Science Mission 4

Submersible single cell and particle analysis

Phytoplankton are of fundamental importance in marine ecosystems as they form the base of marine food chains. They play an important role in the global climate through their draw down of carbon dioxide into the oceans for photosynthesis. They contribute to the formation of cloud condensation nuclei and acid rain through the production of gases.

Measuring phytoplankton

Flow cytometry, an optically-based technique, is used to accurately classify and count phytoplankton. It simultaneously measures multiple light scatter and fluorescence properties of individual particles at high speed, enabling thousands of cells to be analysed per second. It replaces traditional methods such as microscopy, which is very time consuming, or chlorophyll analysis which provide very limited information about the phytoplankton classification.

Phytoplankton blooms

During the campaign it was possible to send Autosub through areas of strikingly different particle composition. A mixed phytoplankton bloom consisting of Phaeocystis colonies and large diatoms was found close to the Isle of Scilly and a second bloom of the coccolithophore Emiliania huxleyi was found approximately five miles to the south.

Why use Autosub?

The development of Autosub provided an ideal opportunity to develop, trial and deploy a novel submersible flow cytometer (Cytosub). Autosub also collected water samples for validation purposes and carried instruments for measuring hydrographic parameters and inherent optical properties.

Related publications

Cunningham, A., McKee, D., Craig, S., Tarran G., and Widdicombe C., 2003. Fine-scale variability in phytoplankton community structure and inherent optical properties measured from an autonomous underwater vehicle. Journal of Marine Systems, 43(1-2), 51-59.