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Towards a better understanding of fish contribution to carbon flux OCB workshop summary

Posted by mmaheigan

· Thursday, August 8th, 2019

Summary

This workshop, held March 4-5, 2019 at Rutgers University, was attended by 14 researchers from 11 different institutions. The workshop focused on synthesizing the existing research on fish carbon flux, discussing challenges in measuring fish carbon flux, and determining approaches for estimating fish contribution to carbon flux on variable scales. Presentations interspersed with group discussions were specifically targeted toward best approaches for determining: fish biomass on regional and global scales, relative amounts of carbon forms produced from fish (i.e., release of sinking fecal pellets, excretion of particulate inorganic carbon and dissolved organic carbon, respiration of carbon dioxide), and carbon flux estimates from fish biomass (i.e., bioenergetics, size-based allometric relationships, stable isotopes).

Participants

Workshop participants: Standing from L to R – Clive Trueman, Rod Wilson, Santiago Hernández-León, Kenneth Rose, Adrian Burd, John Dunne, Angela Martin; Sitting from L to R – Grace Saba, Deborah Steinberg, Stephanie Wilson. Other Fish Carbon working group participants that were unable to attend the meeting include: Nicola Beaumont, Joe Salisbury; Guest presenters at the workshop (not pictured): Olaf Jensen, Charles Stock

Monday, March 4, 2019

Overview of Project and Workshop Goals
Presentation by Grace Saba, Fish Carbon Work Group Lead

From Turner 2015

The ‘biological pump’, the vertical transport of biologically generated dissolved or particulate organic matter from the surface to the ocean’s interior, plays a key role in ocean biogeochemistry and food webs. Active transport of carbon via diel vertically migrating (DVM) organisms as well as passive transport via their rapidly sinking fecal pellets are major contributors to the ‘biological pump’. With more than 500 studies measuring zooplankton flux, there is a wealth of knowledge of zooplankton active and passive transport and their contributions to carbon flux. However, fish contribution to the biological pump is a complete unknown. To our knowledge, less than ten studies have estimated active transport in DVM fish and only five studies focused on direct measurements of fish passive flux. Mesopelagic DVM fishes from these few studies can contribute ~30- 40% of total carbon flux through respired and excreted carbon byproducts. Furthermore, all reports on fish fecal pellets thus far have demonstrated the formation of cohesive, durable, rapidly sinking fecal pellets. Additionally, two studies revealed that fish contribute up to 15% of total oceanic carbonate production (inorganic C) via the formation and excretion of various forms of precipitated (non-skeletal) calcium carbonate from their guts.

This information is essential to not only determine its potential for a food source for benthic organisms, but also to improve parameterization of key processes affecting the biological pump and to develop more accurate regional and global carbon models. Only then can we begin to understand interannual and seasonal/spatial variability and long-term changes of fish fecal flux, food web regulation of carbon flux, and evaluate the potential role of environmental factors and climate change on fish carbon flux. This working group is aimed at synthesizing existing knowledge of fish carbon flux, investigating the challenges associated with estimating fish contribution to the biological pump, and paving a path forward to develop approaches to begin filling some of the gaps in this much needed research. The overarching goals of the working group are to synthesize the existing research on fish carbon flux, recognize the challenges in measuring fish carbon flux and discuss approaches to resolve them, develop research priorities to fill the large gaps in understanding fish carbon flux, and identify opportunities to obtain resources needed to move this research forward. Since its inception, this working group has been meeting virtually, on average, every three months to assign tasks to complete in between calls in order to address these goals. The in-person workshop was aimed at completing some tasks and making significant progress on the more challenging aspects of some of these tasks. The specific goals for the workshop were as follows:

Finalize Paper 1: Synthesis, Challenges, Gaps, Research Priorities, Assign specific tasks with deadlines for completion
Make as much progress as possible on Paper 2: Outline emerging methods, and first attempt at estimating global and/or regional carbon contributions
- Finalize Approaches for Fish Biomass Estimates, Passive and Active Fish Carbon Fluxes, Comparisons to Total Carbon Flux and Zooplankton Flux
- Assign specific tasks with deadlines to complete Paper 2
Discuss Potential Proposals for Filling Gaps

Fish Carbon Synthesis, Challenges, Gaps, and Research Priorities
Presentation by Angela Martin followed by Group Discussion

Through web conference calls and ongoing iterations of a draft manuscript, the group has conducted a synthesis of knowledge on fish carbon flux and has developed a list of research challenges and research priorities. This is still an ongoing process, and the group is still working on incorporating thoughtful content for the manuscript. Specifically, the group is currently in the process of completing a summary of available methods for flux measurements to highlight the gaps, an approach to overcoming identified research challenges, and a prioritized list of the research needs.

Fish Biomass: Challenges and Best Approaches
Presentations by Olaf Jensen and Charles Stock followed by discussion

Dr. Olaf Jensen summarized four approaches to estimate fish biomass. These include:

Scaling up density estimates: Estimate an areal density from data collected from trawl or hydroacoustic surveys and multiplying by area. However, challenges exist in making these estimates. Catch efficiency from trawl surveys has uncertainty due to herding effects or escapes, and bias in scaling up hydroacoustic surveys caused by scattering other types of organisms (i.e., siphonophores) can occur.
Energetic approach: From primary production measurements, scale up energy movement through food chain to fish biomass using an estimated value of trophic transfer efficiency (i.e., 10%). This approach is currently used in EcoPath and EcoSym models, and has also been described previously in Ryther 1969 and Pauly and Christensen 1995. However, uncertainty in this approach occurs when making required assumptions as to what proportions of biomass of each trophic level is fish and the trophic transfer efficiency.
Size-based models: Using size-based relationships between trophic levels such that the slope of the size spectrum is predictable and the proportion of fish at each size in the size spectrum can be estimated (Jennings and Collingridge 2015). This approach assumes predation is size-structured, but not all predation follows this pattern.
Stock assessment data: Mathematical models used to estimate the size and productivity of fish or invertebrate stocks using index of abundance (i.e., trawl surveys) and how much is removed to see if the amount harvested is making an impact on the annual reproduction of stocks. However, this is limited because stock assessments are used only for specific targeted fish and, although there are some global stock assessment data bases (i.e., RAM), the tropics do not have good stock assessment data because of the operational cost. Additionally, productivity and standing stock are confounded and not equal.

