Silvia Vidal Melgosa How Do Microalgae Remove Carbon from the Atmosphere?

Department

Algal poly­sac­char­ides are an im­port­ant com­pon­ent of the flux of car­bon rich or­ganic mat­ter from the sur­face ocean into its depth. Most mar­ine poly­sac­char­ides are syn­thes­ized at the sur­face by mi­croal­gae whose an­nual pro­duc­tion is on par with all plants on land even though they only ac­count for about 1-2% of the mar­ine bio­mass.

This com­pet­it­ive pro­duc­tion is caused by in­tense growth and short lifespans; mi­croal­gae live fast and die young (weeks) com­pared to ter­restrial plants (years). They pur­sue a boom and bust life style with rapid growth and ab­rupt pop­u­la­tion crashes whereby algal blooms can ap­pear and dis­ap­pear within weeks or even days. Dur­ing growth and upon death mi­croal­gae secrete co­pi­ous amounts of an­ionic poly­sac­char­ides. These are known to spon­tan­eously ag­greg­ate into particles, which can more rap­idly sink through the wa­ter column and in­ject car­bon into deeper wa­ters (the bio­lo­gical pump). Bac­teria col­on­ize particles and use en­zymes to re­cycle poly­sac­char­ides lead­ing to in­tense bac­terial growth and particle dis­sol­u­tion. This way the in­ter­play between particle form­a­tion and its dis­sol­u­tion may reg­u­late the bio­lo­gical pump and dic­tate how much car­bon is stored in the oceans.

Des­pite the rel­ev­ance of this pro­cess the struc­tures of algal poly­sac­char­ides and their re­cyc­ling by mar­ine mi­crobes re­main a mys­tery. To shed light on this black box of the mar­ine car­bon cycle we study the func­tional evol­u­tion of the bac­terial en­zymatic ma­chines and how they pro­cess algal poly­sac­char­ides in the ocean