Consideration of Critical Research Priorities

A benefit of each deployment is the opportunity to contribute to advancing the scientific community’s collective understanding of the ocean. Several areas of research that will inform and reduce uncertainty around net carbon removed include:

Deep ocean benthic experiments

Deep-sea benthic research to quantify the ecological and geochemical impacts and rates of degradation of carbon buoys and macroalgae biomass in the deep sea, as well as to quantify potential associated changes in the structure and function of benthic communities, including macroinvertebrates, vertebrates, and microorganisms.

Prior and ongoing research:

• Replicated observational experiments of biomass degradation in coastal and shallow waters. Coastal experiments are similar in design and method to a program of deep-sea benthic experimentation, but afford a higher frequency and quantity of direct water and sediment sampling in addition to method testing. An initial benthic pilot was conducted in Casco Bay, Maine in 2022.

• Running Tide has planned and is preparing to deploy a shallow water fixed site experiment in Q2 2023 on the Icelandic shelf to observe carbon buoys during their degradation life cycle on the seafloor and their impact on species abundance and diversity, as well as to monitor for changes in sediment carbon concentrations. Due to the ease of accessing the shallow water location when compared to the deep ocean, a more intensive monitoring plan will be used to sample water on a weekly/bi-weekly basis, and sediment and substrate on a monthly basis. In-situ image capture and microscopy of samples will be used to identify larger organisms and eDNA will be used to identify microorganisms. Experts at the Southwest Iceland Nature Research Center will perform visual identification, while NatureMetrics will be used for eDNA analysis. In addition, continuous data loggers for temperature, pH, salinity, and dissolved oxygen will measure these environmental conditions.

Planned near-term research:

• Replicated deep-sea benthic experiments on the abyssal plain.

• Running Tide is currently finalizing a research partnership with Ocean Networks Canada (ONC), a non-profit ocean research organization affiliated with the University of Victoria. In this proposed program of experimentation, ONC will place treatments of carbon buoy materials at their established deep-sea observation stations in the Cascadia Basin off the west coast of Canada. ONC will then conduct one-year benthic monitoring of these treatments. The evolution of the carbon buoys will be observed with cameras and environmental sensors (salinity, temperature, and dissolved oxygen) throughout the duration of the experiment. Water samples and sediment cores will also be obtained throughout the experiment by remotely operated vehicles and/or submersibles to allow observation of carbon flux into the sediment, as well as eDNA characterization of changes to the microbial community composition in response to the presence of carbon buoys.

• Running Tide is also engaged in the planning of a sinking seaweed and carbon buoy experiment with researchers at the Alfred Wegener Institute Helmholtz Center for Polar and Marine Research (AWI). The proposed program of research will include observational experiments in the deep sea (4,000m) of the Fram Strait area of the Arctic Ocean. The goal of this work is to understand how different seaweed species (kelp, Sargassum, and Ulva) degrade at 4,000m depth and to replicate Running Tide’s observation of carbon buoy degradation in the deep sea, in a different marine biome.

Ecological investigations

A program of research to study the exposure to ecological risk associated with proposed carbon removal methods. Sinking terrestrial biomass, and eventually macroalgae biomass, will introduce organic matter into pelagic ecosystems and enhance the flux of organic matter to benthic ecosystems (overlapping with the above research area).

Prior and ongoing research:

• Participation in a year-long Ocean Visions working group to support the production of a research framework to guide the investigation of the efficacy and impacts of sinking marine biomass into the deep sea for carbon sequestration.

• Funding of research at the Stubbins Lab at Northeastern University to study the bio-lability of dissolved and particulate organic carbon generated by macroalgae. The outcome of this research will inform questions posed by the Ocean Visions working group considering the degradation rate of macroalgae tissue in the benthos and algal-derived dissolved organic carbon in the water column.

• RADI Modeling: Running Tide has advised researchers at Utrecht University as they perform biogeochemical modeling of the impact of sinking organic carbon into the deep ocean. This research explores the consequences of enhanced organic carbon delivery to the seafloor on oxygen, dissolved carbon, and alkalinity cycling in the deep ocean.

Planned near-term research:

• Fixed site experiments focused on the growing and sinking of macroalgae biomass, studying the metabolic interactions between macroalgae and the pelagic ecology for eventual incorporation into open ocean deployment.

• Running Tide is engaged in conversation with a leading European oceanographic institute to perform in-situ observations of our open ocean deployments and assess their impact on the local carbon cycle and ecological dynamics.

