New OCB Research :: Ocean Carbon & Biogeochemistry

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Archive for New OCB Research – Page 8

How do coccolithophores survive the darkness?

Posted by mmaheigan

· Friday, April 1st, 2022

Coccolithophores have survived several major extinction events over geologic time. The most significant was the asteroid impact at the K/T boundary, followed by months of darkness. Additionally, coccolithophores regularly reside in the twilight zone, just beyond the reach of sunlight. A paper recently published in the New Phytologist addresses how these photosynthetic algae can persist and grow, albeit slowly, in darkness using osmotrophy.

The authors discovered that the osmotrophic uptake of certain types of dissolved organic carbon (DOC) can support survival in low light. They completed a 30-day darkness experiment to determine how the concentration of several DOC compounds affects growth. The coccolithophore species Cruciplacolithus neohelis growth rate increased with the increasing concentration of dissolved organic compounds. They also examined the kinetics of short-term uptake of radiolabeled DOC compounds and found that the uptake rate generally showed Michaelis-Menten-like saturation kinetics. All radiolabeled DOC compounds were incorporated into the POC fraction, but surprisingly also into the particulate inorganic carbon (PIC) fraction (i.e., calcite coccoliths).

These results suggest that osmotrophic uptake in coccolithophores may be significant enough to be included in carbon cycle models, especially if they can simultaneously take up a wide range of organic compounds. Surprisingly, we detected ¹⁴C-DOC in the PIC fraction after only 24 hours. This remarkably rapid incorporation is most likely due to the respiration of radiolabeled DOC into dissolved inorganic carbon (DIC), subsequently used by coccolithophores for calcification. These results have implications for the biological carbon pump and alkalinity pump paradigms, as we confirmed that both POC and PIC originate from DOC on short time scales.

Predators Set Range for the Ocean’s Most Abundant Phytoplankton

Posted by mmaheigan

· Friday, April 1st, 2022

Prochlorococcus is the world’s smallest phytoplankton (microscopic plant-like organisms) and the most numerous, with more than ten septillion individuals. This tiny plankton lives ubiquitously in warm, blue, tropical waters but is conspicuously absent in more polar regions. The prevailing theory was the cold: Prochlorococcus doesn’t grow at low temperatures. In a recent paper, the authors argue ecological control, in particular, predation by zooplankton. Cold polar waters are greener because they contain more nutrients, leading to more life and more organic matter production. This production feeds more and larger heterotrophic bacteria, who then feed larger predators—specifically the same zooplankton that consume Prochlorococcus. If the shared zooplankton increases enough, it will consume Prochlorococus faster than it can grow, causing the species to collapse at higher latitudes. These results show that an understanding of both ecology and temperature is required to predict how these ecosystems will shift in a warming ocean.

Figure 1: Surface populations of Prochlorococcus collapse (dashed lines) moving northward from Hawaii as seen in transects (transect line shown in red on map, lower left) from cruises in April 2016 (black dots) and September 2017 (green triangles). This collapse of the Prochlorococcus emerges in dynamical computer models (lower right, color indicates Prochlorococcus biomass in mgC/m3) when heterotrophic bacteria and Prochlorococcus share a grazer (top schematic). Increased organic production heading poleward first increases the heterotrophic bacterial population, increasing the shared zooplankton population which eventually consumes Prochlorococcus faster than it can grow (dashed contour).

Authors
Christopher L. Follett (MIT)
Stephanie Dutkiewicz (MIT)
François Ribalet (UW)
Emily Zakem (USC)
David Caron (USC)
E. Virginia Armbrust (UW)
Michael J. Follows (MIT)

Decline in spring chlorophyll-a concentrations in response to COVID-19 lockdown in the Yellow Sea

Posted by mmaheigan

· Friday, February 18th, 2022

Recently, it was reported that the coronavirus (COVID-19) pandemic-related lockdowns have led to a reduction in anthropogenic emissions of pollutant nitrogen on a global scale. This reduction may have induced a change in marine environmental conditions, providing a natural experiment for determining its impact on marine ecosystems. However, a direct cause-effect relationship between COVID-19 and the phytoplankton biomass has not yet been fully explored.

