Author: Steven.Beaupre@stonybrook.edu

We are about to embark on the first winter cruise of our NSF sponsored marine aerosol seasonal study to the Bermuda Atlantic Time-series Study (BATS) site, which is located approximately 60 miles southeast of Bermuda. 

Why are we going to sea?  Previously, our team used radiocarbon (¹⁴C) dating to show that very old organic matter in seawater is thrown into the atmosphere as tiny particles (aerosol) when air bubbles burst at the sea surface.  On average, our measurements showed that the organic matter on these particles was ~1,370 years old (Beaupre et al., 2019), suggesting that a significant fraction of old organic matter is removed from the ocean each year by bubbles generated from breaking waves.  In general, the rates at which substances react and move around the Earth control the chemical composition of the land, air, and sea; and it is the chemical composition of our land, air, and sea that makes Earth habitable given its size and position in our solar system.  Therefore, knowing how much and how quickly this process influences our planet’s chemical composition is important.

However, our observations were from aerosol generated in one area of the ocean, during one season of one year: the seas between Bermuda and New England during autumn of 2016. In other words, we discovered that very old organic matter can leave the ocean with aerosol, but we don’t know if it leaves the ocean in the same way all the time.  For example, spring and summer blooms produce new organic matter that mixes with older organic matter already in the ocean.  This natural seasonal variability in both the composition and average age of molecules in the sea surface could influence the proportion of old molecules that are removed by aerosol.  Therefore, we are now going to sea in both summer and winter to measure how seasonal changes in seawater composition affect marine aerosol composition.

One of the best places in the world to perform our study is the BATS site. It has a monthly record of physical, chemical, and biological observations since 1988!  It is an open ocean site that is, in many ways, representative of most of the world ocean.  And yet, it is still accessible due to its close proximity to Bermuda, the resources available at Bermuda Institute of Ocean Sciences (BIOS), and the dependable fleet of UNOLS research vessels.  We are taking advantage of this remarkable site to help us put our comparatively short study of seasonal variability (2 years) into broader context.

Since August 2020, we’ve been working around the clock washing bottles, shipping gear, holding Zoom meetings, and taking countless COVID tests.  We had a successful summer cruise to BATS in July 2021 aboard the R/V Atlantic Explorer, and we’re ready for our first winter cruise aboard the R/V Endeavor.  We have been successful at sea largely because we’re working with truly exceptional ship-ops teams from BIOS and the University of Rhode Island (URI). We can’t thank them enough for their competence, kindness, patience, and ability to safely take us to sea and bring us back home.

We had planned to load half of our gear aboard Endeavor on Jan 10, leave Rhode Island on Jan 11, and arrive in Bermuda on Jan 14.  We then planned to spend 4 days installing a 20′ cargo container that holds a sea-going aerosol generating laboratory, and finally steam to BATS for 10 days of science.

The North Atlantic had other plans, as it often does in winter.  Two back-to-back storms have been sweeping across the ocean with hurricane force winds, whipping up ramparts of “ship killing” waves between us and our destination that forced us to delay our departure by 8 days. We are now scheduled to depart Rhode Island on Wednesday, Jan 19, weather permitting…

Weather delays like this are boons and banes for oceanographers.

Yes, we are behind schedule and we haven’t even left the dock.  A lot of good, hardworking people have to put in more overtime to keep the program moving safely ahead.  There are flights to cancel, cranes to reschedule, and COVID tests to repeat.  We’re losing more family time and accumulating more responsibilities.  Our most precious possession is our time, and we can never get it back when it is taken from us.

However, at this same moment, our ship-board team has been given the gift of some much-needed and mostly distraction-free time to work together, to be creative, and to laugh together as old friends should.  We are a pod of certifiably COVID-free colleagues during an unprecedented worldwide spike in cases. And our dock-side internet connection is strong enough for an occasional Zoom meeting with the people that we love–a luxury oceanographers usually don’t have while they are away.  We have even had time to “leisurely” fasten our gear for a rough ride, to get more than 4 hours of sleep, and to finally post something on a long-neglected website!

