mmaheigan :: Ocean Carbon & Biogeochemistry

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

Author Archive for mmaheigan

Application open for OOI BGC sensor working group

Posted by mmaheigan

· Thursday, March 4th, 2021

Applications open: Participate in online working group to develop guidelines and best practices for using OOI biogeochemical sensor data

We would like to thank everyone who responded to our survey last fall on the planned OOI Biogeochemical Sensor workshop. The feedback we received from the community was incredibly helpful and we have used it to guide our next steps in the process of planning and organizing this activity. The goals of this activity are to

(1) broaden the use of OOI biogeochemical sensor data, and
(2) increase community capacity to produce analysis-ready data products and use them in new and ongoing research projects.

Given the continuing disruption to in-person meetings caused by the COVID-19 pandemic, we have decided to initiate a set of the planned workshop activities online. We will follow this up with an in-person workshop in conjunction with the OCB meeting at WHOI in June 2022.

In late spring 2021, we will convene a working group to develop a set of guidelines and best practices for using OOI biogeochemical sensor data, with participation across online synchronous and asynchronous activities. These guidelines will be published as a white paper for distribution to the broader community.

More detailed information about planned working group activities and the application form to participate in the working group are now available here. Apply by Friday April 2.

Our intention is to create a working group that is inclusive of participants from all backgrounds and a range of career stages. We recognize that everyone’s schedules and availability have been disrupted by the COVID-19 pandemic, and that scheduling may be especially challenging for those with dependent care responsibilities and those in early career stages. We will do our best to accommodate the needs of all accepted applicants.

For those who are interested in this activity and its outcomes but who are not able to commit the time to participate in this working group, we will continue to provide updates to the full community about working group progress and products, including at the in-person workshop and associated OCB meeting in summer 2022.

Organizing committee:
Hilary Palevsky (palevsky@bc.edu)
Sophie Clayton (sclayton@odu.edu)
Heather Benway (hbenway@whoi.edu)

Extreme events are accelerating coastal carbon cycling

Posted by mmaheigan

· Monday, March 1st, 2021

The world is getting stormier, and recent evidence shows significant impacts on coastal carbon cycling. The upticks in extreme weather events such as tropical cyclones have resulted in enhanced delivery of nutrients and organic matter across the land-ocean continuum. Lagoonal estuaries such as the Albemarle-Pamlico Sound (APS) in North Carolina and Galveston Bay in Texas are key coastal environments in which we can observe the long-term carbon cycling consequences of these events. Residence times of these coastal environments are on the order of months to over a year, providing ample opportunity for biogeochemical processing. Emerging from studies of Atlantic and Gulf of Mexico hurricanes in 2016 and 2017 is a clear example of the role of terrestrial dissolved organic carbon (DOC) as a key reactant driving the observed carbon cycling and ecosystem effects ( Figure 1).

Figure. 1. The impact of hurricanes on CO₂ fluxes (top) and terrestrial DOC decay constants (bottom) demonstrate the sustained effect on the coastal carbon cycle caused by extreme weather events. Top panel shows results from Hurricane Matthew in 2016, where date is month and day and Km downstream represents observations taken along the main axis of the Neuse River Estuary and lower Pamlico Sound, eastern North Carolina. F_CO2 is the daily sea-to-air flux of CO₂ estimated from measurements of temperature, salinity, dissolved inorganic carbon, and wind speed. The results indicate the Sound existed as a weak yet sustained CO2 source to the atmosphere well after the storm. Outgassing of CO₂ is driven by the rapid mineralization of terrestrial DOC. Bottom panel shows the high bioreactivity of flood-derived terrestrial DOC indicated by elevated microbial decay constants for Galveston Bay and the coastal Gulf of Mexico in 2017 as compared to high and low latitude coastal environments.

In coastal North Carolina, 36 tropical cyclones (TCs), including three floods of historical significance in the past two decades, have occurred in the past 20 years. The lingering effects of these storms include extensive periods of carbon dioxide (CO₂) supersaturation. For example, Hurricane Matthew in 2016 caused the lower Pamlico Sound to emit CO₂ for months after the passage of the storm. With similar results documented for the Pamlico Sound for storms in 2011 and 2012, there is solid evidence that shifts in the ecosystem state of this mesotrophic estuary from net autotrophic to net heterotrophic are a major effect of this process.

