From meiofauna to ministers: a career reflection on why invisible seafloor fauna matters in decision-making

Meiofauna, microscopic animals living in and on the seafloor, are among the most abundant and diverse metazoans on Earth, yet they remain largely invisible in marine policy and management. Their small size, rapid turnover, and close coupling to seafloor environments mean they respond quickly and predictably to physical, chemical, and biological change, often before impacts are detectable in larger fauna. I reflect on how sustained engagement with meiofauna research, combined with experience working at the science-policy interface, has shaped my understanding of how micro-scale ecological processes can inform ecosystem-scale decisions. Drawing on three decades of experimental, field-based, and applied research, I describe recurring response pathways through which disturbances such as bottom-contact fishing, pollution, invasive species, and climate change reorganize meiofauna communities. These pathways integrate changes in seafloor structure, exposure and physiological tolerance, biotic interactions, rapid colonization dynamics, functional compensation, and lineages of cryptic species. Rather than focusing on basic metrics of abundance or species richness alone, this perspective emphasizes faunal patterns that reveal whether ecosystems are resisting change, reorganizing, or losing resilience. Meiofauna play a critical role as (i) sentinels, indicating environmental changes that might otherwise go unobserved in a timely, measurable, and interpretable way and (ii) mediators of environmental change, sustaining and regulating ecosystem processes, especially when larger fauna is reduced or absent. This buffering capacity can mask structural degradation if interpreted uncritically but, with deeper knowledge and mechanistic understanding, it offers valuable insights into ecosystem trajectories, thresholds, and cumulative impacts. I reflect on the challenge of translating micro-scale science into decision-relevant evidence within policy frameworks that operate at much larger spatial and temporal scales. I also consider how working across these scales has shaped my own approach to advice and what this might offer to others, particularly early-career researchers navigating similar challenges. I argue that integrating meiofauna response pathways alongside conventional macrofauna-based indicators can strengthen the overall weight of evidence available to decision-makers, enabling earlier, more confident and more targeted action. Framed in this way, meiofauna do not compete with existing indicators but complement them, helping to bridge the gap between ecological processes and policy needs.