All of these different approaches incorporate a modeling aspect of variable scale, and they can produce very different estimates by an order of magnitude that could be used to bound the estimates of biomass, and subsequently fish carbon contribution. Using a snapshot of biomass is valuable, but for estimating the role of fish in carbon flux, information about the flux of fish biomass over some time interval is also necessary information. Following the presentation, the group discussed potential spatial and vertical scales at which fish biomass and carbon flux could be determined and approaches that were most appropriate for global vs regional analysis.

The presentation by Dr. Charles Stock focused on the challenges of incorporating fish in biogeochemical models as well as past and ongoing efforts to do so. Energy flows decay very rapidly from phytoplankton to fish, so using net primary productivity to estimate fish biomass or abundance is not sufficient. Incorporating trophodynamics (i.e., trophic transfer efficiency) is a necessary step and there is high uncertainty in these estimations. Uncertainties in biomass estimation at each trophic level can greatly impact the biomass estimate at the highest trophic levels.

Modified from Dr. Olaf Jensen presentation “Estimating Global Fish Biomass” available on this project’s website.

Furthermore, regionally the trophodynamics vary greatly and will likely cause sharp spatial and vertical gradients in fish importance with respect to carbon flux. Newly developed models such as those that include fish size and functional type (Petrik et al. 2019) are promising for mechanistically resolving fish biomass at different trophic levels. From a discussion following the presentation, the group decided that a review of available models for estimating fish biomass should be included in the synthesis paper and should discuss strengths and weaknesses for each.

Tuesday, March 5, 2019

Getting Carbon Estimates from Fish Biomass
Presentations by Kenneth Rose and Clive Trueman

Dr. Rose described several model options to estimate carbon production from fish. These include the classical bioenergetic models (Wisconsin [Kitchell] and Dynamic Energy Budget [DEB]) and an Aquaculture model. The Wisconsin (Kitchell) model considers consumption, respiration, specific dynamic action, egestion, excretion, and egg production. Growth is typically estimated from the model.

Bioenergetics Model: Venfish, 2002 PICES Model/REX Task Team.

It does not incorporate mortality and reproduction. The inclusion terms are not independent as patterns in consumption effect all other parameters in the model equation. The terms of this model relate to Cmax, or the maximum the fish can eat; however, fish are likely not always eating at their full capacity and could bias model output. There are ongoing efforts to uncouple the models and incorporate food availability to reflect more realistic conditions. The model is daily time-stepped, and all processes are temperature and size dependent. Although there are many versions of the equation, typically consumption is the only thing that is changed and the waste product is usually 0.7.

Dynamic Energy Budget: Jusup et al. 2011.

The DEB approach was developed to model energy inputs, storage, energy allocation (to growth, somatic maintenance, reproduction), and waste outputs in individual fish. The big difference between the Wisconsin (Kitchell) and a DEB model is that in a DEB, the energy allocated towards growth and reproduction can be adjusted according to fish species and size.

Aquaculture Model (AQUA): Rensel et al. 2006.
(Above) Three model examples presented by Dr. Kenneth Rose.

Models have recently been developed to determine the fate of aquaculture waste products and potential impacts on local benthic areas and downstream. The models look similar to the bioenergetic models; however, in this case the biomass (fish weight), growth rate, and food availability terms are known and the model incorporates a benthic component. DEPOMOD models the deposition and biological effects of solid wastes by tracking the waste as particles to see the fate of the waste (i.e. advection, settling, resuspension, etc.), and then incorporates a benthic component. The AQUA model incorporates different kinds of waste, and once solid waste reaches the bottom, the benthic community response is modeled.

Dr. Trueman gave two presentations focused on estimating carbon from fish – the first on using size-based macroecological models to estimate fish biomass and the second on using stable isotopes to estimate carbon from fish biomass estimates. First, the aim of size-based models is to predict biomass/abundance through an ecosystem as a function of body size and primary production. Using this model, you can estimate how energy is divided between trophic levels assuming community is size-structured. The advantages for using this method include simplification (easy to understand), ease of coupling to GCM models, and there are large data sets of body size to validate against. The key variables can be constrained a bit with relatively simple field data, and these include available primary production, temperature-dependent consumer metabolic rate, predator prey mass ratio (PPMR), and trophic transfer efficiency (TE). Typically, consumer production depends on body size and temperature. Additionally, biomass size spectrum depends on PPMR and transfer efficiency, whereby at high PPMR/constant TE and High TE/constant PPMR, there is a short food chain and a lot of energy goes through small low trophic animals. Some examples using these types of models include Jennings and Collingridge 2015 and Blanchard et al. 2008. However, as described earlier, TE and PPMR are relatively poorly constrained and cause high uncertainty in the model. But these models can be used to get approximate or range of carbon flux estimates. The models essentially track the remaining carbon after respiratory loss, and the 1-TE term in the model effectively sets available carbon for storage.

