Author Archive for mmaheigan – Page 5

California Current mCDR Node

Posted by mmaheigan 
· Sunday, December 1st, 2024 

The California Current mCDR Node convened a workshop on October 7-8, 2024 in California (in partnership with California Ocean Science Trust and Southern California Coastal Water Research Project). The workshop will address topics related to the environmental effects, both positive and negative, of mCDR. Attendees represent federal, state, and local agencies, NGOs, industry, and scientists. The goal of the workshop is to foster dialogue among these California sectors and advance on a framework for assessing environmental effects of mCDR.

 

New Ocean Metaproteomics paper

Posted by mmaheigan 
· Friday, November 8th, 2024 

New Ocean Metaproteomics paper published (web link and pdf link) to help promote proteomics in environmental settings. The study is open access. This paper is a product of OCB’s Intercomparison of Ocean Metaproteomic Analyses.

Capacity Building in Physical Chemistry for Oceanography

Posted by mmaheigan 
· Friday, October 25th, 2024 

Earlier this year, we conducted an online survey and consultation with the broader ocean science community to assess what we perceive as emerging skills gaps in basic physical chemistry training and expertise in several areas of chemical oceanography, especially (but not exclusively) including the ocean carbonate system. In the survey, we asked just for this information:

  1. Expertise, applications, and professional roles
  2. Opinions concerning skills gaps in physical chemistry for different areas of oceanography and needs for capacity building

We received well over 100 responses, with very many insightful observations and answers to our questions. We invite you to read the brief summary report describing the skill gap survey results and associated community feedback on recommended paths forward. Read the report.

Join us for a virtual community discussion at OA Week in November

To follow up on this survey, we are convening an online community discussion on Tuesday 19 November at 1600-1730 GMT/1100-1230 ET as part of the Global Ocean Acidification Observing Network (GOA-ON)’s Ocean Acidification (OA) Week 2024. The purpose of this discussion will be to discuss next steps for a community activity (most likely a workshop), including its focus, content, participants, and outcomes to help address the emerging skills gap identified in the survey. Register to participate in this community discussion HERE. If you would like further information, or you represent an organization that would like to participate in this effort, please get in touch with either Heather Benway (hbenway@whoi.edu) or Simon Clegg (s.clegg@uea.ac.uk).

Swirling Currents: How Ocean Mesoscale Affects Air-Sea CO2 Exchange

Posted by mmaheigan 
· Friday, October 25th, 2024 

Due to a sparsity of in‐situ observations and the computational burden of eddy‐resolving global simulations, there has been little analysis on how mesoscale processes (e.g., eddies, meanders—lateral scales of 10s to 100s km) influence air‐sea CO2 fluxes from a global perspective. Recently, it became computationally feasible to implement global eddy‐resolving [O (10) km] ocean biogeochemical models. Many questions related to the influence of mesoscale motions on CO2 fluxes remain open, including whether ocean eddies serve as hotspots for CO2 sink or source in specific dynamic regions.

A recent study in Geophysical Research Letters investigated the contribution of ocean mesoscale variability to air-sea CO2 fluxes by analyzing the CO2 flux anomaly within the mesoscale band using a coarse-graining approach in a global eddy-resolving biogeochemical simulation. We found that in eddy-rich mid-latitude regions, ocean mesoscale variability can contribute to over 30% of the total CO2 flux variability. The cumulative net CO2 flux associated with mesoscale motions is on the order of 105 tC per year. The global pattern of cumulative mesoscale-related CO2 flux exhibits significant spatial heterogeneity, with the highest values in western boundary currents, the Antarctic Circumpolar Current, and the equatorial Pacific. The local distribution of cumulative mesoscale-related CO2 flux displays zonal bands alternate between positive (a net source) and negative (a net sink) due to the meandering nature of ocean mesoscale currents, which is related to local relative vorticity and the background cross-stream pCO2 gradient.

Figure caption. Mesoscale (<nominal 2 degree) contribution to air‐sea CO2 flux (F<2°CO2)in the model. (a)–(d) Monthly time series of F<2°CO2 (black lines) and cumulative F<2°CO2 (green/red solid lines) in four locations marked in (e). Dashed lines are the least squares regression of cumulative flux for the period 1982–2000; slopes are indicated in the bottom left; (e) Blue colors imply a CO₂ sink, and red colors represent a source. The figure shows the global distribution of the regressed slopes of cumulative F<2°CO2. Units are converted from mol m-2 per year to kg of CO2 per year using the atomic mass of CO2. This figure shows significant spatial heterogeneity of mesoscale-modulated CO2 flux, showing contributions to both CO₂ sources and sinks across different regions of the ocean, with a magnitude on the order of 105 tC per year.

