The ecophysiological relationship between the behavioural strategies and trophic nature of planktonic flagellates

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Planktonic flagellates are an ecologically important group of motile, eukaryotic microorganisms characterised by a trophic complexity, involving photosynthesis and the uptake of organic nutrients, and a behavioural flexibility, whereby cells are able to actively sense and respond to resources within the environment. Although it is commonly believed that trophic and behavioural strategies combine to facilitate the growth and survival of these organisms, few studies have investigated the ecophysiological relationship between these factors. Using an integrated behavioural, physiological and theoretical approach, this proposal aims to test this relationship in ten, trophically-contrasting species. Preliminary measurements of trophic characteristics in different combinations of essential nutrients will be followed by a series of behavioural experiments quantifying the strength, plasticity and diversity of any responses to ecologically representative gradients of substitutable resources (light, carbon dioxide, dissolved organic carbon and bacteria). Parallel physiological analyses of photosynthetic ability, multi-factorial growth experiments, and cost-benefit analyses will then determine if behavioural preferences are physiologically motivated and will clarify their energetic relationship with trophic nature. Finally, the potential existence of optimal foraging in these planktonic protists will be considered, results will be placed in an ecological context and the functional implications for survival, competition and distribution will be discussed.