIONS. TO TRACK SUBTLE LOW OXYGEN SHIFTS IN THE NEOPROTEROZOIC WE WILL INVESTIGATE THE V ISOTOPE SIGNATURE OF SHALES RANGING IN AGES FROM ~1 000 TO 542 MILLION YEARS. IT IS IMPORTANT TO DECONSTRUCT THIS ~460 MILLION YEARS TO CAPTURE THE EXPANSION AND CONTRACTION OF THE LOCAL AND GLOBAL REDOX STATES OF THE OCEAN. IN THIS PROPOSAL WE SEEK TO BETTER CONSTRAINT: (1) THE REDOX STATE OF THE OUTER SHELF VS. DEEP BASIN SETTINGS BEFORE AND DURING THE CRYOGENIAN TO BETTER CONSTRAIN THE TEMPORAL AND SPATIAL (LOCAL VS. GLOBAL) RELATIONSHIPS BETWEEN THE EXPANSION OF LOW OXYGEN REGIONS AND THE EARLIEST EVIDENCE OF EMERGING OF MULTICELLULAR LIFE (EARLIEST RECORD OF DEMOSPONGES) (2) THE FLUCTUATION OF REDOX STATE DURING THE EDIACARAN TO TEST THE 'OCEAN OXYGENATION EVENTS' POSTULATED FOR THE END-MARINOAN GLACIATION. EXTRACTING THIS INFORMATION FROM ANCIENT SEDIMENTS HAS THE POTENTIAL TO PROVIDE CRUCIAL INFORMATION ABOUT THE LINKS BETWEEN LARGE SCALE ENVIRONMENTAL CHANGE (GLOBAL GLACIAL EVENT) OCEAN OXYGENATION HYDROTHERMAL ACTIVITY AND THE EVOLUTION OF ANIMALS. DEVELOPING V ISOTOPE TO RECONSTRUCT LOW-OXYGEN PALEO-REDOX CONDITIONS AND THE RELATIONSHIP TO MULTICELLULAR EVOLUTION COULD POTENTIALLY BE USED TO SEARCH FOR EXOPLANET LIFE, National High Magnetic Field Laboratory Renewal 2023-2027, Collaborative research: Multi-disciplinary investigation of the links between volcanism, marine redox, and mass extinction during the Late Triassic and Early Jurassic, G844507202
OpenAlex ID: W4415604048