One other potential method for estimating carbon flux from fish biomass is via stable isotopes. Isotopes useful for tracking movement of carbon where this occurs across natural isotopic gradients. Isotopes can be used to determine the PPMR due to the effect of isotopes in eating vs. waste products. And then if biomass size spectrum is known, we can infer the TE or ask if the TE can link the measured PPMR. Community level analyses can also recover PPMR. Additionally, isotope analysis on fish otoliths can be used to measure metabolic rates in the field. Carbonate in the aragonite is sourced from DIC from surrounding water or from carbon respired, and the rate at which respiring dietary carbon is influenced on the isotopic ratio. Additionally, oxygen isotopes in the otolith can be used to derive temperature (thermal history) and therefore metabolic rates. This method is beneficial in estimating field metabolic rates in fish that are difficult to collect and maintain in the laboratory for traditional metabolic experiments (i.e., DVM mesopelagic fish). Combined with biomass data, isotopes could be used to quantify C flux.

Forms of Carbon
Presentations by Joe Salisbury, Rod Wilson, Grace Saba, and Santiago Hernández-León

Dr. Salisbury’s presentation was focused on whether or not the carbon removed from fishing/harvesting activities is a significant loss of carbon. The particulate organic carbon (POC) in ocean fish is brought onto land where it oxidizes relatively quickly. Similarly, consumption of fish stocks by birds is on the same order of magnitude as global fishing effort. Once consumed, they respire this POC directly into the atmosphere, potentially lowering seawater dissolved inorganic carbon and pCO₂. However, bird feces released back into the water may add some of this carbon back but at a lower carbon-to-nitrogen ratio. Preliminary simplified calculations of this potential carbon loss from wild fish and aquacultured products is comparable to about ~10-15% of the coastal air-sea flux (0.2-0.4 Pg/yr vs. ~0.3-0.4 Pg/yr).

From Wilson et al. 2009.

Dr. Rod Wilson suggests that fish are a major producer of new calcium carbonate, CaCO₃. Fish calcium carbonate is not skeletal in origin (bone is actually calcium phosphate), but is instead produced in the gut via osmoregulation physiology. They live in a very salty environment but they have a blood osmolarity of ~330 mOsm/kg. Marine teleosts are constantly suffering or tending towards dehydration, and the only thing they can drink is seawater. Seawater ions are high in magnesium and calcium. As these ions are moving through the fish intestine, they are secreting bicarbonate which promotes calcium carbonate production. The calcium carbonate gets wrapped in a mucus coating and then excreted, along with some magnesium precipitates. Conservative estimates of fish CaCO₃ production equal 40-110 million tonnes/year (0.04-0.11 Pg CaCO₃-c/year = 3 to 15% of global CaCO₃ production. Less conservative, but likely more realistic estimates are 3x greater (9-45% of global CaCO₃ production). And in a warmer, higher CO₂ future (+ 4C/1000uatm CO₂), fish CaCO₃ production could be >70% higher. The rate at which calcium carbonate is produced is proportional to feeding rates, whereby the mean production rate of CaCO₃ in feeding fish is 10x higher than starved fish. Additionally, fecal CaCO₃ content can affect the sinking rate of fecal pellets, whereby higher CaCO₃ content leads to faster sinking rates. But once excreted, the fish carbonates dissolve rapidly, which can add alkalinity to seawater and as such may explain the reason why surface ocean alkalinity is higher than would be expected based solely on salinity estimates. Furthermore, DVM mesopelagic fish may drive an “alkalinity pump” through their vertical movements while excreting CaCO₃.

Northern anchovy fecal pellets collected in Santa Barbara Channel sink up to 1370 m d-1 (from Saba & Steinberg 2012).

Dr. Saba described the body of work focused on fecal pellet flux measurements in zooplankton, and that lessons learned here can be applied to fish flux measurements. There has been much work focused on many different types of zooplankton, and the surface zooplankton community composition plays a big role in the types and sizes of pellets produced and how much carbon is entrained in them. For instance, gelatinous salps produce pellets that are larger and sink more rapidly compared to those produced from other zooplankton such as krill and copepods. The quality of pellets also depend on what the zooplankton were feeding on. There has been much less research focused on fish fecal pellet production and carbon flux. However, fish likely are important exporters too (i.e., northern anchovy fecal pellet sinking rates of 458 – 1370 m/d). Fish create very distinctive and well-packed fecal pellets (high in carbon and nitrogen) likely with minimal remineralization as they sink. Approaches used and challenges in measuring fecal pellet flux were also discussed. Sediment traps can directly collect sinking material in a location, but they miss most of the fish flux due to the heterogeneity of fish movements and distributions. Lab and field studies can directly measure pellet production and sinking rates, but likely fail to reflect in situ feeding conditions and may bias rate measurements. Bioenergetic and allometric modeling techniques can be used, but assumptions have to be made to constrain measurements.

Dr. Hernandez-Leon’s presentation focused on the relationship between respiration rates and electron transfer system (ETS) activity in fishes in relation to swimming activity. ETS activity is used as a proxy for respiration and is used for deep sea fish because it is experimentally difficult to measure true respiration in these fishes from laboratory experiments conducted at surface conditions. However, initial laboratory experiments need to be carried out to determine relationships between respiration and swimming speed. From acoustic approaches, the upward and downward velocities of DVM can be determined for a migration time (1-2 hours). And using an example species in the lab with swim flume techniques, the repiratory/ETS ratios can be determined at different swimming speeds.

Approach for comparisons of Fish C Flux to Total and Zooplankton Flux
Presentations by Deborah Steinberg, Santiago Hernández-León, and John Dunne followed by discussion

From Steinberg and Landry 2017.

