Seagrasses and mangroves can suck carbon from the air

The Economist

They do an even better job than forests on land. Read the piece from The Economist.

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Seaweed farms provide refugia from ocean acidification

Xiao, X. et. al.

Seaweed farming has been proposed as a strategy for adaptation to ocean acidification, but evidence is largely lacking. Changes of pH and carbon system parameters in surface waters of three seaweed farms along a latitudinal range in China were compared, on the weeks preceding harvesting, with those of the surrounding seawaters. Results confirmed that seaweed farming is efficient in buffering acidification, with Saccharina japonica showing the highest capacity of 0.10 pH increase within the aquaculture area, followed by Gracilariopsis lemaneiformis (ΔpH = 0.04) and Porphyra haitanensis (ΔpH = 0.03). The ranges of pH variability within seaweed farms spanned 0.14–0.30 unit during the monitoring, showing intense fluctuations which may also help marine organisms adapt to...

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Australia marine hotspots found to store 2 billion tonnes of 'blue carbon'

Maeve Campbell

Three World Heritage-listed marine sites in Australia store billions of tonnes of carbon dioxide, reports UNESCO. The UN organisation has released its first global scientific assessment of ‘blue carbon’ ecosystems, which double as World Heritage sites. The research shows that preserving these environmental habitats could be “crucial” to fighting climate change due to the amount of carbon stored there. The three sites mentioned are the Great Barrier Reef in Queensland, Shark Bay and the Ningaloo Coast in Western Australia. Although the sites make up less than 1 per cent of the planet’s oceans, they house 15 per cent of blue carbon assets in their...

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Custodians of the globe's blue carbon assets (UNESCO)

Carlos Duarte et al

The 50 marine sites on UNESCO's World Heritage List comprise at least 21% of the global area of blue carbon ecosystems and 15% of global blue carbon assets - carbon stores that are equivalent to about 10% of global greenhouse gas emissions in 2018.  Their protection plays a central role in storing carbon from the atmosphere. But degradation of these ecosystems can also release billions of tons of greenhouse gases.  Read the report from UNESCO here.

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WWF Seaweed Farm Investment

Sophie Yeo

The Faroe Islands see little daylight during the winter; on the solstice, the sun peeks over the horizon for around five hours. During these dark months, beneath the surface of the ocean, a sunken forest prepares to burst into life. Supported by buoys, ropes of seaweed seedlings absorb the North Atlantic’s nutrients and wait for the spring. When spring arrives, photosynthesis begins. Light is transformed into biomass, and suddenly the seaweed is everywhere. Huge sheets of it snake up the ropes that dangle down through the uppermost 30 feet of the ocean—just below the waves that roll across the surface....

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The Case for Seaweed

Megan Reilly Cayten

In the two years since Alexandra inspired my interest in seaweed, I have found that the more you learn about seaweed, the more excited you get about its potential to be restorative to the oceans, the climate, the planet, and all of us who live on it. I hope you will feel the same at the end of this brief piece on the potential of seaweed to address the climate crisis and the ocean crisis, which are inextricably linked. Read the blog post here.

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Seaweed aquaculture: cultivation technologies, challenges and its ecosystem services

Jang, K. et. al.

Seaweed aquaculture technologies have developed dramatically over the past 70 years mostly in Asia and more recently in Americas and Europe. However, there are still many challenges to overcome with respect to the science and to social acceptability.

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Sequestration of macroalgal carbon: the elephant in the Blue Carbon room

Krause-Jensen, D. et. al.

Macroalgae form the most extensive and productive benthic marine vegetated habitats globally but their inclusion in Blue Carbon (BC) strategies remains controversial. We review the arguments offered to reject or include macroalgae in the BC framework, and identify the challenges that have precluded macroalgae from being incorporated so far.

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Nutrient removal from Chinese coastal waters by large-scale seaweed aquaculture

Xiao, X. et. al.