Reactive DOC from the landscape appears to be driving the shift in ecosystem state. Large plumes of brown-colored DOC are observable from space in numerous satellite images of the Atlantic and Gulf coasts following these storms. The color is part of a phenomenon known as “coastal darkening”—spectroscopic, stable isotopic, and biomarker evidence show this darkening is related to the flushing of wetlands in the flood-plain adjacent to the rivers draining into these estuaries.

Along the Texas coast, Hurricane Harvey produced the largest rainfall event recorded in US history and caused extensive flooding in 2017. Similar to results from coastal North Carolina, flood-derived terrestrial DOC in Galveston Bay exhibited high bioreactivity, with decay constants exceeding those observed for terrestrial DOC across coastal environments from high and low latitudes by almost three-fold. The rapid processing of terrestrial DOC was linked to an active microbial community capable of decomposing aromatic compounds that are abundant in colored DOC as indicated by genomic analyses. These recent studies clearly demonstrate the impacts of large storm events on coastal carbon cycling via the transport of reactive terrestrial DOC into coastal waters. Climate-driven increases in the frequency and intensity of such storm events warrant more sustained capacity to monitor episodic deliveries of carbon and nutrients and their impacts on coastal marine ecosystems.

Authors:
Chris Osburn (North Carolina State University) @closburn
Hans Paerl (University of North Carolina, Institute of Marine Sciences)
Ge Yan (Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences)
Karl Kaiser (Texas A&M University, Galveston Campus)

Citations:

Yan, G., Labonté, J. M., Quigg, A., & Kaiser, K. (2020). Hurricanes accelerate dissolved organic carbon cycling in coastal ecosystems. Frontiers in Marine Science, 7, 248.

Osburn, C. L., Rudolph, J. C., Paerl, H. W., Hounshell, A. G., & Van Dam, B. R. (2019). Lingering carbon cycle effects of Hurricane Matthew in North Carolina’s coastal waters. Geophysical Research Letters, 46(5), 2654-2661.

Counterintuitive effects of shoreline armoring on estuarine water clarity

Posted by mmaheigan

· Wednesday, February 24th, 2021

Around the world, human-altered shorelines change sediment inputs to estuaries and coastal waters, altering water clarity, especially in areas of dense human population. The Chesapeake Bay estuary is recovering from historically high nutrient and sediment inputs, but water clarity improvement has been ambiguous. Long-term trends show increasing water clarity in terms of deepening light attenuation depth, yet degrading clarity in terms of shallowing Secchi depth over time. High water clarity is needed to support seagrass meadows, which act as nursery habitats for commercially important fish species such as striped bass. How are these opposing water clarity trends possible?

In a recent paper published in Science of the Total Environment, researchers performed experiments with a coupled hydrodynamic-biogeochemical model to test a simulated Chesapeake Bay under realistic conditions, more shoreline erosion, and highly armored shorelines. Comparing the two extreme conditions (Figure 1), there was a striking difference between (a) an estuary experiencing more shoreline erosion and greater resuspension versus (b) a highly armored estuary with decreased resuspension. Reduced erosion yielded improved water clarity in terms of light attenuation depth, but a shallower Secchi depth (reduced visibility). In estuaries, reducing sediment inputs is often proposed as a strategy for improving water quality. This study shows that, under certain conditions in a productive estuary, reduced sediments can have unintended secondary effects on water clarity due to enhanced production of organic particles. This study also highlights the need to consider other sediment sources in addition to rivers, such as seabed resuspension and shoreline erosion, especially at times and locations of low river input.

Figure 1. Schematic of how shoreline armoring causes deepening light attenuation depth (navy) yet shallowing Secchi depth (green) during the spring growing season in the mid-bay central channel.

