Blue Carbon Initiative: mitigating climate change in the oceans

Listened to this webinar, “Blue Carbon Ecosystems – what’s included, what’s not and why,” by Jenna Howard and Ariana Sutton-Grier about the Blue Carbon Initiative and climate change mitigation to understand how terrestrial carbon sequestration rates compare with those in marine ecosystems.  This talk focused mostly on coastal marine habitats with the best potential — mostly in-air plants (mangroves, marshes) and also seagrass beds.  Here is a video recording

and some of my notes/screengrabs:


Their paper has a more detailed table with equations, sources, etc.

Their paper has a more detailed table with equations, sources, etc.

link to paper — Clarifying the role of coastal and marine systems in climate mitigation

For comparison, humans activities put about 7000 million Mg C yr^-1 into the atmosphere.

Or 7 Gt/yr.

Mitigation potential (and feasibility)

Mitigation potential (and feasibility)

Mangroves and marshes

Range of uptake rates

  • vegetative carbon: 8-126 tons/ha
  • soil carbon: 250-280 tons/ha
  • ratio shows that 2-30 time more carbon is in soil than in vegetation
  • sequestration rate: 2.1-2.6 tons/ha/yr

Global loss of these habitats is ~1.5-2%, so half of habitat gone in 35-50 years


Long-term effect of calcification in coral reefs: a slight net source of CO2, but could reverse if ocean acidification increases dramatically

Dissolution process takes CO2 out of water column.

Take home message: no red arrow, meaning coral isn’t a climate change mitigation option


Most kelp gets consumed or degrades in days, months, or at most a couple years

So, it’s a temporary carbon pool, not a long term storage option


Only 0.1% sinks to ocean floor for long-term storage, but the area is HUGE compared to the geographic extent of the coastal ecosystems.

BUT, it’s not in the running due to policy issues that have been (and are) challenging…

  • who manages, owns carbon sequestered, etc.
  • ethics of seeding with bioengineered cultures (didn’t even mention fertilization)

Screengrab from webinar

Screengrab from webinar

Marine fauna

Calcifiers (e.g. pteropods), krill, teleost fish (feces contain CaCO3 but doesn’t sequester, only affects alkalinity gradient)





My related notes from beyond the webinar:

What is sequestration rate for terrestrial ecosystems (temperate vs tropical forests)?

The Blue Carbon Initiative web site says of marine/coastal ecosystems:

“These ecosystems store up to 10 times more carbon — called “blue carbon” — per hectare than terrestrial forests, and degradation of these ecosystems accounts for up to 19% of carbon emissions from global deforestation.”

Why not great (baleen+sperm) whales as long-term sequestration?  Estimate potential using listed species population assessments and historical baselines?

If we protect and enhance their habitat to maximize their growth rate, how many new whales could be added to the global marine ecosystem each year?

Back of the envelope:

Let’s say blue whales are ~100,000 individuals below carrying capacity (it’s likely closer to 200,000) and each adult whale constitutes a sink of ~100 Mg of carbon (assuming they’re mostly lipid-rich blubber = hydrocarbons).  If the extant population (currently <10,000 whales growing at 8%/yr) manages to add 1,000 new blue whales per year, that would sequester 100,000 Mg/yr.  Maybe multiply that by 10 for other baleen whale species (blue, fin, right, humpback, sei, grey, bowhead, Bryde, minke, Omura/Eden, sperm) of similar mass that are similarly below carrying capacity and we’re at 1 million Mg/yr.  That estimate might be high or low by a factor of ~10 given the uncertainties.  Either way, 1 million Mg C yr^-1 is within the range of interesting numbers listed in the table…

Assuming recovery of the globe’s baleen whale populations takes 100 years, we could expect over that time period an increase in the amount of carbon stored in living whales of about 100 million Mg C.  That’s comparable to the biomass of all phytoplankton (0.5-2.4 billion Mg C, according to their paper and it’s citations).  Then there’s the flux (from dead adult whales) into the deep sea, where it would be sequestered for order 100 years…

It looks like famous folks have already pondered most of this:




Email announcement:​​

Blue Carbon Ecosystems – what’s included, what’s not and why



Wednesday, February 8, 2017, 2pm – 3pm EST

REGISTER online at


Webinar Summary:

With increasing recognition of the role natural systems have in climate mitigation, where should management initiatives focus? While forest have historically had the spotlight of such efforts, coastal wetland ecosystems are now considered important and effective long-term carbon sinks. This attention to “blue carbon” habitats has sparked interest in including other marine systems, such as coral reefs, phytoplankton, kelp forests, and marine fauna.

In this webinar, authors of a recently published paper – Clarifying the role of coastal and marine systems in climate mitigation (Frontiers in Ecology and the Environment, Feb. 2017) – analyze the scientific evidence and potential management role of several coastal and marine ecosystems to determine which should be prioritized within current climate mitigation strategies and policies. Findings can assist decision-makers and conservation practitioners to understand where management actions can have additional carbon benefits.



Dr. Jennifer Howard and Dr. Ariana Sutton-Grier

Dr. Jennifer Howard is the Marine Climate Change Director at Conservation International. Prior to accepting her current position, she was a AAAS Science and Technology Policy Fellow where she served two years at the National Oceanic and Atmospheric Administration’s (NOAA) National Marine Fisheries Service. While at NOAA, Jennifer co-led and coordinated the development of the Ocean and Marine Resources in a Changing Climate Technical Input Report to the National Climate Assessment and coordinated the Interagency Working Group for Ocean Acidification.


Dr. Ariana Sutton-Grier is an ecosystem ecologist with expertise in wetland ecology and restoration, biodiversity, biogeochemistry, climate change, and ecosystem services. Dr. Sutton-Grier is a research faculty member at the University of Maryland in the Earth System Science Interdisciplinary Center and is also the Ecosystem Science Adviser for the National Ocean Service at NOAA.  She holds Honors Bachelor degrees from Oregon State University in Environmental Science and International Studies and a doctoral degree from Duke University in Ecology.


Moderator: Stefanie Simpson, Blue Carbon Program Manager, Restore America’s Estuaries (and paper co-author)


This free webinar is hosted by Restore America’s Estuaries.