A recent study published in Marine Pollution Bulletin, investigated a change in satellite-derived chlorophyll-a concentrations (Chl-a) as a result of the COVID-19 lockdown. The high productivity of the Yellow Sea ecosystem is considered to be significantly attributable to high nutrient supply via atmospheric deposition from nearby anthropogenic sources of air pollution, making it an ideal location to observe this natural experiment. Further, they evaluated a significant contributing factor to change in irradiance, vertical mixing, coastal influence, and air pollutant deposition through a comparative analysis of in situ, reanalysis, and satellite-derived datasets during February‒May 2020 (representing the period of COVID-19 lockdown effect) as compared to the same period in the previous five-years (2015–2019; representing the period of no COVID-19 lockdown).

Figure 1. (a) The spatial distribution of the difference in the monthly mean Chl-a concentrations over the Yellow Sea between 2020 and 2015–2019 (ΔChl-a_{2020 ‒ mean} (2015–2019)) in February, March, April, and May. (b) The monthly mean Chl-a averaged for the Yellow Sea (32.625–41.625 °N, 117.375–127.375 °E) during February to May 2015–2019 (pink marker) and 2020 (cyan marker). The vertical solid lines represent their standard deviation for the 2015–2019.

The authors captured a significant decline in Chl-a (~30%) over the Yellow Sea during February‒May 2020 compared to February‒May 2015‒2019 (Figure 1). Variations of irradiance, vertical mixing, and river discharges, were not major factors affecting this decline. Based on the analysis of transportation and constituent of atmospheric pollutants from Northern China (i.e., representing main source region of atmospheric pollutants) to Yellow Sea, the decline in Chl-a over the Yellow Sea during spring 2020 was mainly attributed to decreased atmospheric nutrient deposition due to the COVID-19 lockdown effect, a consequence of decreased anthropogenic emissions in the Northern China. Thus, further investigation is required to assess the Yellow Sea ecosystem response to re-increasing anthropogenic activities once the COVID-19 lockdown restrictions are lifted.

Authors:
Joo-Eun Yoon (Centre for Climate Repair at Cambridge, Cambridge University)
Seunghyun Son (CIRA, Colorado State University)
Il-Nam Kim (Department of Marine Science, Incheon National University)

New Data Standard for Oceanographic Research

Posted by mmaheigan

· Friday, February 18th, 2022

Effective data management is paramount in oceanographic research. The ocean is a global system, and research to understand regional and global oceanographic processes often involves compiling cruise-based data from different laboratories and expeditions.

The new international data standard covers column header abbreviations, quality control flags, missing value indicators, and standardized calculation of numerous parameters. Released alongside this paper are newly developed tools to calculate some oceanographic properties, and recommendations for dissociation constants of the seawater carbon system calculations. In addition, the use of “content” instead of “concentration” is recommended for mass-based properties.

The column header abbreviation standards presented here are based on the 30-year-old Exchange format of the World Ocean Circulation Experiment (WOCE) Hydrographic Program (Joyce and Corry, 1994; Swift and Diggs, 2008) with updates and refinements by the Climate and Ocean-Variability, Predictability, and Change (CLIVAR) and the Carbon Hydrographic Data Office (CCHDO) of the Scripps Institution of Oceanography. This format has been used as a data file standard for discrete chemical oceanographic observations for several decades.

The new international data standards will facilitate data sharing, quality control, and synthesis efforts to promote climate change and ocean acidification research at regional to global scales. This product is a significant step forward in terms of (a) creating common data standards for the international oceanographic research community to streamline data management, quality control, and data product developments; and (b) bringing the subject matter expertise from the research community to the data management world.

