Via Deep-Ocean Carbon Sequestration Using Mineral-Enhanced Microbial Communities

The Geological Context of Oceanic Carbon Storage

For over 3 billion years, Earth's oceans have served as the planet's primary carbon sink, with marine sediments currently holding an estimated 37,000 gigatons of carbon - nearly 100 times more than all terrestrial and atmospheric reservoirs combined. The natural process of pelagic sedimentation buries approximately 0.1 gigatons of carbon annually through biological pump mechanisms.

Engineered Microbial-Mineral Symbiosis

Core Principles

The via approach (Vertical Integration via Autotrophs) combines three synergistic mechanisms:

• Biomineralization enhancement: Genetic modifications to accelerate extracellular carbonate precipitation
• Electron shuttle optimization: Engineered quinone pathways for improved mineral redox coupling
• Sediment stabilization: Microbial exopolymer production tailored for clay particle binding

Microbial Strains Under Development

Current research focuses on modifying these deep-sea native species:

• Thiomicrospira crunogena (deep-sea vent chemolithoautotroph)
• Shewanella piezotolerans (pressure-adapted iron reducer)
• Pseudomonas bathycetes (barophilic carbonate producer)

Mineral Interaction Mechanisms

Carbonate Precipitation Pathways

The engineered microbes employ four parallel mineralization strategies:

1. Carbonic anhydrase overexpression: Increases local CO₂ hydration rate by 300-500%
2. Alkalinity pumps: Modified proton transporters create pH gradients up to 1.5 units
3. Magnesium sequestration: Expressed metallochaperones prevent inhibitory Mg²⁺ interference
4. Template nucleation: Genetically programmed amyloid fibrils provide structured growth surfaces

Clay-Microbe Interactions

Laboratory mesocosm studies demonstrate that smectite-group clays enhance microbial carbon retention by:

• Providing Fe³⁺/Mn⁴⁺ as terminal electron acceptors
• Stabilizing extracellular enzymes through surface adsorption
• Creating microenvironments with sustained redox gradients

Sequestration Performance Metrics

Parameter	Natural System	Engineered System
Carbonate precipitation rate (mmol/m2/day)	0.02-0.05	1.8-2.4 (lab), 0.3-0.6 (field trials)
Sediment carbon retention (%) after 1 year	12-18%	63-67%
Burial efficiency (fraction reaching 10cm depth)	0.07-0.11	0.39-0.42

Deep-Ocean Deployment Strategies

Depth Optimization

The carbonate compensation depth (CCD) creates critical depth zones for deployment:

• Shallow deployment (1000-2500m): Higher microbial activity but greater dissolution risk
• CCD transition (3500-4500m): Optimal balance between preservation and biomineralization rates
• Abyssal deployment (>5000m): Maximum preservation but reduced microbial metabolic rates

Delivery Systems

Three prototype delivery mechanisms are under testing:

1. Mineral-microbe aggregates: 50-200μm clay-bacteria composites with buoyancy control
2. Vertical migration plumes: Diel cycle-adjusting density columns
3. Benthic biofilm mats: Electrically conductive networks for sustained metabolism

The Historical Precedent of Natural Analogues

The Paleocene-Eocene Thermal Maximum (PETM, 56 million years ago) provides key insights into natural microbial responses to rapid carbon influx:

• Coccolithophore blooms: Deposited 5-10cm carbon-rich layers globally
• Benthic foraminifera turnover: Demonstrated adaptation timescales of 200-500 years
• Clay mineral signatures: Show persistent smectite-illite transformations under high pCO₂

Technical Challenges and Limitations

Metabolic Constraints

The Arrhenius temperature dependence creates fundamental limits at depth:

• Q₁₀ = 2.3 for most deep-sea microbial processes
• 4°C abyssal temperatures reduce metabolic rates 12-18x compared to surface waters
• Pressure effects on enzyme kinetics follow exponential decay above 300 bar

Ecological Impacts

Tiered risk assessment identifies three primary concerns:

1. Redox gradient disruption: Potential to alter sedimentary oxygen penetration depths
2. Trophic transfer: Bioaccumulation risk of engineered exoproducts in benthic food webs
3. Barite dissolution:

The Future of Engineered Biogeochemical Cycles

The next generation of via systems incorporates three evolutionary improvements:

• Cryoprotective exopolymers: For enhanced survivability during surface-to-depth transit
• Quantum dot biosensors:
• Syntrophic consortia engineering:

The Path to Gigaton Scale

Theoretical modeling suggests deployment requirements for meaningful impact:

Scenario	Annual Carbon Sequestration (Gt)
	Theoretical Maximum	Practical Estimate*
Global CCD coverage (10% saturation)	1.8-2.4	0.4-0.6
High-productivity zone focus (5% area)	0.9-1.2	0.2-0.3

The Regulatory Landscape

The London Convention/London Protocol currently classifies via systems under:

• Annex 4, Category L4:
• Special Permit Requirement LC-SP/2023:

The Monitoring Imperative

A 12-parameter verification protocol has been proposed:

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