More Like this

1. A synthesis of mercury research in the Southern Hemisphere, part 1: Natural processes

   https://doi.org/10.1007/s13280-023-01832-5  

   Schneider, Larissa; Fisher, Jenny A.; Diéguez, María C.; Fostier, Anne-Hélène; Guimaraes, Jean R. D.; Leaner, Joy J.; Mason, Robert (March 2023, Ambio)

   Abstract Recent studies demonstrate a short 3–6-month atmospheric lifetime for mercury (Hg). This implies Hg emissions are predominantly deposited within the same hemisphere in which they are emitted, thus placing increasing importance on considering Hg sources, sinks and impacts from a hemispheric perspective. In the absence of comprehensive Hg data from the Southern Hemisphere (SH), estimates and inventories for the SH have been drawn from data collected in the NH, with the assumption that the NH data are broadly applicable. In this paper, we centre the uniqueness of the SH in the context of natural biogeochemical Hg cycling, with focus on the midlatitudes and tropics. Due to its uniqueness, Antarctica warrants an exclusive review of its contribution to the biogeochemical cycling of Hg and is therefore excluded from this review. We identify and describe five key natural differences between the hemispheres that affect the biogeochemical cycling of Hg: biome heterogeneity, vegetation type, ocean area, methylation hotspot zones and occurence of volcanic activities. We review the current state of knowledge of SH Hg cycling within the context of each difference, as well as the key gaps that impede our understanding of natural Hg cycling in the SH. The differences demonstrate the limitations in using NH data to infer Hg processes and emissions in the SH. 

   more » « less
2. Measurement of Atmospheric Mercury: Current Limitations and Suggestions for Paths Forward

   https://doi.org/10.1021/acs.est.4c06011  

   Gustin, Mae Sexauer; Dunham-Cheatham, Sarrah M; Lyman, Seth; Horvat, Milena; Gay, David A; Gačnik, Jan; Gratz, Lynne; Kempkes, Geyan; Khalizov, Alexei; Lin, Che-Jen; et al (July 2024, Environmental Science & Technology)

   Mercury (Hg) researchers have made progress in under- standing atmospheric Hg, especially with respect to oxidized Hg (HgII) that can represent 2 to 20% of Hg in the atmosphere. Knowledge developed over the past ∼10 years has pointed to existing challenges with current methods for measuring atmospheric Hg concentrations and the chemical composition of HgII compounds. Because of these challenges, atmospheric Hg experts met to discuss limitations of current methods and paths to overcome them considering ongoing research. Major conclusions included that current methods to measure gaseous oxidized and particulate-bound Hg have limitations, and new methods need to be developed to make these measurements more accurate. Developing analytical methods for measure- ment of HgII chemistry is challenging. While the ultimate goal is the development of ultrasensitive methods for online detection of HgII directly from ambient air, in the meantime, new surfaces are needed on which HgII can be quantitatively collected and from which it can be reversibly desorbed to determine HgII chemistry. Discussion and identification of current limitations, described here, provide a basis for paths forward. Since the atmosphere is the means by which Hg is globally distributed, accurately calibrated measurements are critical to understanding the Hg biogeochemical cycle. 

   more » « less
3. It's what's inside that matters: physiological adaptations of high‐latitude marine microalgae to environmental change

   https://doi.org/10.1111/nph.16648  

   Young, Jodi N.; Schmidt, Katrin (June 2020, New Phytologist)