 

Authors
Yiming Guo (Yale University; now at Woods Hole Oceanographic Institution)
Mary-Louise Timmermans (Yale University)

How tiny teeth and their prey shape ocean ecosystems

Posted by mmaheigan 
· Friday, October 25th, 2024 

It has long been suggested that diatoms, microscopic algae enclosed in silica-shells, developed these structures to defend against predators like copepods, small crustaceans that graze diatoms. Copepods evolved silica-lined teeth presumably to counteract this. But actual evidence for how this predator-prey relationship may drive natural selection and evolutionary change has been lacking.

Figure caption: Left: Copepod teeth may suffer damage when feeding on thick-shelled diatoms. The red arrows indicate damage to the copepod tooth, cracks or missing setae. When fed a large diatom, the row of spinose cusps was damaged in all analyzed teeth. Scale bar = 10 µm. Right: A Temora longicornis (ca. 750 µm) copepod tethered to a human hair using super glue, allowing for the capture of high-speed videography to quantify the fraction of cells that eaten or discarded by the copepod. The hair was kindly provided by the first author’s wife.

A recent publication in Proceedings of the National Academy of Sciences U.S.A. revealed a fascinating dynamic: Copepods that feed on diatoms may suffer significant damage to their teeth, causing them to become more selective eaters. The wear and tear on the copepod teeth were particularly pronounced when copepods consumed thick-shelled diatoms compared to “softer” prey like a dinoflagellate. By glueing copepods to human hair and filming them with a high-speed video camera, the authors found that copepods with damaged teeth were more likely to reject diatoms with thick shells than those with thin shells as prey. Shell thickness varies among and within diatom species and some can respond to copepod presence by increasing shell thickness. A thicker shell, however, may come at a cost to the cell in terms of reduced growth rate or increased sinking speed.  This suggests that the evolutionary “arms race” between diatoms and copepods plays a crucial role in shaping and sustaining the diversity of these species.

Diatoms and copepods are important organisms in global biogeochemical cycles and hence understanding this microscopic interaction can help predict shifts in marine ecosystems, potentially affecting nutrient cycles and food webs that support fisheries.

 

Authors
Fredrik Ryderheim (Technical University of Denmark/University of Copenhagen)
Jørgen Olesen (University of Copenhagen)
Thomas Kiørboe (Technical University of Denmark)

 

Twitter
@fryderheim (Fredrik Ryderheim)
@OlesenCrust (Jørgen Olesen)
@Thomaskiorboe (Thomas Kiørboe)
@OceanLifeCentre (FR, TK group at DTU)
@NHM_Denmark (Natural History Museum of Denmark, JO employer)

OAIC gathering at AGU Fall Meeting 2024

Posted by mmaheigan 
· Tuesday, October 22nd, 2024 
People interested in ocean-atmosphere interactions and SOLAS are meeting up for drinks at AGU –  please come if you can. Everyone is welcome. The meetup will be on Thurs. Dec. 12 at 6:00 PM in Dacha Beer Garden. 1600 7th St NW, Washington DC 20001

Hawaii Ocean Time-series (HOT) can now be accessed using webODV!

Posted by mmaheigan 
· Thursday, October 10th, 2024 

One of the longest running open ocean time-series on our planet, the Hawaii Ocean Time-series (HOT) can now be accessed using webODV at https://hot.webodv.awi.de.

webODV [Mieruch and Schlitzer, 2023]) is the online version of the Ocean Data View (ODV) software. It is developed at the Alfred Wegener Institute, Bremerhaven, Germany with the aim to provide clients with user-friendly interfaces in their web-browser and access datasets that are centrally maintained and administered on a server using the full capacity of ODV.

This platform has recently been adapted to serve physical, biochemical, and ecological data from the HOT program. Dr. Sebastian Mieruch has generated an automated processing chain to aggregate, harmonize, and convert HOT data to the ODV format. Video tutorials for use of webODV to access, plot, and download HOT data can be found at https://hot.webodv.awi.de/docs.

