Scale-free characteristics of the global marine food web

Abstract The scale-free characteristics of marine food webs reflect the network structural interrelationship, which is ecologically important. Nevertheless, the existence of scale-free networks in marine ecosystems has not been thoroughly discussed. Here, we identify the spatial-temporal pattern of scale-free characteristics and explore the correlation between relevant food web parameters at different scale-free levels. Marine food webs around the globe do not strictly exhibit scale-free characteristics in most regions, and only below 5% of the food webs enter the "strongest fit" level of the scale-free network. We also find food webs in the polar regions indicate relatively high goodness of fit to scale-free networks and state a high latitude dominance hypothesis. The upwelling ecosystem related to ocean currents is prone to form a scale-free web, which exhibits periodic scale-free characteristics. The correlation analysis show that intensified human activities and ocean warming both hinder the formation of food webs with scale-free structures.