Even though most places on a map of the Earth are easily recognizable and shockingly accessible, our delay humbly reminds us that this place we call home is a planet–a massive, powerful, and ever changing system of atoms that move and react.  It is awesome, in the truest sense.  And all of us are part of that planet (also in the truest sense).  I am particularly humbled by the achievements of curiosity-driven people who, over generations, discovered how to turn rocks into rockets, observations into equations, and to develop the systems of satellites and models that tell us which way the atoms will move through our atmosphere and our ocean.  Thank you for nurturing your curiosity.  Thank you for giving us the weather forecasts that advised us to stay in port this week so that we can safely explore our planet next week.  And thank you, curious reader, for visiting our site.

If all goes according to plan, you can follow our ship as it leaves Rhode Island on Wednesday at the EndeavorNow website.

Congratulations to Dr. Xi Lu, who just published her latest paper, “Evaluation of the moderate DI¹³C isotope enrichment method for measuring photochemical mineralization of marine dissolved organic carbon” in Limnology and Oceanography: Methods.

Dr. Lu used monte carlo simulations to study the limits of moderate isotope dilution to measure the rates at which organic matter that is dissolved in seawater (DOM) is naturally converted to carbon dioxide when exposed to sunlight, i.e., the rates of “photochemical mineralization”.  This is a unique and promising application that was originally developed by Dr. Leanne Powers and colleagues (2017)

This study is important because photochemical mineralization is presently believed to be the fastest natural process that destroys the oldest organic matter found in seawater–molecules that are thousands of years old! However, additional high precision measurements of the reaction rates are needed to test whether this is true.  Aside from fundamental improvements in mass spectrometry, Dr. Lu’s work suggests that 1) using fractional isotopic abundances in calculations, 2) partially stripping the original dissolved inorganic carbon (DIC) from seawater and enriching the remaining DIC to higher ¹³C abundances prior to irradiating with sunlight, and 4) maximizing yields should improve the overall measurement precision and decrease the detection limit.

How did she figure this out?  Read all about it in L&O: Methods, available here (and don’t forget to check out the supplemental materials)

Today was a beautiful, sunny day in Stony Brook: just right for a doctoral hooding!  It was an honor to share this day with my wonderful PhD student, Xi Lu.  She is smart, kind, funny, and a special friend who will happily dodge four hurricanes with you on a research vessel… and still be ready to dodge some more! (July is coming…)  Thank you, Lucy, for all that you have done and all that you have taught me.

Xi Lu will formally defend her dissertation at 9:30 am on June 17:

Photochemical mineralization of marine refractory dissolved organic carbon (RDOC): method evaluation and optimization
By Xi Lu

Abstract: Despite its importance in the global carbon cycle, the budget of marine refractory dissolved organic carbon (RDOC) is out of balance. To constrain the flux of RDOC photochemical mineralization, which is presumably the largest sink of marine RDOC, measurements of both the production rate and radiocarbon (¹⁴C) isotopic composition of dissolved inorganic carbon (DIC) photochemically generated from marine DOC (DIC_hν) are required. In this study, methods for precisely achieving these measurements were evaluated and optimized with error propagations and Monte Carlo simulations. The Moderate DI¹³C Isotope Enrichment (MoDIE) method by Powers et al. represents the least invasive approach for precise quantification of DIC_hν, where the ambient DIC pool is isotopically enriched and subsequently “diluted” by the natural isotope-abundance DIC_hν. The decrease in the bulk DIC isotopic signature after irradiation thus indicates the amount of DIChν produced. This study evaluated the analytical uncertainties of the MoDIE method, and optimized its experimental designs for the most precise DIC_hν measurements. Based on the optimized MoDIE method, the study tested the feasibility of a dual isotopic (¹³C and ¹⁴C) dilution method to determine both the quantity and the ¹⁴C signature of DIC_hν. Alas, even with the optimized experimental conditions, these isotopic enrichment/dilution methods are still practically impeded by their sensitivities to precise sample manipulations. A well-designed photochemical reactor combined with a well-calibrated vacuum line may be the preferred approach for determining the RDOC photochemical mineralization rate under near-natural conditions. The DIC_hν collected in a vacuum line is typically quantified with manometry. Its precision depends on the precise measurements of pressure (P), temperature (T), and manometer volume (V). While P and T uncertainties depend on instrument choice and environmental stability, volume uncertainties depend on their method of measurement and are often overlooked. This study elucidated the optimum procedures for measuring V by two common applications of Boyle’s Law: cryogenic transfers and serial gas expansions. The optimized determination of V reduces the minimum achievable relative uncertainties of moles-of-gas to ±0.0026 ~ 0.0027. This optimized manometry improves the precision of marine RDOC photochemical mineralization rate measurements, and therefore our ability to constrain the RDOC budget.