Authors:
Jessica S. Turner
Pierre St-Laurent
Marjorie A. M. Friedrichs
Carl T. Friedrichs
(all Virginia Institute of Marine Science)

Wildfire impacts on coastal ocean phytoplankton

Posted by mmaheigan

· Wednesday, February 24th, 2021

Wildfire frequency, size, and destructiveness has increased over the last two decades, particularly in coastal regions such as Australia, Brazil, and the western United States. While the impact of fire on land, plants, and people is well documented, very few studies have been able to evaluate the impact of fires on ocean ecosystems. A serendipitously planned research cruise one week after the Thomas Fire broke out in California in December 2017 allowed the authors of this study and their colleagues to sample the adjacent Santa Barbara Channel during this devastating extreme fire event.

In a recent paper published in Journal of Geophysical Research: Oceans, the authors describe the phytoplankton community in the Santa Barbara Channel during the Thomas Fire. Phytoplankton community composition was described using a combination of images of phytoplankton from the Imaging FlowCytobot (McLane Labs) and phytoplankton pigments. Dinoflagellates were the dominant phytoplankton group in the surface ocean during the Thomas Fire, according to both methods (Figure 1).

Figure 1. (A) The fraction of total particle volume imaged by the Imaging FlowCytobot (IFCB) comprised of phytoplankton (green) and detritus (brown). Example IFCB images of ash (counted as part of detritus) particles are outlined in brown. (B) The phytoplankton fraction is then further divided by taxonomy, showing the abundance of nano-sized phytoplankton and especially dinoflagellates during the week of sampling. Example IFCB images of Gonyaulax (outlined in dark green), Prorocentrum (outlined in light green), and Umbilicosphaera (outlined in purple) cells are also shown.

While this study was not able to demonstrate a causal relationship between the Thomas Fire and the presence of dinoflagellates, this result is quite different from previous winters in the Santa Barbara Channel, when picophytoplankton and diatoms typically dominate the winter community. The incidence of dinoflagellates in the Santa Barbara Channel in December 2017 was correlated with the warmer-than-average water temperature during this study, which matched observations from other areas along the Central California coast that winter.

At the time this study was conducted, the Thomas Fire was the largest wildfire in California history. Since then, California fires have increased in danger, destruction, and human mortality; the Mendocino Fire complex (summer 2018) and five separate wildfires in summer 2020 exceeded the impacts of the Thomas Fire. With wildfire severity and frequency increasing not only in California but in coastal regions worldwide, this study gives an important first look at the impact of wildfire smoke and ash on oceanic primary productivity and community composition.

Authors:
Sasha Kramer (University of California Santa Barbara)
Kelsey Bisson (Oregon State University)
Alexis Fischer (University of California Santa Cruz)

CO2-in-seawater reference materials: yesterday, today, and tomorrow – Andrew Dickson March 16 webinar

Posted by mmaheigan

· Tuesday, February 23rd, 2021

The U.S. Interagency Working Group on Ocean Acidification presents:

CO2-in-seawater reference materials: yesterday, today, and tomorrow webinar

Professor Andrew Dickson (Scripps Institution of Oceanography, UC San Diego)

March 16, 2021, 9am Pacific (UTC -7:00)/ 12pm EST

We welcome all who work on ocean acidification and ocean carbonate chemistry studies to attend. This is the first community engagement in a larger effort to increase the resilience of the production and distribution of ocean carbonate chemistry reference materials.

Abstract: In 1989, the US National Science Foundation awarded a grant to the Scripps Institution of Oceanography in preparation for the upcoming US JGOFS program. This grant was intended to enable the preparation of standards for the measurement of the CO₂ properties of seawater that could be distributed to laboratories participating in the program so as to assure the production of a coherent data set from the differing labs and methodologies likely to be involved in the program. The model for this activity was the production and distribution of IAPSO Standard Seawater. This initial program was expanded through additional support from the US Department of Energy to enable international distribution to laboratories making CO₂ measurement as part of the extensive joint ocean survey supported by JGOFS and the WOCE Hydrographic Program.

Since then – and despite various setbacks – the Scripps Laboratory has produced such reference materials consistently, and has distributed them to a wide variety of laboratories around the world who are involved in ocean CO₂measurements. Since the early 2000s, and as a consequence of the growth in interest in studies of ocean acidification, this has grown to a substantial activity (~10,000 bottles of reference material distributed per year to a large number of laboratories in many different countries around the world). Throughout this time, Scripps has been supported in this activity by the US National Science Foundation alone (the US DOE withdrew in 1997).

