Synergetic impacts of turbulence and fishing reduce ocean biomass

<jats:title>Abstract</jats:title><jats:p>A universal scaling relationship exists between organism abundance and body size<jats:sup>1,2</jats:sup>. Within ocean habitats this relationship deviates from that generally observed in terrestrial systems<jats:sup>2–4</jats:sup>, where marine macro-fauna display steeper size-abundance scaling than expected. This is indicative of a fundamental shift in food-web organization, yet a conclusive mechanism for this pattern has remained elusive. We demonstrate that while fishing has partially contributed to the reduced abundance of larger organisms, a larger effect comes from ocean turbulence: the energetic cost of movement within a turbulent environment induces additional biomass losses among the nekton. These results identify turbulence as a novel mechanism governing the marine size-abundance distribution, highlighting the complex interplay of biophysical forces that must be considered alongside anthropogenic impacts in processes governing marine ecosystems.</jats:p>