You did it!  It’s been an exceptionally challenging year and you rose to the challenge.  Thank you for inspiring us to persevere, to achieve, to hold each other to high standards, and to be kind.  Wishing you all the best on all of your endeavors, and encouraging you to stay in touch.

To our Seawolf friends and family members: you can virtually participate in this year’s commencement, read the program, and watch a live stream of the ceremony from LaValle stadium, from the heart of Stony Brook University’s main campus.

Jorg Meyer was UC Irvine’s well-known and well-respected scientific glassblower for nearly 56 years.  He was a glass craftsman / artist / magician.  His humor and smile were priceless, never more so than the day he effortlessly encased a magnet inside a pyrex tube for one of my experiments.  He simply pulled the glowing mass out of the flame and watched as it supernaturally flowed and hardened into absolute perfection: perfect hemispheres with perfectly uniform wall-thicknesses and perfect placements. He did this without using any tools other than fire, gravity, skilled hands, and generations of knowledge.  I was utterly and rightly astonished, and he knew it. He kindly handed it over to me and said, “Now you do it. And don’t forget your physics.”

He encouraged me to practice.  He showed me some tricks.  He reminded me that you can’t take shortcuts when you’re learning, but you can when you’ve learned.  He believed in me.  He was a friend and a mentor, and he will be missed.  And if there is a heaven, I assure you, he’ll be one of only three people there with a parking spot.  Just look for the silver GT.

Thank you, Jorg, for all this and more.

UCI: Remembering Jorg Meyer

One common problem in the field of organic isotope geochemistry is the long-term storage of small aliquots of CO₂ that are extracted from samples.  This challenge arises primarily because high-precision, high-accuracy measurements of small samples often require laborious methods.  The CO₂ must be extracted carefully to minimize contamination, transferred from the extraction apparatus to the storage apparatus without losses, and the whole process must proceed without isotopic fractionation.  For these reasons, such methods have a limited throughput that cannot accumulate enough samples in a reasonable timescale for efficient use of an isotope ratio mass spectrometer (IRMS).  Therefore, we devised a simple protocol for storing small aliquots of CO₂ in capillary tubes, allowing the analyst to accumulate batches of samples over time.  The capillaries are easily cracked inside helium-filled Exetainer vials, which are then loaded into a gas bench for automated IRMS analysis.  It’s easy, accurate, and reliable.

In our quest to develop the method, we initially loaded Exetainers with handblown glass marbles in order to increase the likelihood of cracking the capillaries via shaking.  This worked, but created additional challenges that led to lost samples, such as seizing and occasional breakage of the Exetainer.  These challenges were partially alleviated by twisting “nurdles” into the capillaries prior to use.  Ultimately, slow-motion videos revealed that gently smacking the Exetainer against an open palm imparted enough energy to crack the capillary without the marbles or nurdles.  This simplification makes the method much easier to use and it greatly reduces the number of lost samples per batch.

