What are marine biogeoengineering solutions to excess CO2?
Biological transformations of carbon (primary production and respiration)
“Blue Carbon” reservoirs (tidal marshes, mangroves, seagrass meadows)
Peatlands
mCDR (ocean fertilization)
What does biogeoengineering aim to do?
Intentionally accelerate natural processes in order to speed up the rate and extent of CO2 sequestration
What are broad sectors of mCDR?
Blue Carbon
Intensive macrophyte culture
Fertilization of open ocean
Blue Carbon
Protection and restoration of coastal carbon storage organic matter (mangrove forests, seagrass beds, marshes)
Intensive Macrophyte Culture
Deep ocean disposal of biomass (kelp/seaweed)
Open Ocean Fertilization
Export algae to deep layers via Biological Carbon Pump
What are the direct and positive impacts of OAE relative to CO2 in the ocean?
CO2 gets converted into bicarbonate, which helps buffer against OA
Suck more CO2 from the atmosphere
What is electrochemical CO2 scrubbing?
Use electricity to change water chemistry
CO2 bubbles out and gets captured and stored beneath the seabed
Processed water returned to the ocean, where it can absorb more CO2
What would mCDR need to do to enhance photosynthesis and stop respiration to prevent the seasonal sawtooth pattern?
Respiration must either:
Fully stop (bury organic matter in Blue Carbon anoxic soil environments)
Be removed to deep ocean through biological carbon pump
What is carbon sequestration?
Carbon sequestration is the process of removing CO2 from the atmosphere and depositing it in a reservoir –> A rate per unit time; how fast it is being buried
What is carbon storage?
The quantity of carbon stored in a reservoir –> Amount of carbon stored per unit area
What is a mega-gram?
Mg = 10^6 g = 1 ton carbon
Why are sediments carbon rich?
High rate of organic matter input to sediments
Rapid burial
Anoxic conditions
What are salt marshes?
Coastal wetlands flooded and drained by saltwater brought in through tides
What occurs in salt marshes?
Dense vegetation deposits allochthonous material to the sediments, including organic matter, on flood tides
How do salt marshes accrete soil?
By accumulating biomass and sediments faster than sea level rises
Autochthonous
Produced within/native to the system
Allochthonous
Introduced from outside the system; not native
Where is root production highest in a salt marsh?
At the surface because roots grow at the top of sediments rather than down into them
In salt marshes, what happens to roots as they deepen?
They become organic matter
Mangroves
Carbon-rich soils
Vital nursery habitat
Critical ecosystems for birds, fish, etc.
Seagrasses
Fish nursery, high biodiversity, critical food source
Peatlands
Organic matter laid down, flooded, all anoxic
How much carbon do peatlands store?
Globally, store twice as much carbon as all of the world’s forests