Dr. Debbie Steinberg presented recent research focused on zooplankton and the biological carbon pump as a basis to start thinking about comparisons with fish. She pointed to a recent review paper that reviews what we know so far regarding zooplankton and their role in the biological pump (Steinberg and Landry 2017). Recent zooplankton research suggests carcasses play an important role in carbon flux, but it is difficult to measure so there are a lot of unknowns. Active transport through vertical migration is also an important mode of bringing excreted DOC, egested POC/PIC, and respired CO2 to depths after feeding at the surface during the nighttime. The magnitude of active transport in DVM zooplankton can also be estimated because we can directly determine biomass (net tows, acoustics, etc.) and then derive carbon flux through respiration measurements (direct, ETS, Allometric/size-based algorithms of metabolism) and POC/PIC flux estimates. With respect to the fecal pellets, community size structure is very important in determining the magnitude. And recent work using long-term data sets suggests that temperature and changing zooplankton distributions and diversity play important roles in regulating carbon flux. As ocean warms, smaller tropical/subtropical species move poleward, increasing diversity. These smaller zooplankton produce pellets that have long residence times in the surface, effectively decreasing the flux of particulate C to the deep. In regions such as BATS, however, there have been observed increases in zooplankton active transport and fecal pellet production as a result of increases in biomass.

In order to make comparisons between zooplankton and fish, we need more information on fish fecal material (classify for taxa, measure production and sinking rates with respect to feeding rates and size, respectively), fish respiration rates, PIC production/dissolution rates. We will also need global carbon export models that can be used to look at relative contributions of fish and zooplankton fluxes.

From Dr. Hernández-León presentation “Zooplankton and Micronekton Active Flux” available on this project’s website (Sourced from Ariza et al. 2015).

Dr. Santiago Hernández-León presented work from recent cruises that compared zooplankton and micronekton active flux. There are currently very few studies (two published) with direct zooplankton and fish comparisons. Their research team employed net tows to measure biomass and abundance and ETS activity for respiration measurement of zooplankton and micronekton in the Atlantic Ocean from coast of Brazil to the Canary Islands and get a gradient from oligotrophic to eutrophic zones (MAFIA cruise). Through these methods, they determined the proportion of respiratory flux to migrant biomass. However, he noted that capture efficiency of micronekton trawls likely underestimated active flux contributions.

Particle export ratio (ratio of sinking particle flux at the base of the euphotic zone to the Net Primary Productivity from Devries and Weber 2017.

Dr. John Dunne presented past and current efforts of modeling primary production to ecosystems and particle export. His work used empirical and mechanistic models to determine particle export ratio (Dunne et al. 2005). He suggested that any of these methods are considered successful if they come out with 50% or less uncertainty particle export. Additionally, Dunne et al. 2007 conducted a synthesis of global particle export from the surface ocean and cycling through the ocean interior and on the seafloor. The particle export estimates converge quite a bit because uncertainty has to do with temperature and microbial activity. An effort by Laws et al. 2011 used simplified equations to estimate ratios and produced better estimates in the tropics. Finally, Devries and Weber 2017 combined data simulation with geochemistry and satellite estimates through an ecosystem model and came up with a cross calibrated representation to account for sinking particle flux and attenuation.

Next Steps:

Planned products resulting from this workshop and ongoing working group efforts include two peer-reviewed manuscripts focused on the synthesis of fish carbon flux research and a quantitative analysis of fish carbon flux.

OCB workshop report: Ocean Carbonate System intercomparison Forum

Posted by mmaheigan

· Monday, August 5th, 2019

The first of two OCB-funded meetings was held in Woods Hole, MA, June 22-23 by a team of researchers working on identifying the largest remaining challenges for internal consistency of the carbonate system in seawater. Discussion primarily focused on disagreements between measured and calculated seawater pH and on proposing efforts aimed at identifying the source of the disagreements. An inter-laboratory comparison experiment is being planned for the beginning of 2020 that will isolate aspects of seawater pH measurement practices, for example by providing a common purified dye for measurements by all groups and a reference material that is more strongly buffered and less strongly temperature sensitive than alternatives. Other major topics of debate included:

the need for standard distributable purified m-Cresol purple dye,
the feasibility of creating reference materials seawater pH,
the importance of routine measurement of non-certified reference materials for pH,
the inter-consistency of the other aspects of the carbonate system (beyond pH),
the need for additional independent discrete pCO₂ measurements,
the need for a refinement to the boron-to-salinity ratio in seawater,
the need for a refinement to the carbonate system equilibrium coefficients,
best practices for inter-cruise comparisons during data product assembly in light of apparent inter-consistency challenges (i.e. recommendations for GLODAPv2),
many aspects of measurement practices that could be leading to observed or potential inter-consistency challenges (e.g. errors in the pressure dependence of carbonate constants)
and ways to make certified reference materials and purified (or well-characterized) dyes more broadly and inexpensively available.

The main conclusions of the OCSIF team should be made available following their 2^nd meeting planned for summer of 2020. Learn more

OCIM Workshop June 23 at OCB 2019

Posted by mmaheigan

· Tuesday, July 23rd, 2019

OCIM Workshop Report
This workshop, held June 23, 2019 at Woods Hole Oceanographic Institution, was attended by 22 researchers from 18 different institutions. This tutorial-based workshop focused on teaching participants to use the Ocean Circulation Inverse Model (OCIM) for biogeochemical modeling. Participants were introduced to the basics of transport matrix calculations using MATLAB, and learned to build simple to moderate-complexity biogeochemical models using OCIM. Topics covered in the workshop included simulations of ventilation age and water-mass tracers; simulations of preformed tracers and analysis of preformed and regenerated nutrient distributions; gas exchange and simple gas tracer simulations; introduction to multi-tracer models using simple models of organic matter production and remineralization; iterative methods vs. direct methods for solving large systems of equations; and using Newton's method to find equilibrium solutions to non-linear models. Participants received sample codes and an OCIM instruction manual for future reference.

Workshop is full! If you are interested in the OCIM but can't attend the workshop please seek Tim out during OCB2019 or contact him by email.