 

BGC Argo Webinar #8, Oct 16 Comparing BGC-Argo observations with models

Posted by mmaheigan 
· Tuesday, September 24th, 2024 

BGC Argo Webinar #8: Comparing BGC-Argo observations with models
October 16, 2024, 11am Pacific/2pm Eastern

Please join us for the quarterly GO-BGC webinar, hosted by the US Ocean Carbon and Biogeochemistry Project Office. This webinar will be focused on comparisons between BGC-Argo observations and ocean model simulations focusing on bbp and particulate forms of carbon. The webinar will begin with an update on the status of the GO-BGC float array, followed by two short presentations. We’ll then close with a community discussion and Q&A session. Recordings will be available on the OCB and GO-BGC websites.

REGISTER

1) Yui Takeshita (Monterey Bay Aquarium Research Institute, USA, yui@mbari.org): An update on the GO-BGC program

2) Camila Serra-Pompei (Technical University of Denmark): Assessing the potential of backscattering as a proxy for phytoplankton carbon biomass
The particulate backscattering coefficient (bbp) has often been used as an optical proxy to estimate phytoplankton carbon biomass (Cphy). However, total observed bbp is impacted by phytoplankton size, cell composition, and non-algal particles. The scarcity of phytoplankton carbon field data has prevented the quantification of uncertainties driven by these factors. Here, we first review and discuss existing bbp algorithms by applying them to bbp data from the BGC-Argo array in surface waters (<10m) and show that errors can be large when the bbp signal is low. Next, we use a global ocean circulation model (the MITgcm Biogeochemical and Optical model) that simulates plankton dynamics and associated inherent optical properties to quantify and understand uncertainties from bbp-based algorithms in surface waters. In an ideal world where field data has no methodological uncertainties, the model shows that bbp algorithms could estimate phytoplankton carbon biomass with an absolute error close to 20% in most regions.

3) Martí Galí Tàpias (Institute of Marine Sciences [ICM-CSIC], Spain): Constraining stocks and fluxes of Particulate Organic Carbon (POC) through the comparison between particulate backscattering measurements and the PISCESv2 model
BGC-Argo data offers a great opportunity for model evaluation, optimization, and the development of improved parameterizations, ultimately furthering our mechanistic understanding. However, comparison between BGC-Argo observations and models requires careful consideration of the spatiotemporal scales that each of them can resolve. When using particulate backscattering (bbp) as a proxy for particulate organic carbon (POC), additional attention must be paid to the variability in the POC/bbp ratio, its uncertainty, and its underpinning biogeochemical drivers. In this talk I will present comparisons between bbp from BGC-Argo and simulated POC based on both 3D (Eulerian) and 1D (pseudo-Lagrangian) frameworks. I will discuss the potential and limitations of model parameter optimization using BGC-Argo bbp as the observational reference. Finally, I will explore the impacts of optimized model parameters on mesopelagic POC budgets and vertical fluxes in the PISCESv2 model.

4) Discussion

Fast-sinking salp and fish detritus impacts OMZ size and ocean biogeochemical cycles

Posted by mmaheigan 
· Thursday, September 12th, 2024 

Marine fishes and filter-feeding gelatinous zooplankton such as salps and pyrosomes generate detritus in the form of poop and dead carcasses, which sink ~10 times faster than other oceanic detritus. This detritus is hypothesized to have a disproportionally large impact on the marine biological pump as it sequesters carbon and nutrients deeper in the water column. Until now, global models had not considered these fluxes, thus, their impacts on ocean biogeochemical cycles were not well understood.

A recent study in Geophysical Research Letters investigated the sensitivity of deep ocean carbon, oxygen, and nutrient cycles to fast-sinking detritus from filter-feeding gelatinous zooplankton (pelagic tunicates) and fishes, using a modified version of the NOAA-GFDL ocean biogeochemical model COBALT (“GZ-COBALT”). We found the fast-sinking detritus decreased surface productivity and export, while increasing transfer efficiency and sequestration at depth. Ocean oxygen minimum zones (OMZs) also decreased in size: fast-sinking detritus triggered less remineralization, particularly in the mid-depths, resulting in less oxygen consumption and a reduced expansion of OMZs.

