mmaheigan :: Ocean Carbon & Biogeochemistry

Studying marine ecosystems and biogeochemical cycles in the face of environmental change

Author Archive for mmaheigan

Is seaweed farming an effective method to reduce atmospheric CO2?

Posted by mmaheigan

· Tuesday, June 15th, 2021

The world is in need of effective methods to reduce CO₂ in the atmosphere, and the ocean could potentially help us to meet this objective. One idea, explored since the 1980s, is to grow seaweeds on platforms in the open ocean to fix carbon and sequester it at great depth (ocean afforestation). But would that work at scale?

To address this question, we utilized the Great Atlantic Sargassum Belt as a natural analogue for seaweed farms distributed across the (sub)tropical Atlantic. We found that the CO₂ removal potential of ocean afforestation is substantially modified by biogeochemical and physical processes associated with seaweed growth and ecology in the open ocean. Most noticeably, seaweeds provide habitat for calcifying organisms, which form CO₂ through changes to seawater carbonate chemistry occurring during the calcification process. Furthermore, seaweed carbon fixation is fuelled by limiting nutrients, which once taken up by seaweeds are not available any longer to support CO₂ removal by the natural inhabitants of the open ocean – phytoplankton.

After accounting for offsets to carbon fixation we also considered that seaweeds fix CO₂ dissolved in seawater, not atmospheric CO₂. The atmospheric CO₂ has to be subsequently absorbed by the oceans in a second step, which takes much longer (weeks to years) and is more difficult to quantify than one may think.

We also investigated how ocean afforestation influences the albedo (i.e., reflectance) of the Earth. The sign and magnitude of afforestation-related albedo changes on radiative forcing depend on multiple indirect effects linked to the release of substances that influence cloud formation. We didn’t dare to go down this rabbit hole. However, we were surprised to see that even just the brightening of the sea surface through seaweed growth (and thus the direct reflection of light) may have a stronger influence on radiative forcing than the CO₂ removal associated with ocean afforestation.

How did we interpret all this? Most importantly, our study does not suggest that CO₂ removal with seaweed farming is impossible. However, it shows that successful CO₂removal and its verification requires much more than simply generating seaweed biomass. The complexity of this method could be its Achilles heel and hence become its knock-out criterion, because a large number of interacting processes must be quantified to determine the sign and magnitude of the net climatic impact of ocean afforestation.

Figure from Bach et al https://doi.org/10.1038/s41467-021-22837-2

Authors:
Lennart Bach, Catriona Hurd, Philip Boyd (Institute for Marine and Antarctic Studies, University of Tasmania)
Veronica Tamsitt (University of New South Wales and CSIRO Hobart)
Jim Gower (Fisheries and Oceans Canada)
John Raven (University of Dundee at the James Hutton Institute and University of Technology, Sydney and University of Western Australia)

Learn more in the recorded talks and information on the OCB2021 Plenary Session: Ocean-based negative emissions technologies

Just released: Ocean Sciences Across the Solar System

Posted by mmaheigan

· Tuesday, June 15th, 2021

Now available: Ocean Sciences Across the Solar System NASA report

SUMMARY
The discovery that there are major oceans beyond Earth is exciting for Earth oceanographers and planetary scientists alike. As life on Earth began in the ocean, these other worlds offer tantalizing possibilities of finding life beyond our own planet. They also offer the possibility of learning about conditions, including physical and chemical processes, that may be different from Earth, and that affect the ocean’s surfaces and interiors and regulate how those systems function. The innate connection that exists between Earth’s ocean and ocean worlds beyond Earth offers many possibilities, and demands the action, of strong research collaborations between Earth ocean scientists and extraterrestrial ocean scientists. This white paper summarizes six areas of priority where the study of Oceans Across the Solar System would benefit from a close collaboration between Earth and extraterrestrial oceanographers.

