Testing dust-fertilisation in the lab!

Coccolithophores are a group of unicellular marine phytoplankton living in the photic zone of the ocean and drifting with the currents. Like any other marine algae or terrestrial plant, they need light and nutrients to perform photosynthesis and grow, using atmospheric CO2 and releasing oxygen during the process. By doing so, marine phytoplankton profoundly affects important global biogeochemical cycles and climate, being responsible for producing a large part of the Earth’s oxygen (e.g. Thomas et al., 2012) 

Illustration of marine phytoplankton (including coccolithophores) drifting in the ocean (organisms are not to scale). Image obtained from: https://www.youtube.com/watch?v=jsgCjgcp_6g

Illustration of marine phytoplankton (including coccolithophores) drifting in the ocean (organisms are not to scale). Image obtained from: https://www.youtube.com/watch?v=jsgCjgcp_6g

As desert dust transported by the wind carries nutrients and trace metals that are essential for photosynthesis, dust has the potential to act as a fertiliser for marine phytoplankton to grow in regions of the global ocean that are nutrient-depleted. This as the potential of influencing marine biogeochemistry and atmospheric CO2 concentrations. Such may be particularly the case when considering coccolithophores, since they interact with the carbon cycle in three distinct ways: as a CO2 sink (via photosynthesis), as a CO2 source (via calcification), and as a mineral ballast fot the export of CO2 from the surface down to the deep ocean. To investigate the potential of dust as a nutrient fertiliser, we are preparing a coccolithophore batch-culture in which we will introduce dust that has been collected from the Saharan desert. The dust will be pre-adjusted to resemble dust that is naturally deposited in the open ocean and leached in acid conditions (H2SO4 and HNO3) for mimicking acid cloud chemical processing. Finally, we will dilute this acidified dusty-solution for mimicking Wet Dust Deposition, via precipitation. Our experiment is inspired in an incubation led by Laura Korte on board RRV James Cook, during our last transatlantic expedition (March/April 2016). 

Incubation experiment for testing the effects from dry- and wet-dust deposition on the tropical North Atlantic led by Laura Korte during the expedition JCR134 on board RRV James Cook (March/April 2016).

Incubation experiment for testing the effects from dry- and wet-dust deposition on the tropical North Atlantic led by Laura Korte during the expedition JCR134 on board RRV James Cook (March/April 2016).

The coccolithophore culture is being prepared at MARE’s Algoteca under the supervision of Ana Amorim, a marine biologist at MARE and full professor at FCUL, and close guidance by Bernardo Vicente and Luísa Dâmaso both working at MARE. Bernardo is a MSc student working in the lab and is about to finish his thesis focused on the role of SiO2 for cell production and calcification of Coccolithus pelagicus. With his help, we have started culturing Emiliania huxleyi – probably the most opportunistic of the coccolithophores species that we know – but hope to culture other species as well, in the future. We will keep you updated on our progress!!! 

Catarina, doing her very first mono-culture of  Emiliana huxleyi  in the lab!

Catarina, doing her very first mono-culture of Emiliana huxleyi in the lab!

Viewing inside one of the phytoplankton culture-chambers existing at Algoteca. Each of those vials and petri-dishes contain millions of living cells of mono-cultures of phytoplankton. Species are maintained under controlled conditions of temperature, light intensity and nutrient concentrations. Regularly, all of these cultures representing different species have to be changed into new culture medium with fresh nutrients to keep the microalgae alive and healthy.

Viewing inside one of the phytoplankton culture-chambers existing at Algoteca. Each of those vials and petri-dishes contain millions of living cells of mono-cultures of phytoplankton. Species are maintained under controlled conditions of temperature, light intensity and nutrient concentrations. Regularly, all of these cultures representing different species have to be changed into new culture medium with fresh nutrients to keep the microalgae alive and healthy.

This is Bernardo showing us how the work is done. Thank you Bernardo, for you guidance and patience while explaining us all the procedure!

This is Bernardo showing us how the work is done. Thank you Bernardo, for you guidance and patience while explaining us all the procedure!