Basic Research on the Evolution of Silica Biomineralizing Plankton

Current research in the Knoll lab aims to understand how and why the use of silica by marine microplanktonic organisms has changed throughout their evolutionary history, in the context of the silica cycle. The evolutionary innovation of biomineralization tied both radiolarians and diatoms to this biogeochemical system. Thus, the increasing participation of biology in the cycle has both affected the system and, conversely, changes in the system have influenced the evolution of the organisms involved. For example, early Cenozoic radiolarians used more silica per unit cell volume than those in the latest Cenozoic (see image). Ongoing projects include studying changes in radiolarian silica use in pre-Cenozoic time using three-dimensional imaging and models of fossils, and documenting similar evolutionary patterns in the fossil record of diatoms. We are also constructing morphospaces for siliceous plankton and hope examining changes in their occupancy through time will elucidate which general morphologies and evolutionary strategies were favored as silica dwindled as a resource. In culturing and biomechanical studies of diatoms we intend to study the consequences of such changes for the mechanical strength of their mineralized skeletons.