Ocean world research requires the study and understanding of Earth’s ocean. The different sections herein outline some of the priority areas for ocean research across the solar system, identify existing gaps, and provide ideas for developing testable ideas based on the Earth System. It is important to acknowledge that there are no perfect analogs; however, the different sections highlight the strengths and weaknesses of using analogs for different types of research, such as improved understanding of ocean world processes, habitability, and where to search for life beyond Earth. For example, by identifying analogs for specific processes, rather than specific conditions, it may be possible to develop a mechanistic understanding that enables an extrapolation beyond Earthly points of reference. Observation and hypothesis testing in Terrestrial environments that most closely approximate the physical and chemical conditions thought to exist in ice covered oceans can refine our understanding of those in ice-covered oceans and within the ice, though the numerous differences between Earth and other ocean worlds will significantly impact the nature, abundance, and quality of evidence for any life that may exist, relative to what we observe on Earth. On Earth, life and biogenic materials are heterogeneously distributed according to the availability of resources, strength of stressors, and various physical transport processes; understanding the balance of factors that underlie such heterogeneity, and projecting that understanding into the context of environments beyond Earth, can maximize the potential of detecting biosignatures.

As the search for life in ocean worlds continues, technologies to detect such signatures will be critical, as will our understanding of the potential distribution of life in icy worlds. Large-scale synoptic views of ocean worlds can be afforded by active and passive remote sensing methods. Imaging spectrometers, spanning ultraviolet to infrared wavelengths, can assess the composition of inorganic and organic matter in the water or within snow and ice on the surface of an icy body. Active remote sensing technologies, such as radar and lidar, can measure backscattered light off of ocean particles, subsurface observation of ice, and provide information on the surface of worlds that have thick or obscuring atmospheres. In situ technologies for ocean worlds span systems and instruments that operate above, on, under, or within ice, slush, and fluids. These include technologies to determine biological, chemical, and physical properties, including biosignature detection methods.

There is much to be gained between a close collaboration between Earth and extraterrestrial ocean scientists for the study of Oceans Across the Solar System. The knowledge, tools, and different perspectives of the same discipline, applied across our solar system, provide complementary knowledge that will serve to advance the understanding of ocean world workings; this is critical for understanding Earth’s oceans past and it’s possible future under climate change scenarios, and how life began on our planet. This will in turn further the search for life elsewhere and help us understand habitability beyond our Blue Marble.

Lastly, with the advent of space exploration, the protection of Earth’s environment and other solar system bodies from harmful contamination have become an important principle of high priority. Consequently, the exploration of ocean worlds thought to be capable of harboring life (extinct or extant), or processes relevant to prebiotic chemistry, are of relevance to planetary protection initiatives. Both Earth and Planetary science communities, working together, can significantly contribute to the development of policies, procedures, and techniques to meet planetary protection
requirements.

Fig.1 Ocean Worlds of the Solar System shown to scale. Jupiter’s moons Europa, Callisto and Ganymede have all been confirmed to host large-volume salt-water oceans as have Saturn’s moons Enceladus and Titan: all beneath thick ice-shells. Further out in the solar system, other candidate ocean worlds await further investigation, including Neptune’s moon Triton. Image credit: K.P.Hand, NASA-JPL.

Read the full report

June is OCB2021

Posted by mmaheigan

· Friday, May 28th, 2021

June 2021 is the month of OCB - registration is open!

We are excited to present an interactive series of events with early career activities, interactive panel discussions, virtual poster sessions, and opportunities for networking and socializing throughout the month of June. The OCB SSC has been busy for several months planning plenary sessions for this year's workshop.

This year plenary talks will be pre-recorded and available for viewing at your convenience 1-2 weeks prior to a live panel discussion that will be conducted in small group format.

Find full agendas, plenary sessions, online meeting platform and more information on the workshop website.

We will record live sessions and make them available on our website and YouTube Channel.

While we miss seeing everyone in person, we have been excited about the broader participation in virtual OCB meetings and webinars over the past year. See you soon at OCB2021!