Authors (partial, see full list on publication)
Li-Qing Jiang (Univ Maryland, NOAA/NCEI)
Denis Pierrot (NOAA/AOML)
Rik Wanninkhof (NOAA/AOML)
Richard A. Feely (NOAA/PMEL)
Bronte Tilbrook (CSIRO Oceans and Atmosphere and Australian Antarctic Program Partnership)
Simone Alin (NOAA/AOML)
Leticia Barbero (Univ Miami; NOAA/AOML),
Robert H. Byrne (Univ South Florida),
Brendan R. Carter (Univ Washington, NOAA/PMEL)
Andrew G. Dickson (Scripps Institution of Oceanography)
Jean-Pierre Gattuso (CNRS, Laboratoire d’Océanographie de Villefranche, Sorbonne Univ; Institute for Sustainable Development and International Relations, Sciences Po, France)
Dana Greeley (NOAA/PMEL)
Mario Hoppema (Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Sciences Po,)
Matthew P. Humphreys (NIOZ Royal Netherlands Institute for Sea Research, Netherlands)
Johannes Karstensen (GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany)
et al.

Seagrass is not a silver bullet for climate change

Posted by mmaheigan

· Friday, January 21st, 2022

Coastal management actions aimed at protecting or restoring seagrass meadows are often assumed to have the collateral benefit of removing large amounts of carbon dioxide from the atmosphere to combat climate change. Be aware, however: not all seagrass meadows are alike. Under certain conditions, some release more carbon dioxide than they absorb and are net carbon sources to the atmosphere. This is now shown in a new study by an international team of researchers, published in the scientific journal Science Advances. This study combined direct eddy covariance measurements of air-water gas exchange with geochemical approaches to build a comprehensive carbon budget for a tropical seagrass meadow in south Florida. The process of ecosystem calcification released far more CO₂ to the atmosphere than was buried in sediments as “Blue Carbon.” This study questions the reliability of Blue Carbon approaches towards net CO₂ sequestration in tropical waters. But still unclear is how applicable these results are to the global scale, and what fraction of tropical seagrass meadows are net sources, rather than sinks, of CO₂ to the atmosphere.

Figure 1 : Diel trend in CO2 flux presented as discrete 30-min measurements during the study period (black circles) and annual mean fluxes for the year surrounding the study period, binned in 2-hour intervals [colored circles (x ± SD)].

Authors
Bryce R. Van Dam (Helmholtz-Zentrum Hereon)
Mary A. Zeller (Leibniz Institute for Baltic Sea Research)
Christian Lopes (Florida International University)
Ashley R. Smyth (University of Florida)
Michael E. Böttcher (Leibniz Institute for Baltic Sea Research)
Christopher L. Osburn (North Carolina State University)
Tristan Zimmerman (Helmholtz-Zentrum Hereon)
Daniel Pröfrock (Helmholtz-Zentrum Hereon)
James W. Fourqurean (Florida International University)
Helmuth Thomas (Helmholtz-Zentrum Hereon)

Aircraft reveal a surprisingly strong Southern Ocean carbon sink

Posted by mmaheigan

· Friday, December 17th, 2021

The Southern Ocean is indeed a significant carbon sink—absorbing a large amount of the excess carbon dioxide emitted into the atmosphere by human activities—according to a newly published study led by the National Center for Atmospheric Research (NCAR).

The findings provide clarity about the role the icy waters surrounding Antarctica play in buffering the impact of increasing greenhouse gas emissions, after research published in recent years suggested the Southern Ocean might be less of a sink than previously thought. The authors makes use of observations from research aircraft flown during three field projects over nearly a decade, as well as a collection of atmospheric models, to determine that the Southern Ocean takes up significantly more carbon than it releases.

You can’t fool the atmosphere. While measurements taken from the ocean surface and from land are important, they are too sparse to provide a reliable picture of air-sea carbon flux. The atmosphere, however, can integrate fluxes over large expanses. Airborne measurements reveal critical patterns in the global carbon cycle, a drawdown of CO₂ in the lower atmosphere over the Southern Ocean surface in summer, indicating carbon uptake by the ocean.