The recent COVID19 pandemic last year led to a sudden halt in our activities as a consequence of restrictions imposed both by the State of California, and by UC San Diego. We are only now (2021) starting to prepare such reference materials again, and presently only in reduced quantities. Consequently, this provides an incentive to review the needs for such materials (both within the US and world-wide), and to plan for their longer-term future. It should be noted that in the 30+ years during which we have been in operation, the only other country that has even embarked upon a similar activity is Japan.

In addition to a historical overview of the activities and achievements of the Scripps Laboratory, I shall provide a statement as to our current activities and immediate plans and will lay out what I believe is needed in the way of resources to ensure that the current US capacity to produce calibrated reference materials continues unabated. I shall also provide some guidance for others who may wish to embark on similar activities, and outline my own views as to what is required to ensure that the world is able to provide sufficient reference materials to ensure the quality of marine CO₂ measurements into the foreseeable future.

Webinar series on extreme events

Posted by mmaheigan

· Sunday, February 21st, 2021

Please join us for extreme events and the coastal carbon cycle webinars, a joint series with the North American Carbon Program (NACP) and the US Carbon Cycle Science Program.

March 9, 2021 at 1 pm (EST)
Tropical storm impacts on carbon transport across the aquatic continuum - Speakers: Chris Osburn (North Carolina State University), Ge Yan (Chinese Academy of Sciences)
REGISTER

February 23, 2021
Wildfire impacts on coastal productivity and biogeochemistry - Speakers: Sasha Kramer (University of California Santa Barbara), Matt Jones (University of East Anglia)
Watch the recording now

This webinar mini-series will inform discussions for a breakout session on Climate change and extreme hydrologic events: A temporal perspective on carbon fluxes across the aquatic continuum (March 19, 2021, 4:30-6 pm EST) at the 7th NACP Open Science Meeting being held on Friday afternoons in March. Visit the meeting website to learn more and register (free!). To learn more about OCB's ongoing collaboration with NACP and the US Carbon Cycle Science Program, visit the home page of the Aquatic Continuum Science Focus Group.

Visit the OCB webinar home page for more upcoming events and recordings.

Fishes Contribute Roughly 1.65 Billion Tons of Carbon in Feces and Other Matter Annually

Posted by mmaheigan

· Thursday, February 18th, 2021

Press release by Rutgers:

Scientists have little understanding of the role fishes play in the global carbon cycle linked to climate change, but a Rutgers-led study found that carbon in feces, respiration and other excretions from fishes – roughly 1.65 billion tons annually – make up about 16 percent of the total carbon that sinks below the ocean’s upper layers.

Better data on this key part of the Earth’s biological pump will help scientists understand the impact of climate change and seafood harvesting on the role of fishes in carbon flux, according to the study – the first of its kind – in the journal Limnology and Oceanography. Carbon flux means the movement of carbon in the ocean, including from the surface to the deep sea – the focus of this study.

“Our study is the first to review the impact that fishes have on carbon flux,” said lead author Grace K. Saba, an assistant professor in the Center for Ocean Observing Leadership in the Department of Marine and Coastal Sciences in the School of Environmental and Biological Sciences at Rutgers University–New Brunswick. “Our estimate of the contribution by fish – about 16 percent – includes a large uncertainty, and scientists can improve it with future research. Forms of carbon from fish in ocean waters where sunlight penetrates – up to about 650 feet deep – include sinking fecal pellets, inorganic carbon particles (calcium carbonate minerals), dissolved organic carbon and respired carbon dioxide.”

The ocean plays a vital role in the Earth’s carbon cycle by exchanging carbon dioxide, a key greenhouse gas linked to global warming and climate change, with the atmosphere. Carbon dioxide absorbed by the ocean is taken up by phytoplankton (algae), small single-celled plants at the ocean’s surface. Through an important process called the biological pump, this organic carbon can go from the surface to ocean depths when algal material or fecal pellets from fishes and other organisms sink. The daily migration of fishes to and from the depths also contributes organic carbon particles, along with excreted and respired material. Another factor is mixing of ocean waters.

