Upcoming thesis defense: To diversity and beyond?

On Friday the 1st of December Patrick Rozema will defend his thesis 'To diversity and beyond: Shifting Antarctic microbial communities along environmental gradients'.

The Antarctic Peninsula, marine (micro)biology along it, is changing rapidly. This thesis, to be defended on international Antarctica Day, presents insights into the relation between phytoplankton (microscopic plants), bacteria and the environment. Research conducted at the British Antarctic research station Rothera, where the Dutch have opened a lab in 2012, shows that decreasing sea ice cover during winter results in low concentrations of phytoplankton in the following summer and that the summer phytoplankton strongly represents that of the winter. This means a lack of diatoms, pivotal in the classical Antarctic food web and crucial for long term storage of CO2. A future scenario with less sea ice and more wind mixing will result in increased proportions of flagellated species.

Also, we show that diversity is far greater than expected within this group of flagellated species with the presence of multiple different species. Moreover, we looked beyond the classical defined taxonomic levels, to the genetic variability and identify different “ecotypes” for all flagellated species. For example, for a species of cryptophytes, we show that one species (Geminigera cryophila) occurs in at least three ecotypes. Two of which occur at contrasting conditions, one prefers relative fresh water layers often associated with the melting of glaciers, the other prefers the salty conditions of the open ocean. These and other results in this thesis show a level of diversity with ecological relevance that is currently not investigated but holds implication of the Antarctic food web and is strongly linked to the changing environmental conditions.

Prior to the thesis defence of Patrick Rozema, Ocean Ecosystems organizes a mini symposium entitled: Advances in Marine Polar Sciences.