Marine microorganisms control the biogeochemistry and productivity of the global Ocean. Due to the global significance of these microbes, microbial oceanographers typically consider their dynamics across very large spatiotemporal scales (e.g. across ocean-basins). While this approach provides insights into how large-scale physical patterns influence the dynamics of whole microbial communities, the lives and ecological interactions of individual marine microbes are defined on a much smaller scale – the scales of individual drops of seawater. Within this microscale world, marine microbes experience a highly heterogeneous seascape, where sub-millimetre scale patches and pulses of resources can influence their physiology, behaviour and biogeochemical influence. Understanding the ecology of microbes at the ocean’s microscale is important because many key biogeochemical transformations take place within specific microenvironmental scenarios. We have developed and applied a suite of new tools, including microfluidic devices, for investigating the behavioural responses of marine microbial communities to a patchy chemical seascape. Using these approaches we have revealed that diverse groups of marine microbes are highly adapted to use behaviours, including high performance chemtoaxis, to locate and exploit the dynamic marine environment. These behaviours ultimately shape microbial competitive interactions that will influence diversity patterns at the community level and enhance chemical cycling rates, leading to bulk-scale effects on ocean biogeochemistry. My talk will describe what we have learnt about marine microbial ecology at the scale of microbes and will specifically address the implications of microscale behaviours on microbial trophodynamics, pathogen-host interactions, and oceanic biogeochemical cycling.