Monday, November 19, 2012

Seychelles has a Big Stock of Blue Carbon

Sea grasses in Seychelles (

The Seychelles archipelago has huge expanses of sea grasses, one of the largest in the Western Indian Ocean. Most people here mistake sea grasses for “seaweeds”. But sea grasses are flowering plants like plants on land unlike “seaweeds” which are algae.

For years many marine conservationists and agencies have given sea grasses stepdaughter treatment. Yet, these ecosystems have extremely important roles to play as habitats, food sources, and sediment stabilizers. Sea grass meadows are well frequented by fish and therefore are targeted by some trap fishermen. About 50 species of fish are found in the sea grasses around the granitic islands of Seychelles.

Sadly, sea grasses are declining not only in Seychelles but globally as well. In Seychelles, we have lost many hectares of sea grasses through coastal reclamation, siltation and freshwater runoff. A study found that river effluents had a major impact on sea grass meadows near the river mouths.

But now because carbon is such a key factor in climate change, sea grasses have assumed another very important function. They are an important store of ‘blue carbon’, the carbon stored by marine life. A paper published recently in Nature Geoscience estimates that around 3 tonnes of carbon are stored in every hectare of living sea grass. The paper says that an average of 140 tonnes of organic carbon are stored in the top metre of each hectare of sea grass soil, which is around twice that found in soils on land.

Sea grass meadows cover between 30-60 million hectares (around 0.2% of the area of the oceans) and between 4.2 to 8.4 petagrams of organic carbon (one petagram is equal to a thousand million tonnes) are stored in the top metre of seagrass soils. A less conservative estimate suggests the figure could be as high as 19.8 petagrams. Soils on land, by comparison, cover 15 billion hectares and contain between 1500-2000 petagrams of organic carbon. A further 75.5 to 151 teragrams of carbon are stored in seagrass itself (one teragram is equal to one million tonnes).

There are no estimates yet for the Indian Ocean region, but Mediterranean sea grass meadows have the largest stores of organic carbon currently known. In the Mediterranean, sea grass soils containing 11-metre thick organic carbon deposits that have built up over thousands of years have been found.

In Seychelles we have 8 species of sea grasses. Almost thirty percent of the inshore reef areas of Mahe, Praslin and La Digue are covered by sea grasses. On Praslin, where the reef flat is wide, the sea grasses extend to one kilometer in width. Because they need sunlight for photosynthesis, sea grasses are usually found in shallow water.

The outer islands also host sea grass meadows. The marine vegetation of the low coral islands is characterised by dominant communities of Thalassodendron. This sea grass plays an important role in the stabilization of unconsolidated sediments in the atolls. Surprisingly, on African Banks and Providence island, sea grasses have been found at depths of up to 25 meters.

Seychelles has a huge opportunity to trade in “blue carbon”. But first we need to know more about our sea grass meadows - their size, distribution and how much carbon they can capture.

Adapted from the author's column in The People newspaper, 9/11/2012

Reference: Fourqurean, J. W., Duarte, C.M. Kennedy, H. et al. (2012). Seagrass ecosystems as a globally significant carbon stock. Nature Geoscience. 5(7): 505–509.
Click for the paper:

1 comment:

Emilio Fernandez said...

Good morning how are you?

My name is Emilio, I am a Spanish boy and I live in a town near to Madrid. I am a very interested person in knowing things so different as the culture, the way of life of the inhabitants of our planet, the fauna, the flora, and the landscapes of all the countries of the world etc. in summary, I am a person that enjoys traveling, learning and respecting people's diversity from all over the world.

I would love to travel and meet in person all the aspects above mentioned, but unfortunately as this is very expensive and my purchasing power is quite small, so I devised a way to travel with the imagination in every corner of our planet. A few years ago I started a collection of used stamps because trough them, you can see pictures about fauna, flora, monuments, landscapes etc. from all the countries. As every day is more and more difficult to get stamps, some years ago I started a new collection in order to get traditional letters addressed to me in which my goal was to get at least 1 letter from each country in the world. This modest goal is feasible to reach in the most part of countries, but unfortunately it’s impossible to achieve in other various territories for several reasons, either because they are countries at war, either because they are countries with extreme poverty or because for whatever reason the postal system is not functioning properly.

For all this I would ask you one small favor:
Would you be so kind as to send me a letter by traditional mail from Seychelles? I understand perfectly that you think that your blog is not the appropriate place to ask this, and even, is very probably that you ignore my letter, but I would call your attention to the difficulty involved in getting a letter from that country, and also I don’t know anyone neither where to write in Seychelles in order to increase my collection. a letter for me is like a little souvenir, like if I have had visited that territory with my imagination and at same time, the arrival of the letters from a country is a sign of peace and normality and an original way to promote a country in the world. My postal address is the following one:

Emilio Fernandez Esteban
Avenida Juan de la Cierva, 44
28902 Getafe (Madrid)

If you wish, you can visit my blog where you can see the pictures of all the letters that I have received from whole World.

Finally I would like to thank the attention given to this letter, and whether you can help me or not, I send my best wishes for peace, health and happiness for you, your family and all your dear beings.

Yours Sincerely

Emilio Fernandez