“Carbon that makes its way below the sunlit layer becomes sequestered, or stored, in the ocean for hundreds of years or more, depending on the depth and location where organic carbon is exported,” Saba said. “This natural process results in a sink that acts to balance the sources of carbon dioxide.”

Scientists at many institutions contributed to the study, which is a product of the Fish Carbon Working Group led by Saba since 2018 and funded by the Ocean Carbon and Biogeochemistry program, which is supported by the National Science Foundation and National Aeronautics and Space Administration.

Limnol. Oceanogr. 9999, 2021, 1–26, doi: 10.1002/lno.11709

Toward a better understanding of fish-based contribution to ocean carbon flux
Grace K. Saba – Rutgers University
Adrian B. Burd – University of Georgia
John P. Dunne – NOAA/OAR/Geophysical Fluid Dynamics Laboratory
Santiago Hernández-León – Universidad de Las Palmas de Gran Canaria
Angela H. Martin – University of Agder
Kenneth A. Rose – University of Maryland
Joseph Salisbury – University of New Hampshire
Deborah K. Steinberg – Virginia Institute of Marine Science
Clive N. Trueman – University of Southampton
Rod W.Wilson – University of Exeter
Stephanie E. Wilson – Gwynedd, UK

Species loss alters ecosystem function in plankton communities

Posted by mmaheigan

· Monday, February 8th, 2021

Climate change impacts on the ocean such as warming, altered nutrient supply, and acidification will lead to significant rearrangement of phytoplankton communities, with the potential for some phytoplankton species to become extinct, especially at the regional level. This leads to the question: What are phytoplankton species’ redundancy levels from ecological and biogeochemical standpoints—i.e. will other species be able to fill the functional ecological and/or biogeochemical roles of the extinct species? Authors of a paper published recently in Global Change Biology explored these ideas using a global three-dimensional computer model with diverse planktonic communities, in which single phytoplankton types were partially or fully eliminated. Complex trophic interactions such as decreased abundance of a predator’s predator led to unexpected “ripples” through the community structure and in particular, reductions in carbon transfer to higher trophic levels. The impacts of changes in resource utilization extended to regions beyond where the phytoplankton type went extinct. Redundancy appeared lowest for types on the edges of trait space (e.g., smallest) or those with unique competitive strategies. These are responses that laboratory or field studies may not adequately capture. These results suggest that species losses could compound many of the already anticipated outcomes of changing climate in terms of productivity, trophic transfer, and restructuring of planktonic communities. The authors also suggest that a combination of modeling, field, and laboratory studies will be the best path forward for studying functional redundancy in phytoplankton.

Figure caption: Examples of the modelled ecological and biogeochemical responses to the extinction of different phytoplankton species.Figure caption: Examples of the modelled ecological and biogeochemical responses to the extinction of different phytoplankton species.

Authors:
Stephanie Dutkiewicz (Massachusetts Institute of Technology)
Philip W. Boyd (Institute for Marine and Antarctic Studies, University of Tasmania)
Ulf Riebesell (GEOMAR Helmholtz Centre for Ocean Research Kiel)

Does ocean acidification make marine fish grow differently? What about sex-specific effects?

Posted by mmaheigan

· Monday, February 8th, 2021

The question of whether ocean acidification (OA) will impact the growth of marine fish remains surprisingly uncertain. The bulk of available evidence in the form of laboratory experiments suggests that most fish are not impacted by OA-relevant CO₂ levels, but many studies suffer from the inherent methodical constraints of rearing marine fish in captivity. For example, most experiments cover a small fraction of a species’ lifespan and do not employ restricted feeding regimes which may enable fish to increase feeding to offset metabolic deficits associated with high-CO₂ acclimation.

To address these methodological shortcomings, authors of a recent publication in PLOS One synthesized three years of multiple long-term, food-controlled experiments that reared large populations of the model forage fish Menidia menidia (Atlantic silverside) from fertilization to about a third of their lifespan. Results showed modest but consistent negative, temperature-dependent growth effects, in which silversides from high-CO₂ treatments were shorter (-3% to -9%) and weighed less (-6% to -18%) than ambient-CO₂ conspecifics. However, sometimes it takes more than just looking at means and standard deviations to elucidate these effects. Hence, the authors employed powerful shift functions to analyze how the size distributions of experimental populations shifted to smaller quantiles under future CO₂ conditions.