OCB2021 PLENARY TOPICS:

Bridging the divide between ocean biology and geochemistry (Chairs: Dreux Chappell, Adam Martiny, Patrick Rafter)
Optical biogeochemistry: Above and below the waterline (Chairs: Amy Maas, Seth Bushinsky, Maria Tzortziou)
Ocean-based negative emissions technologies (Chairs: Lennart Bach, Jaime Palter, Clare Reimers, Patrick Rafter)
Ocean Worlds (Chairs: Laura Lorenzoni, Paula Bontempi, Adam Martiny)
Opportunities and challenges in ecological forecasting (Chairs: Victoria Coles, Marjorie Friedrichs, Charlie Stock, Susanne Menden-Deuer, Raleigh Hood)

OCB will kick off with a virtual early career mixer on June 4. Virtual partial day OCB sessions are tentatively planned for June 7, 11, 15, 18, 22, and 24. In addition to plenary sessions, OCB 2021 will include targeted community discussions on OCB-relevant topics, OCB activity updates, early career and agency program manager networking events, virtual poster sessions, and more!

Stay tuned via our eNewsletter, workshop website, and Twitter (@US_OCB)! Follow and tweet using #OCB2021

New to the OCB Summer Workshop? You can view recordings from previous workshops on the OCB YouTube channel.

Regional scale production shifts drive global ocean production stoichiometry

Posted by mmaheigan

· Thursday, May 20th, 2021

The C:N:P stoichiometry of global ocean biological production is the gear by which marine biology turns the wheels of the global ocean carbon cycle. From the days of Alfred Redfield until fairly recently, this stoichiometry was assumed a constant in ocean biogeochemistry (e.g., the Redfield ratio). Traditional stoichiometry would predict a carbon export production decline in the future, as warming is generally expected to enhance water column stratification and diminish the vertical supply of nutrients. However, recent observations clearly show that the C:N:P ratio is quite variable: the ratio is higher in oligotrophic waters than in eutrophic waters, and the ratio is higher in cyanobacteria than eukaryotes. How can flexible C:N:P ratio in phytoplankton affect future carbon export?

A recent publication in Environmental Research Letters discusses three drivers of global ocean production stoichiometry in the future: physiological response of phytoplankton, changes in phytoplankton community composition, and shifts in the regional production, which the authors focused most on as it is the least explored. The authors carried out global warming experiments using a numerical model of global ocean biogeochemistry that represents flexible C:N:P ratios in multiple phytoplankton types with dependence on ambient N and P concentrations, temperature, and light. These model results indicate the importance of the physiological response of cyanobacteria to warming and of eukaryotes to P depletion in driving a higher C:N:P ratio (Figure 1).

Figure caption: Diagnosed effect of regional production changes on the future global mean C:P ratio. The diagnosis (c) is given by the product of the sign of the effect (a) and the production changes (b). The sign of the effect of the regional production changes is positive (+1) for locations with local C:P > global mean (red) and negative (−1) for locations with C:P < global mean (blue). The diagnosis shows a N-S dipole response in both the Southern Ocean and the North Atlantic, where changes in production both increase and decrease the global C:N:P ratio.

Global production C:N:P ratio can vary by shifting the regional production, even in the absence of any change in phytoplankton stoichiometry or taxonomy. For example, simply increasing the production in polar waters—which typically have low C:N:P ratios (eukaryote-dominant, P-rich, and cold)—will lower the global C:N:P ratio, because the polar production then makes a relatively larger contribution to the global production. In this model, future Antarctic sea ice retreat has this very effect, but is offset by production changes downstream and elsewhere. Current literature indicates substantial uncertainty in the future projection of regional production changes. This study illuminates regional production as a new driver of global export C:N:P ratio and an important area of future investigation.

Authors:
Katsumi Matsumoto (University of Minnesota)
Tatsuro Tanioka (University of Minnesota, now University of California, Irvine)

Open Meeting: May 26 OCB WG Filling the gaps in observation-based estimates of air–sea carbon fluxes

Posted by mmaheigan

· Monday, May 10th, 2021

The OCB “Filling the gaps in observation-based estimates of air–sea carbon fluxes” working group will be holding a two day online meeting May 26 and 27. May 26 will have a range of presentations and is open to all interested attendees.
Register here.