A 1-day workshop will be held in Woods Hole on Sunday, June 23 just before the OCB workshop for those interested in using an ocean circulation inverse model (OCIM) in their research. The OCIM is a data-constrained, lightweight, MATLAB-based ocean circulation model for global modeling of biogeochemical tracers. It has been used to model nutrients, carbon, oxygen, trace metals, and marine food webs, among others. Workshop participants will be provided with model code and instructions, and will engage in tutorial sessions designed to promote familiarity with the model and ability to design and run biogeochemical simulations. Examples of topics that might be covered include: age and water-mass tracers, preformed tracers, diagnostic calculations, transient tracers, air-sea gas exchange, organic matter production and remineralization, isotopes, non-linear models and Newton's method, iterative solvers, and optimization. Requirements: a laptop computer with MATLAB installed and at least 8 GB RAM. Recommended: Working knowledge of MATLAB. Please direct questions to Tim DeVries at tdevries@geog.ucsb.edu.

CMIP6 Workshop Report

Posted by mmaheigan

· Thursday, December 20th, 2018

The US Ocean Carbon and Biogeochemistry (OCB) Program hosted a two-day workshop December 8-9, 2018 in Washington, DC on Ocean Carbon Uptake in CMIP6 Models: Synthesis and Intercomparison. The international Coupled Model Intercomparison Project (CMIP), now in its 6th incarnation, is generating a wealth of new global numerical simulations that will be available as a resource to the oceanographic community. The coupled simulations, integrating ocean-atmosphere-land dynamics, as well as ocean physics and biogeochemistry, span both the historical period (1850-present) and future scenarios out to 2100 and beyond. The goals of this workshop were to discuss:

high-profile CMIP5 Ocean Carbon Uptake analyses, challenges, and the planned suite of CMIP6 experiments;
new observational constraints, including GLODAPv2, SOCAT, SOCCOM, GO-SHIP, community observational synthesis efforts such as Obs4MIPs, ocean carbon inversions, and atmospheric observations of CO2 and oxygen;
updated model formulations and preliminary analysis of simulated regional and global patterns in heat/carbon/tracer uptake in CMIP6 experiments;
mechanisms underlying heat/carbon/tracer uptake differences across models and observations towards linking physical and biogeochemical drivers and their impact; and
tools and techniques that can lower barriers to analysis.

Participants highlighted the availability of several new decadal-scale synthesis products on air-sea CO2 flux and ocean carbon storage and the urgent need within the OCB community for more comprehensive and efficient computational tools to make optimal use of ‘big data’ resources such as the CMIP6 model archive. Additionally, the group emphasized that the timeline of CMIP6 model analysis is extremely tight: Modeling centers are planning to supply their data publicly in March-June 2019, and the manuscript submission deadline for contribution to the sixth assessment of the Intergovernmental Panel on Climate Change is Dec 31, 2019. Workshop participants made several recommendations to facilitate and coordinate community use of the CMIP6 model archive:

standardize tools for the estimation of ocean biomes
explicitly separate river/coastal factors from open-ocean syntheses for air-sea CO2 flux and ocean storage
incorporate pre-1850 carbon cycle changes
improve understanding of ocean carbon cycling under reversibility and sustainability scenarios

A full workshop report and information about community follow-on activities will be available in the next couple of months.

Report from Ocean Carbon Hot Spots Workshop published

Posted by hbenway

· Friday, September 7th, 2018

Western boundary current (WBC) regions display the largest magnitude air-to-sea carbon dioxide (CO2) fluxes of anywhere in the global ocean, exhibit large spring blooms and high eddy activity, and are hubs for the subduction of anthropogenic carbon-laden waters into the ocean interior during mode water formation. Yet the influence of biophysical interactions on air-sea CO2 exchange and carbon export has not been rigorously evaluated in most WBC regions.

The report from the September 2017 Ocean Carbon Hot Spots workshop jointly organized by US CLIVAR and OCB is now available on the OCB website. This report captures highlights from the presentations, discussions, and survey results, as they align with the motivation of the workshop, and provides a set of recommendations to achieve progress on WBC carbon cycle research. Actions to address some of these recommendations are already underway. While this cross-disciplinary activity was an important first step to build momentum, continued community effort will be required to coordinate scientists around this research topic in the future. Thanks to the organizing committee for putting together an excellent, multi-disciplinary meeting and all of the workshop participants for the thoughtful discussions and engagement.

Research and monitoring in the Ross Sea Marine Protected Area

Posted by mmaheigan

· Wednesday, May 24th, 2017

The Council for the Conservation of Antarctic Marine Living Resources (CCAMLR) held a meeting in Rome, Italy from April 26-28, 2017, which was hosted by the Italian Ministry of Foreign Affairs and International Cooperation, and chaired by Dr. George Watters (USA), Mr. Alistair Dunn (NZ), and Dr. Marino Vacchi (IT). Representatives from Argentina, Chile, China, European Union, Germany, Italy, Korea, New Zealand, Norway, Russia, Spain, Ukraine, United Kingdom, and the United States attended. The objective of the meeting was to discuss plans and develop means for research and monitoring of the newly established Ross Sea Marine Protected Area (Fig. 1). US invited scientific experts were Drs. Grant Ballard (Pt. Blue Conservation Science), Jay Rotella (Montana State University) and Walker Smith (VIMS, College of William & Mary).

Figure 1. Areas designated as part of the Ross Sea Marine Protected Area. KRZ is a krill research zone, and SRZ indicates the location of a special research zone. Areas i, ii, and iii are designated as no-take areas intended to protect the continental shelf, the shelf break, and sea mounts that are thought to be important within the life cycle of Antarctic toothfish. Red box within insert shows the location of the MPA region.