Figure caption: The length of juvenile Atlantic silversides reared from fertilization under control (blue dots) and high-CO₂ treatments (red dots). Exposure to OA conditions imposed a universal shift to a smaller body size across the size frequency distribution. Black vertical bars overlaying each distribution indicate the .1, .25, .5, .75, and .9 quantiles and quantile shifts are indicated by connecting lines.

It took over 100 days of continuous high-CO₂ exposure until size differences were detectable. This means that long-term CO₂effects could exist in other tested species but are missed in relatively short experiments. Furthermore, the authors sexed several thousand fish to enable a rare sex-specific analysis of CO₂ effects. Both sexes were similarly affected by high CO₂, and the hormonal pathways that mediate environmental sex determination in this species are not impacted by CO₂ level. Our results confirm that Atlantic silversides are relatively tolerant of future OA conditions. But even in this robust estuarine species, high CO₂ can reduce growth. This could have cascading effects on population dynamics by impacting size-dependent traits like reproductive success and over-wintering survival of this widespread and ecologically important prey species.

Authors
Christopher S. Murray (University of Washington)
Hannes Baumann (University of Connecticut)

How environmental drivers regulated the long-term evolution of the biological pump

Posted by mmaheigan

· Friday, January 22nd, 2021

The marine biological pump (BP) plays a crucial role in regulating earth’s atmospheric oxygen and carbon dioxide levels by transferring carbon fixed by primary producers into the ocean interior and marine sediments, thereby controlling the habitability of our planet. The rise of multicellular life and eukaryotic algae in the ocean about 700 million years ago would likely have influenced the physical characteristics of oceanic aggregates (e.g., sinking rate), yet the magnitude of the impact this biological innovation had on the efficiency of BP is unknown.

Figure. 1. The impact of biological innovations (left) and environmental factors (atmospheric oxygen level and seawater temperature; right) on the efficiency of marine biological pump (BP). Temperatures are ocean surface temperatures (SST), and atmospheric pO2 is shown relative to the present atmospheric level (PAL). The BP efficiency is calculated as the fraction of carbon exported from the surface ocean that is delivered to the sediment-water interface. The results indicate that evolution of larger sized algae and zooplanktons has little influence on the long-term evolution of biological pump (left panel). The change in the atmospheric oxygen level and seawater surface temperature as environmental factors, on the other hand, have a stronger leverage on the efficiency of biological pump (right panel).

The authors of a recent paper in Nature Geoscience constructed a particle-based stochastic model to explore the change in the efficiency of the BP in response to biological and physical changes in the ocean over geologic time. The model calculates the age of organic particles in each aggregate based on their sinking rates, and considers the impact of primary producer cell size, aggregation, temperature, dust flux, biomineralization, ballasting by mineral phases, oxygen, and the fractal geometry (porosity) of aggregates. The model results demonstrate that while the rise of larger-sized eukaryotes led to an increase in the average sinking rate of oceanic aggregates, its impact on BP efficiency was minor. The evolution of zooplankton (with daily vertical migration in the water column) had a larger impact on the carbon transfer into the ocean interior. But results suggest that environmental factors most strongly affected the marine carbon pump efficiency. Specifically, increased ocean temperatures and greater atmospheric oxygen abundance led to a significant decrease in the efficiency of the BP. Cumulatively, these results suggest that while major biological innovations influenced the efficiency of BP, the long-term evolution of the marine carbon pump was primarily controlled by environmental drivers such as climate cooling and warming. By enhancing the rate of heterotrophic microbial degradation, our results suggest that the anthropogenically-driven global warming can result in a less efficient BP with reduced power of marine ecosystem in sequestering carbon from the atmosphere.

Authors:
Mojtaba Fakhraee (Yale University, Georgia Tech, and NASA Astrobiology Institute)
Noah J. Planavsky (Yale University, and NASA Astrobiology Institute)
Christopher T. Reinhard (Georgia Tech, and NASA Astrobiology Institute)

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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