Wednesday, May 26, 11:00-16:00 EDT
Who: Working group members and open webinar for interested attendees

11:00-11:15	Welcome and Overview of Year 1 activities on Objective 1
Objective 1: Determine how to integrate open-ocean CO₂ air–sea flux with fluxes from the coastal ocean, the Arctic Ocean, and natural outgassing.
11:15 – 12:30	Progress on Objective 1 (10 min talks, 30 min discuss on issues) ● Climatology to the the coast (Landschützer) ● Harmonization of pCO2 product flux calculations (Fay) ● Coastal (Lacroix and Regnier) ● Synthesis of Fant, Fnat (McKinley) ● Discussion and outstanding issues
12:30-12:45 – break
12:45 – 13:05	Models (10 minute talks) ● Carbon and Heat uptake (Bronsealer) ● Data Assimilation for ocean carbon (Mazloff)
13:05 – 13:45	Observations (10 min talks) ● USV air-sea pCO2 technology update (Sutton) ● BGC-Argo surface carbon analysis update (Williams / Bushinsky) ● Sampling studies semi idealized OSSEs (Laique Djeutchouang / Monteiro) ● Benguela-SOCHIC CO₂ and heat flux experiment (Monteiro/Ward)
13:45-14:00 break
14:00 -14:30	Progress on Data Products (10 min talks) ● Extrapolation to the past (Rödenbeck) ● Using hindcast models as a first guess (Gloege) ● DIC products (Gregor)
14:30-14:50	Update on Synthesis Activities (10 min talks) ● GCB (Hauck) ● RECCAP2 (DeVries)
14:30 – 16:00	Discussion

Who’s eating whom in the planktonic food web of the Northeast Shelf?

Posted by mmaheigan

· Wednesday, May 5th, 2021

It is critical to quantify the amount of phytoplankton that microzooplankton consume to better understand the flow of carbon toward higher trophic levels in the ocean. The Northeast US Shelf (NES) sustains intense fisheries with huge economical importance, but the links between the planktonic food web and the fish stocks are poorly constrained.

A recent study, which is part of the NES-LTER site (NES Long-Term Ecological Research, est. 2017), quantified phytoplankton growth rates and microzooplankton grazing rates across the NES during one summer and two winter cruises. The strong seasonal differences of physical and biogeochemical properties, associated with their intense spatial heterogeneity along the shelf, provided a unique opportunity to investigate the planktonic food web dynamics across contrasting environmental conditions.

Seasonal (winter vs. summer) and spatial (coastal vs. offshore) variability of the phytoplankton community structure, phytoplankton growth rates and microzooplankton grazing rates in the Northeast US Shelf.

During both winter and summer, coastal waters, which originate in the Arctic, were colder and fresher, and hosted greater phytoplankton biomass compared to the offshore warm slope-sea waters of the Gulf Stream (Figure 1). In winter the phytoplankton community was dominated by large cells (>10 µm), and most of the primary production was directly consumed by microzooplankton, allowing direct and efficient transfer of carbon to higher trophic levels (Figure 1). In contrast, small phytoplankton cells dominated in summer, when fast growing phytoplankton were not preyed upon by microzooplankton grazers, limiting their role conducting organic matter, yet the lack of phytoplankton accumulation during summer suggests some unidentified loss processes and more complex trophic interactions (e.g., trophic cascades, mixotrophy).

The ongoing NES-LTER project is an outstanding opportunity to investigate the flow of carbon amongst the planktonic food web for a predictive understanding of ecosystem productivity in a changing coastal ocean.

Authors:
Pierre Marrec, Heather McNair, Gayantonia Franzè (present address: Institute of Marine Research, Norway), Françoise Morison, Jacob P. Strock and Susanne Menden-Deuer
(All authors: Graduate School of Oceanography, University of Rhode Island)

Integrated Ocean Carbon Research New Report

Posted by mmaheigan

· Monday, May 3rd, 2021

Integrated Ocean Carbon Research: A Summary of Ocean Carbon Knowledge and a Vision for Coordinated Ocean Carbon Research (IOC-R) and Observations for the Next Decade

The UN Educational, Scientific and Cultural Organization (UNESCO)’s Intergovernmental Oceanographic Commission (IOC) has just published the “Integrated Ocean Carbon Research: A Summary of Ocean Carbon Knowledge and a Vision for Coordinated Ocean Carbon Research and Observations for the Next Decade”, a report which sets out to accomplish the vital task of indicating the current gaps and future directions for the integrated ocean carbon cycle research. The report presents a synthesis of the state of knowledge about the oceans’ role in the carbon cycle and points to the way ahead. Its objective is to provide decision-makers with the knowledge needed to develop climate change mitigation and adaptation policies for the coming decade. It also emphasizes the importance of scientific knowledge to the taking of informed decisions within the United Nations Framework Convention on Climate Change (UNFCCC) in order to achieve the goals of the Paris Agreement and build more resilient societies.