China is facing intense coastal eutrophication. Large-scale seaweed aquaculture in China is popular, now accounting for over 2/3’s of global production. Here, we estimate the nutrient removal capability of large-scale Chinese seaweed farms to determine its significance in mitigating eutrophication.

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The Global Status of Seaweed Production, Trade and Utilization (FAO)


This report is an update of the status of the global seaweed market: production figures from culture and capture, the size of the international market for seaweed and its commercially important extracts, the leading nations by region, developments in processing and utilization technology, and innovations in the industry, as well as the challenges and outlook for the industry. Read the report here.

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Seaweed Aquaculture for Food Security, Income Generation and Environmental Health in Tropical Developing Countries

World Bank

World Bank report on how producing large volumes of seaweeds for human food, animal feed and biofuels could represent a transformational change in the global food security equation and in the way we view and use the oceans. Read the report here. 

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The Science of Seaweeds

Ole G. Mouritsen

A deep dive into the science of what makes up seaweeds, and their many uses.  Read the article from American Scientist here. 

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Key Considerations for the Use of Seaweed to Reduce Enteric Methane Emissions From Cattle

Sandra Vijn et. al.

Enteric methane emissions are the single largest source of direct greenhouse gas emissions (GHG) in beef and dairy value chains and a substantial contributor to anthropogenic methane emissions globally.

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Environmental DNA identifies marine macrophyte contributions to Blue Carbon sediments

Ortega, A. et. al.

Estimation of marine macrophyte contribution to coastal sediments is key to understand carbon sequestration dynamics. Nevertheless, identification of macrophyte carbon is challenging. We propose environmental DNA (eDNA) metabarcoding as a new approach for identification of sediment contributors, and compared this approach against stable isotopes—the traditional approach. eDNA metabarcoding allowed high‐resolution identification of 48 macroalgae, seagrasses, and mangroves from coastal habitats. The relative eDNA contributions of macrophytes were similar to their contributions of organic carbon based on stable isotopes; however, isotopes were unreliable for taxonomical discrimination among macrophyte sources. Additionally, we experimentally found that eDNA abundance in the sediment correlates with...

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Rebuilding Marine Life

Carlos M. Duarte et al.

Substantial recovery of the abundance, structure and function of marine life could be achieved by 2050, if major pressures—including climate change—are mitigated.

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Important contribution of macroalgae to oceanic carbon sequestration

Ortega, A. et. al.

The role of macroalgae in Blue Carbon assessments has been controversial, partially due to uncertainties about the fate of exported macroalgae. Available evidence suggests that macroalgae are exported to reach the open ocean and the deep sea. Nevertheless, this evidence lacks systematic assessment. Here, we provide robust evidence of macroalgal export beyond coastal habitats. We used metagenomes and metabarcodes from the global expeditions Tara Oceans and Malaspina 2010 Circumnavigation. We discovered macroalgae worldwide at up to 5,000 km from coastal areas. We found 24 orders, most of which belong to the phylum Rhodophyta. The diversity of macroalgae was similar across oceanic...

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Blue Growth Potential to Mitigate Climate Change through Seaweed Offsetting

Halley E. Froehlich et. al.

Carbon offsetting—receiving credit for reducing, avoiding, or sequestering carbon—has become part of the portfolio of solutions to mitigate carbon emissions, and thus climate change, through policy and voluntary markets, primarily by land-based re- or afforestation and preservation.

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Can Seaweed Farming Play a Role in Climate Change Mitigation and Adaptation?

Duarte, C. et. al.

Seaweed aquaculture, the fastest-growing component of global food production, offers a slate of opportunities to mitigate, and adapt to climate change. Seaweed farms release carbon that maybe buried in sediments or exported to the deep sea, therefore acting as a CO2 sink. 

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Substantial role of macroalgae in marine carbon sequestration

Krause-Jensen, D. and Duarte, C.

Vegetated coastal habitats have been identified as important carbon sinks. In contrast to angiosperm-based habitats such as seagrass meadows, salt marshes and mangroves, marine macroalgae have largely been excluded from discussions of marine carbon sinks.

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