Modeling and computational experiments

Research to develop capabilities to perform predictive physical and biogeochemical modeling of carbon removal system behavior.

Prior and ongoing research:

• Running Tide worked closely with the Ocean Dynamics research group within the Atmosphere and Ocean Dynamics Group at Cambridge University in their work to run a sugar kelp growth model for macroalgae growth at densely distributed locations across the North Atlantic. This modeling work bounded the carrying capacity of ocean afforestation with sugar kelp as a carbon removal tool.

• Running Tide has adapted the OceanParcels framework for lagrangian advection modeling to create a predictive model for the ocean transport of its system across various ocean basins. The analysis has integrated HYCOM global ocean circulation data with ECMWF reanalysis data for Stoke’s drift. In addition, CMEMS ocean state forecasts were integrated for predictions of deployments. Running Tide continues to explore the application of numerical techniques such as the addition of stochastic noise and refining the contribution of different velocity components in improving the correlation between model predictions and in situ trajectory data.

• Running Tide has begun to adapt the ECCO-Darwin ocean biogeochemistry model to 1) demonstrate the impact and scalability of future carbon removal systems on the coupled Earth system and 2) optimize the efficiency of carbon removal interventions. This includes studying the impact of surface-ocean carbon uptake or alkalinity addition on the air-sea gas exchange of carbon dioxide within the fast carbon cycle, the vertical transport of dissolved inorganic and organic carbon from the sunlit upper-ocean to the seafloor, and the potential nutrient and trace metal competition between proposed macroalgae afforestation projects and the endemic phytoplankton ecology. In addition, open-source biogeochemical datasets have been incorporated into the advection model platform to pair observational and operational model data to material trajectories including data from CMEMS and Aqua/MODIS.

• Running Tide has begun to build software tools to understand and analyze CMIP6 model output data and connect the CESM climate model with a macroalgae growth model for the purpose of understanding the carrying capacity of the ocean for marine carbon removal using macroalgae open-ocean cultivation and sinking.

Planned near-term research:

• Computational experiments within the framework of accepted biogeochemical models of the Earth system.

• Running Tide has engaged in a collaboration with scientists from the ECCO-Darwin project at NASA’s Jet Propulsion Laboratory and Moss Landing Marine Laboratories (San José State University) with the goal of building robust ocean carbon removal modeling packages into this existing data-constrained ocean biogeochemistry modeling tool, as well as designing a suite of easy-to-use analysis tools for end users.

Macroalgae genetics, cultivation, and quantification research

Research to advance foundational work on macroalgae genomics and life cycle in support of the eventual quantification and enhancement of macroalgae biomass cultivated offshore.

Prior and ongoing research:

• Foundational genetics work around the isolation, cultivation, and banking of various developmental stages of macroalgae species in collaboration with Los Alamos National Laboratory, leading to the expected first published long-read genomes for Ulva lactuca and Saccharina latissima.

• Breeding program for the enhancement of survivability and growth of Ulva lactuca in low-nutrient, high wave energy open ocean environments.

• Ecological risk mitigation exploration to understand the natural variation between populations of sugar kelp and Ulva lactuca when separated by geographic distance — i.e., how macroalgae populations differ between the U.S., Iceland, and other coastal countries, providing insight into how distinct macroalgae species move and mix naturally (both genetically and biologically). This research contributes to risk mitigation in that it enables the use of native material in a given deployment area to ensure invasive species or populations are not introduced.

• Abiotic stress testing to determine how Ulva lactuca grows in response to different biogeochemical and abiotic factors (nutrient levels, pH, temperature, light levels, and more), and additional stress testing to better understand how macroalgae survive out of the water (e.g., on ships during transport to deployment zones).

• Ongoing image-analysis of underwater macroalgae growth attached to substrates of interest to inform growth modeling around macroalgae biomass accumulation and carbon content.

Planned near-term research:

• Exploration into the relationship between macroalgae genotype and phenotype — i.e., developing a deeper understanding of what genes or genetic regions contribute to, or drive growth of, phenotypes of interest.

• Abiotic stress testing results that feed into pilot biological modeling that better predicts macroalgae growth in the open ocean based on input biogeochemical and abiotic factors across deployment trajectories.

This list is illustrative and not exhaustive and will be continuously refined based on the best available science and industry need. Additional information regarding ongoing high-priority research questions and recent research conducted can be found in Running Tide’s Ocean Carbon Removal Research Roadmap.