In developing the report, the IOC brought together experts from the five international research and coordination programmes on ocean-climate interaction (the International Ocean Carbon Coordination Project (IOCCP), the Integrated Marine Biosphere Research Project (IMBeR), the Surface Ocean – Lower Atmosphere Study (SOLAS), the Climate and Ocean Variability, Predictability and Change (CLIVAR) project and the Global Carbon Project), which have been working together since 2018 in the IOC Working Group on Integrated Ocean Carbon Research (IOC-R). Together they propose an innovative joint program of medium- and long-term integrated ocean carbon research to fill the gaps in this field. The report was developed as part of the ongoing UN Decade of Ocean Sciences for Sustainable Development (2021-2030). The official press release of IOC-UNESCO is found here.

Full citation:

Aricò, S., Arrieta, J. M., Bakker, D. C. E., Boyd, P. W., Cotrim da Cunha, L., Chai, F., Dai, M., Gruber, N., Isensee, K., Ishii, M., Jiao, N., Lauvset, S. K., McKinley, G. A., Monteiro, P., Robinson, C., Sabine, C., Sanders, R., Schoo, K. L., Schuster, U., Shutler, J. D., Thomas, H., Wanninkhof, R., Watson, A. J., Bopp, L., Boss, E., Bracco, A., Cai, W., Fay, A., Feely, R. A., Gregor, L., Hauck, J., Heinze, C., Henson, S., Hwang, J., Post, J., Suntharalingam, P., Telszewski, M., Tilbrook, B., Valsala, V. and Rojas Aldana, A. 2021. Integrated Ocean Carbon Research: A Summary of Ocean Carbon Research, and Vision of Coordinated Ocean Carbon Research and Observations for the Next Decade. R. Wanninkhof, C. Sabine and S. Aricò (eds.). Paris, UNESCO. 46 pp. (IOC Technical Series, 158.) doi:10.25607/h0gj-pq41

Register now: GO-BCG workshop

Posted by mmaheigan

· Friday, April 30th, 2021

Virtual Workshop on the New Global Ocean Biogeochemistry (GO-BGC) Array - Building a Community of Biogeochemical Float Data Users

The Global Ocean Biogeochemistry (GO-BGC) array is a 5-year effort funded by the US National Science Foundation to produce and deploy 500 profiling floats equipped with biogeochemical sensors in the world ocean. Deployments will begin in the first quarter of 2021. To inform and engage a broad oceanographic user community, the Ocean Carbon & Biogeochemistry (OCB) and the US Climate Variability and Predictability (CLIVAR) Programs are working with GO-BGC leadership to plan a virtual GO-BGC Scientific Workshop from June 28-30, 2021.

The objectives of the workshop are to:

Introduce the GO-BGC plan to the global scientific community
Discuss and innovate on scientific applications of GO-BGC data
Provide background information on the flow of data and archiving
Deliver hands-on tutorials and computer code for accessing GO-BGC data

Presentations and discussions will be scheduled for 3-4 hours on each day. Some presentations will be prerecorded and available online prior to each day’s events for viewing, so that participants can consider discussion items before the meeting. The organizers look forward to a large online participation in the meeting as this new, multi-year program gets underway.

Learn more on the Workshop Website

Apply to join the inaugural cohort of NMDC Ambassadors!

Posted by mmaheigan

· Thursday, April 29th, 2021

The NMDC is launching the NMDC Ambassador program to provide training and support for early career researchers who are motivated to engage with their respective research communities to lower barriers to adoption of metadata standards.

APPLY NOW

Application deadline: May 21, 2021, 11:59PM PT

Eligibility

✔Affiliated with a US institution
Including US-affiliated researchers who are currently working or studying abroad

✔Early career researcher
Graduate student or Researcher within 10 years after receiving a Ph.D.