Figure 1: Observed patterns in atmospheric CO2 over the Southern Ocean during the ORCAS airborne campaign (Jan-Feb 2016). Colors show the observed CO2 dry air mole fraction relative to the average observed within the 295–305 K potential temperature range south of 45°S on each campaign; contour lines show the observed potential temperature.

Authors:
M. C. Long (National Center for Atmospheric Research)
B. B. Stephens (National Center for Atmospheric Research)
K. McKain (University of Colorado, Boulder/NOAA)
C. Sweeney (NOAA)
R. F. Keeling (Scripps Institution of Oceanography)
E. A. Kort (University of Michigan)
E. J. Morgan (Scripps Institution of Oceanography)
J. D. Bent (National Center for Atmospheric Research)
N. Chandra (JAMSTEC)
F. Chevallier (Laboratoire des Sciences du Climat et de l’Environnement)
R. Commane (Columbia University)
B. C. Daube (Harvard University)
P. B. Krummel (CSIRO)
Z. Loh (CSIRO)
I. T. Luijkx (Wageningen University)
D. Munro (University of Colorado, Boulder/NOAA)
P. Patra (JAMSTEC)
W. Peters (Wageningen University)
M. Ramonet (Laboratoire des Sciences du Climat et de l’Environnement)
C. Rödenbeck (Max Planck Institute for Biogeochemistry)
A. Stavert (CSIRO)
P. Tans (NOAA)
S. C. Wofsy (Harvard University)

Eddies oxygenate the upper equatorial Pacific

Posted by mmaheigan

· Friday, December 17th, 2021

As the ocean warms, the future of the tropical Pacific Oxygen Minimum Zones (OMZs) remains highly uncertain, in part due to incomplete understanding of processes and poor model representation of how mesoscale circulation impacts ocean biogeochemistry. To help address these gaps, a recent paper explored how mesoscale eddies modulate dissolved oxygen distributions and variability, with a particular focus on the upper northern equatorial Pacific where eddy kinetic energy is intensified.

Figure 1: Sea Surface Temperature (SST) and oxygen concentrations at 155 m depth in an eddy resolving simulation of CESM. Tropical Instability Vortices (TIVs) are outlined by cusp-like features in SST and oxygenated cores at depth.

The authors used an eddy resolving model simulation of the Community Earth System Model (CESM) and Lagrangian particle analysis to simulate the impacts of mesoscale eddies on oxygen distribution and variability in the upper equatorial Pacific Tropical Instability Vortices (TIVs)—large eddies associated with Tropical Instability Waves—lead to a substantial oxygenation of the upper equatorial Pacific. TIVs are generated from boreal summer through winter, and contribute to the seasonal oxygenation of the northern equatorial Pacific, exhibited as a seasonal shoaling and deepening of the northern eastern tropical Pacific OMZ. The processes governing the simulated TIV oxygenation of the upper equatorial Pacific are dominated by physical eddy advection and mixing, while biogeochemical feedbacks (e.g. enhanced microbial consumption of oxygen in the eddy cores) play a minor role. These simulated TIV oxygenation effects stand in contrast to the deoxygenation effects of Anticyclonic Mode Water Eddies recently observed and simulated along Eastern Boundary Upwelling Systems, suggesting a diverse and complex influence of mesoscale circulation on ocean biogeochemistry.

TIV influence on oxygen is highly relevant to predicting the variability and future of ecosystem habitable space, informing the source of model biases in this region, and guiding the current revamping of the Tropical Pacific Observing System, and should be explored in future observational campaigns.