For a full description of the method, including videos of some righteous tube crackin’, please check out our latest publication in Rapid Communications in Mass Spectrometry:

Walker, B. D., S. R. Beaupre, S. Griffin, J. Walker, E. Druffel, and X. Xu (2020), A sealed‐tube method for offline δ¹³C analysis of CO₂ via a Gas Bench II continuous flow isotope ratio mass spectrometer, Rapid Commun Mass Spectrom, doi:10.1002/rcm.9040.

Life of all sizes is creating fresh organic matter every day (0 years old), but nearly all organic matter in the ocean is very small (<0.000001 m) and really old (4,000 to 6,000 years)!  This sea of organic molecules is analogous to a world populated with babies and retirees, but somehow devoid of toddlers, teenagers, or thirty-somethings.  How can this be?  Is this simply a coincidence based on how we observe the sea?  In our latest paper, we re-examined this unusual age distribution with a simple model of the processes that transport and transform small (“dissolved”) organic molecules at Station M in the eastern North Pacific Ocean.

Beaupré, S. R., B. D. Walker, and E. R. M. Druffel (2020), The two-component model coincidence: Evaluating the validity of marine dissolved organic radiocarbon as a stable-conservative tracer at Station M, Deep Sea Research Part II: Topical Studies in Oceanography, doi:10.1016/j.dsr2.2020.104737.

This work is part of a special issue of Deep-Sea Research II commemorating 30 years of time-series observations at Station M (34°50′N, 123°00′W).

This image (“Courtesy NASA/JPL-Caltech”), and Carl Sagan’s accompanying poetry from Pale Blue Dot, have been an inspiration for 30 years.  To me, they represent the pinnacle of what we can achieve in exploring our universe, in thoughtfully moving forward, and in making that journey worthwhile through kindness and respect.  “For the 30th anniversary of one of the most iconic views from the Voyager mission, NASA’s Jet Propulsion Laboratory in Pasadena, California, is publishing a new version of the image known as the “Pale Blue Dot.”  Check out this new portrait of our Pale Blue Dot, the only home we’ve ever known, and learn more about it at https://www.jpl.nasa.gov/news/news.php?feature=7593

Our latest study, led by outstanding colleague, Dr. Nagissa Mahmoudi, demonstrates differences in microbial reactivity of sedimentary organic matter from Guaymas Basin using a continuous flow Isotopic Carbon Respirometer-Bioreactor (IsoCaRB).

Mahmoudi, N., T. N. Enke, S. R. Beaupré, A. P. Teske, O. X. Cordero, and A. Pearson (2019), Illuminating microbial species-specific effects on organic matter remineralization in marine sediments, Environmental Microbiology, doi:10.1111/1462-2920.14871.

Abstract: Marine microorganisms play a fundamental role in the global carbon cycle by mediating the sequestration of organic matter in ocean waters and sediments. A better understanding of how biological factors, such as microbial community composition, influence the lability and fate of organic matter is needed. Here, we explored the extent to which organic matter remineralization is influenced by species‐specific metabolic capabilities. We carried out aerobic time‐series incubations of Guaymas Basin sediments to quantify the dynamics of carbon utilization by two different heterotrophic marine isolates (Vibrio splendidus 1A01; Pseudoalteromonas sp. 3D05). Continuous measurement of respiratory CO₂ production and its carbon isotopic compositions (¹³C and ¹⁴C) shows species‐specific differences in the rate, quantity and type of organic matter remineralized. Each species was incubated with hydrothermally‐influenced versus unimpacted sediments, resulting in a ~2‐fold difference in respiratory CO₂ yield across the experiments. Genomic analysis indicated that the observed carbon utilization patterns may be attributed in part to the number of gene copies encoding for extracellular hydrolytic enzymes. Our results demonstrate that the lability and remineralization of organic matter in marine environments is not only a function of chemical composition and/or environmental conditions, but also a function of the microorganisms that are present and active.