✔Works with microbiome data from sample environment(s) represented by the Genome Standards Consortium (GSC) Minimum Information about any (x)
Sequence (MIxS) standard

✔Works with at least one NMDC-relevant data type
Amplicon, metagenomics, metatranscriptomics, metaproteomics, or metabolomics

✔Affiliated with a US Institution
Including US-affiliated researchers who are currently working or studying abroad

What will Ambassadors do?

During the course of the 1-year commitment, each Ambassador is expected, at minimum, to:

Ambassador activity	Details
Contribute to metadata training materials	Update the NMDC template training materials to reflect one sample environment relevant to their community
Engage with their research community	With support from the NMDC, host one 4-hour workshop to gather feedback to improve sample metadata standards training
Spread the NMDC mission	Partner with the NMDC to present at one conference session, webinar, panel, or other event of their choice
Share their perspectives	Share updates on two NMDC-relevant activities on a NMDC online platform (social media, website, newsletter)
Learn about metadata standards	Attend all NMDC training sessions (see more details under Program Timeline below)

The estimated time commitment for each Ambassador is, on average, 2-3 hours per month (includes trainings, cohort events, and preparing for and hosting two Ambassador events). Ambassadors should budget time for planning and preparation (specifically, for the metadata standards workshop) during months with fewer activities. The total time commitment for each Ambassador will vary based on factors, such as the target number of attendees or format of the events (virtual or in-person), which is at the discretion of the Ambassador.

Taxonomic and nutrient controls on phytoplankton iron quotas in the ocean

Posted by mmaheigan

· Thursday, April 22nd, 2021

The uptake of iron by phytoplankton is a key part of the marine iron cycle, but we still have a rudimentary understanding of the controls on this process. It is generally assumed that dissolved iron availability controls phytoplankton iron. Combining data from the GP16 GEOTRACES section and three other GEOTRACES-compliant cruises in the eastern Pacific, Twining et al. (2020) show that phytoplankton iron contents (aka, quotas) vary 40-fold across environmental gradients. Further, taxa prone to nitrogen limitation such as diatoms accumulate iron more than expected, even under extremely low iron conditions. Modeling indicates that this is a widespread occurrence in the low-Fe oligotrophic Pacific. This study provides the first direct measurements of luxury iron uptake in natural communities and shows how it can vary between diatom taxa, with Pseudo-nitzschia able to accumulate luxury iron even in the low-Fe sub-Arctic North Pacific. These findings demonstrate the importance of biology and ecology to understanding iron biogeochemistry.

Figure 1. Response of iron quotas to nutrient gradients in the South Pacific Ocean. a) location of stations on GP16 cruise, plotted over bathymetry. b) phytoplankton abundance (total Chl a), nitrate, dFe, and relative diatom abundance (% fucoxanthin, a pigment proxy for diatoms) across the onshore-offshore gradient. Data are means of upper 50m at each station. Dashed blue lines delineate putative coastal, HNLC, and oligotrophic regions. c) Taxon-specific Fe quotas (geometric means +/- SE) as a function of location. Dashed red line indicates the optimal Fe/C estimated for open-ocean phytoplankton under low dFe. d) Taxon-specific Fe quotas as a function of dFe. Also plotted is predicted FeC_opt. e). Response of taxon-specific Fe quotas to gradients in ambient nitrate and dFe. Symbol color indicates Fe/C (μmol/mol). Arrows indicate direction of cruise track, moving from shelf westward into the gyre.

Authors:
B.S. Twining (Bigelow Laboratory for Ocean Sciences)
O. Antipova (Argonne National Laboratory)
P. D. Chappell (Old Dominion University)
N. R. Cohen (Skidaway Institute of Oceanography)
J. Jacquot
E. L. Mann (University of Maine at Machias)
A. Marchetti (University of North Carolina)
D. C. Ohnemus (Skidaway Institute of Oceanography)
S. Rauschenberg (Bigelow Laboratory for Ocean Sciences)
A. Tagliabue (University of Liverpool)

Joint science feature with GEOTRACES

Funding for the Ocean Carbon & Biogeochemistry Project Office is provided by the National Science Foundation (NSF) and the National Aeronautics and Space Administration (NASA). The OCB Project Office is housed at the Woods Hole Oceanographic Institution.

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