   Summary Marine microalgae within seawater and sea ice fuel high‐latitude ecosystems and drive biogeochemical cycles through the fixation and export of carbon, uptake of nutrients, and production and release of oxygen and organic compounds. High‐latitude marine environments are characterized by cold temperatures, dark winters and a strong seasonal cycle. Within this environment a number of diverse and dynamic habitats exist, particularly in association with the formation and melt of sea ice, with distinct microalgal communities that transition with the season. Algal physiology is a crucial component, both responding to the dynamic environment and in turn influencing its immediate physicochemical environment. As high‐latitude oceans shift into new climate regimes the analysis of seasonal responses may provide insights into how microalgae will respond to long‐term environmental change. This review discusses recent developments in our understanding of how the physiology of high‐latitude marine microalgae is regulated over a polar seasonal cycle, with a focus on ice‐associated (sympagic) algae. In particular, physiologies that impact larger scale processes will be explored, with an aim to improve our understanding of current and future ecosystems and biogeochemical cycles. 

   more » « less
4. Impacts of Volcanic Emissions on the Global Biogeochemical Mercury Cycle: Insights From Satellite Observations and Chemical Transport Modeling

   https://doi.org/10.1029/2023GL104667  

   Geyman, Benjamin M.; Thackray, Colin P.; Jacob, Daniel J.; Sunderland, Elsie M. (November 2023, Geophysical Research Letters)

   Abstract Volcanism is the largest natural source of mercury (Hg) to the biosphere. However, past Hg emission estimates have varied by three orders of magnitude. Here, we present an updated central estimate and interquartile range (232 Mg a⁻¹; IQR: 170–336 Mg a⁻¹) for modern volcanic Hg emissions based on advances in satellite remote sensing of sulfur dioxide (SO₂) and an improved method for considering uncertainty in Hg:SO₂emissions ratios. Atmospheric modeling shows the influence of volcanic Hg on surface atmospheric concentrations in the extratropical Northern Hemisphere is 1.8 times higher than in the Southern Hemisphere. Spatiotemporal variability in volcanic Hg emissions may obscure atmospheric trends forced by anthropogenic emissions at some locations. This should be considered when selecting monitoring sites to inform global regulatory actions. Volcanic emission estimates from this work suggest the pre‐anthropogenic global atmospheric Hg reservoir was 580 Mg, 7‐fold lower than in 2015 (4,000 Mg). 

   more » « less
5. Diel light cycles affect phytoplankton competition in the global ocean

   https://doi.org/10.1111/geb.13562  

   Tsakalakis, Ioannis; Follows, Michael J.; Dutkiewicz, Stephanie; Follett, Christopher L.; Vallino, Joseph J. (July 2022, Global Ecology and Biogeography)

   Abstract AimLight, essential for photosynthesis, is present in two periodic cycles in nature: seasonal and diel. Although seasonality of light is typically resolved in ocean biogeochemical–ecosystem models because of its significance for seasonal succession and biogeography of phytoplankton, the diel light cycle is generally not resolved. The goal of this study is to demonstrate the impact of diel light cycles on phytoplankton competition and biogeography in the global ocean. LocationGlobal ocean. Major taxa studiedPhytoplankton. MethodsWe use a three‐dimensional global ocean model and compare simulations of high temporal resolution with and without diel light cycles. The model simulates 15 phytoplankton types with different cell sizes, encompassing two broad ecological strategies: small cells with high nutrient affinity (gleaners) and larger cells with high maximal growth rate (opportunists). Both are grazed by zooplankton and limited by nitrogen, phosphorus and iron. ResultsSimulations show that diel cycles of light induce diel cycles in limiting nutrients in the global ocean. Diel nutrient cycles are associated with higher concentrations of limiting nutrients, by 100% at low latitudes (−40° to 40°), a process that increases the relative abundance of opportunists over gleaners. Size classes with the highest maximal growth rates from both gleaner and opportunist groups are favoured by diel light cycles. This mechanism weakens as latitude increases, because the effects of the seasonal cycle dominate over those of the diel cycle. Main conclusionsUnderstanding the mechanisms that govern phytoplankton biogeography is crucial for predicting ocean ecosystem functioning and biogeochemical cycles. We show that the diel light cycle has a significant impact on phytoplankton competition and biogeography, indicating the need for understanding the role of diel processes in shaping macroecological patterns in the global ocean. 

   more » « less