Topic: diatoms

Brad Gemmell discusses how changing environmental conditions affect the behaviour and ecology of small marine organisms. Topics include ctenophore predation, diatoms and ocean carbon cycling, and the role of upside-down Cassiopea jellyfish as ecosystem engineers. The conversation connects organismal physiology and movement with broader changes in marine ecosystems.

I shall present two recent piece of work investigating how shape effects the transport of active particles in shear. Firstly we will consider the sedimentation of particles in 2D laminar flow fields of increasing complexity; and how insights from this can help explain why turbulence can enhance the sedimentation of negatively buoyant diatoms [1]. Secondly, we will consider the 3D transport of elongated active particles under the action of an aligning force (e.g. gyrotactic swimmers) in some simple flow fields; and will see how shape can influence the vertical distribution, for example changing