Figure caption: Flux of detrital carbon at various depths (A, B, C), shows that incorporating fast-sinking detritus counter-intuitively decreases carbon export from the surface while increasing sequestration at depth. Particulate organic carbon (POC) export flux at (A) 100 m, (B) 1,000 m and (C) seafloor (mgC/m2/d), shows (left) the control simulation with no fast-sinking detritus, (center) the experiment with fast-sinking fish and gelatinous zooplankton detritus, and (right) the differences between the control and fast-sinking detritus simulation. (D) Total ocean volume over the 300-year simulation at the suboxic (O2 ≤ 5 mmol/m3) level, shows the simulation with fast-sinking particulate organic carbon (red) had lower suboxia than the control (black). Large hypoxic and suboxic zones are a common model bias; these results suggest that fast-sinking detritus may be one biogeochemical mechanism to reduce the expansion of these low oxygen zones.

Past observations have shown that fast-sinking, highly reactive detritus reaching the seafloor can fuel significant benthic consumption and respiration. On a global scale, we suggest that the increased fluxes to the seafloor in the model can be supported by observational constraints of seafloor oxygen consumption, suggesting that these processes could be realistically incorporated into future generations of Earth System Models.

 

Authors
Jessica Y. Luo (NOAA GFDL)
Charles A. Stock (NOAA GFDL)
John P. Dunne (NOAA GFDL)
Grace K. Saba (Rutgers University)
Lauren Cook (Rutgers University)

The fate of the 21st century marine carbon cycle could hinge on zooplankton’s appetite

Posted by mmaheigan 
· Wednesday, September 11th, 2024 

Both climate change and the efforts to abate have the potential to reshape phytoplankton community composition, globally. Shallower mixed layers in a warming ocean and many marine CO2 removal (CDR) technologies will shift the balance of light, nutrients, and carbonate chemistry, benefiting certain species over others. We must understand how such shifts could ripple through the marine carbon cycle and modify the ocean carbon reservoir. Two new publications in Geophysical Research Letters and Global Biogeochemical Cycles highlight an often over looked pathway in this response: The appetite of zooplankton.

We have long known that the appetite of zooplankton—i.e. the half-saturation concertation for grazing—varies dramatically. This variability is largely based on laboratory incubations of specific species. An open-ocean perspective has been much more elusive. Using two independent inverse modelling approaches, both studies reached the same conclusion: Even at the community level, the appetite of zooplankton in the open-ocean is incredibly diverse.

Moreover, variability in zooplankton appetites maps well onto the biogeography of phytoplankton species. As these phytoplankton niches evolve, the composition of the zooplankton will likely follow. To help understand the impact of this response on the biological pump, we compared two models, one with only two types of zooplankton, and another with an unlimited amount, each with different appetites, all individually tuned to their unique environment. Including more realistic diversity reduced the strength of the biological pump by 1 PgC yr-1.

Figure Caption. A) Variability in the abundance and characteristic composition of phytoplankton drives B) large differences in the associated appetite and characteristic composition of zooplankton in two independent inverse modelling studies. C) When more realistic diversity in the appetite of zooplankton is simulated in models, the strength of biological pump is dramatically reduced.

That is the same order as the most optimistic scenarios for ocean iron fertilization. This means that when simulating the efficacy of many CDR scenarios, the bias introduced by insufficiently resolved zooplankton diversity could be just as large as the signal. Moving forward, it is imperative to improve the representation of zooplankton in Earth System Models to understand how the marine carbon sink will respond to inadvertent and deliberate perturbations.

Related article in The Conversation: https://theconversation.com/marine-co-removal-technologies-could-depend-on-the-appetite-of-the-oceans-tiniest-animals-227156

Authors (GRL):
Tyler Rohr (The University of Tasmania; Australian Antarctic Program Partnership)
Anthony Richardson (The University of Queensland; CSIRO)
Andrew Lenton (CSIRO)
Matthew Chamberlain (CSIRO)
Elizabeth Shadwick (Australian Antarctic Program Partnership; CSIRO)

Authors (GBC):
Sophie Meyjes (Cambridge)
Colleen Petrick (Scripps Institute of Oceanography)
Tyler Rohr (The University of Tasmania; Australian Antarctic Program Partnership)
B.B. Cael (NOC)
Ali Mashayek (Cambridge)

 

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