Sugar brings carbon dioxide into the deeper sea

The oceans are a very important reservoir for carbon in the system of the earth, but many aspects of the marine carbon cycle are still unknown. Scientists have now discovered that sugar plays an important role in this process.

In the sun­lit sur­face layer of the ocean, pho­to­syn­thetic mi­croal­gae such as di­at­oms con­vert more car­bon di­ox­ide into bio­mass than Earth’s trop­ical forests. Like land plants, di­at­oms se­quester car­bon di­ox­ide into poly­meric car­bo­hydrates, or long-chained sug­ars. However, it has proven dif­fi­cult to quantify how much car­bon di­ox­ide can be stored in the global oceans throughout this pro­cess.

Now, researchers at the Max Planck In­sti­tute of Mar­ine Mi­cro­bi­o­logy and the Uni­versity of Bre­men have dis­sected pho­to­syn­thetic mi­croal­gae and meas­ured con­cen­tra­tions of the long-chained sugar lam­in­arin, an im­port­ant en­ergy source for mi­croal­gae in­clud­ing di­at­oms.

Based on mi­croal­gae ob­tained from the Arc­tic, At­lantic, and Pa­cific Oceans and the North Sea, the re­search­ers es­tim­ated that this bio­mass is on av­er­age com­posed of 26 per­ cent lam­in­arin, according to a statement.

Fur­ther­more, the sci­ent­ists found that lam­in­arin com­prises as much as 50 per­ cent of the or­ganic car­bon in sink­ing di­atom-con­tain­ing particles. “Thus lam­in­arin plays a cent­ral role in car­bon trans­fer from sur­face wa­ters to the deeper ocean,” explained Jan-Hendrik Hehem­ann, leader of the re­search group Mar­ine Gly­cobi­o­logy. “Whether lam­in­arin is fixed in deep wa­ters is an im­port­ant fur­ther ques­tion that we will ad­dress in the fu­ture”.

As mi­croal­gae rep­res­ent the all-im­port­ant base of the mar­ine food web, the find­ings show that lam­in­arin oc­cu­pies a prom­in­ent po­s­i­tion in global ocean eco­logy. The re­search­ers from Bre­men found out that the amount of sugar in mi­croal­gae is high, but is not al­ways the same.

Col­lect­ively, these find­ings high­light the prom­in­ent eco­lo­gical role and bio­chem­ical func­tion of the sugar lam­in­arin in the ocean.

Photo credit: Reeve Jolliffe, flickr/Creative Commons

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