The RSMPA is the largest marine protected area in the world, and is often substantially ice-covered throughout much of the year. Despite the harsh habitat, it is home to the Antarctic toothfish (Dissostichus mawsoni; Fig. 2), a species that is currently being commercially exploited (cost at present is ca. 30 USD per kilogram wholesale, placing it as the most expensive fish in the ocean). Due to its value, illegal catch is of great concern; however, due to recent efforts to monitor and prosecute illegal catches, current illegal catch is relatively small (<10% of the legal catch in the Southern Ocean as a whole). Concerns about the impacts of industrial fishing on the health and stability of large areas both within and outside the MPA have arisen, given its substantial seasonal movement, uncertainties about its life cycle and its role within food webs and biogeochemical cycles. Discussions were held on the means by which ecosystem structure and function can be preserved in the face of this fishing pressure, because CCAMLR is tasked with not only monitoring the exploitation of resources, but ensuring that the structure and function of ecosystems in the Southern Ocean are preserved.

Figure 2. Antarctic toothfish and diver (Credit: Rob Robbins, U.S. Antarctic Program). Adult toothfish are neutrally buoyant and are caught from 300 to 2,200 m. Despite its size, toothfish eggs and larvae have never been collected, and its life history is uncertain. Adults can be over 1.3 m in length and weigh over 160 kg (350 lbs.). Toothfish likely spawn off the continental slope north of the Ross Sea, travel within the Ross Gyre, and return to the shelf to feed as juveniles, eventually migrating off shelf again. Toothfish are largely piscivorous and feed on Antarctic silverfish (Pleurogramma antarcticum). Note the many scars in the picture, which likely are the result of encounters with seals, a known predator of toothfish.

Various proposals by different nations were provided, but two – one jointly introduced by Italy and New Zealand, and one introduced by the Antarctic and Southern Ocean Coalition (ASOC) – were discussed in detail, and the delegates spent a good deal of time merging the two and preserving the strengths of both. The ASOC recommendation suggested a) assessments of the representativeness of the protected regions, b) assessments of the extent to which threats to the achievement of the specific MPA objectives are being mitigated by the MPA, and c) provision for research and monitoring to examine marine systems to understand the role of fishing, environmental variability and climate change. It further suggested that research address the ecosystem resilience to the external disturbance and the potential for creating a degraded and alternate steady state for the system. The New Zealand-Italy proposal was based on previous bioregionalization delineations that included various areas of the shelf, slope and open water zones, including benthic and pelagic systems (Sharp et al., 2010; Mormede et al. 2017). Also included in this proposal were guidelines for any future krill fishery that might develop (none exists at present, but CCAMLR is mandated to manage this fishery). A conveners report from the workshop will be disseminated for comment.

Authors:

Walker Smith (VIMS, College of William & Mary) and Mike Williams (NIWA)

References:

Mormede, S.; Dunn, A.; Parker, S.; Hanchet, S. (2017). Using spatial population models to investigatethe potential effects of the Ross Sea region Marine Protected Area on the Antarctic toothfishpopulation Fisheries Research 190: 164-174.

Sharp, B.R.; Parker, S.J.; Pinkerton, M.H. (lead authors); also B.B. Breen, V.Cummings, A. Dunn, S.M. Grant, S.M. Hanchet, H.J.R. Keys, S.J. Lockhart, P.O’B. Lyver, R.L.O’Driscoll, M.J.M. Williams, P.R. Wilson. (2010). Bioregionalisation and spatial ecosystem processes in the Ross Sea Region. CCAMLR WG-EMM-10/30.

A Report from the 2016 OCB Summer Workshop July 25-28, 2016 (Woods Hole, MA)

Posted by mmaheigan

· Wednesday, October 19th, 2016

The 11th annual Ocean Carbon & Biogeochemistry summer workshop, sponsored by NSF and NASA, convened 186 participants from July 25-28, 2016 at the Woods Hole Oceanographic Institution in Woods Hole, MA.

This year’s summer workshop featured the following six plenary sessions:

Plenary 1. EXport Processes in the Ocean from RemoTe Sensing (EXPORTS)
Plenary 2. The biology of carbon export – New processes and approaches
Plenary 3. Recent advances in quantifying ocean carbon uptake
Plenary 4. Quantifying ocean carbon, oxygen, and nutrient cycles
Plenary 5. The Indian Ocean – Monsoon-driven biogeochemical processes
Plenary 6. Marine ecosystem thresholds and regime shifts

Day 1 kicked off with a presentation on the projected instrumentation and scientific capabilities of the NASA Plankton, Aerosol, Cloud, and ocean Ecosystems (PACE) Mission, which segued into the first plenary session on the proposed NASA EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) field campaign. Speakers in this session provided an overview of both the EXPORTS Science Plan and the Implementation Plan. The session also featured three scientific overview talks on the EXPORTS science questions, the first of which highlighted the influence of ecosystem characteristics such as plankton community structure on organic matter export from the euphotic zone. The second talk focused on key processes in the mesopelagic zone that affect vertical transfer of organic matter to depth.

The third talk focused on how data generated by EXPORTS will reduce uncertainties in current and future estimates of export, including an overview of current modeling capabilities for different export pathways. The second plenary session of Day 1 was convened by organizers of a recent NSF workshop and white paper on novel biological processes and pathways regulating organic matter export and degradation. Speakers in this session explored potential contributions of mixotrophs, marine microgels, and episodic events (e.g., jelly falls) to biological pump function, and provided an overview of our current observational capacity to quantify carbon export and monitor changes in the biological pump over a range of temporal and spatial scales. The plenary session closed with a community-sharing presentation describing the Carbon Flux Explorer, an autonomous float that can quantify and photograph particulate carbon fluxes. After the plenary sessions, graduate students provided short presentations about their research interests and then all participants convened for a welcome reception and poster session.