Authors:
Yassir Eddebbar (Scripps UCSD)
Aneesh Subramanian (Colorado University, Boulder)
Daniel Whitt (NASA Ames Research Center)
Matthew Long (National Center for Atmospheric Research)
Ariane Verdy  (Scripps UCSD)
Matthew Mazloff  (Scripps UCSD)
Mark Merrifield  (Scripps UCSD)

Ocean Acidification drives shifts in global stoichiometry and carbon export efficiency

Posted by mmaheigan

· Friday, November 19th, 2021

Marine food webs and biogeochemical cycles react sensitively to increases in carbon dioxide (CO₂) and associated ocean acidification, but the effects are far more complex than previously thought. A comprehensive study published in Nature Climate Change by a team of researchers from GEOMAR dove deep into the impacts of ocean acidification on marine biota and biogeochemical cycling. The authors combined data from five large-scale field experiments with natural plankton communities to investigate how carbon cycling and export respond to ocean acidification.

The biological pump is a key mechanism in transferring carbon to the deep ocean and contributes significantly to the oceans’ function as a carbon sink. The carbon-to-nitrogen ratio of sinking biogenic particles, here termed (C:N_export), determines the amount of carbon that is transported from the euphotic zone to the ocean interior per unit nutrient, thereby controlling the efficiency of the biological pump. The authors demonstrate for the first time that ocean acidification can change the elemental composition of organic matter export, thereby potentially altering the biological pump and carbon sequestration in a future ocean (Figure 1).

Figure 1: Until now, the common assumption is that changes in C:N (and biogeochemistry, in general) are mainly driven by phytoplankton. In a series of in situ mesocosm experiments in different biomes (left), Taucher et al., (2020) found distinct impacts of ocean acidification on the C:N ratio of sinking organic matter (middle). By linking these observations to analysis of plankton community composition, the authors found a key role of heterotrophic processes in controlling the response of C:N to OA, particularly by altering the quality and carbon content of sinking organic matter within the biological pump (right).

Surprisingly, the observed responses were highly variable: C:N_export increased or decreased significantly with increasing CO₂, depending on the composition of species and the structure of the food web. The authors found that heterotrophic processes driven by bacteria and zooplankton play a key role in controlling the response of C:N_export to ocean acidification. This contradicts the widespread paradigm that primary producers are the principal driver of biogeochemical responses to ocean change.

Considering that such diverse pathways, by which planktonic food webs shape the elemental composition and biogeochemical cycling of organic matter, are not represented in state-of-the-art earth system models, these findings also raise the question: Are currently able to predict the large-scale consequences of ocean acidification with any certainty?

Authors:
Jan Taucher (GEOMAR, Kiel, Germany)
Tim Boxhammer (GEOMAR, Kiel, Germany)
Lennart T. Bach (University of Tasmania, Hobart, Australia)
Allanah J. Paul (GEOMAR, Kiel, Germany)
Markus Schartau (GEOMAR, Kiel, Germany)
Paul Stange (GEOMAR, Kiel, Germany)
Ulf Riebesell (GEOMAR, Kiel, Germany)

Zooplankton evolutionary rescue is limited by warming and acidification interactions

Posted by mmaheigan

· Friday, November 19th, 2021

A key issue facing ocean global change scientists is predicting the fate of biota under the combined effects of ocean warming and acidification (OWA). In addition to the constraints of studying multifactor drivers, predictions are hampered by few evolutionary studies, especially for animal populations. Evolutionary studies are essential to assess the possibility of evolutionary rescue under OWA– the recovery of fitness that prevents population extirpation in the face of environmental change.

Figure 1. Population fitness of the copepod Acartia tonsa vs generation under ambient, AM (18^oC, 400 µat pCO₂), ocean warming, OW (22^oC, 400 µat pCO₂), ocean acidification, ocean acidification (18^oC, 2000 µat pCO₂), and ocean warming and acidification ( 22^oC, 2000 µat pCO₂). Shown are means and 95% confidence intervals around the mean. The purple line shows that while fitness decreased after the 12^th generation, it was still considerably higher than at generation zero. Treatment lines are offset for clarity. N_o and N_τ (Y-axis legend) represent population size at the beginning and end of a generation (τ), and their ratio is the population fitness. Adapted from Dam et al. (2021).

