Role of Life Strategies in Diatom Biodiversity: A Modelling Approach

Stec, Krzystof Franciszek (2016). Role of Life Strategies in Diatom Biodiversity: A Modelling Approach. PhD thesis The Open University.



A theoretical framework explaining what regulates the number of species and their temporal and spatial patterns is still lacking making plankton diversity a challenging issue in ecology. In this study the nature and relevance of some of the drivers of marine diatoms dynamics and diversity over the seasons have been investigated by coupling experimental and numerical approaches. The main focus was on the life cycle, especially important for marine diatoms and overlooked as a possible driver of diversity. The performed laboratory experiments provided evidence of growth rate decrease occurring independently from resource availability during the sexual phase, which is a mandatory component of most diatom life cycles. The ecological and evolutionary implications of this biological mechanism have been explored with a developed ad hoc numerical model of seasonal plankton dynamics in the mixed layer. The model includes a detailed parametrization of the physical and chemical environments, and a set of phytoplankton species characterized by distinct physiological traits. The validation exercise demonstrated model’s applicability to address questions on plankton seasonal dynamics and diversity patterns. The modelling exercise showed that the coordinated growth rate reduction in diatoms during mating, even in presence of plentiful resources, would affect diversity patterns and functioning of the plankton community even if shared only by a subset of species. In addition, other factors including grazers’ migration and phytoplankton species immigration, as well as the role of the seasonal characteristics of the water column affecting plankton succession and species diversity were also investigated. This suggests that the above factors impact the community structure and its time course. In particular, biological regulation in diatoms, and likely in many other protists, can be remarkably sophisticated and should be considered to improve our understanding of plankton diversity, a question made even more important by the current climate change.

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