Day 2 opened with agency updates from NSF, NASA, and NOAA representatives. Speakers in plenary session 3 then described data- and model-based approaches for studying internal variability (interannual to decadal) and anthropogenic change in ocean carbon uptake, and explored the role of physical processes (e.g., subduction, mesoscale and submesoscale processes, etc.) in modulating ocean carbon uptake. A presentation on the Coupled Model Intercomparison Project (CMIP) provided an overview of CMIP5 simulations of the ocean carbon cycle and how well these simulations reproduce anthropogenic CO2 uptake and natural variability in ocean CO2 associated with the biological pump. To provide a broader range of spatial and temporal perspectives, the session included talks on land-ocean exchanges of dissolved carbon across coastal, estuarine, wetland, and riverine systems and differences in ocean carbon storage during the last ice age, as constrained by paleo-proxies of ocean ventilation and deep-sea oxygen concentrations. This session concluded with a community-sharing presentation on Carbon Hot Spot, a nascent process study to characterize biophysical interactions and quantify ocean carbon uptake in Western Boundary Current regions such as the Kuroshio Extension.

During the afternoon of day 2, speakers in plenary session 4 provided an overview of the Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) project and newly emerging seasonally resolved ocean carbon data sets from biogeochemical sensor-equipped Argo floats, which are providing unprecedented constraints on wintertime air-sea CO2 dynamics in the Southern Ocean. The session concluded with a presentation on the rationale and plan for a global biogeochemical observing network based on Argo floats equipped with biogeochemical sensors to more effectively monitor changing ocean conditions. Immediately following the plenary session, communication professionals from COMPASS led interactive communication training workshops to help participants share their science across a broad range of audiences using various tools, outlets, and communication strategies. Participants reconvened in the evening hours for the inaugural OCB ocean festival, featuring recent documentaries on the Palmer LTER in Antarctica and the CARIACO time-series.

After a morning poster session on day 3, participants enjoyed a presentation and Q&A session on the 2015 UN Climate Conference in Paris. Then speakers in plenary session 5 delivered a series of talks on the complex physical oceanographic and climatic drivers that influence biogeochemistry and biological processes in the Indian Ocean, where scientists are amidst planning for the second International Indian Ocean Expedition (IIOE2). The session opened with an overview presentation on key physical oceanographic features and observing resources in the Indian Ocean. Speakers then addressed links between physics, climate, and biogeochemical processes such as dissolved organic carbon (DOC) distribution and dynamics, iron limitation, trace metal cycling and measurements from GEOTRACES, nitrogen fixation, and oxygen deficiency in different parts of the basin and associated effects on biology. The final presentation of the session focused on seasonally variable Indian Ocean boundary currents and their impacts on local ecology and biogeochemistry. Day 3 wrapped up with a presentation by the new US SOLAS (Surface Ocean Lower Atmosphere Study) representative to initiate discussion and brainstorm ideas to facilitate scientific exchanges and new collaborations on topical areas of interest to both OCB and SOLAS.
The final day of the workshop opened with a presentation on the proposed NASA field campaign Arctic-COLORS. The Arctic-COLORS science plan is undergoing revisions, so authors were seeking input from the OCB community. The final plenary session of the workshop, plenary 6, featured a series of talks on marine ecosystem thresholds and regime shifts. In this session, speakers explored phytoplankton response to natural climate variability and anthropogenic climate change (phenology, biogeography, community composition, etc.), implications of climate-driven changes in bloom phenology for higher trophic levels, ecological changes and associated shifts in benthic communities of the Pacific Arctic, and the development of tools such as early warning systems to identify and predict nonlinear shifts in ocean ecosystems. A separate 1.5-day meeting on Arctic-COLORS immediately following the OCB workshop provided an opportunity for more in-depth discussions and opportunities to gather feedback.

For more information, including links to plenary talks and webcast footage, please visit the workshop archive page or contact Heather Benway.

Biogeochemical Cycling of Trace Elements Within the Ocean: A Synthesis Workshop

Posted by mmaheigan

· Sunday, September 18th, 2016

Over 100 scientists from 12 nations met at the Lamont-Doherty Earth Observatory in Palisades New York, USA, on 1 – 4 August 2016 for a synthesis workshop on the Biogeochemical Cycling of Trace Elements within the Ocean. The workshop focused on setting priorities for utilizing GEOTRACES trace element and isotope (TEI) data sets to advance scientific objectives at the interface of marine biogeochemistry and ecology, and was jointly sponsored by the GEOTRACES and OCB Programs.

Workshop activities were organized around three scientific themes:
1. Biological uptake and trace element bioavailability,
2. Abiotic cycling and scavenging, including particulate and dissolved speciation, and
3. Export, recycling and regeneration

Following a series of plenary talks designed to stimulate discussion on these topics, participants spent the remainder of the workshop in smaller group discussions to identify knowledge gaps and develop ideas for synthesis activities and products that combine GEOTRACES TEI data with other biogeochemical and biological data sets.

Tentative activities and products include:
• estimating bioavailability of iron (Fe)
• testing hypothesis for Fe and light co-limitation in the deep chlorophyll maxima;
• exploring Redfieldian concepts using GEOTRACES data and ocean models;
• calculating community trace metal demand vs. supply;
• developing a synthesis paper on existing methods and current state of knowledge on ligand composition and cycling;
• comparing radionuclide-based tracer methods for estimating downward flux of carbon, nutrients and trace metals;
• combining TEI distributions with AOU and preformed TEI concentrations to differentiate biotic (e.g., respiration) and abiotic (e.g., scavenging, physical transport) removal processes;
• estimating elemental scavenging using partition coefficients (Kd);
• combining particulate TEI and beam transmission data to develop algorithms for particle distributions that affect TEI scavenging; and
• developing synthesis paper on TEIs in nepheloid layers.