A paper by Dam et al. published in Nature Climate Change examined the response of a ubiquitous copepod (zooplankter) to OWA for 25 generations to test for evolutionary rescue (Fig. 1). Using a suite of life-history traits, the researchers determined population fitness (the net reproductive rate per generation) under ambient, ocean warming, ocean acidification and OWA conditions. While population fitness decreased drastically under OWA conditions, it recovered in a few generations. However, after 12 generations under OWA, in contrast to OW or OA, fitness started to decrease again, suggesting incomplete evolutionary rescue driven by antagonistic interactions between warming and acidification. Such interactions add complexity to predictions of the fate of the oceanic biota under climate change.

Limited copepod evolutionary rescue would mean lower fisheries yields under OWA conditions as copepods are a main food source for forage fish. Copepods are also important vectors of the sequestration of CO₂ to deeper waters of the ocean. Limited copepod adaptation under OWA could weaken the efficiency of the biological carbon pump.

Authors:
Hans G. Dam (University of Connecticut)
James de Mayo (University of Connecticut)
Gihong Park (University of Connecticut)
Lydia Norton (University of Connecticut)
Xuejia He (Jinan University, China)
Michael B. Finiguerra (University of Connecticut)
Hannes Baumann (University of Connecticut)
Reid S. Brennn (University of Vermont)
Melissa H. Pespeni (University of Vermont)

Introducing the Coastal Ocean Data Analysis Product in North America (CODAP-NA)

Posted by mmaheigan

· Friday, October 22nd, 2021

Coastal ecosystems are hotspots for commercial and recreational fisheries, and aquaculture industries that are susceptible to change or economic loss due to ocean acidification. These coastal ecosystems support about 90% of the global fisheries yield and 80% of the known marine fish species, and sustain ecosystem services worth $27.7 Trillion globally (a number larger than the U.S. economy). Despite the importance of these areas and economies, internally-consistent data products for water column carbonate and nutrient chemistry data in the coastal ocean—vital to understand and predict changes in these systems—currently do not exist. A recent study published in Earth Syst. Sci. Data compiled and quality controlled discrete sampling-based data—inorganic carbon, oxygen, and nutrient chemistry, and hydrographic parameters collected from the entire North American ocean margins—to create a data product called the Coastal Ocean Data Analysis Product for North America (CODAP-NA) to fill the gap. This effort will promote future OA research, modeling, and data synthesis in critically important coastal regions to help advance the OA adaptation, mitigation, and planning efforts by North American coastal communities; and provides a foothold for future synthesis efforts in the coastal environment.

Figure caption. Sampling stations of the CODAP-NA data product.

Authors:
Li-Qing Jiang (University of Maryland; NOAA NCEI)
Richard A. Feely (NOAA PMEL)
Rik Wanninkhof (NOAA AOML)
Dana Greeley (NOAA PMEL)
Leticia Barbero (University of Miami; NOAA AOML)
Simone Alin (NOAA PMEL)
Brendan R. Carter (University of Washington; NOAA PMEL)
Denis Pierrot (NOAA AOML)
Charles Featherstone (NOAA AOML)
James Hooper (University of Miami; NOAA AOML)
Chris Melrose (NOAA NEFSC)
Natalie Monacci (University of Alaska Fairbanks)
Jonathan Sharp (University of Washington; NOAA PMEL)
Shawn Shellito (University of New Hampshire)
Yuan-Yuan Xu (University of Miami; NOAA AOML)
Alex Kozyr (University of Maryland; NOAA NCEI)
Robert H. Byrne (University of South Florida)
Wei-Jun Cai (University of Delaware)
Jessica Cross (NOAA PMEL)
Gregory C. Johnson (NOAA PMEL)
Burke Hales (Oregon State University)
Chris Langdon (University of Miami)
Jeremy Mathis (Georgetown University)
Joe Salisbury (University of New Hampshire)
David W. Townsend (University of Maine)

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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