Our current understanding of marine ecosystems has largely been shaped by observations at broad spatial and temporal scales. Cruise surveys typically provide only scattered transects, while fixed stations capture variability at a single location. Although these approaches have delivered valuable information on seasonal and interannual patterns, they are constrained by low spatial resolution and limited temporal coverage. As a result, the fine-scale dynamics of plankton and their interactions with environmental gradients have remained largely unresolved, leaving an incomplete picture of ecosystem functioning.

Over the past decade, rapid advances in ocean observing technologies have opened new opportunities to resolve fine-scale plankton dynamics. High-resolution satellites (e.g. SWOT), autonomous buoy networks equipped with sensors for temperature, salinity and fluorescence, and in situ plankton imaging systems (e.g. Imaging FlowCytobot, CytoSense/CytoSub, Imaging Plankton Probe, Video Plankton Recorder) now provide continuous, high-frequency records across multiple platforms. These innovations make it possible to observe plankton processes at unprecedented temporal and spatial resolutions, capturing short-lived events and small-scale environmental gradients that were previously undetectable. Together, these advances are reshaping our understanding of plankton variability and their ecological roles in marine ecosystems.

This session invites contributions on meso- to fine-scale plankton variability and its links to environmental gradients. We particularly welcome studies using in situ and high-resolution observing systems, as well as new developments in intensive monitoring technologies. The goal is to advance understanding of how fine-scale plankton–environment interactions shape ecosystem structure and function, and how they connect to larger-scale ocean and climate processes. A special issue in the Journal of Plankton Research will accompany this session.