To learn more about and/or contribute to these activities, please contact Heather Benway (OCB) or Bob Anderson (LDEO). For more information, visit the workshop website or view the plenary presentations.

Marine and Human Systems: Addressing Multiple Scales and Multiple Stressors

Posted by mmaheigan

· Sunday, April 3rd, 2016

Eileen Hofmann (Old Dominion University, Norfolk, VA, USA)
Lisa Maddison (IMBER IPO, Institute of Marine Research, Bergen, Norway)
Ingrid van Putten (CSIRO, Hobart, Tasmania, Australia)
Javier Arístegui (Universidad de Las Palmas de Gran Canaria, Islas Canarias, Spain)

The Integrated Marine Biogeochemistry and Ecosystem Research Project (IMBER) is developed around four research themes, which include: Key interactions in marine ecosystems; sensitivity to global change; feedbacks to the Earth system; and responses of society. When IMBER was initiated in 2005, the responses of society theme represented a new direction for global environmental change programs because it explicitly acknowledged the role of humans as both drivers and recipients of change in marine ecosystems. IMBER project-wide activities, regional programs and working groups have advanced the science associated with each research theme. However, the strength of these activities has been in the identification of theoretical and methodological overlap among the themes, facilitating integration of ideas and synthesis of research outcomes, and highlighting new research directions.

The biennial IMBIZO (Zulu word for a gathering) is an important IMBER-wide activity for assessing current understanding of theoretical and empirical research at the local, regional and global scale, and pointing to future research needs. IMBIZO IV, held in October 2015 in Trieste, Italy, addressed linkages between marine ecosystems and human systems (Fig. 1). In particular, emphasis was on current systems understanding and approaches to predict the effects of multiple stressors, at multiple scales, on marine ecosystems and dependent human populations. A novel aspect of this IMBIZO was the focus on exposing the need for human systems to respond to changes and for governance systems to adequately guide these responses.

IMBIZO IV was developed around four workshops (Fig. 1) that addressed i) marine ecosystem-based governance, ii) upwelling systems as models for interdisciplinary global change studies, iii) integrated modeling to support marine socio-ecological systems under global change, and iv) regime shifts and their socio-ecological implications. Although each workshop had distinct objectives, all addressed aspects of climate, ecosystems and societies with a view towards integrating and synthesizing current understanding and highlighting approaches for developing innovative societal responses to changing marine ecosystems. The workshops were supplemented with plenary presentations that provided overviews of the state of understanding and research needs and joint sessions and debates that allowed cross-workshop interactions (Fig. 2).

Within the context of each workshop, questions were addressed that considered the challenges of multiple stressors, pressures, and drivers, existing knowledge gaps, and the type of expertise needed to move forward. Some workshops also evaluated the need for paradigm shifts to adequately address particular research questions. The overall goal of each workshop was to determine how integration of the diverse array of knowledge and different research outcomes for marine systems could be done to provide useful advice for policy and management.

The results of the individual workshops are being summarized in a variety of ways including white papers, synthesis papers, short communications, and special issues. However, the workshop results have common components with perhaps the clearest message being the need for continued conversations and exchange of information between scientists from different disciplinary backgrounds. To enable this dialogue to take place collaboratively and ultimately to develop workable solutions will mean that a common understanding of language will need to be developed and that jargon be avoided. Facilitating cross-disciplinary communication by domain experts will also help crucially important communication to management authorities and decision makers.

Aside from the need for good communication between scientists that straddle the physical, ecological and human domains, the different workshops considered the linkages and interactions between the driving forces (pressures-state-impacts-responses, DPSIR) and how these are understood and represented. For most marine systems, the system state, how much of what is present and where, can be described with differing degrees of certainty depending on location and factors such as monitoring intensity and accessibility. The connectivity and linkages between marine system components and driving forces are known from a theoretical perspective and for many systems these have been described quantitatively using different modeling approaches. However, there is considerable empirical uncertainty about how marine systems might respond to continued and cumulative anthropogenic stresses and how in turn, this may feed back to the human domain and affect, for instance, future food security.

Marine systems may not be generalizable, sometimes cannot be simply scaled up, or may not respond linearly to anthropogenic stressors. Regime shifts may occur that are not easily (or not at all) reversible, thus requiring adaptation by resource users. The governance system is crucially important in this context as it provides links to management, policy and regulatory systems that influence use of and access to marine resources. Governance institutions are ultimately responsible for the sustainable management of marine resources and any necessary reduction in the pressure exerted on the resources. These governance systems in essence close the loop between the natural and human systems. Natural, socio-economic, and governance systems need to be central to continued research efforts and inform all levels of decision making to ensure informed steps are taken.

Global environmental change is happening and will continue to affect ecosystems and alter the ecosystem services provided to humanity. The need for timely detection and attribution of these changes remains, especially where change is irreversible. Human systems and society at large are both creators of the many stressors that drive change in marine ecosystems as well as recipients of these changes. Human systems can drive positive changes through good governance aimed at reducing vulnerability, and enhancing adaptive capacity and resilience. It is clear that many knowledge gaps remain, in particular the way in which multiple drivers and stressors interact. Much work also remains to be done in further detailing and modeling the crucial dependencies between human and ocean systems. All of these uncertainties place limitations on the predictability of governance outcomes and risk unintended consequences and maladaptation if not addressed adequately. Outcomes from IMBIZO IV will provide guidance for these important research efforts for the next decade of IMBER research.

IMBER gratefully acknowledges the support provided by the OCB Program for IMBIZO IV and its ongoing support of IMBER activities.

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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